And we're back! Sorry about the delay. I was otherwise occupied over the weekend. I would rather not go into the details. Last time I left off with the following question: How do you make a carbon sink?
Carbon sequestration is defined as “a natural or artificial process by which carbon dioxide is removed from the atmosphere and held in solid or liquid form.” Thus, the processes involved in sequestration are directly tied in to the concept of a carbon sink. One can use these ideas to build a sink in one's own garden. Now, at this point you may be thinking “but Haley, aren't gardens just a stupid way to pretend that you care about the environment while secretly burning coal in you attic?” Wrong! Let me elaborate.
To begin, you want to make a healthy, thriving garden environment. Composting is a great way to help. Throw some dead rotting things into your yard (avoid animal corpses). Bacteria, fungi, and other organisms essential for plant growth will thrive on this additional organic matter. A great example of this are the delightful nitrogen-fixing bacteria. These bacteria are able to take in gaseous nitrogen and fix it into something that plants can use. This in turn stimulates plant growth.
Now things get interesting. As plants are growing, the magical process of humification (forming humus) occurs, and sequestration starts. First plants will take in carbon dioxide through their stomata. Next, through photosynthesis the carbon ends up in the form of sugar. Some of the carbon sugar goes into the root cells of plants, seeing as these cells need something for cellular respiration. However, some of this carbon actually leaves the roots and ends up in the soil. Why would this occur? Is it a mystery? Not really. There is a sort of an exchange going on. As carbon exits, it may be used by bacteria and mycorrhizal fungi (look it up, it's interesting). In this mutualism, organisms benefit from the plant, and the plant gets nutrients such as phosphorous from the fungi/bacteria.
So this process is interesting, but it may not be absolutely clear as to how carbon actually gets stored in soil humus (through humification). Mycorrhizal fungi releases a protein (containing over 30% carbon) called glomalin. This in particular works in the formation of humus (made from things such as clay and sand). With high levels of humus in your garden, you have carbon sequestration happening, and a nice little carbon sink.
So then, other than composting, what can you do to encourage humification in a garden? First, make sure that the garden gets a lot of sunlight. It sounds simple, but with increased photosynthesis there is an increase in carbon and thus humus. Avoid excessive digging or tilling in the garden. This can break up important layers of soil that is storing carbon. Also, do not use synthetic fertilizers. Finally, do not use synthetic fertilizers.
Synthetic fertilizers are nasty pieces of work. Introducing this into a garden releases a huge source of nitrogen, stimulating an increase in bacteria and other organisms in the soil. These will consume excessive amounts of organic material, leading to the depletion of carbon and nitrogen. Eventually, the food source will run out and the enormous population of organisms will enter death. At this point, the soil is weak and easily damaged. With less ability to properly hold nitrogen, this nutrient is lost and can increase levels of nitrous oxide (a greenhouse gas). Without the healthy soil activity and consistent availability of good nutrients, plants will become slower in their function; absorbing less carbon. The human response is often to continue adding more fertilizer. These plants are drugged.
This may seem a bit dark, but it's actually an enormous opportunity. Do a gradual removal of fertilizer while working to improve soil fertility. If you remove the fertilizer in one shot, the soil that remains will not have the ability to support the plants. To avoid some of the “withdrawal” difficulties: use mulch, leave leaves and other things on top of the soil, keep soil space large, and introduce compost. The process may be slow, but it is worth it.
So there you have it. The possibility of producing a personal carbon sink. This a great example of a small but tangible environmental action. Also, who doesn't want to do some gardening. I've heard that it's great for the cerebral cortex. Honestly I've never heard that before, but it sounds nice.