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Study Concludes That an Aggressive Global Cellulosic Biofuels Program Could Have Unintended Consequences

Carbon balance associated with all land use change and that directly associated with biofuels over the period 2000-2050 as simulated by the deforestation (a) and intensification (b) scenarios. Melillo et al. (2009) Click to enlarge.

An aggressive global cellulosic biofuels program could contribute substantially to future global-scale energy needs, but could have significant unintended environmental consequences, according to a recent report by the MIT Joint Program on the Science and Policy of Global Change.

Using simulation modeling, the researchers explored two scenarios for cellulosic biofuels production: the clearing of large swathes of natural forest, or the intensification of agricultural operations worldwide. The greenhouse gas implications of land-use conversion differ substantially between the two scenarios, but in both, numerous biodiversity hotspots suffer from serious habitat loss, the study found.

Elements and parameters of the study included:

  • Cellulosic biofuels contribute 141 EJ yr-1 in the deforestation scenario and 128 EJ yr-1 in the intensification scenario—levels of energy supply large enough to meet at least 10% of the projected global energy requirement in 2050.

  • A computable general equilibrium (CGE) model of the world economy, the MIT Emissions Predictions and Policy Analysis model, was coupled with a process-based terrestrial biogeochemistry model, the Terrestrial Ecosystem Model to generate global land-use scenarios and to explore some of the environmental consequences of an aggressive global cellulosic biofuels program over the first half of the 21st century.

  • The biofuels scenarios are linked to a global climate policy to control greenhouse gas emissions from industrial and fossil fuel sources that would, absent feedbacks from land-use change, stabilize the atmosphere’s CO2 concentration at 550 ppmv.

  • The climate policy makes the use of fossil fuels more expensive and speeds up the introduction of biofuels, and ultimately increases the size of the biofuel industry, with additional effects on land use, land prices, and food and forestry production and prices.

At the beginning of the 21st century, about 31.5% of the total earth land area of 133 million km2 was in agriculture; 12.1% (16.1 million km2) in crops and 19.4% (25.8 million km2) in pasture, with no land devoted to cellulosic biofuels.

In the deforestation scenario, the researchers estimate that by 2050, the land area in cellulosic biofuels will grow to 14.8 million km2, which is 11.1% of the earth’s total land area. They also project that the area of croplands will grow to about 20.0 million km2 and the area in pasture will shrink slightly to 24.5 million km2. The growth of croplands by 3.9 million km2 in the deforestation scenario is in response to increased food demands globally.

In the intensification scenario, they estimate that the land area in cellulosic biofuels will grow to 13.9 million km2, and that by mid-century croplands area will grow by about 2 million km2 to almost 18 million km2 (Table 1), while pasture areas will shrink by almost 8 million km2 to just under 18 million km2. Despite the loss of pastures, the intensification of land use allows nearly as much production of food as in the deforestation scenario.

Carbon debt. The combination of energy production from biofuels together with agriculture expansion results in an initial carbon loss from land ecosystems, referred to as a carbon debt.

  • The deforestation scenario results in a direct carbon debt of 21 Pg C by 2050, with much of this carbon coming from areas once covered by tropical forests in Brazil and in Southeast Asia. The indirect carbon debt could be as large as 82 Pg C, giving a total carbon debt of 21-103 Pg C. This carbon debt is equal to 8-37% of the cumulative fossil fuel emissions for the period 2000-2050 in the climate policy imposed here to limit these emissions.

    Even considering the best-case, where total carbon debt is 21 Pg C, we estimate that the carbon debt associated with biofuels establishment in the deforestation scenario will last until the middle of the 21st century; that is, no net greenhouse gas reductions will be realized from biofuels until about 2045. Moving towards the worst-case, where total carbon debt is 103 Pg C, it becomes clear that these large emissions from land-use change would substantially undermine the efforts to stabilize climate.

    —Melillo et al. (2009)
  • The results of the intensification scenario differ dramatically. Energy production from biofuels results in a direct carbon credit of 4 Pg C by 2050. The small carbon gains in many of the areas devoted to bioenergy production are mostly in soils in response to nitrogen fertilization, which stimulates plant growth and carbon inputs to soil. However, the indirect carbon debt is still potentially as large as 38 Pg C, giving a total carbon debt of -4 to 34 Pg C over the first half of the 21st century.

    While the upper bound on the total carbon debt is still substantial, it is much less than the 103 Pg C in the deforestation scenario. This upperbound debt of 34 Pg C in the intensification scenario is nearly repaid by the middle of the 21st century.

    —Melillo et al. (2009)

Impacts on Biodiversity. Both the deforestation and intensification scenarios project that by the middle of the 21st century, many regions will substantially increase the fraction of land they devote to meeting the combined demands for food and biofuels at the expense of natural ecosystems including a number of biodiversity “hotspots” in the sub-tropics and tropics.

The researchers project that sub-Saharan Africa will be the region devoting the largest area to biofuels production during 2050, followed by Latin America.

In both scenarios in our analysis, we project the loss of large areas of forest and savanna habitats due to the direct and indirect effects of implementing a large-scale biofuels program, although the areas lost are smaller in the intensification scenario. These losses have the potential to put thousands of endemic plant and animal species at risk across the globe, especially in the sub-tropical and tropical regions.

—Melillo et al. (2009)

The study did not account for all of the unintended consequences of intensification that are likely to occur—such as the greater use of agricultural chemicals, increased confined livestock production and overgrazing—and these additional effects are likely to differ between the two scenarios, the researchers wrote.

Existing and proposed emissions trading systems are, in principle, a superior approach for controlling greenhouse gases, but also fail to fully protect or provide incentive to increase carbon stocks in vegetation and soils. These poorly designed policies put carbon stocks in vegetation and soils at risk and in doing so potentially undermine the goal of stabilizing the atmospheric concentration of carbon dioxide at the desired target.

