Washington, October 23 : A study examining the impact of a global biofuels program on greenhouse gas emissions during the 21st century has found that carbon loss stemming from the displacement of food crops and pastures for biofuels crops may be twice as much as the CO2 emissions from land dedicated to biofuels production.

Using a global modeling system that links economic and biogeochemistry data, Melillo, Marine Biological Laboratory (MBL) research associate David Kicklighter, and their colleagues examined the effects of direct and indirect land-use on greenhouse gas emissions as the production of biofuels increases over this century.

Direct land-use emissions are generated from land committed solely to bioenergy production.

Indirect land-use emissions occur when biofuels production on cropland or pasture displaces agricultural activity to another location, causing additional land-use changes and a net increase in carbon loss.

No major countries currently include carbon emissions from biofuel-related land-use changes in their carbon loss accounting and there is concern about the practicality of including such losses in a system designed to reduce fossil-fuel emissions.

Moreover, methods to assess indirect land-use emissions are controversial.

All quantitative analyses to date have either ignored indirect emissions altogether, considered those associated from crop displacement from a limited area, confused indirect emissions with direct or general land-use emissions, or developed estimates based on a static framework of today's economy.

Using a modeling system that integrates global land-use change driven by multiple demands for land and that includes dynamic greenhouse-gas accounting, Melillo and his colleagues factored in a full suite of variables, including the potential of net carbon uptake from enhanced land management, N2O emissions from the increased use of fertilizer, environmental effects on carbon storage, and the economics of land conversion.

"Our analysis, which we think is the most comprehensive to date, shows that direct and indirect land-use changes associated with an aggressive global biofuels program have the potential to release large quantities of greenhouse gases to the atmosphere," said Melillo.

The analysis indicates that Indirect land use will be responsible for substantially greater carbon losses (up to twice as much) than direct land use.

"Large greenhouse gas emissions from these indirect land-use changes are unintended consequences of a global biofuels program; consequences that add to the climate-change problem rather than helping to solve it," said Melillo.

"As our analysis shows, these unintended consequences are largest when the clearing of forests is involved," he added. (ANI)