Scientists Expose Devastating False Carbon Accounting for Biofuels
Scientists Expose Devastating False Carbon Accounting for Biofuels
False carbon accounting for biofuels
that ignores emissions in landuse change is a major driver of global natural
habitat destruction, incurring carbon debts that take decades and centuries to
repay; at the same time, the emissions of nitrous oxide from fertilizer use has
been greatly underestimated Dr. Mae-Wan Ho
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Simultaneously as biofuels are blamed for
increasing world hunger and landlessness ( Biofuels and World
Hunger, SiS 49), scientists have been lifting the lid on biofuels’
massive contribution to global warming.
Fatal flaw in bioenergy accounting
A team of thirteen scientists led by
Timothy Searchinger at Princeton University, New Jersey, in the United States,
pointed to a “far-reaching” flaw in carbon emissions accounting for biofuels in
the Kyoto Protocol and in climate legislation. It leaves out CO2
emission from tailpipes and smokestacks when bioenergy is used, and most
seriously of all, it does not count emissions from land use change when biomass
is grown and harvested 
They said that replacing fossil
fuels with bioenergy does not by itself reduce carbon emissions, because the CO2
released by tail pipes and smokestacks is roughly the same per unit of energy
regardless of the source, while emissions from producing and/or refining
biofuels also typically exceed those for petroleum as other critics have
highlighted  (see Biofuels:
Biodevastation, Hunger & False Carbon Credits, SiS 33). The team
maintained that bioenergy reduces greenhouse emission only if the growth and
harvesting of the biomass for energy captures carbon above and beyond
what would be sequestered anyway, and offsets the emissions from energy use.
This additional carbon may result from land management changes that increase
plant uptake or from the use of biomass that would otherwise decompose rapidly.
For example, if unproductive
land supports fast-growing grasses for bioenergy, or if forestry improvements
increase tree growth rates, the additional carbon absorbed offsets emissions
when burned for energy. Energy use of manure or crop and timber residues may
also capture additional carbon. But harvesting existing forests for electricity
adds net carbon to the air. That remains true even if limited harvest rates
leave the carbon stocks of regrowing forests unchanged, because those stocks
would otherwise increase and contribute to the terrestrial carbon sink.
The worst case
is when the bioenergy crops displace forest or grassland, the carbon released
from soils and vegetation, plus lost future sequestration generate huge carbon
debts against the carbon the crops absorb, which could take decades and
hundreds of years to repay (see later).
Unfortunately, the Kyoto
Protocol exempts landuse emissions from bioenergy accounting. It caps the
energy emissions of developed countries; but the protocol applies no limits to
land use or any other emissions from developing countries, and special crediting
rules for “forest management” allow developed countries to cancel out their own
land-use emissions as well. Thus, maintaining the exemption for CO2
emitted by bioenergy use under the protocol wrongly treats bioenergy from all
biomass sources as “carbon neutral”, even if the source involves clearing
forests for electricity in Europe, or converting them to biodiesel crops in Asia.
Massive carbon debts from land use
changes of practically all biofuels
David Tilman and colleagues have earlier
worked out the extent of carbon emissions from landuse changes associated with
They found that
converting rainforests, peatlands, savannas, or grasslands to produce food
crop-based biofuels in Brazil, Southeast Asia, and the United States creates a “biofuel
carbon debt”, through releasing 17 to 420 times more CO2 than the
annual greenhouse gas (GHG) reductions that the biofuels would provide in
displacing fossil fuels, which would take decades to hundreds of years to repay
biofuels made from waste biomass or from biomass grown on degraded and
abandoned agricultural lands planted with perennials incur little or no carbon
debt and can offer immediate and sustained GHG advantage.
Soil and plant biomass are the
two largest biologically active stores of carbon on land that together contain
~2.7 times more carbon than the atmosphere. Converting native habitats to
croplands releases CO2 as the result of burning or decomposition of
organic carbon stored in plant biomass and soils. The amount of CO2
released during the first 50 years of this process is referred to as the
“carbon debt” of land conversion. Over time, biofuels from converted land can
repay this carbon debt if their production and combustion have net GHG emissions
less than the life-cycle emissions of the fossil fuels they displace. For crops
with co-products, the carbon debt can be partitioned into biofuel carbon debt
and co-product carbon debt. These carbon debts are calculated for a range of
biofuel crops grown on different converted ecosystems - from tropical
rainforests, peatland rainforest, wooded cerrado, cerrado and grasslands to
abandoned and marginal lands - in Indonesia, Malaysia, Brazil and the US (see Figure 1).
Figure 1 Carbon debt of biofuels from different land conversions around the world
The biofuel carbon debt varies
from 17 years for sugarcane ethanol grown on land converted from wooded cerrado,
to 423 years for palm biodiesel on land converted from peatland rainforest.
