Tuesday, September 8, 2009

'Maize-based ethanol can reduce greenhouse-gas emissions by 50%'

By: Leandi Cameron, 28th August 2009

Newer maize ethanol facilities show that using this fuel instead of petrol can reduce greenhouse-gas (GHG) emissions by about 50%, according to the Renewable Fuels Association of the US.

“To understand the climate benefits of renewable fuels relative to fossil fuels, it is necessary to compare the life-cycle GHG emissions associated with the production and use of each type of fuel. “The total quantity of cradle-to-grave GHG emissions associated with a fuel’s production and combustion for each unit of energy deli- vered is often referred to as the fuel’s ‘carbon score’,” the association states in a recent report, titled ‘What Do Biofuels Displace and Why Does it Matter?’

The report explains that life-cycle analyses completed in recent years compared the carbon score of biofuels like ethanol and biodiesel to the carbon score of average petrol or diesel fuel, “rather than the carbon scores of the types of petrol and diesel that biofuels are displacing at the margins of the world liquid fuel market”.

“The carbon score of a particular biofuel should be compared with the carbon score of the fuel it is displacing. “It is widely understood that the resource base for conventional liquid fuels is declining, and that new volumes of biofuels are displacing and delaying the need for unconventional high-carbon sources of liquid fuel.

“Unfortunately, traditional analyses of biofuels do not take this into account,” the report states.

It further notes that the analysis is not meant to be definitive, but, rather, high- lights a need for economic modelling and additional research focused on the importance of what biofuels displace, and what GHG emissions are being avoided owing to more biofuels use.

“Substituting biofuels for marginal fossil-based liquid fuels results in the avoidance of significant GHG emissions that are not, currently, accounted for in life-cycle analyses.

“These avoided emissions are in addition to the emissions reduction relative to average petroleum fuels that are already counted in traditional analysis. “In this analysis, avoided emissions result- ing from the displacement of unconven- tional liquid fuels range from approximately 8 g to 22 g of carbon dioxide equivalent for each megajoule of energy delivered by biofuels,” the report concludes.