The Environmental Footprint of Biofuels

//The Environmental Footprint of Biofuels

A new UN report emphasizes the importance of addressing land use, water, and biodiversity impacts of biofuels.
The jury is now in on biofuels: Current government mandates in the United States, Europe and other countries to blend biofuels into ordinary car fuels cause substantial environmental damage, do little to reduce greenhouse gas emissions, and have a questionable contribution to energy security. A new UN report and a new book document many, sometimes fascinating facets of this intricate issue. There are many types of biomass, different options for growing this biomass, a few technologies for converting the biomass to various liquid fuels. It is not surprising that the environmental impacts depend on the particularities of the growing, harvesting, transporting, converting and use of the fuels. However, there are only very few production routes currently used, and these routes are harmful to the environment in several ways.


The report “Towards sustainable production and use of resources: Assessing Biofuels” was produced by the International Panel for Sustainable Resource Management (IPSRM) and relased by the head of the United Nations Environment Program Achim Steiner on 23 October. I am also a member of IPSRM, but have not contributed to this report. The book ‘”Biofuels for Road Transport: A Seed to Wheel Perspective”, was written by the Dutch environmental scientists Lucas Reijnders and Mark Huijbregts. Both works present an extensive review of scientific work on biofuels.

To understand biofuels, one must look at thermodynamics, that is, to account for energy flows in a biomass system similar to how one would account for money flows. Already in 1982, Perezblanco and Hannon published an analysis of the energy required to produce one unit of energy in the form of corn-ethanol and wood-methanol. They showed that the energy used to run tractors, produce fertilizers, and convert corn to ethanol is more or less equal to the energy in the ethanol produced – so that there is little point in whole exercise. Methanol from wood, however, has a substantial net energy gain. These results have since then been confirmed by a great number of studies, also for other biofuel products derived from these biomass resources.

If there is little energy gain, there is also little benefits in terms of greenhouse gas emissions. The figure illustrates the reduction GHG emissions reductions – or the lack thereof – achieved by different biofuel production routes. Today’s biofuel comes all from food crops – maize, wheat, vegetable oil, and sugar cane, which are easy to convert but require high inputs of fertilizer and machine power to produce – with the exception of sugar cane.

The substantial insights of the two new publications, however, is the insight of the high ecological impacts that come from converting land for biofuel production, emissions from land use, as well as the runoff of fertilizer and pesticides. These effects are often not sufficiently considered in life-cycle assessment. In the United States, it is reported that increased fertilizer application for biofuels has lead to increased runoff of phosphorus and nitrogen, which stimulates increased algae growth in waterways and leads to oxygen depletion and fish death as a result.

The issue of land conversion and its effect on carbon stored in soil and plants has been discussed prominently in recent years and months. It is central to determining the greenhouse gas benefit of biofuels. The report underlines that declining yield increases and increasing food demand imply that the current global cropland needs to expand further. Increase biofuels product will hence inevitably require the conversion of virgin land to cropland. Certifying biofuels grown on already established agricultural land has hence little effect, as this only displaces food production to previously marginal land.

The effect of this is quite clear, as the report underlines: “Increased biofuel production is expected to have large impacts on biological diversity in the coming decades, mostly as a result of habitat loss, increased invasive species and nutrient pollution. Habitat loss will mainly result from cropland expansion. Species and genotypes of grasses suggested as future feedstocks of biofuels may become critical as invaders. Nutrient emissions to water and air resulting from intensive fuel cropping will impact species composition in aquatic and terrestrial systems.
We afford climate mitigation measures that are so ineffective in reducing greenhouse gas emissions but destroy ecosystems and biodiversity. It is time to reconsider biofuel mandates!

By | 2017-11-08T21:16:09+00:00 November 15th, 2009|Scientific Issues|0 Comments

About the Author:

Edgar Hertwich
I am a professor at the Yale School of Forestry and Environmental Studies and currently serve as president of the International Society for Industrial Ecology. I grew up in Braunau, Austria, studied physics at Princeton and Energy & Resources at the University of California, Berkeley. From 2003-2015, I directed the Industrial Ecology Programme of the Norwegian University of Science and Technology. My research interests cover life cycle assessment, sustainable consumption and production, trade and environment, risk analysis, and climate mitigation. I am interested in understanding how activities in our society require resources and produce environmental pressures. I would like to better understand the dynamics in our development that affect these driving forces and their resulting environmental pressures, and alternative courses of action that can reduce these pressures. What is the connection between human activities on the one hand and emissions and resource use on the other hand? What are the implications of our current development path? What do we need to change, both in terms of individual actions and policy frameworks, to achieve a more sustainable development.

Publications: See full list here (in Google Scholar)

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