By Mike Buday
Earth’s first forms of life and first forms of food for subsequent species now hold the potential to become the planet’s next major source of energy and a vital part of the solutions to climate change and dependence on fossil fuels. Cyanobacteria have caused more global environmental change than humans could ever cause (1) and are now poised to address many of society’s greatest challenges (2). But given the fuel versus food problems associated with other biofuels, the same issue and other issues relating to the scarcity of resources and impacts on the environment must be considered when it comes to algae.
Algae can grow extremely rapidly – one production facility supplied with carbon dioxide from Arizona Public Service Company’s Redhawk power plant emissions averaged growth rates of 98 grams/m2/day (2). Microalgae do not require the massive tracts of cropland that other biofuels would need in order to meet the nation’s thirst for transportation fuels. Martin Tobias, CEO of biodiesel company Imperium Renewables, said algae could theoretically produce 10,000 gallons of oil per acre, compared with 680 gallons per acre for palm, the current highest-oil-yielding crop (3). The United States could replace all of its petroleum-based transportation fuels on 9.5 million acres, a mere one percent of the 950 million acres dedicated to the growing of crops and grazing of farm animals. Also, because algae are not land-based, degradation of soil organic content is not an issue as it is with other forms of biomass.
Rich in oil content, many varieties of microalgae are suitable for the production of biodiesel. However, they are also rich in proteins, carbohydrates, vitamins and minerals, which make them suitable for human, animal, and plant consumption as food, feed, and fertilizer. Algae oil content ranges from 5-70%, protein content ranges from 10-50%, and carbohydrate content ranges from 25-40% (5) (6). Even after the oil content of algae is extracted for biodiesel production, their carbohydrate content can be converted to bioethanol, and the remaining protein can be used as animal feed. Because algae do not have roots, stems, or leaves, they lack the large quantities of cellulose and lignin other forms of biomass contain. Cellulose and lignin must be broken down in order to convert biomass into a usable biofuel feedstock.
Certain forms of algae are capable of both photosynthesis and nitrogen fixation. Methane can be produced from any of the three constituents of algae – carbohydrates, proteins and fats. Algal bioreactors offer a promising opportunity for biomass feedstock production for bio-methane. Using these systems over open pond systems, microalgae can be grown in large amounts (150-300 tons per ha per year) using closed bioreactor systems. (3)
Algae have a diverse variety of uses and applications and can be found in products ranging from antacids, dentistry molds, energy sources (including biodiesel and ethanol), fertilizers, plastics, prosthetics, pollution controls, and pigments. Many people are unaware of the presence of algae in products such as ice cream and toothpaste.
Algae can capture fertilizer runoff from farms and then be re-used as a fertilizer themselves. Algae fertilizers are produced by fermentation using certain microbes. These are very effective natural products which can be completely absorbed by plants, capable of increasing seed germination rates, enhancing the resistance of plants to stresses, such as drought, cold and diseases, and increasing crops yields (3).
An effective biofilter, algae are used to remove pollutants from wastewaters (4). Also, an effective bioreactor, algae are used to capture carbon dioxide emissions from industrial plants (5).
An abundant source of vitamins, minerals, and other nutrients, many varieties of algae are known to boost the human immune system. Algae are commercially cultivated for pharmaceuticals, nutraceuticals, cosmetics, and aquaculture purposes. Unlike most plant species, algae contain a complete protein with essential fatty acids/amino acids. (2) Over 10 million people in the United States take algae-based nutritional supplements. Annual sales of chlorella exceed $500 million in Japan alone (4).
The wide variety of uses from algae, the relative advantages of their consumption over fossil fuels and other food sources, and the potential to ramp up commercial production, beg the question, how much algae can be grown, before they start to pull more carbon dioxide out of the atmosphere than is released through anthropogenic emissions? Given that 183 grams of carbon dioxide is required to produce 100 grams of biomass (8), an average of 30 percent of algae biomass is oil (this varies by species) (8), approximately 96.4% of crude oil is converted to biodiesel (9), a liter of biodiesel has mass of approximately 850 grams (10), the United States emits approximately 5.987 Gt of carbon dioxide per year from fossil fuel uses (11), and the United States would need 140.8 billion gallons of biodiesel per year to meet its transportation needs (14), biodiesel production alone would consume nearly 48% of the nation’s annual carbon dioxide emissions. Since algae have so many other uses, it is essential that industry develops a better understanding of the impacts of algae production on atmospheric levels of carbon dioxide and the roles of algae in society and ecosystems as it ramps up production.
Algae may be the ultimate answer for the future of biodiesel production and a carbon neutral fuel source, considering that algae produce more than 100 times more oil per acre than traditional biodiesel feedstocks such as soy, (algae produces 4,000-10,000 gallons of oil per acre per year versus 50 gallons per acre for soy),algae eat carbon dioxide and produce oxygen, algae require only sunlight and non-drinkable (salt or brackish) water to grow, algae do not compete with food crops for either agricultural land or fresh water, and algae can reproduce extremely rapidly (7). Still, it is unreasonable to believe that there is a single “silver-bullet” answer to replacing fossil fuels and addressing climate change. For one thing, as with other biofuels, the economics are not there yet. Advances in technology are needed to drive cost per liter from $2.80 to $.48 in order to compete with $60/barrel crude petroleum oil. (6) It will be several years, maybe a decade or more, before these simplest of all organisms can be efficiently processed for fuel. When that day comes, it could go a long way toward easing the world’s energy needs and responding to global warming (2). However, it is vital that algae-based biodiesel offset conventional fossil fuel combustion and not encourage or incentivize increased energy combustion. It is also critical that commercial algae production be appropriately coupled with anthropogenic carbon dioxide emissions and other resource inputs. Finally, the production of algae for biodiesel should be viewed alongside algae’s other uses and applications.
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13. [Online] May 2008. http://www.eia.doe.gov/oiaf/1605/flash/flash.html.
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