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Algae fuel

February 16, 2024

Algae fuel, algal biofuel, or algal oil is an alternative to liquid fossil fuels that uses algae as its source of energy-rich oils. Also, algae fuels are an alternative to commonly known biofuel sources, such as corn and sugarcane.[1][2] When made from seaweed (macroalgae) it can be known as seaweed fuel or seaweed oil.

A conical flask of "green" jet fuel made from algae

In December 2022, ExxonMobil, the last large oil company to invest in algae biofuels, ended its research funding.[3]

History edit

In 1942 Harder and Von Witsch were the first to propose that microalgae be grown as a source of lipids for food or fuel.[4][5] Following World War II, research began in the US,[6][7][8] Germany,[9] Japan,[10] England,[11] and Israel[12] on culturing techniques and engineering systems for growing microalgae on larger scales, particularly species in the genus Chlorella. Meanwhile, H. G. Aach showed that Chlorella pyrenoidosa could be induced via nitrogen starvation to accumulate as much as 70% of its dry weight as lipids.[13] Since the need for alternative transportation fuel had subsided after World War II, research at this time focused on culturing algae as a food source or, in some cases, for wastewater treatment.[14]

Interest in the application of algae for biofuels was rekindled during the oil embargo and oil price surges of the 1970s, leading the US Department of Energy to initiate the Aquatic Species Program in 1978.[15] The Aquatic Species Program spent $25 million over 18 years with the goal of developing liquid transportation fuel from algae that would be price competitive with petroleum-derived fuels.[16] The research program focused on the cultivation of microalgae in open outdoor ponds, systems which are low in cost but vulnerable to environmental disturbances like temperature swings and biological invasions. 3,000 algal strains were collected from around the country and screened for desirable properties such as high productivity, lipid content, and thermal tolerance, and the most promising strains were included in the SERI microalgae collection at the Solar Energy Research Institute (SERI) in Golden, Colorado and used for further research.[16] Among the program's most significant findings were that rapid growth and high lipid production were "mutually exclusive", since the former required high nutrients and the latter required low nutrients.[16] The final report suggested that genetic engineering may be necessary to be able to overcome this and other natural limitations of algal strains, and that the ideal species might vary with place and season.[16] Although it was successfully demonstrated that large-scale production of algae for fuel in outdoor ponds was feasible, the program failed to do so at a cost that would be competitive with petroleum, especially as oil prices sank in the 1990s. Even in the best case scenario, it was estimated that unextracted algal oil would cost $59–186 per barrel,[16] while petroleum cost less than $20 per barrel in 1995.[15] Therefore, under budget pressure in 1996, the Aquatic Species Program was abandoned.[16]

Other contributions to algal biofuels research have come indirectly from projects focusing on different applications of algal cultures. For example, in the 1990s Japan's Research Institute of Innovative Technology for the Earth (RITE) implemented a research program with the goal of developing systems to fix CO
2 using microalgae.[17] Although the goal was not energy production, several studies produced by RITE demonstrated that algae could be grown using flue gas from power plants as a CO
2 source,[18][19] an important development for algal biofuel research. Other work focusing on harvesting hydrogen gas, methane, or ethanol from algae, as well as nutritional supplements and pharmaceutical compounds, has also helped inform research on biofuel production from algae.[14]

Following the disbanding of the Aquatic Species Program in 1996, there was a relative lull in algal biofuel research. Still, various projects were funded in the US by the Department of Energy, Department of Defense, National Science Foundation, Department of Agriculture, National Laboratories, state funding, and private funding, as well as in other countries.[15] More recently, rising oil prices in the 2000s spurred a revival of interest in algal biofuels and US federal funding has increased,[15] numerous research projects are being funded in Australia, New Zealand, Europe, the Middle East, and other parts of the world.[20]

In March 2023, researchers said that the commercialization of biofuels would require several billion dollars of funding, plus a long-term dedication to overcoming what appear to be fundamental biological limitations of wild organisms. Most researchers think that large scale production of biofuels is either "a decade, and more likely two decades, away."[3]

Food supplementation edit

Algal oil is used as a source of fatty acid supplementation in food products, as it contains mono- and polyunsaturated fats, in particular EPA and DHA.[21] Its DHA content is roughly equivalent to that of salmon based fish oil.[22][23]

Fuels edit

Algae can be converted into various types of fuels, depending on the production technologies and the part of the cells used. The lipid, or oily part of the algae biomass can be extracted and converted into biodiesel through a process similar to that used for any other vegetable oil, or converted in a refinery into "drop-in" replacements for petroleum-based fuels. Alternatively or following lipid extraction, the carbohydrate content of algae can be fermented into bioethanol or butanol fuel.[24]

Biodiesel edit

Main article: Biodiesel

Biodiesel is a diesel fuel derived from animal or plant lipids (oils and fats). Studies have shown that some species of algae can produce 60% or more of their dry weight in the form of oil.[13][16][25][26][27] Because the cells grow in aqueous suspension, where they have more efficient access to water, CO
2 and dissolved nutrients, microalgae are capable of producing large amounts of biomass and usable oil in either high rate algal ponds[28] or photobioreactors. This oil can then be turned into biodiesel which could be sold for use in automobiles. Regional production of microalgae and processing into biofuels will provide economic benefits to rural communities.[29]

As they do not have to produce structural compounds such as cellulose for leaves, stems, or roots, and because they can be grown floating in a rich nutritional medium, microalgae can have faster growth rates than terrestrial crops. Also, they can convert a much higher fraction of their biomass to oil than conventional crops, e.g. 60% versus 2-3% for soybeans.[25] The per unit area yield of oil from algae is estimated to be from 58,700 to 136,900 L/ha/year, depending on lipid content, which is 10 to 23 times as high as the next highest yielding crop, oil palm, at 5 950 L/ha/year.[30]

The U.S. Department of Energy's Aquatic Species Program, 1978–1996, focused on biodiesel from microalgae. The final report suggested that biodiesel could be the only viable method by which to produce enough fuel to replace current world diesel usage.[31] If algae-derived biodiesel were to replace the annual global production of 1.1bn tons of conventional diesel then a land mass of 57.3 million hectares would be required, which would be highly favorable compared to other biofuels.[32]

Biobutanol edit

Main article: Butanol fuel

Butanol can be made from algae or diatoms using only a solar powered biorefinery. This fuel has an energy density 10% less than gasoline, and greater than that of either ethanol or methanol. In most gasoline engines, butanol can be used in place of gasoline with no modifications. In several tests, butanol consumption is similar to that of gasoline, and when blended with gasoline, provides better performance and corrosion resistance than that of ethanol or E85.[33]

The green waste left over from the algae oil extraction can be used to produce butanol. In addition, it has been shown that macroalgae (seaweeds) can be fermented by bacteria of genus Clostridia to butanol and other solvents.[34] Transesterification of seaweed oil (into biodiesel) is also possible with species such as Chaetomorpha linum, Ulva lactuca, and Enteromorpha compressa (Ulva).[35]

The following species are being investigated as suitable species from which to produce ethanol and/or butanol:[36]

Biogasoline edit

Biogasoline is gasoline produced from biomass. Like traditionally produced gasoline, it contains between 6 (hexane) and 12 (dodecane) carbon atoms per molecule and can be used in internal-combustion engines.[38]

Biogas edit

Main article: Biogas

Biogas is composed mainly of methane (CH4) and carbon dioxide (CO2), with some traces of hydrogen sulphide, oxygen, nitrogen, and hydrogen. Macroalgae has high methane production rate compared to plant biomass. Biogas production from macroalgae is more technically viable compared to other fuels, but it is not economically viable due to the high cost of macroalgae feedstock.[39] Carbohydrate and protein in microalgae can be converted into biogas through anaerobic digestion, which includes hydrolysis, fermentation, and methanogenesis steps. The conversion of algal biomass into methane can potentially recover as much energy as it obtains, but it is more profitable when the algal lipid content is lower than 40%.[40] Biogas production from microalgae is relatively low because of the high ratio of protein in microalgae, but microalgae can be co-digested with high C/N ratio products such as wastepaper.[41] Another method to produce biogas is through gasification, where hydrocarbon is converted to syngas through a partial oxidation reaction at high temperature (typically 800 °C to 1000 °C). Gasification is usually performed with catalysts. Uncatalyzed gasification requires temperature to be about 1300 °C. Syngas can be burnt directly to produce energy or used a fuel in turbine engines. It can also be used as feedstock for other chemical productions.[42]

Methane edit

Methane,[43] the main constituent of natural gas can be produced from algae in various methods, namely gasification, pyrolysis and anaerobic digestion. In gasification and pyrolysis methods methane is extracted under high temperature and pressure. Anaerobic digestion[44] is a straightforward method involved in decomposition of algae into simple components then transforming it into fatty acids using microbes like acidogenic bacteria followed by removing any solid particles and finally adding methanogenic archaea to release a gas mixture containing methane. A number of studies have successfully shown that biomass from microalgae can be converted into biogas via anaerobic digestion.[45][46][47][48][49] Therefore, in order to improve the overall energy balance of microalgae cultivation operations, it has been proposed to recover the energy contained in waste biomass via anaerobic digestion to methane for generating electricity.[50]

Ethanol edit

The Algenol system which is being commercialized by BioFields in Puerto Libertad, Sonora, Mexico utilizes seawater and industrial exhaust to produce ethanol. Porphyridium cruentum also have shown to be potentially suitable for ethanol production due to its capacity for accumulating large amount of carbohydrates.[51]

