Carbon Sequestration and Storage in Soils Could Solve Global Warming
by Christine Lepisto, Berlin on 05.17.08
Soils contain more than twice as much carbon as the atmosphere according to estimates (Food and Agriculture Association of the United Nations, FAO). Increasing the amount of carbon naturally stored in soils could provide the short-term bridge to reduce the impacts of increasing carbon emissions until low-carbon and sustainable technologies can be implemented. A group called Soil Carbon, based in Australia, makes the case for soil carbon storage in a presentation available in English, German, Spanish, Italian, Mexican and Portuguese. The Soil Carbon report includes impressive photographs, such as those above, demonstrating the difference between well-managed and poorly managed soils.
The Soil Carbon report makes a good read in a powerpoint format rich in pictures, and is an easy introduction to a complex topic for the interested layman. The more scientifically oriented, and truly committed, will want to review the FAO report, Carbon Sequestration in Dryland Soils which goes much more in depth in the science and facts behind soil carbon.
The FAO report sheds some doubt on the optimism in the figures presented by Soil Carbon. For example, Soil Carbon calculates the potential for CO2 sequestration in soil by starting from the assumption that soil organic matter can be increased 1% of the total weight of the soils to a depth of 1 meter. By this calculation, Soil Carbon claims a potential increase of 47 tons of carbon per hectare. As reasonable as a simple "1 % increase" may sound, it appears not to be scientifically valid.
According to the FAO (FAO report, page 28): the carbon content of dryland soils is estimated to be 4 tons/hectare. Carbon content ranges between 7 tons and 24 tons in normal (non-depleted) soils, depending on the climate zone and vegetation. Studies show that non-degraded savannahs can have up to 18 tons C/hectare (top 20 cm). Based on this, one can conclude that an increased carbon sequestration of 18 - 4 = 14 tons/hectare is the most optimistic potential achievement, well under the 47 tons/hectare that Soil Carbon suggests is achievable. Nonetheless, the FAO report point out that increasing the carbon content by only 1.5 tons/hectare on 2 billion hectares of degraded lands could balance out predicted increases in CO2 concentrations in the atmosphere due to annual emissions increases. (FAO report, page 6) This would buy time while fossil-fuel free technologies are developed.
Soil Carbon also targets exclusively the use of ruminant grazing as a soil restoration method. This is only one of many methods, which must be used in combinations depending on the local conditions. As much as the beef lovers amongst us may cheer the finding that cattle are an essential part of a healthy farming eco-system, the FAO points out that there is a large amount of disagreement about the value of ruminants in soil carbon cycling. That manure is the most efficient manner to incorporate carbon into soils is undebated. But some studies point out that feed must be grown on adjoining land, thereby depleting it, so the carbon added to one piece of land is in effect merely displaced from other land, rather than a net positive addition. The question of methane production, a 23-times more potent greenhouse gas than carbon dioxide, must also be considered. Somehow humorous in the multi-faceted evaluations required to make good decisions is the statement in the FAO report that when conducting carbon audits: "it is essential to remember that the purpose of agriculture is to feed people."
The most interesting facet of the FAO report for the non-scientist may be the discussions of using funding available from carbon offsetting to implement soil restoration projects and help farmers apply methods which benefit soil carbon levels. The additional income from carbon offsetting would help alleviate poverty, and the more productive farming possible after restoration of soils could break farmers out of the cycle of land depletion for mere survival. Although the development of accurate models to measure carbon offsets and the implementation of measures to reduce the risk of reversal of the gains present obstacles, the prospect of carbon sequestration in soils is a win-win for developed and developing nations.
Via ::Soil Carbon
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shhhhh... Thats way to convenient of a solution. Like nuclear power, that would eliminate the majority of emmissions, this scheme does not involve taxation and mass redistribution of wealth.
Something tells me the Green movement will ignore this like nuke power and keep pushing the taxation and redistribution.
"... case for soil carbon storage in a presentation available in English, German, Spanish, Italian, Mexican and Portuguese. "
Really? Spanish AND Mexican? English, but not American? What gives?
"But some studies point out that feed must be grown on adjoining land, thereby depleting it"
Only if you subscribe to the current broken practice of raising ruminants, i.e., growing corn to feed them in a concentrated feed lot. For millennia, ruminants (first bison, then cattle) grazed freely across the US great plains. They evolved specifically to eat the scrub grass that grows on the prairie. We only went away from that because it was more convenient and cheaper to keep them in one place. Grass fed cattle also produce far less methane than those fed corn (cows can't really digest corn completely, hence the methane). There would be many, many benefits to making a concerted effort to restore the US prairie and go back to raising cattle primarily on grass.
This is the sort of approach that makes a lot of sense. Nice article thank you.
RE: superbad
We can certainly create a list of reasons to avoid eating feedlot-finished beef. However, the statement "Grass fed cattle also produce far less methane than those fed corn (cows can't really digest corn completely, hence the methane). " is untrue.
Due to a range of variables, including the increased methane from a forage diet vs grain diet, grass-finished cattle actually produce more methane than feedlot-finished animals.
Thank you for posting our information. Our case is based on changing grazing management to more closely mimic nature. We use no fertilisers, no herbicides, no tractors, just new knowledge.
The pictures in the presentations are of land changed by this management - there was no "food grown next door".
Our numbers on carbon sequestration recognise that some 50% of the carbon sequestered will be in the top 30cm of the soil, but that roots of perennial grasses can go down more than 100cm, and carbon will be sequestered to this depth.
Recent Australian research has recorded general increases of carbon of 1% with patches of up to 4%.
PS - We were advised by our colleagues in Mexico and Spain that there were sufficient subtle differences between the languages to justify different versions.
I just checked the Mexican and Spanish and it´s the same presentation (at least the pdf). Strange, plus as someone mentioned, Mexican is not a language and I didn´t expect that it would be written in Nahuatl.