Algae fuel
[3][4] Following World War II, research began in the US,[5][6][7] Germany,[8] Japan,[9] England,[10] and Israel[11] on culturing techniques and engineering systems for growing microalgae on larger scales, particularly species in the genus Chlorella.
[12] 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.
[15] The research program focused on microalgae cultivation in open outdoor ponds, systems that are low in cost but vulnerable to environmental disturbances like temperature swings and biological invasions.
[15] 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.
[15] 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.
[16] 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,[17][18] an important development for algal biofuel research.
[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.
"[20] 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.
[12][15][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.
[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.
[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.
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.
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.
[62] 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.
[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] The amount of oil each strain of algae produces varies widely.
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.
[85] 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).
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.
[94]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.
[26] 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).
[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.
A possible nutrient source is wastewater from the treatment of sewage, agricultural, or flood plain run-off, all currently major pollutants and health risks.
[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.
[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.
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.
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.
[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.
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.
[150] 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.
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".
