Generations of biofuels

Biofuels research and development has led us to three different generations of biofuel.  Each generation has a unique feedstock and its own potential benefits and draw backs.  When we talk about first generation biofuel, we are referring to biofuels from an existing row crop such as corn ethanol or soy biodiesel.  Second generation biofuels are derived from cellulosic biomass such as perennial grasses.  Third generation biofuels are to be made from algae.

First generation biofuels are derived from vegetable oil, starch, or sucrose. Processing these elements to become a transportation fuel requires simple biochemical treatments for vegetable oil to biodiesel or starch and sucrose to ethanol. These processes have already been developed in the food industry, limiting the need for further research and development before producing transportation fuels.  However, those crops require intensive agricultural input (fertilizer), as opposed to less input for perennial grasses.

Canola oil can be used to produce biodiesel. Photo credit: USDA-ARS

Corn is often used for ethanol production. Photo credit USDA-ARS

The U.S. Domestic Corn Use chart below shows that ethanol is the primary consumer of domestically grown corn in the United States since 2010.  As many as 5 billion bushels are produced annually for ethanol production.  

Source from USDA-ERS

Second Generation Biofuel

Second generation biofuels are expected to be derived from cellulosic biomass sources including crop residues, perennial grasses, and trees.  They may be grown on marginal cropland where row crop production is not profitable.  By focusing on areas that are highly erodible or have marginal soil quality, this avoids competition with fertile ground that may be best used to grow food crops.

Although these crops require little initial input, they do require additional treatment to break down cellulose for creating an end product such as a liquid fuel.  In addition, transporting high quantities of biomass can be a logistical and financial challenge for producers.

Harvesting perennial grasses for bioenergy. Image credit: NREL

Fast growing willow is a good candidate for bioenergy. Image courtesy of Dr. Tim Volk at SUNY

Third Generation Biofuel

To create third generation biofuels biomass or oil is harvested from algae. Oil producing algae (so call Oilgae) does not require pretreatment, and grows quickly. However, controlling the environment for optimal growth is challenging, and expensive. Maintaining strict environmental control often requires expensive facilities and equipment.

Algae bioreactor (Photo from creative commons)

Testing ideal algae growth environments for biofuel (NREL)