When plant-based fuels are mentioned, people may think of corn-based ethanol mixed with gas during the winter months or specific products like biodiesel. However, algae can be converted into many types of biofuels, depending on the species and process.
Algae can be used to produce biodiesel by extracting its oily parts, or it can be converted into replacements for other petroleum-based fuels. Even after oil extraction, the remaining carbohydrate content of algae can be fermented into bioethanol.
Since microalgae don’t have to devote resources to structures like leaves, stems, and roots, they’re able to grow much faster than crops grown on land. In fact, if algae-derived fuels were to replace all petroleum fuel used in the US, it would require about 15,000 square miles of land devoted to production, which is equivalent to about half the land area of Maine, or 0.40% of total US land area.
Biodiesel
Biodiesel Is derived from plant or animal lipids. Corn and soybeans are common sources, but they are rapidly being overtaken by algae. In fact, some species of algae can produce an astonishing 60% or more of their dry weight in the form of oil due to their minimal structure and efficient growth processes. Soybeans, in contrast, can convert only about 2-3%.
Biobutanol
Biobutanol can be converted from algae in a biorefinery, which itself can be powered by solar energy. Its energy density is only 10% less than gasoline and is greater than either ethanol or methanol. In most gasoline engines, butanol can be directly substituted for gasoline with no modifications, while reflecting similar consumption levels. Even more encouraging, butanol can be produced not only from the microalgal biomass left over after oil extraction, but also directly from macroalgae (seaweed).
Bio gasoline
Bio gasoline is produced from biomass, much like butanol. It is similar enough to gasoline that it can be used directly in internal-combustion engines with no modifications.
Biogas
Natural gas is composed primarily of methane and carbon dioxide and is obtained primarily as a byproduct of fossil fuel extraction. In contrast, biogas is a renewable resource, produced through anaerobic digestion processes. Biogas is composed with the same primary components as natural gas and can be used in fuel cells and heating applications. Similar to natural gas, it can be compressed to CNG and used to power motor vehicles. Biogas that has been cleaned and upgraded becomes bio-methane.
Aside from easy compatibility with current natural gas applications, biogas qualifies as a carbon-neutral renewable resource. As organic material grows, it’s converted and used, and regrowth continues in an endlessly repeating cycle; meanwhile an equal amount of carbon dioxide is absorbed from the atmosphere as is released when it’s converted to energy.
Green diesel
Green diesel, also known as renewable diesel, is produced from algae through a refinery process that breaks molecules into short hydrocarbon chains. The resulting product has the same chemical properties as petroleum-based diesel, so it functions as a “drop in” substitution for diesel with no need for modifications. While green diesel isn’t currently competitive with petroleum, further study is justified as the need to move away from fossil fuels becomes more urgent.
