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
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.
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.
David Tilman and colleagues have earlier worked out the extent of carbon emissions from landuse changes associated with different biofuels.
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 .
In contrast, 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 conversion.
That’s not all that counts against biofuels
Nitrous oxide, 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 fuels.
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).
Table 1 Relative warming of crops and nitrogen content
|Crop||gN/kg dry matter||Relative warming*||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 .
Thus, 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.
Article first published 29/11/10
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Linda Graff Comment left 2nd December 2010 07:07:16
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. SINCERELY, LINDA
Bioblogger Comment left 2nd December 2010 07:07:54
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 2nd December 2010 07:07:56
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. Regards
mae-wan ho Comment left 3rd December 2010 00:12:05
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 21st December 2010 09:09:27
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 23:11:51
hello ...i am doing a research on the future posibilities of biofuels so please can i use the information..i will reference it properly..