Green diesel edit

Main article: Biodiesel production

Algae can be used to produce 'green diesel' (also known as renewable diesel, hydrotreating vegetable oil[52] or hydrogen-derived renewable diesel)[53] through a hydrotreating refinery process that breaks molecules down into shorter hydrocarbon chains used in diesel engines.[52][54] It has the same chemical properties as petroleum-based diesel[52] meaning that it does not require new engines, pipelines or infrastructure to distribute and use. It has yet to be produced at a cost that is competitive with petroleum.[53] While hydrotreating is currently the most common pathway to produce fuel-like hydrocarbons via decarboxylation/decarbonylation, there is an alternative process offering a number of important advantages over hydrotreating. In this regard, the work of Crocker et al.[55] and Lercher et al.[56] is particularly noteworthy. For oil refining, research is underway for catalytic conversion of renewable fuels by decarboxylation.[57] As the oxygen is present in crude oil at rather low levels, of the order of 0.5%, deoxygenation in petroleum refining is not of much concern, and no catalysts are specifically formulated for oxygenates hydrotreating. Hence, one of the critical technical challenges to make the hydrodeoxygenation of algae oil process economically feasible is related to the research and development of effective catalysts.[58][59]

Jet fuel edit

Main article: Aviation biofuel

Trials of using algae as biofuel were carried out by Lufthansa and Virgin Atlantic as early as 2008, although there is little evidence that using algae is a reasonable source for jet biofuels.[60] By 2015, cultivation of fatty acid methyl esters and alkenones from the algae, Isochrysis, was under research as a possible jet biofuel feedstock.[61]

Algae-based energy harvester edit

In May 2022, scientists at University of Cambridge announced they created an algae energy harvester, that uses natural sunlight to power a small microprocessor, initially powering the processor for six months, and then kept going for a full year. The device, which is about the size of AA battery, is a small container with water and blue green algae. The device does not generate a huge amount of power, but it can be used for Internet of Things devices, eliminating the need for traditional batteries such as lithium ion batteries. The goal is to have more a environmentally friendly power source that can be used in remote areas.[62]

Species edit

Research into algae for the mass-production of oil focuses mainly on microalgae (organisms capable of photosynthesis that are less than 0.4 mm in diameter, including the diatoms and cyanobacteria) as opposed to macroalgae, such as seaweed. The preference for microalgae has come about due largely to their less complex structure, fast growth rates, and high oil-content (for some species). However, some research is being done into using seaweeds for biofuels, probably due to the high availability of this resource.[63][64]

As of 2012 researchers across various locations worldwide have started investigating the following species for their suitability as a mass oil-producers:[65][66][67]

The amount of oil each strain of algae produces varies widely. Note the following microalgae and their various oil yields:

In addition, due to its high growth-rate, Ulva[71] has been investigated as a fuel for use in the SOFT cycle, (SOFT stands for Solar Oxygen Fuel Turbine), a closed-cycle power-generation system suitable for use in arid, subtropical regions.[72]

Other species used include Clostridium saccharoperbutylacetonicum,[73] Sargassum, Gracilaria, Prymnesium parvum, and Euglena gracilis.[74]

Nutrients and growth inputs edit

Main article: Algaculture

Light is what algae primarily need for growth as it is the most limiting factor. Many companies are investing for developing systems and technologies for providing artificial light. One of them is OriginOil that has developed a Helix BioReactorTM that features a rotating vertical shaft with low-energy lights arranged in a helix pattern.[75] Water temperature also influences the metabolic and reproductive rates of algae. Although most algae grow at low rate when the water temperature gets lower, the biomass of algal communities can get large due to the absence of grazing organisms.[75] The modest increases in water current velocity may also affect rates of algae growth since the rate of nutrient uptake and boundary layer diffusion increases with current velocity.[75]

Other than light and water, phosphorus, nitrogen, and certain micronutrients are also useful and essential in growing algae. Nitrogen and phosphorus are the two most significant nutrients required for algal productivity, but other nutrients such as carbon and silica are additionally required.[76] Of the nutrients required, phosphorus is one of the most essential ones as it is used in numerous metabolic processes. The microalgae D. tertiolecta was analyzed to see which nutrient affects its growth the most.[77] The concentrations of phosphorus (P), iron (Fe), cobalt (Co), zinc (Zn), manganese (Mn) and molybdenum (Mo), magnesium (Mg), calcium (Ca), silicon (Si) and sulfur (S) concentrations were measured daily using inductively coupled plasma (ICP) analysis. Among all these elements being measured, phosphorus resulted in the most dramatic decrease, with a reduction of 84% over the course of the culture.[77] This result indicates that phosphorus, in the form of phosphate, is required in high amounts by all organisms for metabolism.

There are two enrichment media that have been extensively used to grow most species of algae: Walne medium and the Guillard's F/2 medium.[78] These commercially available nutrient solutions may reduce time for preparing all the nutrients required to grow algae. However, due to their complexity in the process of generation and high cost, they are not used for large-scale culture operations.[78] Therefore, enrichment media used for mass production of algae contain only the most important nutrients with agriculture-grade fertilizers rather than laboratory-grade fertilizers.[78]

Cultivation edit

See also: Culture of microalgae in hatcheries
 
Photobioreactor from glass tubes
 
Design of a race-way open pond commonly used for algal culture

Algae grow much faster than food crops, and can produce hundreds of times more oil per unit area than conventional crops such as rapeseed, palms, soybeans, or jatropha.[30] As algae have a harvesting cycle of 1–10 days, their cultivation permits several harvests in a very short time-frame, a strategy differing from that associated with annual crops.[26] In addition, algae can be grown on land unsuitable for terrestrial crops, including arid land and land with excessively saline soil, minimizing competition with agriculture.[79] Most research on algae cultivation has focused on growing algae in clean but expensive photobioreactors, or in open ponds, which are cheap to maintain but prone to contamination.[80]

Closed-loop system edit

The lack of equipment and structures needed to begin growing algae in large quantities has inhibited widespread mass-production of algae for biofuel production. Maximum use of existing agriculture processes and hardware is the goal.[81]

Closed systems (not exposed to open air) avoid the problem of contamination by other organisms blown in by the air. The problem of a closed system is finding a cheap source of sterile CO
2. Several experimenters have found the CO
2 from a smokestack works well for growing algae.[82][83] For reasons of economy, some experts think that algae farming for biofuels will have to be done as part of cogeneration, where it can make use of waste heat and help soak up pollution.[84]

To produce micro-algae at large-scale under controlled environment using PBR system, strategies such as light guides, sparger, and PBR construction materials required should be well considered.[85]

Photobioreactors edit

Most companies pursuing algae as a source of biofuels pump nutrient-rich water through plastic or borosilicate glass tubes (called "bioreactors" ) that are exposed to sunlight (and so-called photobioreactors or PBR).[86]

Running a PBR is more difficult than using an open pond, and costlier, but may provide a higher level of control and productivity.[26] In addition, a photobioreactor can be integrated into a closed loop cogeneration system much more easily than ponds or other methods.

Open pond edit

Open pond systems consist of simple in ground ponds, which are often mixed by a paddle wheel. These systems have low power requirements, operating costs, and capital costs when compared to closed loop photobioreactor systems.[87][86] Nearly all commercial algae producers for high value algal products utilize open pond systems.[88]

Turf scrubber edit

 
2.5 acre ATS system, installed by Hydromentia on a farm creek in Florida

The Algae scrubber is a system designed primarily for cleaning nutrients and pollutants out of water using algal turfs. An algal turf scrubber (ATS) mimics the algal turfs of a natural coral reef by taking in nutrient rich water from waste streams or natural water sources, and pulsing it over a sloped surface.[89] This surface is coated with a rough plastic membrane or a screen, which allows naturally occurring algal spores to settle and colonize the surface. Once the algae has been established, it can be harvested every 5–15 days,[90] and can produce 18 metric tons of algal biomass per hectare per year.[91] In contrast to other methods, which focus primarily on a single high yielding species of algae, this method focuses on naturally occurring polycultures of algae. As such, the lipid content of the algae in an ATS system is usually lower, which makes it more suitable for a fermented fuel product, such as ethanol, methane, or butanol.[91] Conversely, the harvested algae could be treated with a hydrothermal liquefaction process, which would make possible biodiesel, gasoline, and jet fuel production.[92]

There are three major advantages of ATS over other systems. The first advantage is documented higher productivity over open pond systems.[93] The second is lower operating and fuel production costs. The third is the elimination of contamination issues due to the reliance on naturally occurring algae species. The projected costs for energy production in an ATS system are $0.75/kg, compared to a photobioreactor which would cost $3.50/kg.[91] Furthermore, due to the fact that the primary purpose of ATS is removing nutrients and pollutants out of water, and these costs have been shown to be lower than other methods of nutrient removal, this may incentivize the use of this technology for nutrient removal as the primary function, with biofuel production as an added benefit.[94]

 
Algae being harvested and dried from an ATS system

Fuel production edit

After harvesting the algae, the biomass is typically processed in a series of steps, which can differ based on the species and desired product; this is an active area of research[26] and also is the bottleneck of this technology: the cost of extraction is higher than those obtained. One of the solutions is to use filter feeders to "eat" them. Improved animals can provide both foods and fuels. An alternative method to extract the algae is to grow the algae with specific types of fungi. This causes bio-flocculation of the algae which allows for easier extraction.[95]

Dehydration edit

Often, the algae is dehydrated, and then a solvent such as hexane is used to extract energy-rich compounds like triglycerides from the dried material.[1][96] Then, the extracted compounds can be processed into fuel using standard industrial procedures. For example, the extracted triglycerides are reacted with methanol to create biodiesel via transesterification.[1] The unique composition of fatty acids of each species influences the quality of the resulting biodiesel and thus must be taken into account when selecting algal species for feedstock.[26]

