David T. Brown Dept. of Tourism and Environment Brock University COMPOSTING David T. Brown Dept. of Tourism and Environment Brock University

Composting:

The controlled biological decomposition of organic materials Composting: The controlled biological decomposition of organic materials

Composting natural biological process, but for rapid composting and consistent quality, environmental conditions must be controlled end product (compost) bears little resemblance to original wastes from which the compost was made typically dark brown to black in colour, with crumbly texture and earthy odour

Finished compost humus-like, resembling rich topsoil resistant to further microbial decomposition

Composting typical volume reductions in excess of 50% of the original volume of the waste; effective & useful waste diversion strategy good compost is devoid of organisms that may be harmful to human health

Uses of compost high organic matter content => valuable soil amendment may be used as low-grade fertilizer to supplement plant nutritional needs may be used to condition heavy clay or mineral soils promotes proper balance between air and water in soils aids water infiltration, absorption, and ion exchange in soils

What can be composted? any waste material with a high organic matter content is a potential candidate used for centuries to stabilize human and animal wastes used more recently for: sewage sludges industrial wastes (e.g. food, pulp & paper) yard and garden wastes municipal solid wastes (up to 70% organic matter by weight)

Controlling composting To achieve maximum composting for any organic material, certain environmental conditions must be maintained in the compost pile => may be classified into interdependent biological conditions physical conditions chemical conditions

THE BIOLOGICAL ENVIRONMENT Key organisms: bacteria fungi Actinomycetes - play active role in decomposing organic matter

THE BIOLOGICAL ENVIRONMENT Secondary organisms: earthworms insects other soil invertebrates play a less significant role in decomposition process compared to microorganisms more important in mechanical breakdown of wastes (chewing, burrowing, movement, aeration)