Updated 5/1/2011

Biofuels

Much has been said elsewhere on this alternative, but the limitations of biofuels, both from a climate and from an energy perspective, are not well appreciated by the general public:

(A) the carbon debt from cultivation of new land will often take a century or more to repay;
(B) after a decade of efforts (and ~$1.5B), no cellulosic processes have come close to being competitive, and the prospects are recently looking bleaker, not better;
(C) rapid inflation in food prices will continue, caused by biofuel-driven crop switching;
(D) under 29% of the carbon in cellulosic feedstocks ends up in the ethanol that will be produced from them;
(E) the size of the dead zones in the oceans around the world (mostly caused by fertilizer runoff and CO₂-induced acidification) has (for a number of years) been increasing annually by an area the size of Texas, and
(F) waste feedstocks for cellulosic processes are limited, so their prices too will skyrocket if cellulosic ethanol begins to come online.
(G) A recent study says local biomass in the U.S. Northeast could sustainably replace only 1.5% of their fossil fuel usage with bio-energy.

When new land is tilled, much of the carbon that has been sequestered in the soil for many centuries is released over the next few years. This “carbon debt” can take more than a century for the biofuels to repay. Virtually all recent papers on biofuels projections and analysis acknowledge this problem, especially its effect on indirect land-use change, but then proceed to explicitly ignore it in their “Life Cycle Analysis” (LCA) because, as they usually put it, “the science is unsettled”. A more accurate explanation might be that if they included it (and the loss of biodiversity), almost all the biofuels options would look worse than conventional gasoline.

We realize the above strong statements may cause many readers to stop reading at this point. We hope you will hang with us here. (We read all the good biofuels papers we find, and we try very hard to look objectively at the complete picture.) Later, we introduce the concept of “Direct Land-Use Change in Un-tilled Soils”, which has been completely ignored in all studies we have seen on use of forest residues, switchgrass, and other feedstocks that do not involve tilling of the soil.

The EU-sponsored Teeb report (Economics of Ecosystems and Biodiversity), headed by Deutsche Bank economist Pavan Sukhdev, has concluded that the global annual economic cost of the loss of forests and biodiversity has been exceeding $2 trillion for several years, and it is steadily increasing. They believe it is greater than the banking crisis, year after year.

A recent article “Global Economy is World’s Biggest Ponzi Scheme” by Lester R. Brown that appeared in EVWorld http://evworld.com/article.cfm?storyid=1761 , puts it best: . “In a 2002 study published by the U.S. National Academy of Sciences, a team of scientists concluded that humanity’s collective demands first surpassed the earth’s regenerative capacity around 1980.... As of mid-2009, nearly all the world’s major aquifers were being overpumped.... A similar situation exists with the melting of mountain glaciers.... The reality is that an estimated 400 million people are today being fed by overpumping... This water-based food bubble is about to burst... Three fourths of oceanic fisheries are now being fished at or beyond capacity or are recovering from overexploitation.... If we continue with business as usual—with overpumping, overgrazing, overplowing, overfishing, and overloading the atmosphere with carbon dioxide—how long will it be before the Ponzi economy unravels and collapses?”

Conventional Biofuels.
The awakening against biofuels is just beginning, but a sea change will occur within a year as inflation in food prices resumes. The UN Secretary General has called biofuels “A Crime Against Humanity”, as 960 million people are going hungry today. The rapid growth in biofuels will soon end, but decline is unlikely because of institutional forces and vested interests. At this point, even a decline in biofuels would not end the hyperinflation in agricultural commodities, as other factors (especially the increased meat in the diets of the hundreds of millions who have become more wealthy in China) are also major factors. Hence, inflation in agricultural commodities will continue, though certainly at a much lower rate than the 60% annual increase seen in 2005-2008.

Global biofuel usage in 2006 was approximately 38 MMT, or about 1.5% of the total transportation fuel energy. The gross biofuel contribution in 2008 was about 2%, but the net contribution was only about 0.5%, as the extra fossil fuel consumption for the production of most biofuels is 70-85% of their gross fuel energy. Brazilian sugarcane ethanol by some measures has appeared to be much better, but several recent peer-reviewed scientific studies have concluded that because of the rainforest destruction it causes, it too is worse for the planet than burning fossil fuels.