Hydrothermal liquefaction edit

An alternative approach called Hydrothermal liquefaction employs a continuous process that subjects harvested wet algae to high temperatures and pressures—350 °C (662 °F) and 3,000 pounds per square inch (21,000 kPa).[97][98][99]

Products include crude oil, which can be further refined into aviation fuel, gasoline, or diesel fuel using one or many upgrading processes.[100] The test process converted between 50 and 70 percent of the algae's carbon into fuel. Other outputs include clean water, fuel gas and nutrients such as nitrogen, phosphorus, and potassium.[97]

Nutrients edit

Main article: Algal nutrient solutions

Nutrients like nitrogen (N), phosphorus (P), and potassium (K), are important for plant growth and are essential parts of fertilizer. Silica and iron, as well as several trace elements, may also be considered important marine nutrients as the lack of one can limit the growth of, or productivity in, an area.[101]

Carbon dioxide edit

Bubbling CO
2 through algal cultivation systems can greatly increase productivity and yield (up to a saturation point). Typically, about 1.8 tonnes of CO
2 will be utilised per tonne of algal biomass (dry) produced, though this varies with algae species.[102] The Glenturret Distillery in Perthshire percolate CO
2 made during the whisky distillation through a microalgae bioreactor. Each tonne of microalgae absorbs two tonnes of CO
2. Scottish Bioenergy, who run the project, sell the microalgae as high value, protein-rich food for fisheries. In the future, they will use the algae residues to produce renewable energy through anaerobic digestion.[103]

Nitrogen edit

Nitrogen is a valuable substrate that can be utilized in algal growth. Various sources of nitrogen can be used as a nutrient for algae, with varying capacities. Nitrate was found to be the preferred source of nitrogen, in regards to amount of biomass grown. Urea is a readily available source that shows comparable results, making it an economical substitute for nitrogen source in large scale culturing of algae.[104] Despite the clear increase in growth in comparison to a nitrogen-less medium, it has been shown that alterations in nitrogen levels affect lipid content within the algal cells. In one study[105] nitrogen deprivation for 72 hours caused the total fatty acid content (on a per cell basis) to increase by 2.4-fold. 65% of the total fatty acids were esterified to triacylglycerides in oil bodies, when compared to the initial culture, indicating that the algal cells utilized de novo synthesis of fatty acids. It is vital for the lipid content in algal cells to be of high enough quantity, while maintaining adequate cell division times, so parameters that can maximize both are under investigation.

Wastewater edit

Main article: Wastewater treatment facility

A possible nutrient source is wastewater from the treatment of sewage, agricultural, or flood plain run-off, all currently major pollutants and health risks. However, this waste water cannot feed algae directly and must first be processed by bacteria, through anaerobic digestion. If waste water is not processed before it reaches the algae, it will contaminate the algae in the reactor, and at the very least, kill much of the desired algae strain. In biogas facilities, organic waste is often converted to a mixture of carbon dioxide, methane, and organic fertilizer. Organic fertilizer that comes out of the digester is liquid, and nearly suitable for algae growth, but it must first be cleaned and sterilized.[106]

The utilization of wastewater and ocean water instead of freshwater is strongly advocated due to the continuing depletion of freshwater resources. However, heavy metals, trace metals, and other contaminants in wastewater can decrease the ability of cells to produce lipids biosynthetically and also impact various other workings in the machinery of cells. The same is true for ocean water, but the contaminants are found in different concentrations. Thus, agricultural-grade fertilizer is the preferred source of nutrients, but heavy metals are again a problem, especially for strains of algae that are susceptible to these metals. In open pond systems the use of strains of algae that can deal with high concentrations of heavy metals could prevent other organisms from infesting these systems.[79] In some instances it has even been shown that strains of algae can remove over 90% of nickel and zinc from industrial wastewater in relatively short periods of time.[107]

Environmental impact edit

In comparison with terrestrial-based biofuel crops such as corn or soybeans, microalgal production results in a much less significant land footprint due to the higher oil productivity from the microalgae than all other oil crops.[108] Algae can also be grown on marginal lands useless for ordinary crops and with low conservation value, and can use water from salt aquifers that is not useful for agriculture or drinking.[84][109] Algae can also grow on the surface of the ocean in bags or floating screens.[110] Thus microalgae could provide a source of clean energy with little impact on the provisioning of adequate food and water or the conservation of biodiversity.[111] Algae cultivation also requires no external subsidies of insecticides or herbicides, removing any risk of generating associated pesticide waste streams. In addition, algal biofuels are much less toxic, and degrade far more readily than petroleum-based fuels.[112][113][114] However, due to the flammable nature of any combustible fuel, there is potential for some environmental hazards if ignited or spilled, as may occur in a train derailment or a pipeline leak.[115] This hazard is reduced compared to fossil fuels, due to the ability for algal biofuels to be produced in a much more localized manner, and due to the lower toxicity overall, but the hazard is still there nonetheless. Therefore, algal biofuels should be treated in a similar manner to petroleum fuels in transportation and use, with sufficient safety measures in place at all times.

Studies have determined that replacing fossil fuels with renewable energy sources, such as biofuels, have the capability of reducing CO
2 emissions by up to 80%.[116] An algae-based system could capture approximately 80% of the CO
2 emitted from a power plant when sunlight is available. Although this CO
2 will later be released into the atmosphere when the fuel is burned, this CO
2 would have entered the atmosphere regardless.[109] The possibility of reducing total CO
2 emissions therefore lies in the prevention of the release of CO
2 from fossil fuels. Furthermore, compared to fuels like diesel and petroleum, and even compared to other sources of biofuels, the production and combustion of algal biofuel does not produce any sulfur oxides or nitrous oxides, and produces a reduced amount of carbon monoxide, unburned hydrocarbons, and reduced emission of other harmful pollutants.[117] Since terrestrial plant sources of biofuel production simply do not have the production capacity to meet current energy requirements, microalgae may be one of the only options to approach complete replacement of fossil fuels.

Microalgae production also includes the ability to use saline waste or waste CO
2 streams as an energy source. This opens a new strategy to produce biofuel in conjunction with waste water treatment, while being able to produce clean water as a byproduct.[117] When used in a microalgal bioreactor, harvested microalgae will capture significant quantities of organic compounds as well as heavy metal contaminants absorbed from wastewater streams that would otherwise be directly discharged into surface and ground-water.[108] Moreover, this process also allows the recovery of phosphorus from waste, which is an essential but scarce element in nature – the reserves of which are estimated to have depleted in the last 50 years.[118] Another possibility is the use of algae production systems to clean up non-point source pollution, in a system known as an algal turf scrubber (ATS). This has been demonstrated to reduce nitrogen and phosphorus levels in rivers and other large bodies of water affected by eutrophication, and systems are being built that will be capable of processing up to 110 million liters of water per day. ATS can also be used for treating point source pollution, such as the waste water mentioned above, or in treating livestock effluent.[91][119][120]

Polycultures edit

Nearly all research in algal biofuels has focused on culturing single species, or monocultures, of microalgae. However, ecological theory and empirical studies have demonstrated that plant and algae polycultures, i.e. groups of multiple species, tend to produce larger yields than monocultures.[121][122][123][124] Experiments have also shown that more diverse aquatic microbial communities tend to be more stable through time than less diverse communities.[125][126][127][128] Recent studies found that polycultures of microalgae produced significantly higher lipid yields than monocultures.[129][130] Polycultures also tend to be more resistant to pest and disease outbreaks, as well as invasion by other plants or algae.[131] Thus culturing microalgae in polyculture may not only increase yields and stability of yields of biofuel, but also reduce the environmental impact of an algal biofuel industry.[111]

Economic viability edit

There is clearly a demand for sustainable biofuel production, but whether a particular biofuel will be used ultimately depends not on sustainability but cost efficiency. Therefore, research is focusing on cutting the cost of algal biofuel production to the point where it can compete with conventional petroleum.[26][132] The production of several products from algae has been mentioned[weasel words] as the most important factor for making algae production economically viable. Other factors are the improving of the solar energy to biomass conversion efficiency (currently 3%, but 5 to 7% is theoretically attainable[133])and making the oil extraction from the algae easier.[134]

In a 2007 report[26] a formula was derived estimating the cost of algal oil in order for it to be a viable substitute to petroleum diesel:

C(algal oil) = 25.9 × 10−3 C(petroleum)

where: C(algal oil) is the price of microalgal oil in dollars per gallon and C(petroleum) is the price of crude oil in dollars per barrel. This equation assumes that algal oil has roughly 80% of the caloric energy value of crude petroleum.[135]

The IEA estimates that algal biomass can be produced for a little as $0.54/kg in open pond in a warm climate to $10.20/kg in photobioreactors in cooler climates.[136] Assuming that the biomass contains 30% oil by weight, the cost of biomass for providing a liter of oil would be approximately $1.40 ($5.30/gal) and $1.81 ($6.85/gal) for photobioreactors and raceways, respectively. Oil recovered from the lower cost biomass produced in photobioreactors is estimated to cost $2.80/L, assuming the recovery process contributes 50% to the cost of the final recovered oil.[26] If existing algae projects can achieve biodiesel production price targets of less than $1 per gallon, the United States may realize its goal of replacing up to 20% of transport fuels by 2020 by using environmentally and economically sustainable fuels from algae production.[137]

Whereas technical problems, such as harvesting, are being addressed successfully by the industry, the high up-front investment of algae-to-biofuels facilities is seen by many as a major obstacle to the success of this technology. Only few studies on the economic viability are publicly available, and must often rely on the little data (often only engineering estimates) available in the public domain. Dmitrov[138] examined the GreenFuel's photobioreactor and estimated that algae oil would only be competitive at an oil price of $800 per barrel. A study by Alabi et al.[139] examined raceways, photobioreactors and anaerobic fermenters to make biofuels from algae and found that photobioreactors are too expensive to make biofuels. Raceways might be cost-effective in warm climates with very low labor costs, and fermenters may become cost-effective subsequent to significant process improvements. The group found that capital cost, labor cost and operational costs (fertilizer, electricity, etc.) by themselves are too high for algae biofuels to be cost-competitive with conventional fuels. Similar results were found by others,[140][141][142] suggesting that unless new, cheaper ways of harnessing algae for biofuels production are found, their great technical potential may never become economically accessible. In 2012, Rodrigo E. Teixeira[143] demonstrated a new reaction and proposed a process for harvesting and extracting raw materials for biofuel and chemical production that requires a fraction of the energy of current methods, while extracting all cell constituents.

