One statistic makes clear why — soils and plants growing on them contain 2.7 times more carbon than the atmosphere. Outside the oceans they represent the Earth's largest store of biological carbon. Using soils and plants in ways that release carbon intensifies climate change. This is the second greatest source of climate-disrupting greenhouse gases after fossil-fuel burning.  

On the other hand, employing the land to soak up atmospheric carbon increasingly appears central to averting global climate meltdown, quite literally. Carbon levels in the atmosphere may have already reached a point where simply stopping the increase in greenhouse gas concentrations may not be enough to stop the worst climate change impacts. Whether massive loss of polar ice and sea level rises measured in the tens of feet can be prevented may very well depend on the skill of farmers and foresters in growing soil carbon.  

Biofuels play a critical role in this picture. Two new studies detailed in my first article on this topic show how biofuels feedstock production can potentially release huge amounts of soil carbon. Though biofuels themselves reduce greenhouse gases (GHGs) converting lands from non-farm uses to grow feedstocks could cause a net increase in GHGs.  One of the studies called "Land Clearing and the Biofuel Carbon Debt," (Joseph Fargione et al, Sciencexpress, Feb. 7, 2008) is the source of the above statistic.

The second study, "Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land Use Change" (Timothy Searchinger et al, Sciencexpress, Feb. 7, 2008), calculates prospective impacts from expanding U.S. corn ethanol production six times over the current amount.  This study looks at indirect land use change, the new farmlands opened to replace corn diverted to fuel uses, and finds it could swamp GHG reductions from fuel use.  

Both studies highlight the need to direct biofuels growth in sustainable directions, using feedstocks that minimize competition for prime croplands. These include farm, forest and municipal waste streams; energy crops grown on marginal lands, and algaes. These second generation biofuels feedstocks are expected to dramatically reduce GHGs compared to first generation biofuels such as corn ethanol. They could also increase storage of carbon in soils.  

In other words, biofuels done unsustainably could make the climate problem worse, while biofuels done sustainably could play a leading role in solving the carbon challenge.

The Larger Carbon Context

The new studies raise questions about the environmental benefits of first-generation biofuels. But it is important to note that biofuels growth has not been primarily driven by environmental concerns. Instead, worries over energy security and demands for rural development have provided the greatest impetus. With oil at record prices and supply uncertainties increasing, these drivers are only becoming stronger. Placed in this economic and political context, it becomes clear that the choice is not between biofuels or not, but between sustainable and unsustainable biofuels.

As Worldwatch Institute notes in its recent book, Biofuels for Transport, "Today the question is not whether biofuels will play a significant role in providing energy for transportation, but rather what the implications of their use will be — for the economy, for the environment, for global security and for the health of societies. Decisions made in the next few years will determine whether biofuels will have a largely positive impact or whether the gains from biofuels use will be coupled with equally daunting circumstances."

Creating the political and economic context in which biofuels grow sustainably is important not only for biofuels, but for broader global carbon picture. To understand why, consider that the Searchinger study is based on increased food prices — creating a new demand for fuel feedstock drives up prices. This provides farmers with market incentives to expand their croplands, thus causing soil carbon releases.  

But fuels are hardly the only factor. Growing populations that are becoming more affluent, especially in Asia, are well capable of driving up prices on their own and are doing so. In other words, land conversions Searchinger envisions as a result of growing corn ethanol demand could well take place even if corn ethanol was taken out of the picture. The timing might be a few years different, but the carbon releases would be the same, and without any balancing effect of biofuels displacing petroleum fuels.  

The great bulk of grassland and tropical forest land conversions taking place today are for traditional needs of food, feed and fiber. Ironically, the palm oil boom that draws so much concern from biofuels critics is primarily driven by the demand for healthy food oils. This demand has even caused suspension of plans to build biodiesel refineries in Southeast Asia, in a case of food beating fuel in the marketplace. 

"Crude palm oil is very expensive now, it's impossible for companies to make profit if it's used as biodiesel," said Alhilal Hamdi, head of Indonesia's National Team on Biofuel. 

Soybean conversions in Brazil are almost entirely driven by food demand. A competitive low-cost producer, Brazil nearly tripled production to 51 million metric tons between 1988-2003. Exports represent 20 million tons.

The Oil Demand Driver

On March 4 oil prices reached as high as $103.95/barrel, reaching an all-time record high — the figure exceeded the inflation-adjusted peak reached in 1980 during the second oil shock. Oil prices have been on a mostly upward curve since 2001, with indications $100 could look cheap in the rear-view mirror.   

Prices are being pushed by growing demand, again especially in Asia, pressing on tight supplies. Whether global oil production has reached a peak, as many fear, production has hovered around 84-87 million barrels per day since 2005. The CEOs of ConocoPhillips and Total recently said it appears production has reached a plateau, while Deutsche Bank has concluded "that steep decline rates in existing oil fields (now around 4-5 percent annually) will make it all but impossible for producers to break beyond a 100-million-barrel-a-day ceiling," the Wall Street Journal Environmental Capital blog reports. "The bank says supply constraints could push the price of oil to $150 a barrel by 2010."   

These prices will drive demand for all sorts of alternatives including biofuels, and that will add to feedstock demand and push up prices. Biofuels critic Lester Brown cites a University of Illinois study that finds, "... with oil at $100 a barrel, distillers can pay more than $7 a bushel for corn and still break even. If oil climbs to $140, distillers can pay $10 a bushel for corn-double the early 2008 price of $5 per bushel."   

