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The Pan American Congress
on Plants and BioEnergy convened in Mérida, Mexico, June 22 to
25, 2008. The program was organized by Steve Long (University of Illinois)
and Nick Carpita (Purdue University), along with co-organizers Marcos
Buckeridge (University of São Paulo, Brazil) and Federico Sánchez
(Universidad Nacional Autónoma de México). More than 200
scientists from over a dozen nations around the world gathered to discuss
key issues surrounding the development of biofuel feedstocks and to report
on their research in this area.
There have been a
multitude of meetings on biofuels and bioenergy over the past 18 months.
This one stood out for its focus on plant biology and explored how recent
advances in the field are being or could be applied to achieve more sustainable
bioenergy systems. This article highlights just a few of the issues presented
and discussed.
Drivers and Barriers
to the Development of Biofuels
In his opening lecture,
Steve Long outlined major driving forces for and barriers to the development
of biofuels. Major drivers include increasing fuel costs and the desire
for national energy security as world petroleum output declines, as well
as the need to develop sustainable fuel sources and mitigate global climate
change. Major barriers to the development of biofuels include the following:
- the low efficiency
of energy conversion via plants
- the need to ensure
mitigation of CO2 emissions
- the notion that
development of biofuels competes with land for food
- the need to translate
model plant advances into crops
- farmer, landowner,
and system recalcitrance.
Adequately dealing
with all of these issues will require a strong commitment and collaborative
effort involving not only plant scientists and agronomists, but also economists,
environmentalists, whole systems engineers, farmers, and politicians.
Long noted that the
maximum conversion efficiency of plants is 4% to 6% but that the maximum
achieved with food crops is 1% to 2%, and the most efficient biofuel plants
are still far from the maximum. Therefore, there is huge potential for
improving this trait with many of the crops under development.
Long leads the Energy
Biosciences Institute at the University of Illinois, where economists,
ecologists, agronomists, and plant scientists are integrated under one
roof to focus on issues of feedstock development; fuel synthesis; and
related environmental, economic, and political issues. The development
of perennial grasses such as Miscanthus is one focus of their program.
Brazil: A Model
for Biofuels Development and Implementation
Carlos Henrique Brito
Cruz discussed the history of bioenergy in Brazil and strategies for the
future. Brito Cruz is scientific director of the Foundation for the Support
of Research in the State of São Paulo (FAPESP). Although now a
close second to the United States in overall production of ethanol (with
China a distant third), Brazil is clearly the world leader in the use
of energy from renewable sources, and ethanol from sugarcane has played
a major role.
Brazil is home to
180 million people and ranks eighth in the world in GNP, and remarkably,
44% of energy use nationwide comes from renewable resources. A full 15%
of the country’s energy comes from sugarcane (in the form of ethanol
or electrical energy from burning the stalks or bagasse, the biomass remaining
after ethanol extraction). The remaining renewable resources are principally
hydroelectric power and wood.
Sugarcane, originally
from Asia, has been grown in Brazil since 1532. The government mandated
the addition of ethanol to fuel as early as 1929, and today gasoline in
Brazil is ~25% ethanol. Flex-fuel vehicles were introduced in 2003, and
by 2006 ~90% of new vehicles sold were flex-fuel capable. Interestingly,
government subsidies for ethanol ended in 2000, yet production has continued
to rise dramatically. The cost of ethanol has been decreasing, and it
now costs less than petroleum.
Sugarcane is among
the most efficient crops so far developed for the production of ethanol,
compared to other feedstocks in use worldwide, such as maize and sugar
beet. Breeding programs have been in place for years, and the number of
sugarcane varieties used for ethanol production has expanded. Accordingly,
since the 1970s, productivity in terms of tons per hectare and liters
of ethanol per ton dry weight has risen dramatically.
In terms of land use,
sugarcane is grown on 7.8 million hectares in Brazil, half of which is
for ethanol production and half for food, and therefore ethanol production
uses ~1% of the arable land in the country. Meanwhile, pastureland represents
48% of the arable land, and much of this pastureland could be converted
to biofuel production, as grazing traditionally has not been done on an
efficient basis. Brito Cruz noted that Brazil does not grow sugarcane
in the Amazon basin and has no plans to expand production in this region.
Historically, the
highest productivity area for sugarcane has been in the southeast (São
Paulo state), and the main expansion area is in the west-central region
of the country, more than 2,000 km distant from the Amazon. FAPESP is
funded by tax revenues and has active programs directed at sugarcane improvement
(molecular biology and breeding directed toward increasing yields and
drought resistance) and expansion into underutilized pasture land.
Food Versus Fuel
Many of the speakers
addressed the food versus fuel debate. There are concerns in the public
sector and political arenas internationally that there may not be enough
land to support the cultivation of biofuel feedstocks to provide a significant
percentage of fuel needs and that biofuel crops are in large part responsible
for rising food costs and declining grain stocks worldwide. A number of
speakers noted that these fears are not borne out by statistics. The consensus
was that there are many reasons for declining grain stocks and rising
food costs, and biofuels have played only a minor role.
For example, Long
described the “Billion Ton Vision,” a 2005 study by the U.S.