Annual biofuel production growth rates of 20% have been projected by industry officials, but we doubt its growth rate exceeds 10% within another year. We do not expect to see more than a 5% gross contribution from biofuels to global transportation-fuel energy 20 years from now – even with advanced cellulosic processes from waste. Wood pellets and other biomass usage (in power plants) may be several times larger (in energy content) than that of liquid biofuels. Such modest biofuels contributions offer little hope for addressing either global warming or the fuel needs of a growing world economy.

Cellulosic Reality.
The relevant chemistry is pretty simple for fermentation of sugar. Ideally, half of the carbon atoms from C₆H₁₂O₆ go into the ethanol, and half go into CO₂. In practice, a lot of energy is needed for the milling, distillation, and other processes, so the amount of carbon released as CO₂ from the processing plant is over 2.5 times the amount that ends up in the ethanol. The amount of carbon that ends up in the solid byproducts (mostly for animal feed) is more than half as much as goes into the ethanol. There’ll be less byproduct available from cellulosic ethanol production, as much more process heat is needed.

The processes are much more complex with cellulosic feedstocks. Under 29% of the carbon in the cellulosic feedstock that goes into the processing plant ends up in the cellulosic ethanol. Most of the rest is emitted from the ethanol plant as CO₂, though quite a bit ends up in co-products. How can it be that bad? A metric ton of high-grade dry cellulosic feedstock (containing 540 kg of carbon) may eventually produce ~100 gallons (300 kg) of ethanol, which is 52% C. The 300 kg of ethanol contains 156 kg of carbon, which is 29% of 540 kg. The above assumes that no additional fuels are needed for the processing, though no plants are yet operating at this level of performance. The ethanol produced per ton from the first cellulosic ethanol plants is expected to be only 65% of what was optimistically assumed above.

A quick response to the above might be that it doesn’t matter because all that carbon is bio-carbon and it will get recycled. One overlooked problem is that before the feedstock was harvested, the carbon in it was sequestered, and it might have remained sequestered for many decades. Another is that there is often even more carbon released from change in land use.

About $1.5B has been invested in cellulosic ethanol over the past decade. Still, the current cost of producing cellulosic ethanol is about $2/gal plus the cost of the feedstock. Later, we show why feedstock costs are likely to add over $4/gal to the cost of cellulosic ethanol in many areas by 2015. The EIA has recently downgraded their projections of the expected contribution of cellulosic ethanol in 2025 to about 2% of total liquid fuels. The following sections show why that is still probably very optimistic.

Land-Use Change in Tilled Soils.
Trees, shrubs, and grasses sequester two orders of magnitude more carbon above the ground than is being released annually by burning fossil fuels, and an even greater amount (1600 GT) is sequestered in soils. Three seminal studies published in Science in 2008 (Fargione et al, Searchinger et al, Running et al, see end notes for reference details) clearly showed the enormous carbon debt that is created when native ecosystems are tilled and used for biofuel production. Most of the soil CO₂ is emitted over the first five years, but it continues for decades.

The best conversion-case studied was sugarcane ethanol from a lightly-wooded Brazilian ecosystem. There, the carbon released from clearing and tilling was repaid by the use of the biofuel produced in only 17 years.

A more typical U.S. case was corn ethanol from central native grassland. There it required 93 years for the biofuel to repay the carbon debt of 134 MG-CO2/ha. For a well used cropland that had lain idle as grassland for 15 years, its soil carbon would have recovered to about half of its native level. It then took only 48 years for the corn ethanol to repay the carbon debt.

The worst case studied was converting a peatland rainforest to production of palm biodiesel. There, it took 423 years to repay the carbon debt.

