Use of ethanol as a partial substitute for gasoline is mandated in the United States on the grounds that it will help mitigate our dependence on foreign petroleum sources and reduce greenhouse gas emissions. But in the U.S. most ethanol is produced from corn and that production has had detrimental effects on a food crop.

Another main way to produce ethanol is from sugarcane. This method has been promoted in other countries, especially Brazil. It is seen as a green solution to the pretended problem of carbon dioxide emissions from burning fossil fuels. But is it?

A new study finds, that when all productions steps are taken into account, the greenhouse gas emissions from sugarcane ethanol are higher than those from burning fossil fuels.

Reference:

Lisboa, C.C., Butterbach-Bahl, K., Mauder, M. and Kiese, R. 2011. Bioethanol production from sugarcane and emissions of greenhouse gases — known and unknowns. Global Change Biology Bioenergy 3: 277-292

Abstract:

Bioethanol production from sugarcane is discussed as an alternative energy source to reduce dependencies of regional economies on fossil fuels. Even though bioethanol production from sugarcane is considered to be a beneficial and cost-effective greenhouse gas (GHG) mitigation strategy, it is still a matter of controversy due to insufficient information on the total GHG balance of this system. Aside from the necessity to account for the impact of land use change (LUC), soil N2O emissions during sugarcane production and emissions of GHG due to preharvest burning may significantly impact the GHG balance. Based on a thorough literature review, we show that direct N2O emissions from sugarcane fields due to nitrogen (N) fertilization result in an emission factor of 3.87±1.16% which is much higher than suggested by IPCC (1%). N2O emissions from N fertilization accounted for 40% of the total GHG emissions from ethanol–sugarcane production, with an additional 17% from trash burning. If LUC-related GHG emissions are considered, the total GHG balance turns negative mainly due to vegetation carbon losses. Our study also shows that major gaps in knowledge still exist about GHG sources related to agricultural management during sugarcane production, e.g. effects of irrigation, vinasse and filter cake application. Therefore, more studies are needed to assess if bioethanol from sugarcane is a viable option to reduce energy-related GHG emissions.

Another factor is that ethanol production, at least in the United States, is heavily subsidized and probably would not be viable without the subsidy. This is not an efficient use of our resources.

See also:

Death Toll from Biofuels

Ethanol fuel not as green as you think

 Also in the category of not as green as you think, see:

Which Vehicles Are Most Energy Efficient?

This entry was posted on Tuesday, August 30th, 2011 at 8:16 am and is filed under Climate change, Energy. Tags for this post: biofuels, corn ethanol, ethanol, sugar cane. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.