Sewage treatment is carried out in two stages.
Biogas is a mixture of gases ( containing predominantly methane ) produced by the microbial activity.
Certain bacteria grow anaerobically on cellulosic material and produce large amount of methane along with CO2 and H2 which are collectively called as methanogens.
One common is methanobacterium.
These bacteria are commonly found in the anaerobic sludge during sewage treatment and in the rumen of cattle to digest cellulose in the food of the cattle , thus the excreta cattle, commonly called gobar can be used for generation of biogas, commonly called gobar gas.
Bio control the use of biological methods for controlling plant diseases and pests .
Chemicals insecticides and pesticides are extremely harmful to human beings and also these pollute our environment.
The use of bio control measures will greatly reduce our dependence on toxic chemical and pesticides.
The ladybird, a beetle with red and black markings and dragon flies are useful to get rid of aphids and mosquitoes respectively.
Bacteria bacillus thuringiensis (Bt) used to get rid of butterfly caterpillars where dried spores of bacillus thuringiensis are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees and these are eaten by the insect larvae and in the gut of the larvae, the toxin is released and the larvae get killed.
Trichoderma species are free- living fungi found in the root ecosystem these are effective as bio control agents of several plant pathogens.
Baculoviruses are pathogens that attack insects and other arthropods and the baculo viruses used as biological control agents are in the genus nucleopolyhedrovirus.