WASTE TYPES MUNICIPAL SOLID WASTE
Composting is a biological process used for the conversion of organic waste materials into stable humus-like material known as compost. Application of this process includes yard waste, separated and commingled MSW. Most aerobic composting processes (windrow, static pole and in-vessel) involve three steps of preprocessing of waste, aerobic decomposition, and product preparation or marketing. The process offer simple operation however it is a net energy user due to the need of oxygen supply (forced aeration). This process also requires large land area. Other problem associated in this process includes odor, and the quality of compost for marketing. To enhance the economics of compost, it should be of consistent size, free from contaminants such as glass, plastic, and metals, and free of objectionable odor. Composting is an excellent method of biodegradable waste from an ecological point of view. However, many large and small composting schemes have because composting is regarded as a disposal process, and not a production process. It is essential to consider the marketing and quality of the product.
The composting process occurs in two major phases. In the first stage,
microorganisms decompose the composting feedstock into simpler compounds,
producing heat as a result of their metabolic activities. The size of the
composting pile is reduced during this stage. In the second
stage, the compost product is “cured” or finished. Microorganisms deplete the supply of readily available nutrients in the compost, which, in turn, slows their activity. As a result, heat generation gradually diminishes and the compost becomes dry and crumbly in texture. When the curing stage is complete, the compost is considered “stabilized” or “mature.” Any further microbial decomposition will occur very slowly.
The Composting can be classified into two broad Categories
It is the end-product of the breakdown of organic matter by some species of earthworm. Vermi compost is a nutrient-rich, natural and soil conditioner. The process of producing vermi compost is called vermi composting. The earthworm species most often used are Eudrillus eugineae, Eisenia foetida or Lumbricus rubellus. Small scale vermi composting is done in bins of varying size and style and three different types of practices, such as non-continuous, continuous vertical flow and continuous horizontal flow, are adopted. The methods for large scale vermi composting are windrow and raised bed or flow through systems. Flow-through systems are well suited to indoor facilities, making them the preferred choice for operations in colder climates. Kitchen waste, except oily and spicy items are suitable for worms. But too much kitchen waste leads to putrification before the worms can process it and becomes harmful to the worms. Similarly, material sprayed with pesticides, high-water-content materials like watermelon, woody part of garden waste etc are hindrance to the process. The worms digest proteins and fats in meat scraps, but these materials attract scavengers. Regular removal of composted material, adding holes to the bin, or using a continuous-flow bin etc improve oxygen supply to worms. Insufficient oxygen leads to anaerobic reactions, producing strong odor and creating toxic environment for the worms.
Research Paper on Composting
Links for Composting
Advanced Biological Treatment of Municipal Solid Waste
Composting municipal waste in the UK: some lessons from Europe
Composting of Mechanically Segregated Fractions of Municipal Solid Waste – A Review
INFLUENCE OF MUNICIPAL SOLID WASTE COMPOST ON SOIL PROPERTIES AND PLANT REESTABLISHMENT IN PERI-URBAN ENVIRONMENTS
Municipal Solid Waste Organics Processing
On-Site Composting: Technology Options and Process Control Strategies
The and Science of Composting Science of Composting