Some thoughts on carbon sequestration

by George Looby, DVM
Most of the carbon in the atmosphere is in the form of CO2 — carbon dioxide. Much of it is generated by emissions from engines, boilers and other sources where carbon rich materials such as fossil fuels are burned.
The problem with CO2 is that once it is released into the air it does not dissipate but rather becomes a gaseous barrier that encircles the earth. Mother Nature’s grand design was that once sunlight hit the surface of the earth it would be reflected back into space. With a barrier of CO2 encircling the planet much of the sunlight does not find its way back into the atmosphere but is deflected back to the surface of the earth. This ongoing process leads to global warming. Despite the assertion of the present administration that this theory is a hoax the evidence is too strong to disregard. Until proven otherwise most of the scientific community worldwide accepts it as fact.
Carbon sequestration is the long-term storage of carbon in the oceans, soils and vegetation of all kinds including forests and in geologic formations. Interestingly the oceans store most of the carbon that exists but soils store about 75 percent of the carbon found on land, far more than is found in all of the plants and animals on earth. Carbon is found in all living organisms and is the major building block for life on earth. It is found in many forms predominantly in plant biomass, soil organic matter and as CO2.
Most of us remember that photosynthesis is the process by which plants carry out their life cycles with CO2 playing a major role. Some of the carbon is retained in the soil while some is released into the air as CO2. Plant material which remains unharvested decomposes and its carbon content becomes part of soil organic matter. This material is a complex mixture of decomposing plant and animal matter, all containing carbon. A wide variety of factors determine how and how long carbon can remain in the soil.
Agricultural practices need to be modified in such a way as to ensure that its overall contribution to global warming is kept to the lowest possible level. It has been estimated that the world food system may account for up to 24 percent of greenhouse gas emissions. Whatever measures can be incorporated into farming practices to increase carbon uptake by the soil and reduce CO2 emissions during the growing season need to be given the highest possible priority.
One study suggests that the world farmland soils have the potential to capture all of the carbon the U.S. emits each year if they were managed in a better way. This would be equivalent to removing all of the carbon that the transportation sector generates each year. Some of the suggested innovations are high tech while others are more modest. Sensor and camera equipped drones are equipped to send information regarding soil health in a target area to computers which provide information regarding the types and quantities of fertilizer to apply. This information in turn should help maximize soil health thus enabling it to trap carbon.
Not everything needs to be computer driven to make soil better able to trap carbon. The use of heavy machinery compacts the soil making it physically less able to trap carbon. Mulching the soil is better. Vast areas of cropland in Africa have the potential to serve as a reservoir for trapped carbon but the issue is convincing native farmers that the investment is worthwhile.
Removing carbon has a lot of benefits. Those benefits include but are not limited to improved soil and water quality, decreased nutrient loss, less soil erosion, increased water conservation and an increase in crop production. It is well to recognize the many benefits associated with carbon sequestration. Some of the techniques for carbon sequestration have been recognized for years and merely need to be amplified and intensified.
Conservation tillage minimizes or eliminates manipulation of the soil for crop production as the increasingly popular practice of “no till” would suggest. A bit of a culture shock for those brought up plowing and harrowing every spring but it is the wave of the future as far as cropping is concerned. Among the practices to achieve this one would include the practice of mulch tillage and the use of a greater variety of cover crops. An indirect benefit of this type of cultural practice could be the lesser amount of fuel required to complete the tillage and harvesting of a given crop.
The use of cover crops is far from new. It has been advocated long before the concept of carbon sequestration came to light. It has been found that its long-recognized ability to improve soil structure improves carbon retention in addition to adding organic matter to the soil. Another old concept that has been reinforced as an aid in carbon retention is that of crop rotation. Varying the type of crop grown on a given parcel can contribute to the amount of organic matter in that parcel with the effectiveness dependent on the type of crops grown.
Nitrogen is often one of the elements that is in limited supply in many cropping activities. Nitrogen is a high cost item in any fertilization program so will there be a pay back when getting to the bottom line? All along the production, delivery and application line there is CO2 generated, so the impact of those activities must be weighed against the perceived benefits derived from making the soil better able to retain and store large amounts of CO2. An idea that has been advocated is to make semiarid lands more productive by increasing the amount of irrigation. Here again the question of fossil fuels to power the equipment necessary to do the irrigation comes into play. Will the amount of CO2 generated by this activity be offset by increased carbon retention accomplished by more productive soil? Perhaps in these situations the use of alternative power sources such as solar is the answer. This would fit nicely into irrigating semiarid regions.
A large amount of the world’s surface remains forested and this resource is an invaluable one when discussing carbon management. Carbon uptake is greatest in young forests and decreases as they mature. Old forests can sequester carbon for a long time but they provide little in the way of carbon uptake. When trees are harvested, the carbon they contain is quickly returned to the atmosphere when the wood is burned or when converted to products such as paper and cardboard.
As we move forward the whole idea of carbon retention must be given attention with the newer concepts adopted if we are to adequately feed an ever-increasing world population and successfully manage global warming.

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