Exploring trade-offs in the use of biomass for greenhouse gas mitigation

Image credit: ORNL

The chemical production industry is currently among the largest users of fossil fuel and is responsible for about seven per cent of global greenhouse gas (GHG) emissions. Yet the majority of policies and government programs around the world incentivize biofuel usage in the transportation section while few programs exist to encourage using biomass in the chemicals industry.

Dr. Daniel Posen, an Assistant Professor in the University of Toronto’s Departments of Civil Engineering, spoke about the use of biomass as a strategy for reducing GHG emissions in the North America at the SOCAAR seminar on April 5.

Ethylene is a widely used raw material in the chemical industry, including the production of plastics. Ethylene can be manufactured from fossil fuels or biomass in the form of ethanol. Currently, most ethylene is produced from fossil fuels. But biomass can also be used as a raw material to produce bio-ethylene. Bio-ethanol is produced by the fermentation of plant biomass and then converted into bio-ethylene. In his talk, Posen compared the GHG emissions of producing ethylene from corn, switchgrass and sugarcane to the fossil fuel method. Both switchgrass and sugarcane have the potential reduce or capture GHG emissions.

In addition to being a raw material, biomass can be used to generate renewable energy for the manufacturing of fossil fuel based ethylene. Posen discussed whether the reduction of GHG emissions is more significant in manufacturing bio-based plastics or in using renewable energy to produce conventional plastics. He reported that switching to low carbon energy can flatten plastic emissions for three to four decades but it’s not enough for a long-term strategy. The near-term energy substitution with renewable energy achieves greater GHG reductions at lower cost and with less uncertainty than by switching to corn-based biopolymers. But in the long term, bio-based plastics from advanced feedstocks and/or with renewable energy can get to carbon negative plastics.