Biomass Biodiesel
What is biomass biodiesel?
Biomass biodiesel is a biofuel derived from biomass feedstocks such as trees, grasses, straw, or various wastes. Biodiesel, by contrast, is derived from virgin vegetable oils and animal fats through a process called transesterification. Advanced biodiesel conversion pathways seek to unlock the ubiquitous supply of biomass throughout the world to offset dependency on petroleum and improve the sustainability of alternative fuels.
How is biomass-based biodiesel defined?
Under FTC rules, biomass-based diesel means the following:
A diesel fuel substitute produced from non-petroleum renewable resources that meets the registration requirements for fuels and fuel additives established by the Environmental Protection Agency under 42 U.S.C. 7545, and includes fuel derived from animal wastes, including poultry fats and poultry wastes, and other waste materials, or from municipal solid waste and sludges and oils derived from wastewater and the treatment of wastewater, except that the term does not include biodiesel.
Biomass-based diesel is also referred to under the EPA’s Renewable Fuel Standard (RFS2). The EPA defines biomass-based diesel as follows:
Renewable fuel that has lifecycle greenhouse gas emissions that are at least 50 percent less than baseline lifecycle greenhouse gas emissions…
and meets all of the following requirements:
(a) it is a transportation fuel, transportation fuel additive, heating oil, or jet fuel;
(b) it meets the definition of either biodiesel or non-ester renewable diesel; and
(c) it is registered as a motor vehicle fuel or fuel additive under 40 CFR part 79, if the fuel or fuel additive is intended for use in a motor vehicle.
The EPA clarifies that a renewable fuel that is co-processed with petroleum is not biomass-based diesel.
How is biomass-based diesel made?
Under RFS2, several conversion pathways may qualify for the biomass-based diesel category so long as certain conditions are met. The definition includes both biodiesel (mono-alkylesters) and non-ester renewable diesel (including cellulosic diesel).
Conventional biodiesel is typically derived from oils through three primary routes, including: base catalyzed transesterification of the oil with alcohol; direct acid catalyzed esterification of the oil with methanol; or conversion of the oil to fatty acids, and then to Alkyl esters with acid catalysis. Biomass biodiesel (or diesel fuel derived from biomass feedstocks), can be produced through a number of processes.
Fischer-Tropsch (FT), the technology pathway for “gas-to-liquids” (GTL) and “biomass-to- liquids” (BTL) production, is the primary conversion pathway being pursued today and utilizes catalysts, heat, and pressure to turn synthetic gas into diesel fuels. Despite its green reputation, FT has a checkered past and was used by the Axis Powers during World War II and then further developed by the Apartheid government of South Africa in response to international trade embargoes. Aviation biofuels can be processed in a similar fashion.
What are biomass-based diesel’s pros and cons?
A lot depends on the feedstock and conversion process. Generally, biomass biodiesel can utilize waste feedstocks that would otherwise end up in landfills or provide additional revenue for rural markets by establishing a market for agricultural residue. Biomass-based diesel can also play a key role in meeting RFS2 mandates given the cost hurdles currently faced by cellulosic ethanol. But biomass-based diesel faces its own cost hurdles and aggregating a sufficient supply of feedstock presents a logistical challenge.
Market opportunity?
Currently, the market opportunity for biomass biodiesel is strong as RIN prices have remained high and other advanced biofuel categories under RFS2 are failing to meet their targets. OECD-FAO project that biomass-based diesel will represent almost 6.5% of total biodiesel production worldwide by 2019.
Image: Flickr/letouj
