What is green fuel and how is it produced?

Some green fuels that have been used since ancient times, such as wood, can be used directly as a source of heat. This heat can then be used in power plants to generate electricity. Several power generation facilities still get their energy from burning biomass resources such as grass, wood or other types of plant material.

Today, liquid green fuels have attracted much attention due to the extensive infrastructure provided for their use, especially in transportation. Ethanol, which is the most common green fuel, also known as biofuel, is a type of fuel obtained by distilling plant, microbial, and animal materials. Known as liquid, it is produced by fermenting starch or sugar. Brazil and the United States are the largest producers of ethanol. In the United States, this fuel is made mainly from corn kernels and is used in the production of benzol, which is a mixture of 10% ethanol and 90% gasoline.

In Brazil, ethanol is mainly extracted from sugarcane and is typically used as 100% ethanol or blended with gasoline (containing 85% ethanol). “First generation” ethanol, which is produced from food crops, is distinguished from “second generation” ethanol, which is produced from low-value biomass containing high amounts of cellulose, such as wood chips, agricultural residues, and municipal waste.

Cellulosic ethanol is typically made from sugarcane bagasse (the residue left over after sugarcane is processed to produce sugar) or from grasses that can be grown on poor quality land. Given the low conversion rates of first-generation green fuels, cellulosic ethanol is often used as an additive to gasoline.

Biodiesel, the second most common liquid green fuel, is produced primarily from oilseeds such as soybeans or palm, and to a lesser extent from other oil sources (such as recycled frying oils). Biodiesel, which has been most popular in Europe, is used in diesel engines and is usually blended with diesel fuel in varying percentages.

The use of algae and cyanobacteria as a source of “third-generation” biodiesel is also promising, although the development of this industry still faces many economic challenges. Some species of algae can convert up to 40% of their weight into lipids that can be converted into biodiesel or synthetic oil. Some estimates suggest that algae and cyanobacteria can produce 10 to 100 times more fuel per unit of fuel than second-generation fuels.

Other green fuels include methane gas and biogas, which are produced from the decomposition of biomass in the absence of oxygen and can lead to the production of methanol, butanol, and dimethyl ether.