Use of byproducts edit

Many of the byproducts produced in the processing of microalgae can be used in various applications, many of which have a longer history of production than algal biofuel. Some of the products not used in the production of biofuel include natural dyes and pigments, antioxidants, and other high-value bio-active compounds.[80][144][145] These chemicals and excess biomass have found numerous use in other industries. For example, the dyes and oils have found a place in cosmetics, commonly as thickening and water-binding agents.[146] Discoveries within the pharmaceutical industry include antibiotics and antifungals derived from microalgae, as well as natural health products, which have been growing in popularity over the past few decades. For instance Spirulina contains numerous polyunsaturated fats (Omega 3 and 6), amino acids, and vitamins,[147] as well as pigments that may be beneficial, such as beta-carotene and chlorophyll.[148]

Advantages edit

Ease of growth edit

One of the main advantages that using microalgae as the feedstock when compared to more traditional crops is that it can be grown much more easily.[149] Algae can be grown in land that would not be considered suitable for the growth of the regularly used crops.[80] In addition to this, wastewater that would normally hinder plant growth has been shown to be very effective in growing algae.[149] Because of this, algae can be grown without taking up arable land that would otherwise be used for producing food crops, and the better resources can be reserved for normal crop production. Microalgae also require fewer resources to grow and little attention is needed, allowing the growth and cultivation of algae to be a very passive process.[80]

Impact on food edit

Many traditional feedstocks for biodiesel, such as corn and palm, are also used as feed for livestock on farms, as well as a valuable source of food for humans. Because of this, using them as biofuel reduces the amount of food available for both, resulting in an increased cost for both the food and the fuel produced. Using algae as a source of biodiesel can alleviate this problem in a number of ways. First, algae is not used as a primary food source for humans, meaning that it can be used solely for fuel and there would be little impact in the food industry.[150] Second, many of the waste-product extracts produced during the processing of algae for biofuel can be used as a sufficient animal feed. This is an effective way to minimize waste and a much cheaper alternative to the more traditional corn- or grain-based feeds.[151]

Minimalisation of waste edit

Growing algae as a source of biofuel has also been shown to have numerous environmental benefits, and has presented itself as a much more environmentally friendly alternative to current biofuels. For one, it is able to utilize run-off, water contaminated with fertilizers and other nutrients that are a by-product of farming, as its primary source of water and nutrients.[149] Because of this, it prevents this contaminated water from mixing with the lakes and rivers that currently supply our drinking water. In addition to this, the ammonia, nitrates, and phosphates that would normally render the water unsafe actually serve as excellent nutrients for the algae, meaning that fewer resources are needed to grow the algae.[80] Many algae species used in biodiesel production are excellent bio-fixers, meaning they are able to remove carbon dioxide from the atmosphere to use as a form of energy for themselves. Because of this, they have found use in industry as a way to treat flue gases and reduce GHG emissions.[80]

Disadvantage edit

High water requirement edit

The process of microalgae cultivation is highly water-intensive. Life cycle studies estimated that the production of 1 liter of microalgae based biodiesel requires between 607 and 1944 liters of water.[152] That said, abundant wastewater and/or seawater, which also contain various nutrients, can theoretically be used for this purpose instead of freshwater.

Commercial viability edit

Algae biodiesel is still a fairly new technology. Despite the fact that research began over 30 years ago, it was put on hold during the mid-1990s, mainly due to a lack of funding and a relatively low petroleum cost.[20] For the next few years algae biofuels saw little attention; it was not until the gas peak of the early 2000s that it eventually had a revitalization in the search for alternative fuel sources.[20]

Increasing interest in seaweed farming for carbon sequestration, eutrophication reduction and production of food has resulted in the creation of commercial seaweed cultivation since 2017.[153] Reductions in the cost of cultivation and harvesting as well as the development of commercial industry will improve the economics of macroalgae biofuels. Climate change has created a proliferation of brown macroalgae mats, which wash up on the shores of the Caribbean. Currently these mats are disposed of but there is interest in developing them into a feedstock for biofuel production.[154]

Stability edit

The biodiesel produced from the processing of microalgae differs from other forms of biodiesel in the content of polyunsaturated fats.[149] Polyunsaturated fats are known for their ability to retain fluidity at lower temperatures. While this may seem like an advantage in production during the colder temperatures of the winter, the polyunsaturated fats result in lower stability during regular seasonal temperatures.[150]

International policies edit

Canada edit

Numerous policies have been put in place since the 1975 oil crisis in order to promote the use of Renewable Fuels in the United States, Canada and Europe. In Canada, these included the implementation of excise taxes exempting propane and natural gas which was extended to ethanol made from biomass and methanol in 1992. The federal government also announced their renewable fuels strategy in 2006 which proposed four components: increasing availability of renewable fuels through regulation, supporting the expansion of Canadian production of renewable fuels, assisting farmers to seize new opportunities in this sector and accelerating the commercialization of new technologies. These mandates were quickly followed by the Canadian provinces:

BC introduced a 5% ethanol and 5% renewable diesel requirement which was effective by January 2010. It also introduced a low carbon fuel requirement for 2012 to 2020.

Alberta introduced a 5% ethanol and 2% renewable diesel requirement implemented April 2011. The province also introduced a minimum 25% GHG emission reduction requirement for qualifying renewable fuels.

Saskatchewan implemented a 2% renewable diesel requirement in 2009.[155]

Additionally, in 2006, the Canadian Federal Government announced its commitment to using its purchasing power to encourage the biofuel industry. Section three of the 2006 alternative fuels act stated that when it is economically feasible to do so-75% per cent of all federal bodies and crown corporation will be motor vehicles.[156]

United States edit

Policies in the United States have included a decrease in the subsidies provided by the federal and state governments to the oil industry which have usually included $2.84 billion. This is more than what is actually set aside for the biofuel industry. The measure was discussed at the G20 in Pittsburgh where leaders agreed that "inefficient fossil fuel subsidies encourage wasteful consumption, reduce our energy security, impede investment in clean sources and undermine efforts to deal with the threat of climate change". If this commitment is followed through and subsidies are removed, a fairer market in which algae biofuels can compete will be created. In 2010, the U.S. House of Representatives passed a legislation seeking to give algae-based biofuels parity with cellulose biofuels in federal tax credit programs. The algae-based renewable fuel promotion act (HR 4168) was implemented to give biofuel projects access to a $1.01 per gal production tax credit and 50% bonus depreciation for biofuel plant property. The U.S Government also introduced the domestic Fuel for Enhancing National Security Act implemented in 2011. This policy constitutes an amendment to the Federal property and administrative services act of 1949 and federal defense provisions in order to extend to 15 the number of years that the Department of Defense (DOD) multiyear contract may be entered into the case of the purchase of advanced biofuel. Federal and DOD programs are usually limited to a 5-year period[157]

Other edit

The European Union (EU) has also responded by quadrupling the credits for second-generation algae biofuels which was established as an amendment to the Biofuels and Fuel Quality Directives[158]

See also edit

References edit

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Further reading edit

  • Worldwatch Institute (2007). Biofuels for Transport: Global Potential and Implications for Sustainable Agriculture and Energy in the 21st century. Earthscan. ISBN 978-1-84407-422-8.
  • McKay, David JC (3 November 2008). Sustainable Energy-Without Hot Air. 3.5.2. UIT Cambridge Ltd. ISBN 978-0-9544529-3-3.
  • Lane, Jim (18 April 2010). "Salt Water: The Tangy Taste of Energy Freedom". Renewable Energy World. Retrieved 21 April 2010.
  • Bhatnagar, S.K.; Atul Saxena; Stefan Kraan, eds. (2011). Algae biofuel. New Delhi: Studium Press (India) Pvt. Ltd. ISBN 978-93-8001-244-5.
  • Darzins, Al; Pienkos, Philip; Edye, Les (2010). Current status and potential for algal biofuels production (PDF). IEA Bioenergy Task 39.

