A report from GRAIN discusses how agriculture can put back much of the excess carbon dioxide in the atmosphere into the soil.
Soils contain enormous amounts of carbon, mostly in the form of organic matter. The report shows that industrial agriculture, and thus the global food system, has spewed large amounts of this carbon into the atmosphere. Policies focused on restoring soil fertility – restoring the organic matter in the soil which has been lost – would make a huge contribution to resolving the rapidly escalating climate crisis.
In 50 years, soils could capture about 450 billion tons of carbon dioxide – more than two thirds of the current excess in the atmosphere.
The role of the global industrial food system in creating the climate crisis has been seriously underestimated, says the report. Calculations reveal the global food system is the most important single factor behind global warming, responsible for almost half of the world’s greenhouse gas emissions. This includes oil-dependent industrial farming, together with the expansion of the meat industry, the destruction of world’s savannahs and forests to grow agricultural commodities, the use of fossil-fuel energy to transport and process food, and the extensive use of chemical fertilizers.
To transform the world’s food system so that it cools the planet rather than heats it up would require fundamental changes in how we produce food. The current trends towards increased land concentration and expansion of industrial farming would have to be reversed. Only if millions of small farmers and farming communities have access to land and can count on policies to support their livelihoods, can we restore the billions of tons of organic matter that the world’s soils have lost.
"The evidence is irrefutable. If we can change the way we farm and the way we produce and distribute food, then we have a powerful solution for combating the climate crisis. There are no technical hurdles to achieving these results, it is only a matter of political will," says Henk Hobbelink, coordinator of GRAIN.
Fertilizers & Climate Change
Soil experts and farmers have long known that chemical fertilizers destroy soil fertility by destroying organic matter. When chemical fertilizers are applied, soluble nutrients become immediately available in huge amounts, provoking a surge of microbial activity and multiplication. This increased microbial activity, in turn, speeds up the decomposition of organic matter, as it is consumed at high speed, and CO2 is released into the atmosphere. When nutrients from fertilizers become scarce, most micro-organisms die, and the soil is left with less organic matter. As this process has been going on for decades, and is reinforced by tilling, soil organic matter is depleted. It is made worse because the same technological approach that promotes chemical fertilizers rules that crop residues should be discarded or burnt, not put back into the soil.
As soils lose organic matter, they become more compact, absorb less water and have a diminished capacity to retain nutrients. Roots grow less and have less capacity to absorb nutrients, nutrients are more easily lost from the soil, and less water in the soil is available for growth. The result is that the use of nutrients from fertilizers becomes less and less efficient, and the only way to overcome such inefficiency is to increase fertilizer doses, as world trends show. But increased application only compounds the problem; inefficiency and soil destruction continue apace. It is not uncommon to hear organic farmers say that they converted to organic because their yields collapsed after years of heavy industrial fertilizer use.
Problems with industrial fertilizers do not end there. The forms of nitrogen provided by chemical fertilizers are readily transformed in the soil, so that nitrous oxides are emitted into the air. Nitrous oxides have a greenhouse effect more than two hundred times as strong as that of CO2, and are responsible for more than 40% of the greenhouse effect caused by current agricultural practices. Worse, nitrous oxides also destroy the ozone layer.
Mineralizing the Soil
In 1992, the official report of the Rio Earth Summit concluded "there is deep concern over continuing major declines in the mineral values in farm and range soils throughout the world." The statement was based on data that shows, over the last 100 years, average mineral levels in agricultural soils had fallen worldwide, by 72% in Europe, 76% in Asia and 85% in North America. As a result, most of the food produced is deficient in minerals, as well as contributing to climate change.
The Rodale Institute, based in Pennsylvania, has conducted research on organic farming for almost 30 years. Their soil carbon data show conclusively that improved global terrestrial stewardship – including regenerative organic agricultural practices – is the most effective available strategy for mitigating CO2 emissions.
"During the 1990s, results from the Compost Utilisation Trial (CUT) at Rodale Institute – a 10-year study comparing the use of composts, manures and synthetic chemical fertiliser – show that the use of composted manure with crop rotations in organic systems can result in carbon sequestration of up to 2,000 lb/acre/year. By contrast, fields under standard tillage relying on chemical fertilizers, lost almost 300 lb of carbon per acre per year. "In 2006, US carbon dioxide emissions from fossil fuel combustion were estimated at nearly 6.5 billion tons. If 7,000 lb/CO2/ac/year sequestration rate was achieved on all 434 million acres of cropland in the United States, nearly 1.6 billion tons of carbon dioxide would be sequestered per year, mitigating close to one quarter of the country’s total fossil fuel emissions."
One of the ways being explored to regenerate soil structure is to remineralize with finely ground rock dust as a sustainable alternative to chemical fertilizers. Add minerals to the soil quickly leads to phenomenal growth of the microorganisms in the soil. Remineralization of the world’s soils and forests will propagate carbon sinks, thereby absorbing carbon dioxide from the atmosphere – and contributing to climatic stability.
Some view mineralization as a more practical alternative to sequestering carbon underground, which requires extensive site-characterization and long-term monitoring. NYSERDA is funding one such project.
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Read GRAIN’s Report
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