Interview Date: September 2008
Prof. Daniel Kammen and Mr. Richard
From the Special Topic of
According to our Special Topics analysis on Biofuels,
the paper "Ethanol can contribute to energy and
environmental goals," (Farrell AE, et al.,
Science 311: 506-8, 27 January 2006) is a core
paper in the Research Front Map of Ethanol Biofuels. At
present, it has 114 citations. This month,
ScienceWatch.com talks to two of the paper's authors,
Dr. Daniel Kammen and Mr. Richard Plevin.
Dr. Kammen is the Class of 1935 Distinguished Professor of
Energy in the Energy and Resources Group and the Goldman
School of Public Policy at the University of California,
Berkeley. Mr. Plevin is a Ph.D. candidate in the Energy and
Resources Group at Berkeley.
Below, Dr. Kammen and Mr. Plevin discuss
this paper and its impact on the biofuels
How did you become involved in this research,
and were there any particular successes or obstacles that stand
In 2005, the debate over whether corn ethanol had a positive or negative
net energy value was raging, with reputable researchers from top
universities arriving at opposing conclusions. A group of graduate students
in the Energy and Resources Group, who were already working on various
aspects of biofuels, were interested to understand how this could be the
case. Together with Professors Farrell (deceased), Kammen, and
O’Hare, we decided to build a meta-model to compare several corn
ethanol studies on an equal footing.
One of the outcomes of this effort was developing a better quantitative
understanding of a number of the agricultural inputs to corn production.
Studies citing various USDA documents for application rates of agricultural
lime showed values spanning three orders of magnitude, but in the course of
reviewing this data, we discovered that the high and low values were due to
errors. This resulted in corrections from the USDA to their data sets, and
an update of the well-known and widely used GREET fuel and vehicle life
Our model, EBAMM, is, and has since the time of publication of our paper,
been available to download for free. The model is updated
The objective of this modeling effort has been transparency of assumptions
and the sources of the values used in the analysis, as well as maximum
flexibility for users to take the model (in Excel®) and conduct runs
with parameters of their choosing.
Would you please describe the major points of your
paper and why it is garnering citation attention?
Our paper illustrated clearly where several well-known corn ethanol studies
differed in their assumptions and how these differences drove the divergent
results. Some of these differences were due to legitimate disagreements
about system boundaries; other differences were due to the use of outdated
data. We cataloged these and normalized system boundaries across studies
allowing a meaningful comparison to be made.
We also determined that ethanol from cellulosic feedstocks might be
dramatically less greenhouse gas (GHG) intensive than corn ethanol, which
even if refined properly, offered at best a slight reduction in GHG
emissions versus gasoline. We noted that even this result ignored possible
GHG emissions from so-called "indirect" land use conversion induced by
increasing the acreage devoted to biofuel feedstock production. When our
paper was published this effect had not yet been quantified. The
Searchinger et al. paper in Science ("Use of US croplands
for biofuels increases greenhouse gases through emissions from land-use
change," 319: 1238-40, 29 February 2008) quantified that effect, and
we now believe that substituting corn ethanol for gasoline increases net
GHG emissions, and a key determinant of the GHG benefits of cellulosic
biofuel will be whether it is grown on land that could grow food.
Another key—though less-often noted—point of our paper is that
the entire debate over Net Energy Value (NEV) is largely irrelevant.
Summing across different types of primary energy doesn't answer any useful
question. It's like addressing hunger by shipping biomass to a poor country
without distinguishing between food, feed, fiber, and building materials.
For example, upgrading coal and natural gas to electricity or to a liquid
fuel has a valid societal purpose that is completely outside a calculation
of NEV. Minimizing NEV, we wouldn’t produce electricity owing to the
inevitable losses in generation, transmission, and distribution. This is
obviously nonsense, and we are pleased to see little discussion of NEV in
the current policy debate.
Our paper computes two metrics that we feel are more salient: petroleum
used per unit of ethanol produced and life cycle GHG emissions. These
metrics directly address two questions we care about as a society, namely
reducing petroleum consumption and mitigating climate change.
Where do you see your research and broader field
leading in the future?
"Summing across different types of
primary energy doesn't answer any useful
question. It's like addressing hunger by shipping
biomass to a poor country without distinguishing
between food, feed, fiber, and building
We are now focused on the issue of indirect land use change, with several
modeling efforts underway and papers in the works addressing two related
challenges: (a) quantifying this effect given the large uncertainties and
coarse models available, and (b) understanding how to include such an
uncertain—yet critically important—effect in fuel regulations
that are currently under development. While the GHG emissions from indirect
land use change are highly uncertain, our estimates indicate that they are
high enough to negate the climate benefits we calculated earlier for fuels
like corn ethanol and soybean biodiesel.
The issue of indirect land use effects of biofuel production have led to an
expanded analytical basis, as well as academic and commercial interest in
biofuels that do not compete with food, such as those produced from algae,
municipal solid waste, agricultural residues, and forest wastes.
What are the implications of your work for this
Many jurisdictions are already regulating or planning to regulate the GHG
effects of biofuels or transportation fuels more generally. In the US, both
the California Air Resources Board and the US EPA are studying the issue,
and our team is contributing to these efforts. Various European regulatory
agencies are also grappling with this issue, and in the UK, the Renewable
Fuels Agency just released an important report on the subject of indirect
land use change (the so-called Gallagher Review).
The move from volumetric standards, which ignored the differential GHG
profiles of different fuel production systems, to performance-based
standards based on life cycle GHG emissions is a major improvement in
regulation. At the moment, the science is racing to catch up with the
regulations. Our work, and the work of our colleagues around the world,
helps inform these critical regulatory efforts.
As a result of these efforts we are now exploring:
• Opportunities for "food-friendly" biofuels, notably in poor regions
where food production and biofuel production could both be increased.
• Certification schemes for "sustainably produced" biofuels.
• An expansion of the EBAMM methodology to reflect fuel impacts on
water, biodiversity, community livelihoods, and other less easily
quantified aspects of sustainability.
Daniel Kammen, Ph.D.
Energy and Resources Group
Goldman School of Public Policy
Department of Nuclear Engineering
University of California, Berkeley
Berkeley, CA, USA
Richard Plevin, Ph.D. candidate
Energy and Resources Group
University of California, Berkeley
Berkeley, CA, USA
Prof. Daniel Kammen and
Mr. Richard Plevin's most-cited
paper with 114 cites to date:
Farrell AE, et al., "Ethanol can contribute to
energy and environmental goals," Science
311(5760): 506-8, 27 January 2006. Source:
Essential Science Indicators from
Keywords: biofuels, ethanol, net energy value, corn
production, GREET, EBAMM, fuel life cycle modeling, indirect land
use, greenhouse gas emissions, sustainably produced