External links edit

 
Wikimedia Commons has media related to Algae fuel.
  • A Report on Commercial Usage and Production of Algal Oil
  • A Sober Look at Biofuels from Algae (Biodiesel Magazine)
  • US National Renewable Energy Laboratory Publications
  • Current Status and Potential for Algal Biofuels Production

February 16, 2024
algae, fuel, algal, biofuel, algal, alternative, liquid, fossil, fuels, that, uses, algae, source, energy, rich, oils, also, algae, fuels, alternative, commonly, known, biofuel, sources, such, corn, sugarcane, when, made, from, seaweed, macroalgae, known, seaw. Algae fuel algal biofuel or algal oil is an alternative to liquid fossil fuels that uses algae as its source of energy rich oils Also algae fuels are an alternative to commonly known biofuel sources such as corn and sugarcane 1 2 When made from seaweed macroalgae it can be known as seaweed fuel or seaweed oil A conical flask of green jet fuel made from algaeIn December 2022 ExxonMobil the last large oil company to invest in algae biofuels ended its research funding 3 Contents 1 History 2 Food supplementation 3 Fuels 3 1 Biodiesel 3 2 Biobutanol 3 3 Biogasoline 3 4 Biogas 3 5 Methane 3 6 Ethanol 3 7 Green diesel 3 8 Jet fuel 3 9 Algae based energy harvester 4 Species 5 Nutrients and growth inputs 6 Cultivation 6 1 Closed loop system 6 2 Photobioreactors 6 3 Open pond 6 4 Turf scrubber 7 Fuel production 7 1 Dehydration 7 2 Hydrothermal liquefaction 8 Nutrients 8 1 Carbon dioxide 8 2 Nitrogen 8 3 Wastewater 9 Environmental impact 9 1 Polycultures 10 Economic viability 11 Use of byproducts 12 Advantages 12 1 Ease of growth 12 2 Impact on food 12 3 Minimalisation of waste 13 Disadvantage 13 1 High water requirement 13 2 Commercial viability 13 3 Stability 14 International policies 14 1 Canada 14 2 United States 14 3 Other 15 See also 16 References 17 Further reading 18 External linksHistory editIn 1942 Harder and Von Witsch were the first to propose that microalgae be grown as a source of lipids for food or fuel 4 5 Following World War II research began in the US 6 7 8 Germany 9 Japan 10 England 11 and Israel 12 on culturing techniques and engineering systems for growing microalgae on larger scales particularly species in the genus Chlorella Meanwhile H G Aach showed that Chlorella pyrenoidosa could be induced via nitrogen starvation to accumulate as much as 70 of its dry weight as lipids 13 Since the need for alternative transportation fuel had subsided after World War II research at this time focused on culturing algae as a food source or in some cases for wastewater treatment 14 Interest in the application of algae for biofuels was rekindled during the oil embargo and oil price surges of the 1970s leading the US Department of Energy to initiate the Aquatic Species Program in 1978 15 The Aquatic Species Program spent 25 million over 18 years with the goal of developing liquid transportation fuel from algae that would be price competitive with petroleum derived fuels 16 The research program focused on the cultivation of microalgae in open outdoor ponds systems which are low in cost but vulnerable to environmental disturbances like temperature swings and biological invasions 3 000 algal strains were collected from around the country and screened for desirable properties such as high productivity lipid content and thermal tolerance and the most promising strains were included in the SERI microalgae collection at the Solar Energy Research Institute SERI in Golden Colorado and used for further research 16 Among the program s most significant findings were that rapid growth and high lipid production were mutually exclusive since the former required high nutrients and the latter required low nutrients 16 The final report suggested that genetic engineering may be necessary to be able to overcome this and other natural limitations of algal strains and that the ideal species might vary with place and season 16 Although it was successfully demonstrated that large scale production of algae for fuel in outdoor ponds was feasible the program failed to do so at a cost that would be competitive with petroleum especially as oil prices sank in the 1990s Even in the best case scenario it was estimated that unextracted algal oil would cost 59 186 per barrel 16 while petroleum cost less than 20 per barrel in 1995 15 Therefore under budget pressure in 1996 the Aquatic Species Program was abandoned 16 Other contributions to algal biofuels research have come indirectly from projects focusing on different applications of algal cultures For example in the 1990s Japan s Research Institute of Innovative Technology for the Earth RITE implemented a research program with the goal of developing systems to fix CO2 using microalgae 17 Although the goal was not energy production several studies produced by RITE demonstrated that algae could be grown using flue gas from power plants as a CO2 source 18 19 an important development for algal biofuel research Other work focusing on harvesting hydrogen gas methane or ethanol from algae as well as nutritional supplements and pharmaceutical compounds has also helped inform research on biofuel production from algae 14 Following the disbanding of the Aquatic Species Program in 1996 there was a relative lull in algal biofuel research Still various projects were funded in the US by the Department of Energy Department of Defense National Science Foundation Department of Agriculture National Laboratories state funding and private funding as well as in other countries 15 More recently rising oil prices in the 2000s spurred a revival of interest in algal biofuels and US federal funding has increased 15 numerous research projects are being funded in Australia New Zealand Europe the Middle East and other parts of the world 20 In March 2023 researchers said that the commercialization of biofuels would require several billion dollars of funding plus a long term dedication to overcoming what appear to be fundamental biological limitations of wild organisms Most researchers think that large scale production of biofuels is either a decade and more likely two decades away 3 Food supplementation editAlgal oil is used as a source of fatty acid supplementation in food products as it contains mono and polyunsaturated fats in particular EPA and DHA 21 Its DHA content is roughly equivalent to that of salmon based fish oil 22 23 Fuels editAlgae can be converted into various types of fuels depending on the production technologies and the part of the cells used The lipid or oily part of the algae biomass can be extracted and converted into biodiesel through a process similar to that used for any other vegetable oil or converted in a refinery into drop in replacements for petroleum based fuels Alternatively or following lipid extraction the carbohydrate content of algae can be fermented into bioethanol or butanol fuel 24 Biodiesel edit Main article Biodiesel Biodiesel is a diesel fuel derived from animal or plant lipids oils and fats Studies have shown that some species of algae can produce 60 or more of their dry weight in the form of oil 13 16 25 26 27 Because the cells grow in aqueous suspension where they have more efficient access to water CO2 and dissolved nutrients microalgae are capable of producing large amounts of biomass and usable oil in either high rate algal ponds 28 or photobioreactors This oil can then be turned into biodiesel which could be sold for use in automobiles Regional production of microalgae and processing into biofuels will provide economic benefits to rural communities 29 As they do not have to produce structural compounds such as cellulose for leaves stems or roots and because they can be grown floating in a rich nutritional medium microalgae can have faster growth rates than terrestrial crops Also they can convert a much higher fraction of their biomass to oil than conventional crops e g 60 versus 2 3 for soybeans 25 The per unit area yield of oil from algae is estimated to be from 58 700 to 136 900 L ha year depending on lipid content which is 10 to 23 times as high as the next highest yielding crop oil palm at 5 950 L ha year 30 The U S Department of Energy s Aquatic Species Program 1978 1996 focused on biodiesel from microalgae The final report suggested that biodiesel could be the only viable method by which to produce enough fuel to replace current world diesel usage 31 If algae derived biodiesel were to replace the annual global production of 1 1bn tons of conventional diesel then a land mass of 57 3 million hectares would be required which would be highly favorable compared to other biofuels 32 Biobutanol edit Main article Butanol fuel Butanol can be made from algae or diatoms using only a solar powered biorefinery This fuel has an energy density 10 less than gasoline and greater than that of either ethanol or methanol In most gasoline engines butanol can be used in place of gasoline with no modifications In several tests butanol consumption is similar to that of gasoline and when blended with gasoline provides better performance and corrosion resistance than that of ethanol or E85 33 The green waste left over from the algae oil extraction can be used to produce butanol In addition it has been shown that macroalgae seaweeds can be fermented by bacteria of genus Clostridia to butanol and other solvents 34 Transesterification of seaweed oil into biodiesel is also possible with species such as Chaetomorpha linum Ulva lactuca and Enteromorpha compressa Ulva 35 The following species are being investigated as suitable species from which to produce ethanol and or butanol 36 Alaria esculenta Laminaria saccharina Palmaria palmata 37 Biogasoline edit Biogasoline is gasoline produced from biomass Like traditionally produced gasoline it contains between 6 hexane and 12 dodecane carbon atoms per molecule and can be used in internal combustion engines 38 Biogas edit Main article Biogas Biogas is composed mainly of methane CH4 and carbon dioxide CO2 with some traces of hydrogen sulphide oxygen nitrogen and hydrogen Macroalgae has high methane production rate compared to plant biomass Biogas production from macroalgae is more technically viable compared to other fuels but it is not economically viable due to the high cost of macroalgae feedstock 39 Carbohydrate and protein in microalgae can be converted into biogas through anaerobic digestion which includes hydrolysis fermentation and methanogenesis steps The conversion of algal biomass into methane can potentially recover as much energy as it obtains but it is more profitable when the algal lipid content is lower than 40 40 Biogas production from microalgae is relatively low because of the high ratio of protein in microalgae but microalgae can be co digested with high C N ratio products such as wastepaper 41 Another method to produce biogas is through gasification where hydrocarbon is converted to syngas through a partial oxidation reaction at high temperature typically 800 C to 1000 C Gasification is usually performed with catalysts Uncatalyzed gasification requires temperature to be about 1300 C Syngas can be burnt directly to produce energy or used a fuel in turbine engines It can also be used as feedstock for other chemical productions 42 Methane edit Methane 43 the main constituent of natural gas can be produced from algae in various methods namely gasification pyrolysis and anaerobic digestion In gasification and pyrolysis methods methane is extracted under high temperature and pressure Anaerobic digestion 44 is a straightforward method involved in decomposition of algae into simple components then transforming it into fatty acids using microbes like acidogenic bacteria followed by removing any solid particles and finally adding methanogenic archaea to release a gas mixture containing methane A number of studies have successfully shown that biomass from microalgae can be converted into biogas via anaerobic digestion 45 46 47 48 49 Therefore in order to improve the overall energy balance of microalgae cultivation operations it has been proposed to recover the energy contained in waste biomass via anaerobic digestion to methane for generating electricity 50 Ethanol edit The Algenol system which is being commercialized