What is a Biogas Plant?

Low cost biogas plant in China

Biogas plants produce a high calorific value gas which similar to natural gas and do this using the anaerobic digestion process. Biomass is digested in plants ranging from the size which might serve one house or a small farm up to much larger plants which tend to be highly complex and take a variety of feedstocks from various sources.

A biogas plant normally comprises two main components, including:

  • a digester (or fermentation tank)
  • and, a gas holder (like a gasometer as used for coal gas and natural gas).

The feature which distinguishes these plants from composting which is the other form of digestion, is that the biogas plant reaction takes place in the absence of any oxygen. The gas contains up to 70 percent methane and 30 percent carbon dioxide. Fermentation is a normally a reasonably robust process when the biomass is kept within a certain pH value range. However, care is needed during operation to ensure that the pH range is maintained within limits or the biological process will be inhibited and gas production will reduce.

For reliable production of biogas in most plants the operator of the plant must be well trained, and select the right combination of feeds. He must be aware that if fermentation materials are fed into the plant which are excessively dilute, or too highly concentrated, either of these will result in a low biogas production rate, and this will be the result of low fermentation activity.

Segregation of the input to ensure that at all times, a suitable combination of nutrients is present in the feed to the process. This is of utmost importance for smooth running of the biogas plant.  Success of biogas plants depends a great deal on proper segregation of, for example, kitchen waste from large pieces of material grit and dust which can be present choke and fill up the plant.

Biogas production provides a public health benefit beyond that of any other treatment in managing the rural health environment of developing countries. Because the heat and biological action in the process especially in high temperature digestion is very good at reducing pathogen content, plus other disease vectors, and also kills many weed seeds.

Anaerobic digesters can also be fed with specially grown energy crops such as silage for dedicated biogas production.  Substrate composition is a major factor in determining the methane yield and methane production rates from the digestion of biomass.

The biogas can also be used for heat production as steam or hot water.  The evaporation plant uses the surplus heat out of the energy production for the concentration of the digester effluent up to a dry matter content where it is suited for drying (drier plant) or composting.

Renewable

Anaerobic digestion is a renewable energy source because the process produces a methane and carbon dioxide rich biogas suitable for energy production helping replace fossil fuels.  Especially in such situations where there are few (or no) consumers on the farm that need electricity, the farmer earns money by selling the surplus electricity.

Biomass constitutes a renewable organic resource, and its utilization as energy source will serve for environmental clean-up and mitigation of global warm-up.  Power generated from renewable energy will foster sustainable use of natural resources and alleviate the domestic environmental burden.  Biogas is part of renewable energies worldwide.

The future increase use of biogas is a strong goal in most countries, not only because is it a renewable energy source but it will help to reduce greenhouse gas emissions, water pollution and soil degradation and last not least it will change agriculture sectors in many countries worldwide to produce partly energy.

At all levels, success will be seen by neighbours and this will persuade his relative and neighbors to install a biogas plant as well, while a poorly constructed plant will do harm to the reputation of biogas technology the
implementation of government schemes with and constant optimisation of components is leading to a perpetual increase in biogas plant efficiency. The profit potential for biogas plant operators is also rising dramatically as the oil and natural gas price climbs.

As there are many people who now recognize the potential of the biogas system many are asking the next question: ‘Where is there a site where we can find out more about the technical aspects of these little biogas plants’!

You may like to read: Biogas Plants in Pakistan

Biogas Plants in Pakistan

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