When fully degraded soils (soils that have been tilled annually for more than 5-20 years, depending on the ecosystem) are converted to biofuels, there is no carbon debt associated with direct land-use change. Of course, if that land is no longer used for growing food or feed, other new land will need to be used for that purpose. The CO₂ release from this other new land is referred to as indirect land-use change, and it is routinely ignored in almost all life cycle analyses (LCAs) that are supportive of the use of biofuels.

Ignoring indirect land-use change is obviously disingenuous if the biofuel is to be grown on land previously used for crops. Hence, the universal assumption now is that advanced biofuels will be grown only on new land with no tilling or on abandoned cropland that has been fully degraded and is no longer usable for normal agricultural crops. (Obviously, there is a very limited amount of fully degraded land available that would produce useful yields of biofuels.) Hence, there would be no carbon debt associated with these advanced biofuels – which normally means forest residues or perennial grasses. Below, we show the fallacy of this assumption.

Direct Land-Use Change in Un-tilled Soils.
Normally when forests are harvested, only a fraction gets to the processing plant. The branches, crown, bark, and leaves are usually left to decay on the forest floor (for economic reasons) and their decay contains soil carbon.

Most prior studies advocating production of cellulosic ethanol from forest residues have assumed essentially the entire tree except the stump and roots would be used in sawlogs, pulpwood, wood pellets, or cellulosic ethanol production.

Prior studies advocating production of cellulosic ethanol from perennial grasses have assumed essentially all of the above-ground growth will be harvested for woody pellets or cellulosic ethanol production.

What will happen to carbon currently sequestered in these soils and forest floors? It will steadily decrease.

Where will that sequestered carbon go? Into the atmosphere.

Since only 20-29% of the cellulosic feedstock going into the plant ends up in the ethanol, making cellulosic ethanol from living trees immediately (within a few years) 3 to 6 times worse than using conventional gasoline (because of decay of unused residue, harvesting, processing, and end use). From a GHG perspective, it is immaterial if the CO₂ in the atmosphere is from fossil or biological sources. Its IR absorption is the same.

The new trees that are planted to replace the harvested trees don’t start taking as much CO₂ from the atmosphere as the mature trees they replace for at least 15 years. (Of course, for the next 4 to 6 years, we’ll have a semi-infinite source of dead forests in the U.S., as discussed shortly, and it makes sense to use as much of this resource as possible before it’s destroyed by forest fires. )

A more in-depth look at carbon depletion in un-tilled soils. We can approach the effect of biofuels grown on un-tilled soils from another perspective. The amount of carbon sequestered in the soils of maintained forests and wild grasslands represents an equilibrium that has been reached over decades or centuries of little or no harvesting. When the plants die, much of the above ground carbon oxidizes in a few years (for grasses) or a few decades (for trees). However, not all of the above-ground carbon goes into the atmosphere. Some of the above-ground carbon will be in soluble sugars that are leached from the plant residue into the soil. Some of the insoluble starches and other components will be broken down by microbes, insects, and larger animals into soluble compounds (sugars, alcohols, ureas, other organics) and leached into the soil. Thus, both root decay and above-ground decomposition contribute to the carbon flux into soils. The carbon flux from un-tilled soils is dependent on decomposition by organisms within the soil (followed by slow outgassing) and on transport from root systems to the plants above ground. When the above-ground decomposition source is eliminated from a grassland or forest, the new soil-carbon equilibrium level will be lower since the outward fluxes are unchanged. How much lower is not well known, though several studies suggest about 25% lower. Below-ground biomass in typical native grasslands in the central U.S. is about 35 MG-C/ha (see Fargione et al). If the new equilibrium is 25% lower when the grasses are regularly harvested, then the carbon debt associated with un-tilled grassland converted to switchgrass (without tilling, which is very difficult to do) would be about 9 MG-C/ha. The annual repayment from the cellulosic ethanol produced could be 0.5-2 MG-C/ha (will vary widely depending on climate and soil). Hence, there would typically be a 9-year carbon debt on grassland converted to switchgrass by a no-till method – though this debt would be spread out over 20-30 years. Making ethanol from corn stover and other “waste” from annual crops similarly robs the soil of carbon, increases erosion, and reduces soil fertility. Below-ground biomass in native temperate forests is likely to be about 50 MG-C/ha. Again, if the new equilibrium is 25% lower when the forests are regularly fully harvested, then the carbon debt associated with use of forest residues would be about 12 MG-C/ha. The annual repayment from the cellulosic ethanol produced from the residue would be 0.1-1 MG-C/ha. Hence, there would typically be a 15 to 30-year carbon debt on use of forest residues for cellulosic ethanol, but again it would be spread out over 30-50 years. Excessive thinning of forests will also reduce long-term forest productivity and wildlife habitat.

