Biology_Today_-_October_2016

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.