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The smallprint of the RFS2 renewable fuel standard

As by volume the most relevant renewable fuel standard world
wide, a closer look at the details of this regulation is worthwhile – to
understand the issues behind decarbonization policies in transport.  The RFS2 details that

“EPA is making
threshold determinations based on a methodology that includes an analysis of
the full lifecycle of various fuels, including emissions from international
land-use changes resulting from increased biofuel demand. EPA has used the best
available models for this purpose, and has incorporated many modifications to
its proposed approach based on comments from the public, a formal peer review,
and developing science. EPA has also quantified the uncertainty associated with
significant components of its analyses, including important factors affecting
GHG emissions associated with international land use change.”

Specific lifecycle GHG emission thresholds for each of four
types of renewable fuels were established, requiring a percentage improvement
compared to lifecycle GHG emissions for gasoline or diesel. One of these fuels,
ethanol produced from corn starch produced at a new natural gas facility using
advanced efficient technologies will meet
the 20% reduction threshold compared to the 2005 gasoline baseline
). Other fuels meet the 50% or 60% benchmark.

Iowa harvest 2009 (Bill Whittaker, licenced under GNU free documentation licence)

While the life cycle methodology of the EPA if fairly
comprehensive, a few important caveats were noted in a review of the RFS2 by
Richard Plevin:

    • EPA performs its analysis in a projected 2022
      world, assuming a variety of technology changes. This is similar to accounting
      for today’s emissions from coal power plants as if they had implemented anticipated
      CCS technology. In 2012 all and in 2017 most corn ethanol pathways analyzed by
      the EPA do not meet the 20% GHG reduction requirement, or even produce greater GHG
      emissions than the gasoline baseline.
    •  In the EPA model corn ethanol achieves
      productivity gains without additional use of fertilizer. The peak of corn
      ethanol production is achieved in 2016 – 
      inducing most ILUC – while productivity assumptions refer to 2022 with
      additional 9.4% crop yield. Hence, ILUC are systematically underestimated.
    •  EPA attributes large soil carbon sequestration
      to biodiesel, most likely for increased used of no-till. However, no-till may
      increase N2O emissions (Six et. al). There is uncertainty on this issue, but
      EPA treats net soil carbon sequestration as a fact.
    •  Cellulosic ethanol obtains a low GHG rating by
      co-product credits generated by electricity from biochemical cellulosic
      refineries that displaces the average US grid electricity. Taking the average
      US grid as benchmark is a courageous assumption. More detailed analysis could
      significantly change the life cycle emissions.
    •  An additional supply of biofuels reduces the
      world market price of petroleum, by this increasing its demand. In one study, the
      global petroleum effect is estimated to be around 27% implying that each MJ of
      biofuel replaces 0.73 MJ of petroleum (Stoft, 2009). Hence, biofuels that are
      less then 27% below gasoline baseline could have a net positive global warming
      effect. This effect is acknowledged but not modeled by EPA.

Interested readers should consult the detailed analysis of Richard Plevin (here). Most importantly perhaps is the treatment of uncertainty.
EPA performs a basic  uncertainty
analysis. A number of uncertainties are completely ignored, most importantly
the uncertainty about the fraction of land displaced by biofuels that must be
replaced elsewhere and the assumed production period (Plevin et al., forthcoming). As a result, numbers are presented with relative certainty where
epistemic uncertainty dominates. There are two additional important issues that go beyond
pure carbon accounting. First, there is considerabe interaction between biofuel
and food production. The EPA’s comprehensive analysis treats reduction in food
consumption, e.g. in India and Africa, as a GHG benefit. Without these shift
from food to fuel production, biodiesel from soybean would not meet the
threshold. Second, the economic feasability of large scale cellulosic ethanol
production is unclear. For example, target values for biodiesel have already
been scaled down by more than 90% for 2010. 

In summary, EPAs carbon accounting should be taken with some
care. In particular, today’s corn ethanol may have higher than baseline
gasoline GHG emissions (e.g., Hertel et al., 2010). By focussing on potential
2022 technologies, this emission disbenefit is insufficiently reflected. Some
policy maker pressure the EPA with respect to corn ethanol, arguing that corn
ethanol production decreases energy independence and produces jobs. However, from this perspective, pro-corn ethanol policies should be
designed from the perspective of jobs and energy independence, rather than using
the RSF2 as camouflage.


Hertel, T. W.,
A. Golub, et al. (2010). “Global Land Use and Greenhouse Gas Emissions
Impacts of U.S. Maize Ethanol: Estimating Market-Mediated Responses.”
BioScience 60(3): 223-231.

Plevin, R. J., M. O’Hare, et al. (forthcoming). The
greenhouse gas emissions from market-mediated land use change are uncertain,
but potentially much greater than previously estimated, UC Berkeley.

Six, J., S. M. Ogle, et al. (2004). “The potential to
mitigate global warming with no-tillage management is only realized when
practised in the long term.” Global Change Biology 10(2): 155-160.

Stoft, S. (2009). “The Global Rebound Effect Versus California’s
Low-Carbon Fuel Standard

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One comment to The smallprint of the RFS2 renewable fuel standard

  1. Megan C

    This was a very informative article about the dispute over biofuel on an economic level. I think it’s important for society and companies to understand the importance and relevance of using biodiesel fuel. People looking for more information should definitely check out

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