WASTE MANAGEMENT SYSTEM / COMPOSTING
Composting is nature’s way of recycling. Composting biodegrades organic waste. i.e. food waste, manure, leaves, grass trimmings, paper, wood, feathers, crop residue etc., and turns it into a valuable organic fertilizer.
Composting is a natural biological process, carried out under controlled aerobic conditions (requires oxygen). In this process, various microorganisms, including bacteria and fungi, break down organic matter into simpler substances. The effectiveness of the composting process is dependent upon the environmental conditions present within the composting system i.e. oxygen, temperature, moisture, material disturbance, organic matter and the size and activity of microbial populations.
The humification of organic material under most conditions occurs in three stages:
1. Mesophilic stage. This is the initial stage of decomposition, lasting for about a week, during which sugars and other simple carbohydrates are rapidly metabolized. This is an exothermic process and may cause an increase in temperature by 40°C.
2. Thermophilic stage. This is the second stage, lasting for about two weeks, during which the temperature may rise to about 50 to 75°C. Such a drastic increase in temperature is accompanied by the decomposition of cellulose and other resistant materials. It is important that the material be thoroughly mixed and kept aerated during this stage.
3. Curing stage. The temperature decreases during this final stage and the material being composted is recolonized by mesophillic organisms, which often produce plant-growth stimulating compounds. Mesophillic organisms are usually fungal-dominated and useful to restore bacteria dominated soils.
At the completion of this process, the plant or other organic parts (leaves, roots, etc.) are no longer identifiable in the compost. The humification of organic material is characterized by an increase in concentration of humic acids from approximately 4 to 12 percent, and a decrease in the C/N ratio from thirty in the original material to about ten in the final product.
Since approximately 45 – 55% of the waste stream is organic matter, composting can play a significant role in diverting waste from landfills thereby conserving landfill space and reducing the production of leachate and methane gas. In addition, an effective composting program can produce a high quality soil amendment with a variety of end uses.
There are three different types of composting technologies, open pile – windrow (covered with plastic or tarp), aerated static pile and in-vessel (rotating drum) composting.The compost coming from the biodegradable fraction of waste, which is not separated at the source, has various pollutants immixtures; hence it cannot be used to agriculture. For that reason it is usually used as daily cover material in landfills.