A new study of CO2 emissions, cropland area requirements, and other environmental consequences of corn- and sugarcane- ethanol production in the US and Brazil concludes that despite the net energy and CO2 benefits offered by the fuel, using ethanol as a full substitute for gasoline is neither sustainable nor environmentally friendly once the ecological footprint values are factored in.
The researchers also concluded, however, that as part of a diverse energy and fuel portfolio of alternatives to petroleum, “ the ethanol option probably should not be wholly disregarded.”
The paper, “Ethanol as Fuel: Energy, Carbon Dioxide Balances, and Ecological Footprint,” is to be published in the July 2005 issue of BioScience, the journal of the American Institute of Biological Sciences (AIBS).
The researchers, Marcelo E. Dias de Oliveira, Burton E. Vaughan, and Edward J. Rykiel, Jr., use the “ecological footprint” concept to frame the requirements for ethanol production from sugarcane, now widespread in Brazil, and from corn, the main feedstock in the United States.
The ecological footprint is an accounting tool based on two fundamental concepts, sustainability and carrying capacity. It allows the estimation of the resource consumption and waste assimilation requirements of a defined human population or economy sector in terms of corresponding productive land area.
Based on their assumptions and analysis, ethanol carries a positive energy balance (i.e., yielding more energy than directly required to produce it). That conclusion will be somewhat contentious on its own, as the academic debate over ethanol continues to volley back and forth over that precise question.
The energy comes with a fairly steep ecological footprint, however, based on extrapolation from modeled vehicles.
In their calculations, the team used a 2001 Ford Taurus flex-fuel vehicle for the US and a 2003 Volkswagen Golf 1.6 for Brazil.
|Fuel Consumption of Modeled Cars|
|2001 Taurus (US)||2003 Golf (Brazil)|
|Fuel Consumption||11.2 l/100km||14.7 l/100km||7.16 l/100km||9.81 l/100km|
|Miles per Gallon (US)||21 mpg||16 mpg||32.9 mpg||24 mpg|
Dias de Oliveira and colleagues then looked at some consequences of moving to greater fuel ethanol use. The results were unfavorable to fuel ethanol in either country. In Brazil, reducing the rate of deforestation seemed likely to be more effective for taking carbon dioxide out of the atmosphere. In the United States, reliance on ethanol to fuel the automobile fleet would require enormous and ultimately unachievable areas of corn agriculture, and the environmental impacts would outweigh its benefits.
However, the ethanol option probably should not be wholly disregarded. The use of a fuel that emits lower levels of pollutants when burned can be important in regions or cities with critical pollution problems. Also, in agricultural situations where biomass residues would otherwise be burned to prepare for the next planting cycle, there would be some advantage in using the residues for alcohol production. However, further research should be done to improve the conversion process.
Considering that, eventually, petroleum may no longer be available in the amounts currently consumed, one must conclude that substitution of alternatives to fossil fuel cannot be done using one option alone. It will prove more prudent to have numerous options (e.g., ethanol, fuel cells, solar energy), each participating with fractional contributions to the overall national and global need for fuel energy. Finally, it is important to notice that no option comes free from significant environmental problems. [Emphasis mine.]
As a corollary to this, we can note that consuming less is better than consuming more—for example, using a plug-in hybrid architecture to reduce the size of the engine required and the fuel consumed.