Compost is mixture of decomposable material. It is a key ingredient in organic farming. The process of composting simply requires making a heap of wetted organic matter known as green waste (leaves, food waste) to break down into humus after a period of weeks or months. MSW composting facility is divided into two major functional areas,
(i) The MSW processing area and
(ii) The composting area.
Receiving of the MSW, separation for recyclables and pulverizing of the organic fraction are carried out within a single building, the MSW processing area. MSW is delivered to the receiving building and dumped on the tipping floor. After initial sorting of loads that may contain high percentages of recyclables, paper or wood, for example, the MSW is loaded by front-end loader into two apron feeder conveyors. From the elevating conveyors, MSW is then transferred to a horizontal sorting belt. Recyclers on each side of the belt manually remove up to six commodities for recycling. Recyclables taken from the picking belt are dropped into chutes alongside the recyclers, falling into portable bins on the floor below. These bins are emptied as necessary, and the recyclables are stored for removal and sale. Recyclers are trained to recognize and intercept hazardous materials such as paint products, oils, and batteries. Water is added to the material in the drum, bringing the moisture content to desired levels for optimum processing. The organic fraction, now termed raw compost, compostable fraction, or fines, contains a percentage of glass, plastics, ferrous metal, and other inorganic. With the exception of ferrous metal, this material is left in the raw compost, as it won’t harm the process and actually enhances the subsequent composting process by allowing a freer passage of air. It is conveyed to the loading area, passed under a magnetic separator, which removes most of the ferrous material. The residue is then conveyed into a waste compactor for consolidation into containers for shipment to a landfill.
Within the composting area, the three stages of the composting process are accomplished.
These areas are
(i) The aeration beds,
(ii) The maturation beds, and
(iii) Finished compost processing.
Aeration Beds- Deposition of the material is accomplished by a shuttle conveyor mounted on a bridge conveyor that straddles the beds. These areas are sufficient to process a 3 week throughput of compost, with a retention time of 21 days on the aeration bed. Aerobic composting requires a regulated flow of air through the composting mass. This is accomplished by a specially designed bed, perforated with a large number of openings through which air is introduced. Air is supplied individually to each bed by large-capacity blowers.
Compost Maturation- At the end of the 3 week retention time on the aeration beds, the remaining material is removed by front-end loader and deposited in the maturation area. It is retained for another 3 weeks, drying and completing the composting process.
Finished Compost Processing- Once the compost has reached maturity (about 6 weeks), final processing can be performed. The compost is transported by front-end loader from the maturation beds to a hopper feeding the conveyor that elevates the material to a vibratory screen. The finished compost product is stockpiled by a radial stacker adjacent to the air classifier.