Interview Date: September 2008
From the Special Topic of
This month, ScienceWatch.com talks with Roel
Hammerschlag about his paper, "Ethanol's energy return on
investment: A survey of the literature 1990-present,"
(Environ. Sci. Technol. 40: 1744-50, 15 March
2006), which is a core paper in the Biofuels Special Topic
Research Front Map of
Hammerschlag is a Staff Scientist at the US branch of
the Stockholm Environment Institute, where he works in the
Climate and Energy Program. In 2007, he received a
fellowship from the University of Washington Program on
Climate Change and was inducted into the National Honor
Society for Public Affairs and Administration.
In this interview,
ScienceWatch.com Roel Hammerschlag discusses the paper and
how it has influenced biofuels
Would you please describe the major points of
your paper and why it is garnering citation attention?
The paper is a literature review of energy-return-on-investment (EROI)
analyses for corn and cellulosic ethanol. The paper has received citation
attention because it succeeds in normalizing and comparing multiple
research teams' results, and because it is transparent and easy to read. At
the time it was written and published, there was a great deal of dispute in
the popular press about the EROI of corn ethanol. The paper cut neatly
through that dispute because it showed that all but one of the research
teams' results led to uniform conclusions, namely that:
corn ethanol marginally reduces fossil fuel use; and
cellulosic ethanol can displace far more nonrenewable energy than
"Though the current effect of bioenergy
demand on food prices is probably overstated, the
potential for EU and US bioenergy policies to
affect global food access and prices is very
How did you become involved in this research, and
were there any particular successes or obstacles that stand out?
I have been assisting various organizations with greenhouse gas accounting
and greenhouse gas policy for a long time. Two environmental
advocates—NRDC and Climate Solutions—wanted to get to the
bottom of the debate happening in the press; I had worked with both of
these organizations before so they turned to me to do the review. They were
in a rush and I was due to be married in two weeks and go on a honeymoon,
so I did the whole project in just two weeks. It was a real rush to
capitalize on my experience to deliver such a thorough piece of work in
such a short amount of time. Of course there was still plenty of work after
my honeymoon, adapting my original report to become a manuscript for
Environmental Science & Technology!
Where do you see your research and the broader
field leading in the future?
Right now we are seeing a similar rush of press activity around bioenergy,
but this time regarding competition with food crops rather than the more
esoteric issue of EROI. Though the current effect of bioenergy demand on
food prices is probably overstated, the potential for EU and US bioenergy
policies to affect global food access and prices is very real. I am moving
into global trade modeling and agricultural sector modeling, to learn more
about how social, environmental, and economic variables can affect the
balance of energy and food crops globally, especially keeping in mind the
livelihoods of populations in developing nations. So I am happy to see the
press focusing on this issue, since it deserves attention.
What are the implications of your work for this
I think the biggest value of the ES&T article was to underscore the
trifling climate benefits of corn ethanol and highlight the large, positive
step cellulosic ethanol could offer in contrast. When I first researched
the article just three years ago, most policymakers had never heard the
word "cellulosic." Now that word is encoded in federal legislation (the
Energy Independence and Security Act of 2007). I hope that I might have
played some small role in that new awareness.
Stockholm Environment Institute
Seattle, WA, USA
Hammerschlag's most-cited paper
with 20 cites to date:
Hammerschlag R, "Ethanol's energy return on investment: A
survey of the literature 1990-present," Environ. Sci.
Technol. 40(6): 1744-50, 15 March 2006. Source:
Essential Science Indicators from
Keywords: literature review, energy-return-on-investment,
corn ethanol, cellulosic ethanol, greenhouse gas accounting,
greenhouse gas policy, environmental advocates.