Grasslands predominate naturally in regions where rainfall or soil conditions are inadequate to support forests. “Range Fuels” may be a catchy name, but any attempt to produce cellulosic ethanol from most range land will result in a huge release of sequestered carbon and not enough ethanol to matter.

Cellulosic Feedstock Costs.
The cost of delivered, dry biomass was often only about $20/ton when much of the enthusiasm for cellulosic ethanol began about a decade ago. . Of course, a lot of cheap municipal solid waste (MSP) is continuously generated that must be disposed of. A very small fraction of that is being burned to produce power. The best new example is in Lee County, Florida, (pop. 600K) where over 200K tons/yr (from a waste-water treatment facility, http://www.industcards.com/wte-usa-fl.htm) are burned to produce up to 19 MW_PE. There may be few dozen other similar plants in operation. The total combustible MSP potential in the U.S. is about 80 Mt/yr. It has been suggested that some of it could be used to produce cellulosic ethanol, but most MSP is too dirty and variable in composition for practical conversion to liquids. It would be much better to simply burn it – by just building several hundred more plants like that in Lee County. Doing so could provide about 50 TWhr/yr of grid energy (about 1.3% of total domestic demand) and eliminate most of what is currently going into landfills and subsequently releasing a lot of methane.

Wood-pellet-stove sales have soared over the past decade all over the world, and the global market for wood pellets grew from about 3 MMT (million metric tons) in 2000 to over 12 MMT in 2009. Wood pellets have sold at over $350/ton throughout Europe and above $230/ton in the U.S., though prices in 2010 were depressed (~$150/ton) because of oversupply from new plants Industry experts are projecting the wood-pellet market to increase by an order of magnitude in less than a decade.

A severe pine-beetle blight began in North American in 1999, and today vast expanses of the forests in the northwestern states of the U.S. and in southwestern Canada are dead from the blue fungus carried by the beetle. These forests had previously been considered to be a carbon sink of about 100 MMT-C/yr. Today they represent an annual carbon source of about that amount, and this carbon source is growing rapidly as destruction of the dead trees by wildfires and normal decomposition steadily increases.

Even as hundreds of megatons of these large forests were dying off, the price of wood pellets increased dramatically from 2000-2008. The wood of these destroyed trees is not useful for lumber after two years, so that leaves an enormous supply for the wood pellet and cellulosic industry. Not surprisingly, wood pellet factories are beginning to be built throughout the dying forests about as fast as the fledgling industry can manage, so as to recover some value from trees that have been dead for more than two or three years. These wood pellet factories are receiving their lumber for free, and forestry management is trying to get the dead and decaying lumber removed before it fuels large forest fires.

While the price of cord wood and wood pellets both increased by about 50% from mid-2007 to mid-2008, prices then dropped along with the drop in the price of oil. Typical prices in the U.S. in January of 2009 were $190/ton (while oil was ~$42/bbl)), and $150/ton in June 2010 (while oil was ~$75/bbl). The price of wood pellets relative to the price of oil may continue to drop over the next several years, depending on what Mother Nature brings in the fire seasons. This relative price drop will encourage more enthusiasm in the growth of the wood-burning stove industry, as well as encouraging cellulosic ethanol start-ups. However, when the dead pines (several gigatons worth) are gone, the price of wood pellets and all other cellulosic feedstocks will soar. Vast regions of the Rocky Mountains that were previously mature forests, both pines and mixed species, will be bare or in seedlings by 2011-2015. Wood pellets could be above $500/ton ($30/GJ, similar to the price of NG) even in the U.S. by 2016 – unless the newly developing epidemic of the emerald ash borer in the eastern U.S. and Canada decimates more forests in the next five years than is currently expected.

