Lecture7
Model Answers to Learning Activities
LEARNING ACTIVITY 7.1
Composting is the transformation of organic material (e.g., plant matter) through decomposition
into a soil-like material called compost. Invertebrates (e.g., insects and earthworms) and
microorganisms (e.g., bacteria and fungi) help in transforming the material into compost.
Composting is a natural form of recycling, which continually occurs in nature. Decomposition
occurs naturally wherever plants grow. Creating ideal conditions can encourage this natural
decomposition. The microorganisms and invertebrates fundamental to the composting process
require oxygen and water to successfully decompose the material. The end products of the
process are soil-enriching compost, carbon dioxide, water and heat. For example, composting
of organic wastes such as vegetable wastes produce an organic manure, which is good for
garden plants.
LEARNING ACTIVITY 7.2
There are 3 processes of composting, viz., biological, chemical and physical. In biological
processes, microorganisms such as bacteria, fungi and actinomycetes break down the organic
matter present in the waste. As microorganisms begin to decompose the organic material, the
carbon in it is converted to by-products like carbon dioxide and water and a humic end product
called compost. Inoculum is added in case of a lack of microbial organisms. If all conditions are
ideal for a given microbial population to perform at its maximum potential, composting will occur
rapidly. The chemical environment is largely determined by the composition of material to be
composted. Several factors determine the chemical environment for composting: carbon energy
source, the correct amount of water, adequate oxygen, appropriate pH and the absence of toxic
constituents that could inhibit microbial activity. A physical environment is essential for the
composting process to proceed efficiently. This includes factors such as temperature, particle
size, mixing and pile size. Smaller particle size is preferred, as it has more surface per unit
weight, and therefore, facilitates more microbial activity, which leads to rapid decomposition.
The optimum temperature range is between 320C and 600C. Temperature above 650C is not
Docsity.com
