"Our results will be important for policy makers who need to understand the trade-offs associated with different ethanol pathways," researcher Yimin Zhang of the University of Toronto told environmentalresearchweb. "They are also useful to ethanol process developers as well as fuel providers subject to the LCFS. Large scale use of ethanol will also require many more flexfuel vehicles, which affects vehicle manufacturers."
Transport currently releases around 40% of California's total emissions. About 70% of these transport emissions come from gasoline, which is used almost entirely by light-duty vehicles, such as cars. To address this problem, the governor of California issued the LCFS at the beginning of 2007; it aims to reduce the carbon footprint of transport in the state by at least 10% by 2020, and was adopted by law in April 2009.
Analysis completed by Heather MacLean of the University of Toronto and colleagues suggests all sources of ethanol, except Midwest corn ethanol, are viable options for helping to meet this target. The fraction of ethanol required for blending with gasoline varies from 15% to 41% by volume, depending on the feedstock used. Although California can't currently make enough ethanol from biomass sources to meet the LCFS target, it can supplement this from other sources.
Ethanol produced in the US today primarily comes from corn (maize), which requires substantial amounts of fertilizer, fuels and other chemicals. Producing ethanol from lignocellulosic feedstocks, such as maize stalk and forest residues, should be better for the environment as it requires less fertilizer and pesticide. However, there aren't yet any commercial lignocellulose-to-ethanol facilities, although a few companies, such as Iogen Corporation of Canada, have set up pilot plants. Scientists are still developing enzymes that can depolymerize cellulose to produce soluble sugars. The sugars can then be fermented by microorganisms, in the same way as sugars derived from corn or sugarcane, to produce ethanol at reasonable cost. Scaling up ethanol production also remains a challenge.
The team is now investigating the broader environmental and economic impacts of using biofuels on a large scale. "The effects of land-use change, water consumption and increased agricultural activity will need to be explored, as well the competition between producing food or fuel from land," said Zhang. The work was published in Environmental Research Letters.