Several years ago the European Union committed to generating over 21% of their power and 20% of their heat from renewable resources by 2020. They have begun to appreciate that solar is too expensive and there are limited opportunities for further growth in wind before a commercially viable solution for energy storage is available. Hence, they are turning more strongly to use of wood pellets in power plants, and their primary sources will be the U.S., Canada, Brazil, and Russia. The EIA has forecast co-firing of biomass in the US will triple over the next decade, but recent indications suggest that is a conservative estimate.

There were about 40 wood-pellet factories in the U.S. in early 2007 producing a total of about 1 MMt/yr. U.S. production capacity doubled in 2008, and strong growth is continued at least through 2009. For example, RWE Innogy has announced it will begin construction soon on the largest pellet plant in the world (in southern Georgia, US, costing $180M), with pellet capacity of 750 kt/yr and fresh wood consumption of 1.5 MMt/yr. European coal consumption is currently 1 Gt/yr – about the same as in the U.S. The energy content of wood pellets averages about 40% less than in typical coals used in importing countries. In late 2009, Europe was importing about 1.5 MMT/yr of wood pellets, and it is expected to be importing 80 MMT/yr by 2020. Europe will need to increase its imports of wood pellets to 270 MMT/yr to replace 20% of its coal usage with wood pellets.

There are growing voices for a similar commitment in the U.S. (and elsewhere) to greatly increased wood usage. For the world to replace 20% of its current coal usage (~7 Gt/yr) with wood pellets, it would require global forest devastation at 5 times the rate the pine-beetle was able to achieve in North America over the past decade.

Spend a few days driving through thousands of miles of dead pine forests in the Great Northwest before deciding that we want to deforest the planet over the next 15 years to reduce global CO₂ emissions by just 4-6%.

Another useful indicator for the price of cellulosic feedstocks is the price of low-grade hay, which is currently ( in April 2010) between $30 and $80/ton in the U.S. As with corn, the price of low-grade hay too will soar if ethanol creates a new market for it. There will be no possibility of cellulosic ethanol being viable beyond a minimal level, as there will be a much more lucrative market for most cellulosic feedstocks.

Cellulosic Summary.
Most natural grasslands cannot be converted to efficient energy crops because of rainfall limitations. Well under 29% of the carbon in the cellulosic feedstock that goes into the cellulosic ethanol plant will end up in the ethanol. The amount of carbon sequestered in soils (for centuries) is about 200 times as much as is currently released annually from the burning of fossil fuels. The amount sequestered on forest floors (usually for one to two decades) is about an order of magnitude more than current annual fossil fuel consumption. Converting this sequestered carbon into transportation fuel will cause a steady decline in sequestered carbon, both in forest floors and in soils. Hence, it will cause a steady increase in atmospheric carbon.

Making liquid fuels from living forests is probably three times worse for the planet over a time period of less than 5 years than using conventional oil, though the climate effect probably turns positive for a time horizon of more than 10 years. Even with cheap feedstocks, cellulosic ethanol (CE) is currently (in early 2011) twice as expensive as corn ethanol. The process development has a long way to go before the cost of CE drops from its current level of ~$3/gal plus feedstocks to the needed $1/gal plus feedstocks. Cellulosic feedstocks are going to get very expensive after the vast pine forests killed by the pine beetle are destroyed by wildfires over the next five years while use of wood pellets soarsin home heating and co-firing. Hence, there is no plausible path for CE to scale to the level needed to bring its processing costs down. Cellulosic ethanol is dead on arrival.

Fertilizers.
Some fertilizer issues should also be mentioned, as their prices soared in early-2008. Prices dropped during the second half of 2008 back to their early 2007 levels, but they will soar again when oil and gas prices recover. There have also been concerns over environmental factors and scarcity issues.