Even corn ethanol grown on abandoned agricultural land incurs a debt of 48
years. The only debt-free options are ethanol made from biomass harvested from
natural prairies regenerated with native perennials from abandoned croplands
and marginal croplands in the US.
The team commented that their
estimates are conservative because they have only counted CO2
generated from decaying material of former habitats for only 50 years. The
results indicate that biofuels remain net carbon emitters long after
That’s not all that counts
oxide emissions cancel out carbon savings
N2O, a greenhouse gas with a 100-yr average global warming potential
(GWP) of 296 compared with an equal amount of CO2, is emitted as a
by-product of the nitrogen fertilizers used for agriculture, including
agri-biofuels. It turns out that the amounts of N2O emitted is
considerable; in some cases sufficient to more than cancel out the biofuels’
savings in carbon emissions, and contribute to global warming instead .
An international team led by Paul Crutzen at Max Planck Institute
for Chemistry, Mainz, Germany, showed that when the extra N2O
emissions from biofuels production is calculated in CO2 equivalent,
and compared with the CO2 emissions “saved” in burning the biomass
grown instead of fossil fuels, common agri-biofuel crops such rapeseed (for
biodiesel) and corn (for ethanol), offer little or no net saving, thereby
contributing as much, or more, to global warming than simply burning fossil
The researchers took a global approach to work out the amount of N2O
generated by N fertilization in industrial agriculture. By comparing (1) the
pre-industrial N2O concentration, assumed to be the natural source,
with (2) the current concentration plus the atmospheric growth rate, the
anthropogenic source was obtained by subtracting (1) from (2), correcting for
an amount due to 30 percent global deforestation since preindustrial times.
This gave an anthropogenic source of 5.6-6.5 Tg N2O-N per year.
To obtain the agricultural contribution, an estimated industrial
source of 0.7 to 1.3 Tg N2O-N per year was subtracted, giving a
range of 4.3-5.8 Tg N2O-N per year. This is 3.8 to 5.1 percent of
the anthropogenic input in N fertilizers of 114 Tg N2O-N per year
for the early 1990s, derived from 100 Tg of N fixed by the Haber-Bosch process
plus 24.2 g of N fixed due to fossil fuel combustion, plus 3.5 Tg of excess
biological N fixation between current and pre-industrial levels, and minus 14
Tg of the Haber-Bosch N not used as fertilizer.
This global ratio of 3.8 to 5.1 percent N2O will be the
same in agri-biofuel production systems; and is much larger than the 1 percent
value typically assumed, which was recommended by the Intergovernmental Panel
on Climate Change.
When compared in CO2 equivalents with the carbon dioxide
emissions “saved” simply by counting the carbon contained in the biomass
harvested, a relative global warming potential of the biofuel, due to N2O
alone, can be readily calculated (see Table 1).
Relative warming of crops and nitrogen content
gN/kg dry matter
Type of fuel produced
In Table 1, the
N2O emissions are calculated taking into account the nitrogen fixed
in the plant, thus, rapeseed with the highest concentration of N, will emit
proportionately more than maize and sugarcane. The N use efficiency (efficiency
with which nitrogen is taken up and converted into grain or biomass) is assumed
to be 0.4. The current average N use efficiency of cereals is 0.33 .
simply growing the crop is sufficient to cancel out a substantial part of the
potential saving, even before any processing to turn the crop into biofuels;
and this does not include fossil fuels used in making and transporting
fertilizers and pesticides for the crop. When you add the fossil fuel energy
required for the many stages of processing to biofuels, etc., it is clear that
not a single biofuel actually saves any carbon emissions, even if we disregard
the huge amounts of extra emissions caused by deforestation and destruction of
natural ecosystems to make place for biofuel plantations.