Even though we see the potential for considerable intensification of production on land, and therefore a less than one-for-one conversion of land to meet biofuels demands, the risks of converting land in biodiversity hotspots are substantial. With the loss of biodiversity comes a cascade of environmental consequences including the loss of critical ecosystems services. It is clear that we must think holistically and proceed cautiously as we develop policies to use plant-based biofuels to combat global warming.

—Melillo et al. (2009)




Well No Sh%^ Scherlock

We currently have a net add of 210,000 mouths per day. That is equvilent to the population of California times 2, every year. By the middle of the century we will have 11+ billion people on the planet. Land use is going to skyrocket no matter what we do.



Actually, 11Billion is higher than even the max projection according to the UN. (

The most realistic estimate is that the population growth slows down as resources become more expensive (sort of like what we're currently seeing in Europe and North America, see figures 2 and 3 of that same UN report).

Furthermore, I think any major new industry has unintended consequences as has been the case for the last 10,000 years. I do agree with joseph that this article is a bit unnecessary. It sensationalizes the obvious. It would be like me writing an article that says, "Report concludes that the economy causes pollution." Thanks for the groundbreaking journalism.


What we are seeing in Europe is a disaster. The shrinking indigenous population is being overwhelmed by immigrants from North Africa and Turkey. These new arrivals have a totally foreign culture to the European host countries. This is an explosive mix. It would not be surprising to see civil war errupt in the not too distant future.


I'll bet there is a lot of oil company money involved in this study. There have been some real studies done that completely contradict evey claim made here. One study calculated that using waste water plant effluent and cattails alone we could replace all the gas we currently use in this country with ethanol and only use 1.46% of the current agricultural land.

Also everything that is produced during fermentation and distillation of ethanol is a useful product that could be used in place of petroleum fertilizers or as animal feed(much higher quality than the corn or grain is) or to raise high protein mushrooms or to ferment into methane to use as fuel for the distillery, etc,etc...

Archer Daniels Midland is doing some very interesting work using the grains and stillage left from ethanol production to produce fish(farms), grow algea to produce oxygen for the fish and absorb CO2 produced by the fish. Just 5 acres of fish ponds produces enough nitrogen to fertilize over 100 acres of crops. They use the CO2 procuced to rasie the CO2 levels in greenhouses and double and triple the out put of food crops.

If done properly in a permaculture manner any land used would become more fertile using what is left after disillation of ethanol. There are energy crops that grow wild and can be sustainably harvested to produce billions of gallons of ethanol with no planting, fertilizing or irrigating. There are energy crops that grow in arid lands that will not support food crops.



1.46% of current agricultural land to cover 100% of current gas buy ethanol ?

Are you kiding or are you misinformed ?

Or maybe you have a problem with numbers...


I believe the UN projection is flawed. They seem to assert that scarcity will dramatically slow the birth rate, when everything real world says the opposite. The most poor areas have had the most growth in population. We are currently in a global recession, track the birth rates in the industrialized countries over the next 18 months. Millions are being laid off, guess what humans do for entertainment when they can't afford to go out.

Figure 2 only tells you that the # of children per female is going down. Even though the % is getting smaller the # of people is getting bigger. Ex:

3,000,000,000 x .025 = 75,000,000 add
6,500,000,000 x .018 = 117,000,000 add

Perpetuality kicked in at about 4B, 11B by 2050 might just be a little low, barring a major event.


Gee Whiz.

Another hallowed eco-loon idea, cellulosic fuel, turns out to have run into the Law of Unintended Consequences.

What a surprise. Has there been ANY eco-Loon idea that turned out to work without unexpected side effects? Pesticides? Acid-rain? Halogens? Ozone holes? Windmills? Corn Ethanol? Nuclear energy? Taxes? More Taxes? and even more Taxes?

Might it be that you have to actually have some Scientific training, instead of a loud Demagogic mouth, and a closed ideological Marxist mind. Despite the same attempts in some 68 countries over 150 years, has a perfect record of failing every single time ?

Some of the assumptions in this study are simply patently wrong. They are based on wishful fund raising conventional wisdom, not reality. Satellite measurement show that tropical forests are actually re-foresting, even faster than they are being cut down. Despite the conventional wailing, and fund raising appeals for the disappearing Amazon rain forest.

Another assumption is that it will happen in tropic impoverished areas. If it happens at all, Agriculture using an attempt to harvest fast growing cellulosic materials will more than likely happen in advanced societies with advanced agricultural systems. Just look at where the cellulosic attempts are being made. It is in the temperate zone advanced countries. It is not in impoverished Marxist Zimbabwe, or Venezuela.

Another erroneous assumption is that the demand for hydrocarbon fuels will continue to mount. That is typical of eco-loon fearful, we-are-doomed, thinking. Realistically, we are on the verge of a great decrease in the demand for fossil fuels over the next few decades.

Just read these GCC pages to see the last expanding market for fossil fuels wilt, before your eyes, daily. Do you really doubt that the demand per vehicle is not going to plunge? Every Volt EREV will use anywhere from 1/12th to 1/16th the fossil than a current vehicle. Any PHEV will consume 1/5 to 1/7th the fossil in drayage vehicles. Even conventional vehicles will double their mileage in the next decade due to simple ICE efficiency improvements, or HEV additions.


You obviously have no idea what kind of land can be used for cattails or how much ethanol can be produced for the large starchy bulb at the bottom. The study suggested using just five foot wide paths on road sides that are normally just covered with grass and mowed and sprayed with chemicals.


"I believe the UN projection is flawed."

Ha! Understatement of the century!!

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