Higher oil prices are themselves a powerful driver toward increased food prices.  Oil is involved at all levels of food production from the farm to transportation and processing. Economist John Urbanchuk finds that a 33 percent increase in oil prices drives up food prices 0.6-0.9 percent, compared to 0.3 percent for an equivalent rise in corn prices. Urbanchuk notes that food prices are escalating generally rather than just in areas affected by increased corn costs — meat, eggs and dairy products.   

A Comprehensive Address to Carbon

So food and energy demands are engaged in a great dance with one another that results in rising crop prices and global pressures on the land. Clearly land conversion for biofuels is only one part of a larger global picture involving increased demands for everything the land can produce. The threats of soil carbon releases are multiple.

If Searchinger and Fargione underscore anything, it is the importance of soil carbon in a global context.  Therefore, the world must seek to conserve the great soil carbon reserves, and the developing nations are home to the greatest. A comprehensive approach to global agricultural and forestry systems is needed, one which creates large and competitive markets for soil and forest carbon. These revenue streams should promote practices that soak carbon, and that create strong grassland and forest reserves.  

This approach serves equity. The U.S., for instance, cannot very well ask Brazil to avoid converting its natural grasslands and forests without significant economic payments. After all, the U.S. converted most of its forests and prairies to farming and other human uses in the 18th and 19th century, so we have accumulated a carbon debt of our own. If we now recognize the global carbon value of such lands, we can begin paying back that carbon debt by making sure developing nations receive payments for that value.

Addressing the carbon challenge for the system that already produces food, feed and fiber will have an ancillary benefit — it will create a framework for sustainable biofuels growth that does not threaten natural ecosystems.  

Soil Carbon to the Center

Creating farm and forestry systems with strong incentives for growing soil carbon could well be at the center of climate stabilization.  NASA Goddard Institute researcher James Hansen, generally a forerunner for the climate science community, maintains that humanity reached the point of dangerous interference in the climate when cumulative carbon dioxide concentrations in the atmosphere reached 350 parts per million.   The level is now 385 ppm.  

On the current trajectory, polar ice and tropical rainforests could well be lost, setting up "point of no return" dynamics in which global warming begins to feed itself.  Hansen says avoiding such catastrophic impacts will require reducing CO2 levels to 300-350 ppm.  A rapid transition to non-fossil energy sources such as wind and sun is vital, but not enough.  Humanity must now actively seek to soak CO2 out of the air, Hansen says.  He points to improved farming and forestry practices as the most economical and feasible pathway to achieve this.  

Thus it may well be that no groups have a more vital role to play in stabilizing the climate than farmers and foresters. But for them to play this role, it must be economically feasible. This underscores the critical need for systems that pay farmers and foresters to grow soil carbon. Synergies between growing biofuels and biocarbon could create multiple revenue streams that promote both.

Part 1 noted University of Minnesota research on "carbon-negative biofuels" produced from mixed-species perennial grasses — the deeply rooted plants lock up more carbon in soils than is released in burning the fuels. Perennial grasses share the characteristic with certain species of fast-growing trees such as poplars that could provide bioenergy feedstocks. Farmers can also grow soil carbon by shifting annual crops including corn to conservation tillage that reduces soil disturbance.  This can result is a 56 percent increase in soil carbon in the first decade with carbon stores growing over 25-50 years.

Another option that is drawing new attention is combined production of bioenergy and charcoal, with charcoal returned to the soil. USDA Agricultural Research Service scientist David Laird calls this the "Charcoal Vision." He envisions networks of small-scale pyrolyzers that employ heat to convert biomass into bio-oils, biogas and charcoal. The scale would reduce transportation costs and keep the charcoal product close to the biomass source. Bio-oils would be shipped to energy markets, while biogas would run the pyrolyzers. Charcoal buried in soils would retain at least half its carbon after 1,000 years. Other benefits include increased water retention and improved fertility.  

Says Laird, "... The scientific debate should be focused on how to design integrated agricultural biomass-bioenergy systems that build soil quality and increase productivity so that both food and bioenergy crops can be sustainably harvested."

Finding Common Ground

Addressing our critical global challenges in time will require alliance-building around solutions that are mutually beneficial. The fact that the biofuels boom has brought farmers on board for renewable energy, whatever one might think of the specific biofuels feedstock, is a political development whose significance cannot be underestimated. It is one of the great bipartisan political breakthroughs of the last decade, with impacts at state and federal levels.

Political involvement by farm industry groups and the farmer-led 25x25 Coalition has built bipartisan support for an unprecedented level of federal investment in cellulosic biofuels technologies. As a result six large-scale pilot cellulosic plants and a number of small ones will be operating within several years. These plants will all employ waste streams, including municipal waste, wood waste and farm residues. These are the feedstocks that both Searchinger and Fargione call out as sustainable.

"The current generation of biofuels is leading to a new stage of cellulosic biofuels development that will not only minimize land use changes, but will actually enhance the environment," 25x'25 noted in its response to the studies.

Now, with the climate need for soil carbon storage powerfully emerging, it will be even more important to engage farmers and foresters in collaborative efforts with policymakers, citizen advocates and the biofuels industry. All these groups must work together to develop systems and markets that grow bioenergy and biocarbon while improving productivity of traditional food, feed and fiber crops. That will take public policies and support along with private innovation.

If Hansen and other climate scientists are right about the need to soak carbon out of the atmosphere, it means that the people who work the working lands might well save the world. But they will need the tools and markets that enable them to do this. Creating these will take a broad alliance that joins to find common ground on how we use the soil to meet our diverse needs for food, fuel, feed, fiber and carbon storage.   

Patrick Mazza is research director for Climate Solutions. This is part of a series of articles on Growing Sustainable Biofuels.