Compost and improved farming practices provide a significant opportunity for soil to act as a carbon sequester.
There are now many articles and reports pointing out the significant environmental benefits that can be gained by composting our 'compostable' waste and feeding it back into our soils, rather than dumping it in landfill. A recent article that discusses 'The Potential Role of Compost in Reducing Greenhouse Gases' can be found at this link http://wmr.sagepub.com/cgi/reprint/26/1/61
Or a simple summary by 'The Compost Man' Jim McNelly is below:-
A short summary on carbon sequestration in the soil.
Carbon is an element found throughout the biosphere. The word, organic, in its purest definition, means "contains carbon". Our atmosphere consists of approximately 79% nitrogen, 20.6% oxygen, .365% carbon dioxide and micro trace gasses.
When carbon is combined with oxygen as carbon dioxide, it is a clear, odorless gas. When carbon is by itself, it is black, even called "carbon black". When organic matter is oxidized, or burned, some of the carbon is released as C02, some remains as black soot in the ash.
Before life began, our atmosphere consisted of nitrogen and carbon dioxide. There was a billion year period of algae development prior to the appearance of complex plant forms around 600 million years ago. Vast quantities of C02 were removed from the atmosphere and stored in the biosphere as plant mass and in the geosphere as limestones and fossil fuels, shales and other deposits containing organic matter. Plants consume C02 and release 02.
These plants increased the level of oxygen to a point around 450 million years ago to its current level in the atmosphere, where it has remained constant ever since. This is the optimum level of oxygen for animal respiration, which enabled land breathing animals to follow shortly thereafter.
According to James Lovelock's Gaia theory, oxygen levels do not fluctuate, among other things, due to the interaction of lightning. If oxygen levels go up, lightning starts more fires. If oxygen levels go down, lightning starts fewer fires. Fires consume oxygen, and thus keep 02 levels constant.
Over the past 400 million years, plants continued to remove C02 from the atmosphere until level of C02 reached a low of .278% of the atmosphere, resulting in atmospheric cooling. Over time, polar caps developed, plant species that required high levels of CO2 suffocated and went extinct. Within the past two million years, ice sheets spread over more and more of the planet. This trend of plant induced atmospheric cooling would have continued were it not for the action of humans who have systematically oxidized organic matter and fossil fuels back into gaseous C02.
Over the past 100 years, the level of CO2 in the atmosphere has increased from less than .3% and is now approaching .4% This increase in atmospheric C02 is resulting in warmer temperatures around the globe which has varying impacts on the biosphere. Although total rainfall is increasing up to 10%, climatic zones are shifting toward the polar regions, ice packs and glaciers are melting, oceans are rising, islands are sinking, bioregions are becoming stressed, the heat pump of weather forces is becoming more intense, storms are growing in severity, diseases are spreading to wider areas, and climate is becoming unpredictable for growing crops.
Plant growth, however, as a result of increased C02, is increasing an estimated 27% over the turn of the century. There may also be other benefits of atmospheric warming such as increased shipping routes and navigation periods, longer growing seasons, and the stress of increased heat may be partially offset by the lack of stress of cold and ice. New areas of the planet may become habitable such as parts of Canada and northern Europe and Russia.
Some people are opposed to humans adding CO2 to the atmosphere simply because of their belief systems which assume that everything human or a result of human action is "unnatural" and "pollution". Human induced change in the biosphere is automatically "bad", and increased levels of CO2 is an example.
Following this reasoning, plants that created atmospheric oxygen are somehow "good" and the resulting loss of species and global cooling was "OK and natural". They would argue that the recent few million years of a cold planet is more "normal" than the previous billion years of a warmer planet. This point is mostly to illustrate that there are political and cultural, if not religious implications to the issue of human induced changes in the biosphere.
The greatest concerns regarding atmospheric warming seem to be climatic change that impacts agriculture, causing flooding, drought and crop failure. The general consensus has been that regardless of any potential benefits, the *rate* of increased warming is more rapid than bioregions and agriculture can adjust. The goal of the Kyoto greenhouse gas summit in 1995 was to reduce atmospheric warming emissions to a rate that is less disruptive on human populations and the biosphere.
Just as nations try to decrease the tons of tons of atmospheric gas that is put into the air, there is also the approach of removing existing C02 from the atmosphere and returning it to the biosphere. This process of converting carbon from a gas back to a solid stored in the earth is called "carbon sequestering".
There is a natural "carbon respiration cycle" that is very similar to the water respiration cycle taught in every fifth grade science class. We know how water can be converted from a liquid to a gas and a solid and back to a liquid through evapotranspiration and back to the earth through precipitation. The carbon respiration cycle converts atmospheric C02 through photosynthesis into plant mass, which subsequently dies, and is partially stored in the humusphere as organic matter, humus in the topsoil.
The topsoil is therefore an important part, a link in the carbon respiration cycle, where carbon is temporarily stored.
The topsoil can become a great carbon reservoir where many hundreds of
millions, if not billions of tons of compost can be incorporated. A dry ton of compost contains approximately 400 lbs of carbon. 100 tons of compost in an acre of soil can store 20 tons of carbon. If 300 million acres each received 20 tons of carbon, that represents over 6 billion tons of carbon that the agricultural soils of the United States could store, or sequester.
The rate of oxidation, release of C02 back to the atmosphere, would have to be calculated and compensated for in order to ensure that this carbon was stored in the topsoil for many decades, thus having more than a short term effect of carbon removal from the atmosphere.
Humus in the topsoil also has the benefit of mitigating the climatic effects of climate change. Organic matter helps a soil hold moisture, resulting in less run-off reducing floods and more water available to plants during dry periods, lessening the impact of drought. But before the public even addresses the issue of lessening the effect of atmospheric warming, they have to be convinced that it is even happening in the first place. My opinion is that people are not completely stupid. They know the weather is changing just based upon what they remember as children. People know that summers are hotter, winters are warmer, and storms are freakier.
Carbon sequestration in the humusphere is not the only answer to the problem of atmospheric warming, nor are my loading rates realistic or practical. They are merely illustrative of the potential of the role of organic matter, compost, in the arsenal of greenhouse gas management weapons. I often state that composting is to the atmospheric warming discussion what weatherization and insulation is to the energy conservation debate. It is an area in which we can all make a difference, and a little bit goes a long way.
In summary, making and using compost stores carbon in the topsoil. If composting were practiced more widely, it could have a great impact on reducing the rate of global warming.
Jim~ McNelly "The Compost Man"
compost@cloudnet.com
NaturTech Composting Systems, Inc.
HTTP://www.composter.com