There is considerable confusion from some environmental advocates on nitrate fertilizers. The prices of nitrate fertilizers increased 5-fold over the 6 years prior to their mid-2008 peak, and current processes for manufacturing these fertilizers require a great deal of natural gas or oil. However, it will be easy (relatively) soon to produce as much renewable ammonia and most nitrate fertilizers as needed from wind energy and air at prices that are competitive with natural-gas-based fertilizers. The process will utilize renewable hydrogen – generated using off-peak wind energy to electrolyze water, as in WindFuels – and nitrogen separated from air by membranes. There will never be a shortage of renewable sulfate urea and ammonium nitrate fertilizers, and they will not be much more expensive than what was seen in mid-2008 for fossil-based nitrogen fertilizers.

The long-term outlook for phosphate fertilizers, however, is somewhat worrisome. The prices for phosphate fertilizers nearly quadrupled between 2007 and mid-2008. This jump was largely due to the tripling of the price of sulfuric acid, which in turn was due mostly to the rise in copper mining and refining – from the demands for process plants in China. The high-quality global phosphate (P₂O₅) reserves will be largely depleted within a century. While this is not a threat of the same urgency as either global warming or fossil-fuel depletion, it is one for which the long-range solutions will be challenging. Low-grade ores will still be available, but their utilization will become quite expensive, especially in a carbon-constrained and energy-constrained world.

The prices for potassium compounds in fertilizers (mostly potash, or KO₂) also more than tripled between 2007 and mid-2008. Even though the natural abundance of potassium in the earth’s crust is 20 times that of phosphorus, both of these primary fertilizer components (KO₂ and P₂O₅) peaked in 2008 in the range of $800 to $1200/ton. The main reason for the high price of potash was inadequate development of mines by the three primary suppliers – in Russia, Canada, and the U.S. The price of oil and gas are also major components in the mining, refining, and distribution of potash, but the price of potash should still be able to be reduced over the coming decade from increased competition, now that its profit margin is very high. There are plenty of other locations of high quality reserves (in Belarus, Germany, Israel, Jordon, Spain, Brazil, Sweden, etc.) that can be developed, though their ore grades may not match those in Canada (20-28% KO₂). There should never be a shortage of the other essential nutrients – calcium, magnesium, sulfur, zinc, iron, manganese, boron, copper, and molybdenum

Best Biofuel References:

Food prices have doubled in less than a year:
http://finance.fortune.cnn.com/2011/02/16/food-spike-puts-44-million-in-poverty/
http://www.dailyfinance.com/story/investing/why-global-food-price-inflation-really-matters/19827378/

EU legislation requires biofuels to guarantee 60% GHG reduction by 2018:
http://www.biofuelsb2b.com/B2B_news.php

2011 RAND report on Biofuels
http://www.rand.org/pubs/monographs/MG969.html

Recent study says local biomass in US Northeast could sustainably replace only 1.5% of fossil fuel usage:
http://www.renewableenergyworld.com/rea/news/article/2011/02/turning-forests-into-fuel-report-outlines-promise-and-limits-of-biomass-energy-in-the-northeast??cmpid=WNL-Friday-February25-2011

Range Fuels fails:
http://www.renewableenergyworld.com/rea/blog/post/2011/02/government-loses-bet-on-khosla-and-range-fuels?cmpid=WNL-Friday-February18-2011
Just like other Khosla ethanol projects, including E3 Biofuels.

Coskata gets $250M loan guarantee to build 55 Mgal/yr CE plant
http://coskata.com/

Sweden gets 32% of its energy from biomass:
http://www.renewableenergyworld.com/rea/news/article/2010/06/biomass-generates-32-of-all-energy-in-sweden?cmpid=WNL-Friday-June4-2010

Ethanol subsidies total $4.18/gal:
http://switchboard.nrdc.org/blogs/ngreene/study_shows_tax_payers_subsidi.html

Biodiversity crisis:
http://www.bbc.co.uk/news/science-environment-11563513

BC Innovation Council publications:
http://www.bcic.ca/media-and-press/publications/life-sciences-publications

Cellulosic ethanol, “Going against the Grain”:
http://www.renewableenergyworld.com/rea/magazine/story?id=54346

Mark Z Jacobson, “Review of Solutions to Global Warming, Air Pollutions, and Energy Security”, Energy Environ. Sci. 2009,
http://www.stanford.edu/group/efmh/jacobson/EnergyEnvRev1008.pdf.