by BioFields in Puerto Libertad Sonora Mexico utilizes seawater and industrial exhaust to produce ethanol Porphyridium cruentum also have shown to be potentially suitable for ethanol production due to its capacity for accumulating large amount of carbohydrates 51 Green diesel edit Main article Biodiesel production Algae can be used to produce green diesel also known as renewable diesel hydrotreating vegetable oil 52 or hydrogen derived renewable diesel 53 through a hydrotreating refinery process that breaks molecules down into shorter hydrocarbon chains used in diesel engines 52 54 It has the same chemical properties as petroleum based diesel 52 meaning that it does not require new engines pipelines or infrastructure to distribute and use It has yet to be produced at a cost that is competitive with petroleum 53 While hydrotreating is currently the most common pathway to produce fuel like hydrocarbons via decarboxylation decarbonylation there is an alternative process offering a number of important advantages over hydrotreating In this regard the work of Crocker et al 55 and Lercher et al 56 is particularly noteworthy For oil refining research is underway for catalytic conversion of renewable fuels by decarboxylation 57 As the oxygen is present in crude oil at rather low levels of the order of 0 5 deoxygenation in petroleum refining is not of much concern and no catalysts are specifically formulated for oxygenates hydrotreating Hence one of the critical technical challenges to make the hydrodeoxygenation of algae oil process economically feasible is related to the research and development of effective catalysts 58 59 Jet fuel edit Main article Aviation biofuel Trials of using algae as biofuel were carried out by Lufthansa and Virgin Atlantic as early as 2008 although there is little evidence that using algae is a reasonable source for jet biofuels 60 By 2015 cultivation of fatty acid methyl esters and alkenones from the algae Isochrysis was under research as a possible jet biofuel feedstock 61 Algae based energy harvester edit In May 2022 scientists at University of Cambridge announced they created an algae energy harvester that uses natural sunlight to power a small microprocessor initially powering the processor for six months and then kept going for a full year The device which is about the size of AA battery is a small container with water and blue green algae The device does not generate a huge amount of power but it can be used for Internet of Things devices eliminating the need for traditional batteries such as lithium ion batteries The goal is to have more a environmentally friendly power source that can be used in remote areas 62 Species editResearch into algae for the mass production of oil focuses mainly on microalgae organisms capable of photosynthesis that are less than 0 4 mm in diameter including the diatoms and cyanobacteria as opposed to macroalgae such as seaweed The preference for microalgae has come about due largely to their less complex structure fast growth rates and high oil content for some species However some research is being done into using seaweeds for biofuels probably due to the high availability of this resource 63 64 As of 2012 update researchers across various locations worldwide have started investigating the following species for their suitability as a mass oil producers 65 66 67 Botryococcus braunii Chlorella Dunaliella tertiolecta Gracilaria Pleurochrysis carterae also called CCMP647 68 Sargassum with 10 times the output volume of Gracilaria 69 The amount of oil each strain of algae produces varies widely Note the following microalgae and their various oil yields Ankistrodesmus TR 87 28 40 dry weight Botryococcus braunii 29 75 dw Chlorella sp 29 dw Chlorella protothecoides autotrophic heterotrophic 15 55 dw Crypthecodinium cohnii 20 dw Cyclotella DI 35 42 dw Dunaliella tertiolecta 36 42 dw Hantzschia DI 160 66 dw Nannochloris 31 6 63 dw Nannochloropsis 46 31 68 dw Nannochloropsis and biofuels Neochloris oleoabundans 35 54 dw Nitzschia TR 114 28 50 dw Phaeodactylum tricornutum 31 dw Scenedesmus TR 84 45 dw Schizochytrium 50 77 dw 70 Stichococcus 33 9 59 dw Tetraselmis suecica 15 32 dw Thalassiosira pseudonana 21 31 dwIn addition due to its high growth rate Ulva 71 has been investigated as a fuel for use in the SOFT cycle SOFT stands for Solar Oxygen Fuel Turbine a closed cycle power generation system suitable for use in arid subtropical regions 72 Other species used include Clostridium saccharoperbutylacetonicum 73 Sargassum Gracilaria Prymnesium parvum and Euglena gracilis 74 Nutrients and growth inputs editMain article Algaculture Light is what algae primarily need for growth as it is the most limiting factor Many companies are investing for developing systems and technologies for providing artificial light One of them is OriginOil that has developed a Helix BioReactorTM that features a rotating vertical shaft with low energy lights arranged in a helix pattern 75 Water temperature also influences the metabolic and reproductive rates of algae Although most algae grow at low rate when the water temperature gets lower the biomass of algal communities can get large due to the absence of grazing organisms 75 The modest increases in water current velocity may also affect rates of algae growth since the rate of nutrient uptake and boundary layer diffusion increases with current velocity 75 Other than light and water phosphorus nitrogen and certain micronutrients are also useful and essential in growing algae Nitrogen and phosphorus are the two most significant nutrients required for algal productivity but other nutrients such as carbon and silica are additionally required 76 Of the nutrients required phosphorus is one of the most essential ones as it is used in numerous metabolic processes The microalgae D tertiolecta was analyzed to see which nutrient affects its growth the most 77 The concentrations of phosphorus P iron Fe cobalt Co zinc Zn manganese Mn and molybdenum Mo magnesium Mg calcium Ca silicon Si and sulfur S concentrations were measured daily using inductively coupled plasma ICP analysis Among all these elements being measured phosphorus resulted in the most dramatic decrease with a reduction of 84 over the course of the culture 77 This result indicates that phosphorus in the form of phosphate is required in high amounts by all organisms for metabolism There are two enrichment media that have been extensively used to grow most species of algae Walne medium and the Guillard s F 2 medium 78 These commercially available nutrient solutions may reduce time for preparing all the nutrients required to grow algae However due to their complexity in the process of generation and high cost they are not used for large scale culture operations 78 Therefore enrichment media used for mass production of algae contain only the most important nutrients with agriculture grade fertilizers rather than laboratory grade fertilizers 78 Cultivation editSee also Culture of microalgae in hatcheries nbsp Photobioreactor from glass tubes nbsp Design of a race way open pond commonly used for algal cultureAlgae grow much faster than food crops and can produce hundreds of times more oil per unit area than conventional crops such as rapeseed palms soybeans or jatropha 30 As algae have a harvesting cycle of 1 10 days their cultivation permits several harvests in a very short time frame a strategy differing from that associated with annual crops 26 In addition algae can be grown on land unsuitable for terrestrial crops including arid land and land with excessively saline soil minimizing competition with agriculture 79 Most research on algae cultivation has focused on growing algae in clean but expensive photobioreactors or in open ponds which are cheap to maintain but prone to contamination 80 Closed loop system edit The lack of equipment and structures needed to begin growing algae in large quantities has inhibited widespread mass production of algae for biofuel production Maximum use of existing agriculture processes and hardware is the goal 81 Closed systems not exposed to open air avoid the problem of contamination by other organisms blown in by the air The problem of a closed system is finding a cheap source of sterile CO2 Several experimenters have found the CO2 from a smokestack works well for growing algae 82 83 For reasons of economy some experts think that algae farming for biofuels will have to be done as part of cogeneration where it can make use of waste heat and help soak up pollution 84 To produce micro algae at large scale under controlled environment using PBR system strategies such as light guides sparger and PBR construction materials required should be well considered 85 Photobioreactors edit Most companies pursuing algae as a source of biofuels pump nutrient rich water through plastic or borosilicate glass tubes called bioreactors that are exposed to sunlight and so called photobioreactors or PBR 86 Running a PBR is more difficult than using an open pond and costlier but may provide a higher level of control and productivity 26 In addition a photobioreactor can be integrated into a closed loop cogeneration system much more easily than ponds or other methods Open pond edit Open pond systems consist of simple in ground ponds which are often mixed by a paddle wheel These systems have low power requirements operating costs and capital costs when compared to closed loop photobioreactor systems 87 86 Nearly all commercial algae producers for high value algal products utilize open pond systems 88 Turf scrubber edit nbsp 2 5 acre ATS system installed by Hydromentia on a farm creek in FloridaThe Algae scrubber is a system designed primarily for cleaning nutrients and pollutants out of water using algal turfs An algal turf scrubber ATS mimics the algal turfs of a natural coral reef by taking in nutrient rich water from waste streams or natural water sources and pulsing it over a sloped surface 89 This surface is coated with a rough plastic membrane or a screen which allows naturally occurring algal spores to settle and colonize the surface Once the algae has been established it can be harvested every 5 15 days 90 and can produce 18 metric tons of algal biomass per hectare per year 91 In contrast to other methods which focus primarily on a single high yielding species of algae this method focuses on naturally occurring polycultures of algae As such the lipid content of the algae in an ATS system is usually lower which makes it more suitable for a fermented fuel product such as ethanol methane or butanol 91 Conversely the harvested algae could be treated with a hydrothermal liquefaction process which would make possible biodiesel gasoline and jet fuel production 92 There are three major advantages of ATS over other systems The first advantage is documented higher productivity over open pond systems 93 The second is lower operating and fuel production costs The third is the elimination of contamination issues due to the reliance on naturally occurring algae species The projected costs for energy production in an ATS system are 0 75 kg compared to a photobioreactor which would cost 3 50 kg 91 Furthermore due to the fact that the primary purpose of ATS is removing nutrients and pollutants out of water and these costs have been shown to be lower than other methods of nutrient removal this may incentivize the use of this technology for nutrient removal as the primary function with biofuel production as an added benefit 94 nbsp Algae being harvested and dried from an ATS systemFuel production editAfter harvesting the algae the biomass is typically processed in a series of steps which can differ based on the species and desired product this is an active area of research 26 and also is the bottleneck of this technology the cost of extraction is higher than those obtained One of the solutions is to use filter feeders to eat them Improved animals can provide both foods and fuels An alternative method to extract the algae is to grow the algae with specific types of fungi This causes bio flocculation of the algae which allows for easier extraction 95 Dehydration edit Often the algae is dehydrated and then a solvent such as hexane is used to extract energy