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
