Data from the Rodale Institute’s long-running comparison of organic and conventional cropping systems confirms that organic methods are far more effective at removing the greenhouse gas, carbon dioxide, from the atmosphere and fixing it as beneficial organic matter in the soil.

By Laura Sayre

The Rodale Institute announces a partnership with Pennsylvania's Department of Environmental Protection and Department of Agriculture to explore ways these findings can benefit farmers and the environment. One possibility: carbon credits could be in your agricultural future.

OCTOBER 10, 2003: Kutztown, PA Discussions of global warming in the popular press seldom fail to note its potentially disastrous consequences for agriculture as we know it: more extreme and unpredictable weather, coastal flooding, even the loss of pollen viability for some crop species at higher temperatures all threaten to push the usual unpredictability of farming into the realm of the completely unworkable. But while these threats are indeed grave--and many farmers believe they are witnessing such effects already--researchers at the Rodale Institute have been looking at the problem from the other direction: what impact do agricultural practices have on global warming?

On October 10, the Rodale Institute (TRI), the Pennsylvania Department of Environmental Protection (PDEP), and the Pennsylvania Department of Agriculture (PDA) signed a memorandum of understanding designed to help answer that question. Twenty-three years of ongoing research at The Rodale Institute Experimental Farm already provides strong evidence that organic farming helps combat global warming by capturing atmospheric carbon dioxide and incorporating it into the soil, whereas conventional farming exacerbates the greenhouse effect by producing a net release of carbon into the atmosphere.

The key lies in the handling of organic matter (OM): because soil organic matter is primarily carbon, increases in soil OM levels will be directly correlated with carbon sequestration. While conventional farming typically depletes soil OM, organic farming builds it through the use of composted animal manures and cover crops. Now, in a unique new partnership, PDEP, PDA and The Rodale Institute are interested in working together to see how organic farming practices can be used to help Pennsylvania--and the world--curb greenhouse gases.

In recent months, TRI Research Manager Paul Hepperly and President John Haberern have drafted a White Paper summarizing TRI's research findings and their relevance to global climate change. The formal agreement, signed last Friday, will provide a platform for further research into the environmental and economic benefits of organic and sustainable farming. By coordinating with PDEP and PDA, Haberern explains, "we can undertake a systematic review of all the existing data on this issue, and examine how the process could be accelerated."

What they learn could be used in reclaiming strip-mined areas of Pennsylvania or in processing waste materials, as well as in improving the state's farming practices. As a regional leader in the agricultural management community and a global leader in sustainable agriculture, TRI also hopes to play an active role within the Northeast Greenhouse Gas Region recently designated by the US Department of Energy.

What we know already:

Over 23 years, there’s been a 15 to 28% increase in soil carbon in organic systems, with virtually no increase in non-organic systems.

The data demonstrating that organic farming practices can reduce atmospheric carbon levels come from TRI's longest-running field study, the Rodale Institute Farming Systems Trial (FST). Launched in 1981, the FST is a 12-acre, side-by-side experiment comparing three agricultural management systems: one conventional, one legume-based organic, and one manure-based organic. In 23 years of continuous recordkeeping, the FST's two organic systems have shown an increase in soil carbon of 15-28%, while the conventional system has shown no statistically significant increase. For the organic systems that translates into more than 1000 lbs of captured C (or about 3670 lbs of CO2) per acre-foot per year—and that’s not even counting the reductions in CO2 emissions represented by the organic systems' lower energetic requirements. A comparative analysis of FST energy inputs, conducted by Dr. David Pimentel of Cornell University, found that organic farming systems use just 63% of the energy required by conventional farming systems, largely because of the massive amounts of energy required to synthesize nitrogen fertilizer.

"Results like these are a bright spot within the otherwise dreary picture of global climate change research," notes Daniel Desmond, Director of the Office of Pollution Control at PDEP. Organic farmers "are the only group or philosophy that looks at carbon as a resource rather than carbon as a waste product."

Global climate change and the carbon cycle

While a handful of political conservatives continue to dispute the seriousness of global warming and the necessity for a concerted international effort to mitigate its effects, the vast majority of scientists have concluded that global climate change is a reality:

• Atmospheric carbon dioxide levels--the major factor in the greenhouse effect--are now twice as high as they were during the last Ice Age, have risen from 280 parts per million (ppm) to 365 ppm in the last two centuries alone, and are now increasing at a rate of 1.3 ppm per year.
• Consumption of remaining fossil fuel reserves would boost CO2 by a factor of four to eight.
• Other greenhouses gases, including methane (CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFCs), have also proliferated and would take decades to stabilize even if emissions were magically cut tomorrow.
• Global mean surface temperatures have climbed 0.6ºC since the 1850s and are expected to rise 1.5 - 5.0ºC by 2100. Paleoclimatic evidence indicates that the 1990s were the warmest decade since the year 1000.

In their efforts to understand and to address the effects of global warming, scientists are developing an increasingly sophisticated picture of the global carbon cycle. Total carbon storage provided by different parts of the global system--terrestrial vegetation, the surface ocean, the deep ocean--have been quantified, as have the annual fluxes of carbon among them. CO2 emissions from human and animal activities now stand at about 8.9 billion U.S. tons per year, while net atmospheric CO2 accumulation is 3.5 billion US tons. In other words, 40% of annual human-induced carbon emissions contribute to build-up, while the remaining 60% are absorbed by the oceans and terrestrial plants.