rich compounds like triglycerides from the dried material 1 96 Then the extracted compounds can be processed into fuel using standard industrial procedures For example the extracted triglycerides are reacted with methanol to create biodiesel via transesterification 1 The unique composition of fatty acids of each species influences the quality of the resulting biodiesel and thus must be taken into account when selecting algal species for feedstock 26 Hydrothermal liquefaction edit An alternative approach called Hydrothermal liquefaction employs a continuous process that subjects harvested wet algae to high temperatures and pressures 350 C 662 F and 3 000 pounds per square inch 21 000 kPa 97 98 99 Products include crude oil which can be further refined into aviation fuel gasoline or diesel fuel using one or many upgrading processes 100 The test process converted between 50 and 70 percent of the algae s carbon into fuel Other outputs include clean water fuel gas and nutrients such as nitrogen phosphorus and potassium 97 Nutrients editMain article Algal nutrient solutions Nutrients like nitrogen N phosphorus P and potassium K are important for plant growth and are essential parts of fertilizer Silica and iron as well as several trace elements may also be considered important marine nutrients as the lack of one can limit the growth of or productivity in an area 101 Carbon dioxide edit Bubbling CO2 through algal cultivation systems can greatly increase productivity and yield up to a saturation point Typically about 1 8 tonnes of CO2 will be utilised per tonne of algal biomass dry produced though this varies with algae species 102 The Glenturret Distillery in Perthshire percolate CO2 made during the whisky distillation through a microalgae bioreactor Each tonne of microalgae absorbs two tonnes of CO2 Scottish Bioenergy who run the project sell the microalgae as high value protein rich food for fisheries In the future they will use the algae residues to produce renewable energy through anaerobic digestion 103 Nitrogen edit Nitrogen is a valuable substrate that can be utilized in algal growth Various sources of nitrogen can be used as a nutrient for algae with varying capacities Nitrate was found to be the preferred source of nitrogen in regards to amount of biomass grown Urea is a readily available source that shows comparable results making it an economical substitute for nitrogen source in large scale culturing of algae 104 Despite the clear increase in growth in comparison to a nitrogen less medium it has been shown that alterations in nitrogen levels affect lipid content within the algal cells In one study 105 nitrogen deprivation for 72 hours caused the total fatty acid content on a per cell basis to increase by 2 4 fold 65 of the total fatty acids were esterified to triacylglycerides in oil bodies when compared to the initial culture indicating that the algal cells utilized de novo synthesis of fatty acids It is vital for the lipid content in algal cells to be of high enough quantity while maintaining adequate cell division times so parameters that can maximize both are under investigation Wastewater edit Main article Wastewater treatment facility A possible nutrient source is wastewater from the treatment of sewage agricultural or flood plain run off all currently major pollutants and health risks However this waste water cannot feed algae directly and must first be processed by bacteria through anaerobic digestion If waste water is not processed before it reaches the algae it will contaminate the algae in the reactor and at the very least kill much of the desired algae strain In biogas facilities organic waste is often converted to a mixture of carbon dioxide methane and organic fertilizer Organic fertilizer that comes out of the digester is liquid and nearly suitable for algae growth but it must first be cleaned and sterilized 106 The utilization of wastewater and ocean water instead of freshwater is strongly advocated due to the continuing depletion of freshwater resources However heavy metals trace metals and other contaminants in wastewater can decrease the ability of cells to produce lipids biosynthetically and also impact various other workings in the machinery of cells The same is true for ocean water but the contaminants are found in different concentrations Thus agricultural grade fertilizer is the preferred source of nutrients but heavy metals are again a problem especially for strains of algae that are susceptible to these metals In open pond systems the use of strains of algae that can deal with high concentrations of heavy metals could prevent other organisms from infesting these systems 79 In some instances it has even been shown that strains of algae can remove over 90 of nickel and zinc from industrial wastewater in relatively short periods of time 107 Environmental impact editIn comparison with terrestrial based biofuel crops such as corn or soybeans microalgal production results in a much less significant land footprint due to the higher oil productivity from the microalgae than all other oil crops 108 Algae can also be grown on marginal lands useless for ordinary crops and with low conservation value and can use water from salt aquifers that is not useful for agriculture or drinking 84 109 Algae can also grow on the surface of the ocean in bags or floating screens 110 Thus microalgae could provide a source of clean energy with little impact on the provisioning of adequate food and water or the conservation of biodiversity 111 Algae cultivation also requires no external subsidies of insecticides or herbicides removing any risk of generating associated pesticide waste streams In addition algal biofuels are much less toxic and degrade far more readily than petroleum based fuels 112 113 114 However due to the flammable nature of any combustible fuel there is potential for some environmental hazards if ignited or spilled as may occur in a train derailment or a pipeline leak 115 This hazard is reduced compared to fossil fuels due to the ability for algal biofuels to be produced in a much more localized manner and due to the lower toxicity overall but the hazard is still there nonetheless Therefore algal biofuels should be treated in a similar manner to petroleum fuels in transportation and use with sufficient safety measures in place at all times Studies have determined that replacing fossil fuels with renewable energy sources such as biofuels have the capability of reducing CO2 emissions by up to 80 116 An algae based system could capture approximately 80 of the CO2 emitted from a power plant when sunlight is available Although this CO2 will later be released into the atmosphere when the fuel is burned this CO2 would have entered the atmosphere regardless 109 The possibility of reducing total CO2 emissions therefore lies in the prevention of the release of CO2 from fossil fuels Furthermore compared to fuels like diesel and petroleum and even compared to other sources of biofuels the production and combustion of algal biofuel does not produce any sulfur oxides or nitrous oxides and produces a reduced amount of carbon monoxide unburned hydrocarbons and reduced emission of other harmful pollutants 117 Since terrestrial plant sources of biofuel production simply do not have the production capacity to meet current energy requirements microalgae may be one of the only options to approach complete replacement of fossil fuels Microalgae production also includes the ability to use saline waste or waste CO2 streams as an energy source This opens a new strategy to produce biofuel in conjunction with waste water treatment while being able to produce clean water as a byproduct 117 When used in a microalgal bioreactor harvested microalgae will capture significant quantities of organic compounds as well as heavy metal contaminants absorbed from wastewater streams that would otherwise be directly discharged into surface and ground water 108 Moreover this process also allows the recovery of phosphorus from waste which is an essential but scarce element in nature the reserves of which are estimated to have depleted in the last 50 years 118 Another possibility is the use of algae production systems to clean up non point source pollution in a system known as an algal turf scrubber ATS This has been demonstrated to reduce nitrogen and phosphorus levels in rivers and other large bodies of water affected by eutrophication and systems are being built that will be capable of processing up to 110 million liters of water per day ATS can also be used for treating point source pollution such as the waste water mentioned above or in treating livestock effluent 91 119 120 Polycultures edit Nearly all research in algal biofuels has focused on culturing single species or monocultures of microalgae However ecological theory and empirical studies have demonstrated that plant and algae polycultures i e groups of multiple species tend to produce larger yields than monocultures 121 122 123 124 Experiments have also shown that more diverse aquatic microbial communities tend to be more stable through time than less diverse communities 125 126 127 128 Recent studies found that polycultures of microalgae produced significantly higher lipid yields than monocultures 129 130 Polycultures also tend to be more resistant to pest and disease outbreaks as well as invasion by other plants or algae 131 Thus culturing microalgae in polyculture may not only increase yields and stability of yields of biofuel but also reduce the environmental impact of an algal biofuel industry 111 Economic viability editThere is clearly a demand for sustainable biofuel production but whether a particular biofuel will be used ultimately depends not on sustainability but cost efficiency Therefore research is focusing on cutting the cost of algal biofuel production to the point where it can compete with conventional petroleum 26 132 The production of several products from algae has been mentioned weasel words as the most important factor for making algae production economically viable Other factors are the improving of the solar energy to biomass conversion efficiency currently 3 but 5 to 7 is theoretically attainable 133 and making the oil extraction from the algae easier 134 In a 2007 report 26 a formula was derived estimating the cost of algal oil in order for it to be a viable substitute to petroleum diesel C algal oil 25 9 10 3 C petroleum dd where C algal oil is the price of microalgal oil in dollars per gallon and C petroleum is the price of crude oil in dollars per barrel This equation assumes that algal oil has roughly 80 of the caloric energy value of crude petroleum 135 The IEA estimates that algal biomass can be produced for a little as 0 54 kg in open pond in a warm climate to 10 20 kg in photobioreactors in cooler climates 136 Assuming that the biomass contains 30 oil by weight the cost of biomass for providing a liter of oil would be approximately 1 40 5 30 gal and 1 81 6 85 gal for photobioreactors and raceways respectively Oil recovered from the lower cost biomass produced in photobioreactors is estimated to cost 2 80 L assuming the recovery process contributes 50 to the cost of the final recovered oil 26 If existing algae projects can achieve biodiesel production price targets of less than 1 per gallon the United States may realize its goal of replacing up to 20 of transport fuels by 2020 by using environmentally and economically sustainable fuels from algae production 137 Whereas technical problems such as harvesting are being addressed successfully by the industry the high up front investment of algae to biofuels facilities is seen by many as a major obstacle to the success of this technology Only few studies on the economic viability are publicly available and must often rely on the little data often only engineering estimates available in the public domain Dmitrov 138 examined the GreenFuel s photobioreactor and estimated that algae oil would only be competitive at an oil price of 800 per barrel A study by Alabi et al 139 examined raceways photobioreactors and anaerobic fermenters to make biofuels from algae and found that photobioreactors are too expensive to make biofuels Raceways might be cost