Biofuels Watch
http://www.foodfirst.org/files/pdf/Agrofuels_in_the_Americas.pdf

http://www.biofuelwatch.org.uk./files/agrofuelquotes.pdf

http://www.biofuelwatch.org.uk./

The EU Teeb Report – Nature loss “Dwarfs Bank Crisis”
http://news.bbc.co.uk/2/hi/science/nature/7662565.stm

Biomass Research and Development Board, National Biofuels Action Plan, October 2008,
http://www1.eere.energy.gov/biomass/pdfs/nbap.pdf

GP Robertson VH Dale et al, “Sustainable Biofuels Redux”, Science, 322, 49-50, Oct 3, 2008.

J Fargione, J Hill, D Tilman, S Polasky, P Hawthorne, “Land Clearing and the Biofuel Carbon Debt”, Science 319, 1235-1238, Mar 21, 2008.

JF Kreider and PS Curtiss, “Comprehensive Evaluation of Impacts from Potential Future Automotive Fuel Replacements”, Proc. Energy Sustainability 2007, ES2007-36234.

SW Running, “Ecosystem Disturbance, Carbon, and Climate”, Science 321, 652-3, 1 Aug, 2008.

T Searchinger et al, “Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change”, Science 319, 1238-1240, Feb 29, 2008.

Coskata expects to spend $40M building a demo plant to produce 40,000 gal/yr.
http://www.greentechmedia.com/articles/read/coskata-sapphire-amyris-ranked-top-10-biofuel-firms-5423

Rentech is talking about building 9 Mgal/yr wood-to-ethanol plant
http://www.greentechmedia.com/articles/read/rentech-plans-wood-waste-to-biofuel-electricity-plant-in-california-4600

Bark-beetle Epidemic:

http://pubs.acs.org/cen/science/86/8651sci1.html

Fertilizer market:

http://www.fertilizerworks.com/html/market/TheMarket.pdf

http://www.fuelsandenergy.com/papers/ES2007-36234.pdf

http://www.cnn.com/2008/TECH/science/08/14/dead.zones.ap/index.html

Forest Products:

http://www.unece.org/trade/timber/docs/fpama/2008/executive-summary-2008.pdf

http://www.redorbit.com/news/business/1266327/adding_alternative_fuel_to_the_fire/index.html

http://www.nwp-online.de/fileadmin/redaktion/dokumente/Tisch-20/tisch-204.pdf

DD Richter, DH Jenkins, JT Karakash, J Knight, “Wood Energy in America”, Science, 323, p 1432-1433, 13 Mar, 2009.

Wood pellet update, 2010:
http://www.pellet.org/linked/2010-07%20gordon-murray%20pfi.pdf

Wood pellet update, 2009:
http://www.renewableenergyworld.com/rea/news/article/2009/04/burning-issues-an-update-on-the-wood-pellet-market?cmpid=WNL-Wednesday-April8-2009

Recent wood-pellet articles:
world’s largest pellet plant to be built in southern Georgia.
http://www.renewableenergyworld.com/rea/news/article/2010/01/worlds-largest-pellet-factory-planned-in-us?cmpid=WNL-Thursday-January21-2010

http://www.renewableenergyworld.com/rea/news/article/2010/02/biomass-an-emerging-fuel-for-power-generation?cmpid=WNL-Friday-February26-2010

http://online.wsj.com/article/SB124691728110402383.html

http://www.greentechmedia.com/articles/read/woodpellets.com-gets-11m-to-spread-its-fuel

Outstanding study on wood pellets, 2003:
http://www.pelletcentre.info/resources/1093.pdf


Forest floors:
http://www.fs.fed.us/ne/newtown_square/publications/research_papers/pdfs/2002/rpne722.pdf