Reforestation not enough to handle rise in greenhouse gas emissions. Farmlands are a better carbon “sink.”

Proposals to expand natural carbon sinks as a partial remedy for global warming initially focused on reforestation. Changes in land use, including the loss of forests to tillage and grazing, were known to be a major contributor to the greenhouse effect--as recently as the 1970s, total accumulated C emissions from land-use change exceeded total emissions from the burning of fossil fuels--and it was thought that escalating fossil fuel consumption could be balanced by vast forests breathing in all that CO2.

Data like those emerging from the Farming Systems Trial, however, are revising that image: It may be that the soil itself makes more of a difference than what's growing in it. On a global scale, soils hold more than twice as much carbon (an estimated 1.74 trillion U.S. tons) as does terrestrial vegetation (672 billion U.S. tons), and practices like reduced tillage, the use of cover crops, and incorporation of crop residues can dramatically alter the C storage of arable lands.

"Agriculture and forestry are a very potent sink--they will make the emissions problem easier to get a handle on," explains Haberern. "Especially if you do the agriculture right. If you practice conventional agriculture, then any low to non-existent C gain you get will have to have subtracted from it the C emissions created by conventional agricultural methods. With organic farming it can be pure gain. Using bio-diesel [for tractor power], you don't need to use any fossil fuels at all."

Organic farming for carbon capture is also compatible with other environmental and social goals such as reducing erosion, minimizing impact on native ecosystems, and improving farmer livelihoods. Compared to forests, moreover, agricultural soils may be a more secure sink for atmospheric carbon, since they are not vulnerable to logging and wildfire.

Although it is well established that sustainable and organic farming methods sequester atmospheric carbon, researchers have yet to flesh out the precise mechanisms by which this takes place. In the FST, soil carbon levels increased more in the manure-based organic system than in the legume-based organic system, presumably because of the incorporation of manures, but the study also showed that soil carbon depends on more than just total C additions to the system--cropping system diversity or carbon-to-nitrogen ratios of inputs may have an effect. "We believe that the differences in decay rates [of soil organic matter] have a lot to do with it," says Hepperly, since "soluble nitrogen fertilizer accelerates decomposition" in the conventional system.

On the other hand, the work of another Rodale research collaborator, Dr. David Douds of the Agricultural Research Service, suggests that healthy mycorrhizal fungi populations in the organic systems slow down the decomposition of organic matter. (Visit Cultivating diversity underground for better yields above for more on Douds' mycorrhizal research.) All of these factors lead Hepperly to conclude that "it's crucial to look at the biological nature of the soil carbon system," rather than just to consider it as a geochemical process.

Should organic farmers get 'carbon credits'?

A further goal of the partnership between the Rodale Institute, the PA Department of Agriculture and the PA Department of Environmental Protection is to explore policy mechanisms by which farmers and landowners could quantify the carbon sequestered on their properties and receive a payment from the state or federal government for ecosystem services provided, or even participate in emerging 'carbon-trading' markets around the world. Although the development of carbon-trading markets in the US was put on hold by the Bush administration's decision, in 2001, to pull out of the Kyoto Protocol (citing projected deleterious effects on the struggling US economy), such markets are rapidly expanding in the European Union and elsewhere. (See, for example, co2e.com, a greenhouse gas brokerage firm based in London.)

"The Kyoto Protocol [the 1997 global agreement to reduce greenhouse gases] talks about agriculture and forestry as carbon sinks, but fails to distinguish between the different effects of different types of agriculture," notes Daniel Desmond of the PA Department of Environmental Protection. In fact, the whole business of credit for carbon-sequestration activities under the Kyoto accord is problematic, because of the lack in 1997 of good carbon inventory data that could be factored into the nation-by-nation emissions-reduction targets.

Nevertheless, although sequestration in agricultural soils can vary by climate and by soil type, multiplying 3,670 pounds of captured CO2 per acre across the 160 million acres planted to corn and soybeans in the US yields a potential CO2 capture on the order of 293 million tons per year, or as much as three-quarters of the reductions required if the US were to adhere to its Kyoto targets. (Total U.S. cropland is 431 million acres.)

Thinking globally, the British Royal Society has estimated potential CO2 sequestration on the world's 2.5 billion acres of agricultural soils at 6.1 to 10.1 billion U.S. tons per year for the next 50 years. Another estimate puts the total amount of CO2 that could be captured in developing countries at 1.7 billion U.S. tons over the next decade. In short, carbon sequestration via adoption of organic agriculture could have a substantial impact on global warming.

Still, carbon sequestration by organic farming, like carbon capture through reforestation, is a short-term or 'bridge' solution, a way of buying time for more fundamental changes. Ultimately, global climate change can only be fully addressed through rationalization of energy policies, reductions in fossil fuel consumption, and improvements in emissions-control technologies. Among the possible short- to medium-term solutions, however, organic farming has a lot going for it. "There are a number of 'Star Wars'-like solutions being proposed" for carbon and carbon dioxide capture, observes Hepperly, including pumping CO2 deep into the ocean or underground--in July of this year the US Department of Energy announced that drilling had begun on a 10,000-ft 'well' to funnel CO2 deep beneath West Virginia.

Compared to expensive, experimental, high-technology projects like these, global transitioning to organic farming looks cheap and easy. "It's a no-brainer," Hepperly concludes. "Organic farming is not a technological fix, not an untried experiment that could have its own unforeseen consequences." Instead, it's a step toward solving global warming that brings with it a wealth of other environmental benefits.