Linda Graff Comment left 1st December 2010 20:08:16 TO WHOM IT CONCERNS,
THEY ARE LOOKING FOR TAX CUTS IN WASHINGTON WELL I KNOW THREE THINGS THAT MAY HELP THEM BALANCE THE BUDGET AND HELP SAVE OUR PLANET. LET'S CUT OUT GOVERNMENT FUNDING BOTH STATE AND FEDERAL WHEITHER THEY BE STIMULUS, LOANS OR GRANTS MONEY USING OUR TAX MONEY FOR ALL BIOMASS PLANTS (THIS WOULD INCLUDE WOOD BURNING, NATURAL GAS BURNING WITH COAL, ENERGY MAKING AND ALL FUELS TO MAKE ETHANOL), BCAP PROGRAMS (THAT SUPPORT BIOMASS PLANTS FEEDSTOCK) OUR FEEDSTOCK IS BEING DEPLEATED AND WE WILL BE FACING WORLD HUNGER. THEY RUINING OUR PLANET, DISTROYING OUR WAY OF LIFE, CAUSING ILLNESSES AND PREMATURE DEATH THROUGHOUT OUR COUNTRY AND OVERSEA AND DEVASTATING OUR FOREST. THIS ALL NEEDS TO COME TO AN IMMEDIATE STOP WRITE OR CALL YOUR SENATORS AND GOVENORS OF ALL OF OUR STATES WE DON'T WANT TO BE POISONED WITH OUR OWN TAX MONEY THAT WE WORK HARD TO EARN WE WANT ALL OF THE BIOMASS TO BE CUT FROM THE BUDGET ACROSS THE COUNTRY NOW. LET EVERYONE YOU MEET KNOW THAT WE NEED TO STAND UP FOR OURSELVES AND THE CHILDREN TO WHOM WILL INHERIT THE EARTH ONCE WE HAVE EXPIRED. WE'D LIKE TO RAISE OUR CHILDREN NOT BURY THEM BECAUSE OF THE POLLUTION. THIS IS AN AMERICAN BOONDOGGLE AND NEEDS TO BE STOPPED.
Bioblogger Comment left 1st December 2010 20:08:54 The way you present it, it sounds like biofuel production is an evil alternative to the status quo. It is hard to imagine any alternative worse than the oil paradigm we now have from an energy security (diplomatic coercion, wars), environmental sustainability (peak oil, tar sands, oil spills), or economic (transfer of wealth to tyrannical nations) standpoint. The truth is that oil exploration is going to more remote areas to uncover reserves that are riskier to extract and dirtier to refine. Biofuels aren't perfect but they are also predominantly carbon neutral. Now that we focus on the challenge of meeting new low carbon standards (which oil is strangely unconstrained to) we are making significant progress. Biofuels are getting cleaner all the time (and cheaper, and more sustainable). You will NEVER be able to say that about oil and oil derivatives. Knocking biofuels indiscriminately perpetuates the oil paradigm - that's what I detest most about the highly speculative indirect land use argument (which, again, oil is strangely absolved of).
Louise Naude Comment left 1st December 2010 20:08:56 Hello
Please may I use information in your report 'Scientists Expose Devastating False Carbon Accounting for Biofuels', in presenting the case for renewable low-carbon energy options in the energy supply mix in southern Africa? I will of course properly acknowledge the source.
mae-wan ho Comment left 2nd December 2010 13:01:05 Hi Louis, yes please put the information in the report to good use!
Bioblogger, there are numerous really green sustainable options for renewable energies, do read our Green Energies report. The only sustainable 'biofuels' are biogas methane from biological wastes such as food wastes and livestock manure, as well as crop wastes that would otherwise decay relatively rapidly. We are presenting scientific and other well-documented evidence, and not in the business of demonising anything. There is much ignorance around, including wilful ignore, that's what we are targetting.
Robert Palgrave Comment left 20th December 2010 22:10:27 Bioblogger - so far the use of biofuels has not stopped exploration for new oil and unconventional oil. Nor for Coal. It never will.
All that biofuels are doing is delaying by a few years (at most) when the oil runs out. There simply isn't enough land to feed a growing population and to grow enough energy to replace what we get from fossil fuels.
Read about soil depletion, desertification, fertiliser shortages, competition for water resources. Further pressure on agriculture to produce energy is just nonsense.
And biofuels make no meaningful difference at all to climate change. The proponents make claims like a 50% saving in GHG emissions compared with a fossil fuel. But if you can't grow enough biofuel to replace a good proportion of fossil fuel, that 50% saving translates into a tiny contribution to overall emissions reduction.
Here in the UK where I work, we currently have around 3.5% blend biodiesel and bioethanol in road transport. Assuming the official GHG saving figure of 50% is correct - I don't since they don't allow for indirect land use change - then the actual contribution from biofuels is a 1.75% reduction in emissions. We can and should get that and much much more from enforcing speed limits, improving public transport, teaching eco driving and mandating more efficient vehicles. Or even travelling less. What a crazy idea that would be...
But in order to achieve that tiny 1.75% GHG emissions saving we go to other parts of the world to grab land, force up food prices and destroy pristine habitats for endangered species.
This is one of the worst responses to climate change - inflicting more pain on other parts of the world while we continue business-as-usual consumption.
Yes cut oil, gas and coal consumption, but let's not pretend that biofuels will do anything significant to help with that.
vaishali ghosh Comment left 1st March 2011 12:12:51 hello ...i am doing a research on the future posibilities of biofuels so please can i use the information..i will reference it properly..