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numbers are potentially catastrophic.
Recall that a global average conceals
uneven distribution spatially and over
the seasons. W. Michael Haneman at
the University of California, Berkeley,
estimates that summertime temperatures
in the agriculturally rich Central
Valley in California would rise some
2.5 times the global average. Using the
upper bound of Sokolov’s estimate, this
suggests a rise of 33.3 degrees Fahrenheit,
far above catastrophic levels.
Second, we also do not know what,
if any, binding international agreements
on mitigating greenhouse gas emissions
will emerge following the termination
of the Kyoto Protocol obligations in
2012. The aspirational target of capping
temperature rise to 2 degrees Celsius
agreed to at the U.N. climate summit in
Cancun, Mexico, last year is ambitious
but has no legal force, does not reflect
either a scientific or economic consensus,
and—despite local initiatives—is
unlikely to be achieved.
Finally, we do not know whether
productivity gains through agricultural
research and development, and possible
productivity gains from carbon fertilization,
can offset production declines
due to global warming. Declines can
be anticipated even if not predicted
with certainty. They will result from
heat stress on plants, greater scarcity
and seasonal variability of water for
rain-fed and irrigated crops, and the
loss of highly fertile delta and river bottomlands
as sea levels rise and flooding
increases. The challenge will be more
difficult because world population and
income growth are expected to double
food demand during the first half of
this century.
In this fraught context, should promotion
of biofuels be part of a green
energy strategy?
Dubious Subsidies and Mandates
If one considers reducing greenhouse
gas emissions and especially carbon
dioxide as the centerpiece of climate
policy, mandates requiring that biofuels
be blended into transportation fuels
appear superficially attractive. Fossil
fuel takes carbon from under the earth,
where it is harmless, burns it and emits
Year of
Agriculture
atSAIS
that carbon as carbon dioxide to the
atmosphere, where it is harmful. In
contrast, biofuel crops extract carbon
dioxide from the atmosphere during
the growth phase and release carbon
dioxide when they are burned or
decompose. The goal with biofuels is to
recycle carbon, not to add to the active
stock. Let sleeping carbon lie.
This simple idea has been taken up
by many governments with perhaps
more enthusiasm than good sense.
Aside from cost, two major problems
have emerged: indirect increases in
carbon emissions via the conversion
of land to biofuel crops, and pressures
on food production and prices. To
understand these problems, recall that
biofuels come in three main flavors,
depending on their feedstock: ethanol,
made from sugars and starches (corn,
sugarcane); biodiesel from fats and oils
(palm oil, rapeseed, soy); and cellulosic
ethanol from cellulose (woody material,
grasses). The technology for the
first two has been well established for
decades, but except for sugar in Brazil,
the costs are high and large subsidies
are needed. Cellulosic technology is at
an early stage.
Biofuels do not float down from the
heavens like manna. They or their feedstocks
must be cultivated and harvested.
Shifting land from its current status to
biofuel feedstock production can initially
increase carbon emissions from
surface biomass (often by burning vegetation)
and from carbon stored in soils.
For example, clearing marginal land for
corn and preparing the soil will result in
a pulse of carbon emissions today.
Readers inside the Washington
Beltway may have seen the loss of
scrub forest and loblolly pine and the
expansion of soy and corn fields over
the past 20 years as they traversed the
Eastern Shore in their summer trek to
Rehoboth, Delaware. This sort of land
conversion creates a “carbon debt” that
can be repaid over time by the carbonneutral
crop (corn, sugarcane, soy)
displacing the use of fossil fuels. The
debt and timescale can be significant,
however, and lie at the heart of allegations
that biofuels accelerate rather
than moderate global warming.
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