By adopting grazing practices that build humus, enough carbon could be sequestered to bring global carbon dioxide levels back to pre-industrial levels within 20 years, says Abe Collins, co-founder of Carbon Farmers of America.
“It’s looking like we’re about to leave the oil age, but the oil age is really just the tail end of a longer age, which has been one of soil degradation,” said Collins, who also operates a 75-head organic dairy farm in Swanton, Vermont.
The group markets carbon sinks to buyers seeking offsets for their polluting activities and recruits, trains and monitors farmers who pull carbon out of the atmosphere and store it using various methods to build topsoil quickly.
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Collins, a speaker at the Holistic Management International conference in Brandon last week said farming practices that ignore the buffering effect of ecological diversity not only waste topsoil, but contribute to the breakdown of the carbon cycle.
To replenish the soil, carbon needs to be put back where it belongs.
Farmers can do this by adopting production systems that mimic the original process that captured and stored it as humus, or soil carbon, over thousands of years. In most cases, this involved huge herds of ruminants grazing over large areas.
But contrary to popular belief, it does not take 1,000 years to build an inch of topsoil, said Collins.
He cited research undertaken by the P.A. Yeomans family in Australia, inventors of the Keyline system that combines biological activity with deep, low surface disturbance tillage to open up compacted subsoil and allow water to infiltrate down to plant roots.
The Yeomans, who have used the practice to restore fertility to ruined farms and pasturelands, have found that soil can be built up in a matter of years, not millennia, he said.
“They figured out over 60 years ago that they could build many inches of topsoil per year,” said Collins.
“It is the fastest strategy on Earth that I know of to increase soil organic matter. You can make your soil black and deep fast. It’s downward, not upward, so you won’t bury your buildings and cover up your fence posts,” he joked.
While the task of sucking excess carbon dioxide out of the atmosphere may seem insurmountable, he said, it is easily within the reach of human beings given the right approach: air-to-humus sequestration.
Some scientists are skeptical of his group’s soil building claims, he said, but that’s because they are stuck to the notion that it takes 10 pounds of organic matter to create one lb. of humus.
“C02 and water are taken up by plants and turned into sugars by photosynthesis,” said Collins.
“But usually more than half of the production of a plant is being turned into the sap that is being pumped down into the roots. This is where most of the action is happening.”
When grazing animals bite off the tops of plants at the appropriate stage of growth, the plant draws the remaining available sap in above ground tissues down to the root system.
The sugars then stimulate soil micro-organisms to produce more nutrients, which in turn restart plant growth.
Within hours, the roots are sloughed off, leaving carbon-rich exudates trapped in the soil.
Exploiting this phenomenon offers humanity the cheapest, most efficient and most beneficial form of sequestering carbon where it belongs, he said.
Calling an immediate halt to fossil fuel use, both coal and petroleum, is not only impractical but also would be ineffective, since it would take until 2100 to see a 40 parts per million drop in C02 levels.
Covering the landscape with trees would take far too long.
The only solution that is immediately workable and has the massive capacity to undo the damage already done is to pay farmers to adopt agricultural and grazing practices that rebuild the soil, said Collins.
Citing figures from the Intergovernmental Panel on Climate Change about the total carbon in the biosphere, some six billion tonnes are dumped into the atmosphere each year as a result of burning fossil fuels, while land use changes such as clearing forests for agriculture account for another billion tonnes.
Total carbon stored in the soil, on the other hand, is 1.6 trillion tonnes, with some 39 trillion tonnes in the oceans in the form of carbonic acid.
The problem is the estimated 200 billion tonnes of excess C02 in the atmosphere that is altering the climate.
“It’s obvious that the soils are the largest carbon sink on Earth that we have to play with. We could do this in 10, 20 years. Nothing else is offering a window like that.”
Sequestering 10 billion tonnes per year of carbon requires a two percent increase in soil organic matter on 12.3 billion acres of agricultural land worldwide.
“Two percent is not a big deal, if you really apply yourself to the job,” said Collins, adding that most of the work would involve restoring what has been destroyed in recent decades.
“But we need to rethink carbon pricing. Just based on the value of the water and nutrients contained in a kilogram of humus, the logical, rational price for a tonne of soil carbon is $200.”
Bruce McCarl, a professor of Agricultural Economics at Texas A&M University, who worked on the issue of soil carbon sequestration for a number of years, warned that the wholesale switch to coal that will result as petroleum supplies dwindle in the coming years will dwarf total global fossil fuel emissions since the Industrial Revolution.
Soil works as an effective carbon sink over the short term, but it becomes saturated after a decade or so, he added.