effective in warm climates with very low labor costs and fermenters may become cost effective subsequent to significant process improvements The group found that capital cost labor cost and operational costs fertilizer electricity etc by themselves are too high for algae biofuels to be cost competitive with conventional fuels Similar results were found by others 140 141 142 suggesting that unless new cheaper ways of harnessing algae for biofuels production are found their great technical potential may never become economically accessible In 2012 Rodrigo E Teixeira 143 demonstrated a new reaction and proposed a process for harvesting and extracting raw materials for biofuel and chemical production that requires a fraction of the energy of current methods while extracting all cell constituents Use of byproducts editMany of the byproducts produced in the processing of microalgae can be used in various applications many of which have a longer history of production than algal biofuel Some of the products not used in the production of biofuel include natural dyes and pigments antioxidants and other high value bio active compounds 80 144 145 These chemicals and excess biomass have found numerous use in other industries For example the dyes and oils have found a place in cosmetics commonly as thickening and water binding agents 146 Discoveries within the pharmaceutical industry include antibiotics and antifungals derived from microalgae as well as natural health products which have been growing in popularity over the past few decades For instance Spirulina contains numerous polyunsaturated fats Omega 3 and 6 amino acids and vitamins 147 as well as pigments that may be beneficial such as beta carotene and chlorophyll 148 Advantages editEase of growth edit One of the main advantages that using microalgae as the feedstock when compared to more traditional crops is that it can be grown much more easily 149 Algae can be grown in land that would not be considered suitable for the growth of the regularly used crops 80 In addition to this wastewater that would normally hinder plant growth has been shown to be very effective in growing algae 149 Because of this algae can be grown without taking up arable land that would otherwise be used for producing food crops and the better resources can be reserved for normal crop production Microalgae also require fewer resources to grow and little attention is needed allowing the growth and cultivation of algae to be a very passive process 80 Impact on food edit Many traditional feedstocks for biodiesel such as corn and palm are also used as feed for livestock on farms as well as a valuable source of food for humans Because of this using them as biofuel reduces the amount of food available for both resulting in an increased cost for both the food and the fuel produced Using algae as a source of biodiesel can alleviate this problem in a number of ways First algae is not used as a primary food source for humans meaning that it can be used solely for fuel and there would be little impact in the food industry 150 Second many of the waste product extracts produced during the processing of algae for biofuel can be used as a sufficient animal feed This is an effective way to minimize waste and a much cheaper alternative to the more traditional corn or grain based feeds 151 Minimalisation of waste edit Growing algae as a source of biofuel has also been shown to have numerous environmental benefits and has presented itself as a much more environmentally friendly alternative to current biofuels For one it is able to utilize run off water contaminated with fertilizers and other nutrients that are a by product of farming as its primary source of water and nutrients 149 Because of this it prevents this contaminated water from mixing with the lakes and rivers that currently supply our drinking water In addition to this the ammonia nitrates and phosphates that would normally render the water unsafe actually serve as excellent nutrients for the algae meaning that fewer resources are needed to grow the algae 80 Many algae species used in biodiesel production are excellent bio fixers meaning they are able to remove carbon dioxide from the atmosphere to use as a form of energy for themselves Because of this they have found use in industry as a way to treat flue gases and reduce GHG emissions 80 Disadvantage editHigh water requirement edit The process of microalgae cultivation is highly water intensive Life cycle studies estimated that the production of 1 liter of microalgae based biodiesel requires between 607 and 1944 liters of water 152 That said abundant wastewater and or seawater which also contain various nutrients can theoretically be used for this purpose instead of freshwater Commercial viability edit Algae biodiesel is still a fairly new technology Despite the fact that research began over 30 years ago it was put on hold during the mid 1990s mainly due to a lack of funding and a relatively low petroleum cost 20 For the next few years algae biofuels saw little attention it was not until the gas peak of the early 2000s that it eventually had a revitalization in the search for alternative fuel sources 20 Increasing interest in seaweed farming for carbon sequestration eutrophication reduction and production of food has resulted in the creation of commercial seaweed cultivation since 2017 153 Reductions in the cost of cultivation and harvesting as well as the development of commercial industry will improve the economics of macroalgae biofuels Climate change has created a proliferation of brown macroalgae mats which wash up on the shores of the Caribbean Currently these mats are disposed of but there is interest in developing them into a feedstock for biofuel production 154 Stability edit The biodiesel produced from the processing of microalgae differs from other forms of biodiesel in the content of polyunsaturated fats 149 Polyunsaturated fats are known for their ability to retain fluidity at lower temperatures While this may seem like an advantage in production during the colder temperatures of the winter the polyunsaturated fats result in lower stability during regular seasonal temperatures 150 International policies editThis section may contain an excessive amount of intricate detail that may interest only a particular audience Please help by removing excessive detail that may be against Wikipedia s inclusion policy April 2023 Learn how and when to remove this template message Canada edit Numerous policies have been put in place since the 1975 oil crisis in order to promote the use of Renewable Fuels in the United States Canada and Europe In Canada these included the implementation of excise taxes exempting propane and natural gas which was extended to ethanol made from biomass and methanol in 1992 The federal government also announced their renewable fuels strategy in 2006 which proposed four components increasing availability of renewable fuels through regulation supporting the expansion of Canadian production of renewable fuels assisting farmers to seize new opportunities in this sector and accelerating the commercialization of new technologies These mandates were quickly followed by the Canadian provinces BC introduced a 5 ethanol and 5 renewable diesel requirement which was effective by January 2010 It also introduced a low carbon fuel requirement for 2012 to 2020 Alberta introduced a 5 ethanol and 2 renewable diesel requirement implemented April 2011 The province also introduced a minimum 25 GHG emission reduction requirement for qualifying renewable fuels Saskatchewan implemented a 2 renewable diesel requirement in 2009 155 Additionally in 2006 the Canadian Federal Government announced its commitment to using its purchasing power to encourage the biofuel industry Section three of the 2006 alternative fuels act stated that when it is economically feasible to do so 75 per cent of all federal bodies and crown corporation will be motor vehicles 156 United States edit Policies in the United States have included a decrease in the subsidies provided by the federal and state governments to the oil industry which have usually included 2 84 billion This is more than what is actually set aside for the biofuel industry The measure was discussed at the G20 in Pittsburgh where leaders agreed that inefficient fossil fuel subsidies encourage wasteful consumption reduce our energy security impede investment in clean sources and undermine efforts to deal with the threat of climate change If this commitment is followed through and subsidies are removed a fairer market in which algae biofuels can compete will be created In 2010 the U S House of Representatives passed a legislation seeking to give algae based biofuels parity with cellulose biofuels in federal tax credit programs The algae based renewable fuel promotion act HR 4168 was implemented to give biofuel projects access to a 1 01 per gal production tax credit and 50 bonus depreciation for biofuel plant property The U S Government also introduced the domestic Fuel for Enhancing National Security Act implemented in 2011 This policy constitutes an amendment to the Federal property and administrative services act of 1949 and federal defense provisions in order to extend to 15 the number of years that the Department of Defense DOD multiyear contract may be entered into the case of the purchase of advanced biofuel Federal and DOD programs are usually limited to a 5 year period 157 Other edit The European Union EU has also responded by quadrupling the credits for second generation algae biofuels which was established as an amendment to the Biofuels and Fuel Quality Directives 158 See also edit nbsp Renewable energy portal nbsp Energy portalAcetone butanol ethanol fermentation Chemical process Biochemical engineering Manufacturing by chemical reactions of biological organisms Biological hydrogen production algae Hydrogen that is produced biologicallyPages displaying short descriptions of redirect targets Carbon neutrality Rate of human caused greenhouse gas emissionsPages displaying short descriptions of redirect targets Culture Biosystems Renewable energy company Cyanotoxin Toxin produced by cyanobacteria Direct air capture Method of carbon capture from carbon dioxide in air International Renewable Energy Alliance Joule Unlimited List of algal fuel producers Ocean thermal energy conversion Extracting energy from the ocean Phycology Branch of botany concerned with the study of algae Phytoplankton Autotrophic members of the plankton ecosystem Residual sodium carbonate index Scottish 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Policies S amp T 2 Consultants Inc June 2011 pp 1 19 Gao Y Gregor C Liang Y Tang D Tweed C 2012 Algae biodiesel a feasibility report Chemistry Central Journal 6 Suppl 1 S1 doi 10 1186 1752 153X 6 S1 S1 PMC 3332261 PMID 22540986 G20 G20 Leaders Statement Archived 10 March 2013 at the Wayback Machine 2009 Pittsburgh Summit 2009 European biofuels technology platform R amp D amp D funding Archived 18 May 2013 at the Wayback Machine accessed 28 January 2013 Further reading editWorldwatch Institute 2007 Biofuels for Transport Global Potential and Implications for Sustainable Agriculture and Energy in the 21st century Earthscan ISBN 978 1 84407 422 8 McKay David JC 3 November 2008 Sustainable Energy Without Hot Air 3 5 2 UIT Cambridge Ltd ISBN 978 0 9544529 3 3 Lane Jim 18 April 2010 Salt Water The Tangy Taste of Energy Freedom Renewable Energy World Retrieved 21 April 2010 Bhatnagar S K Atul Saxena Stefan Kraan eds 2011 Algae biofuel New Delhi Studium Press India Pvt Ltd ISBN 978 93 8001 244 5 Darzins Al Pienkos Philip Edye Les 2010 Current status and potential for algal biofuels production PDF IEA Bioenergy Task 39 External links edit nbsp Wikimedia Commons has media related to Algae fuel A Report on Commercial Usage and Production of Algal Oil A Sober Look at Biofuels from Algae Biodiesel Magazine US National Renewable Energy Laboratory Publications Current Status and Potential for Algal Biofuels Production Retrieved from https en wikipedia org w index php title Algae fuel amp oldid 1193428335, wikipedia, wiki, book, books, library,

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