BIOGAS
s Biogas is a methane rich fuel gas produced by
anaerobic breakdown or digestion of biomass
with the help of methanogenic bacteria.
Biogas Composition
s Methane (CH 4 ): 50 - 70%
s Carbon dioxide (CO 2 ): 30 - 40%
s Traces of nitrogen, hydrogen sulphide and
hydrogen
Biogas Generation:
s Biogas generation is a three stage anaerobic
digestion of animal and other organic wastes.
Support for pipe
Fig.: A Biogas Plant
Partition wall
Outlet pipe
Gas control valve (outlet for biogas)
Gas storage tank
Biogas
collects here
Slurry of cattle
dung and water
Mixing tank
Inlet pipe
Inlet tank
Underground
digester tank
Dung and
water mixture
Over flow tank
Spent slurry
BIOCONTROL AGENTS
s Chemical pesticides were used in agricultural land to give protection to plant crops by killing or removing pathogens and pests.
But despite of being advantageous there are various disadvantages of chemical herbicides:
Disadvantages of Chemical Pesticides
Continuous use of pesticides develops resistance
amongst pests and pathogens against pesticides.
These are toxic and
biocides.
They kill even useful organisms, harm human beings
and animals, pollute soil, fruits, vegetables.
s Therefore, instead of trying to eradicate pests and pathogens through chemicals, it is better to use biological agents for
controlling them. Biological control is the natural method of controlling pests and pathogens, involving use of viruses, bacteria
and other insects. For example, Lady bird beetle (Beetle with red and black markings) feeds on aphids, while Dragonflies prey
upon mosquitoes. Free living fungus Trichoderma found in root ecosystem, exerts biocontrol over several plant pathogens.
Baculoviruses (mostly of genus Nucleopolyhedrovirus) are useful in controlling many insects and other arthropods. Baculoviruses
are, therefore, an important component of integrated pest management (IPM) programme and is dealing with ecological
sensitive areas.
s Advantage of using biocontrol agents is that they do not eradicate pests and pathogens, but keep their levels manageable. As
the eradication of pest in undesirable because without them the beneficial predatory and parasitic organisms which depend
upon them for food would also be annihilated.
BIOPESTICIDES
s Biopesticides are biological agents used for control of weeds, insects and pathogens.
s Microorganisms like viruses, bacteria, fungi, protozoa are used as biopesticides.
s E.g., Bacillus thuringiensis (Bt), insecticidal Cry protein present in spores of bacterium kill larvae of certain insects.
Biopesticides
Bioherbicides
Bioinsecticides
Predators Parasites and pathogens Natural insecticides
Fig.: Stages in anaerobic digestion during biogas formation
Biogas (Methane + CO 2 )
Stage I
Stage II
Stage III
Amino acids, Glycerol, Sugar, Xylose
Methanogenic Bacteria (Methanococcus, Methanobacterium)
Fermentative Microbes (Bacteria, yeast)
Decomposer Microbes (Earthworm, fungi)
Proteins Fats Cellulose Hemicellulose
Organic acids (Lactate, Butyrate, Propionate, Ethanol)
s Biogas provides energy and
manure.
s It does not add to pollution.
s Separation of methane as pipeline
gas.
s It minimises the chance of spread
of faecal pathogens.