Department of Energy and the USDA that concluded that 1.3 billion dry
tons of biomass for energy could be produced in the United States with
modest changes in land use. Miscanthus could be an important part
of this equation in the future, as it is highly productive, can be grown
on marginal land, and has many other attributes of the “ideal”
bioenergy crop.
Long further noted
that the United States has large land reserves that could be used for
biofuels without affecting food production, and land reserves also exist
in Brazil, Ukraine, and other countries. Brazil provides another case
in point. As noted above, sugarcane is grown on ~1% of the arable land
in Brazil, yet ethanol from sugarcane supplies 15% of the country’s
energy, and 15% to 20% of the ethanol produced is exported.
Nevertheless, it was
acknowledged that the scientific community must address public fears about
the food versus fuel debate. A number of presenters voiced the opinion
that the industry should move away from food sources for fuel and toward
nonfood cellulosic crops as soon as possible, and this would likely require
government subsidies at the outset. One exception to this might be sugarcane,
which has many positive qualities as a biofuel crop and is unlikely to
be replaced as the major biofuel in Brazil anytime soon.
Emerging Biofuel
Crops
Many sessions and
posters were devoted to research being carried out on numerous emerging
biofuel crops as feedstocks for biodiesel (seed oil crops), ethanol (from
sugar and/or lignocellulosic crops), lignocellulosics for direct conversion
to fuel, and hydrogen. Among perennial grasses, Miscanthus is being
intensively investigated as a future biofuel crop in many parts of the
world, especially in the United States and Europe. Other perennial grasses
being studied include sweet sorghum, napier grass, and the giant reed
Arundo donax.
Lászlo Márton
(University of South Carolina) reported on the many positive characteristics
of A. donax as a biofuel crop. It is one of the most photosynthetically
efficient C3 perennials, with an exceptionally high biomass yield, but
it also poses a weed risk in riparian systems and is already considered
an invasive species in some areas of the world. Avoiding crops that carry
a high risk of becoming invasive species is an important consideration,
as many of the qualities that make a plant an ideal biofuel crop are also
qualities of invasive weeds. Márton reported that if used in appropriate
areas, A. donax could nonetheless become an important biomass and
remediation crop.
Larry Smart (State
University of New York) spoke on the development of shrub willow as a
biofuels crop. It can be burned directly in wood-fired plants, cofired
with coal in existing power plants, gasified to generate heat and power,
or pretreated and fermented to make ethanol. Smart reported that biofuels
from crops such as shrub willow could make a significant contribution
to localized production of energy in New York State and the northeastern
United States, and there are at least five emerging commercial companies
in the region gearing up to use willow and poplar.
Among oil crops, Jatropha
curcas, a perennial Euphorb, is receiving a lot of attention. The
seeds produce large quantities of oil that can be processed to high-quality
biodiesel, and the plant is highly drought resistant, so it can easily
be grown on marginal (non-food-producing) land. Although widely grown
in parts of Asia and Africa, where it is used as a natural fence, Jatropha
is native to Central America. Therefore, it is of great interest to investigate
the native species of Jatropha in this region. Among other reports,
Maricela Rodríguez Acosta and colleagues from Benemérita
Universidad Autónoma de Puebla in Mexico presented data on their
efforts to characterize the ecology, distribution, growth, and seed oil
yield of several species of Jatropha found in Mexico.
Another crop that
appears to hold much promise as a biodiesel and hydrogen feedstock is
halophytic green algae. As reported by John Cushman (University of Nevada,
Reno), unicellular green algae such as Dunaliella are an ideal
biofuel crop for the western United States and other arid regions, as
they can be grown on marginal land with saline water, may be more productive
than terrestrial oilseed crops, and provide a large potential for sequestration
of CO2.
Concluding Remarks
Nina Federoff (science
and technology adviser to the U.S. secretary of state) spoke eloquently
on problems related to energy security facing the world. She noted that
only rarely do reports in the media connect all of the attendant issues
of food, energy, water, the environment, and socioeconomics (the human
dimension). Her words sounded a call to the plant science community that
what is needed is a 21st-century green revolution that addresses all of
these issues at the local level.
Neal Gutterson (Mendel
Biotechnology) ended his presentation on Mendel Biotechnology’s focus
on Miscanthus with the quotation from Thomas Jefferson that “the
greatest service which can be rendered any country is to add a useful
plant to its culture.” In light of the food versus fuel debate, it
is interesting to note that the full quotation from Jefferson ends with
the words “especially a breadgrain.” Of course, Jefferson was
writing in 1787, before the advent of the petroleum age.
A mere 220 years later,
there are increasing signs that we are already at the beginning of the
end of the age of petroleum. Most of the world’s major oil fields
are experiencing decreasing outputs, and we are searching for renewable,
climate-friendly fuels. Jefferson’s quotation updated for the 21st
century might well be amended to end with the words “especially a
biofuel crop.” As Federoff noted, there is a growing urgency to provide
food, energy, and water for a growing population while protecting the
environment, mitigating global climate change, and preserving biodiversity.
Reports from this conference suggest that the plant science community
has the potential and is willing and able to help provide the answers.
Nancy Eckardt
News and Reviews Editor, The Plant Cell
neckardt@aspb.org
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