What is Biogas

Without oxygen, bacteria break down organic matter to produce gases called biogas. It is mainly produced from agricultural waste like manure, food waste, sewage, etc. The main constituents of biogas are methane (CH4) and carbon dioxide (CO2). Other substances like carbon monoxide, nitrogen, hydrogen, and hydrogen sulphide are in lower percentages.

Biogas is a non-fossil renewable energy source that provides self-sufficient energy.  This causes a reduction of air pollution and the greenhouse effect. Methane, hydrogen, and carbon monoxide (CO) can be oxidized with oxygen. This releases energy that allows biogas to be used as fuel.

Biogas plant system construction companies

There are many companies in Kenya that make biogas plants. One of the most reputable companies that design and constructs biogas production plants is BlueFlame Energy Solutions.  To make enquiries, click here to get BlueFlame Energy Solutions contact details.

How is Biogas Produced

The production of biogas goes through the following stages;

Biowaste is prepared for anaerobic digestion by being crushed into small particles. A liquid is then added to make it easier to process.
The biowaste is then heated to around 37 °C. This is to provide a warm environment for the microbes to begin decomposition.
The resulting gas is then purified by removing carbon dioxide and other impurities.

It is produced when various types of organic waste are thoroughly processed. Materials that may be used for its production include:
Biodegradable waste from industries and treatment plants.

  • Rotten food from shops and homes.
  • Biowaste is given by consumers
  • Sludge given from wastewater treatment plants
  • Manure and biomass from agriculture
Animal waste used in production of biogas
Animal waste used in the production of Biogas

Preparation of material

The biowaste is crushed into very small pieces to give it a very even consistency. Water with nutrients from a further stage in the process is added to make the mixture 10% less solid. It is at this point that non-biodegradable waste like plastic is separated from this mixture. It is treated to generate heat and electricity. Before the mixture is put in a biogas digester, it’s sanitized by heating it above 70 °C for one hour. This is to remove any harmful bacteria.

Since it is made from local feedstocks, it’s friendly to the environment. It is also renewable making it ideal for uses like motor vehicle fuel and some industrial uses. The most important step in the production of biogas is when microbes begin the decomposition of biomass. This action causes the release of the gas methane. This gas can be used without further processing. It can also be purified to become biogas which is almost equivalent to natural gas. The process also gives out organic nutrients which can be used for agricultural purposes.

 Advantages of biogas

Biogas has been championed as very important in creating a circular economy. But how beneficial is it a source of energy? It has several functions in different fields such as economically, agriculturally and also domestically which include;

  • Compared to fossil fuels, it produces much lower gas pollutants making it a clean source of energy.
  • Biogas can be used as an alternative for gasoline and diesel which are derived from petroleum.
  • It can be used as a source of income when the producing parties sell it.
  • Electrical energy can be produced by biogas when put in generators.
  • Due to its organic properties, it makes a great fertilizer.
  • It is a safe, convenient and affordable source of energy.
  • Biogas is responsible for the friendly recirculation of organic waste from industries and households making it environmentally friendly.
  • It does not have a very strong odour and the smell decreases faster.
  • Plants absorb the biowaste slurry better making soils more fertile hence higher yields.
  • The decontamination of waste protects subsoil water by reducing contamination of drinking water hence reducing leaching.
  • Creation of competition for the artificial fertilizers causing their costs to decrease.
  • It gives a very clear and clean flame that leaves no soot or residue on cooking utensils.
  • Curbs the greenhouse effect. This is by capturing emissions of methane gas hence limiting the amount of harmful gases released into the atmosphere.
  • It is a sustainable source of energy since it relies on natural materials that can be planted again.
  • Reduces littering of the environment with smelly organic waste since it uses this waste in its production.
  • Source of employment since labour is required especially when obtaining and preparing the bio-waste.

Biogas production process

Its production begins when organic waste is taken to the bio plant for anaerobic digestion.

Microbes turn the biomass into biogas.

Microbial action begins in the reactor in a process called fermentation. This means the organic waste, such as proteins, carbohydrates, and lipids are fed on by the microbes. The microbes digestion turns the waste into methane and carbon dioxide.

In approximately three weeks, most of the organic matter is already broken down into biogas. This is a mixture of methane and carbon dioxide. It is collected from the top of the reactors in a spherical gas holder.

Purification of the biogas

Gas straight from the plant can already be used for several things. However, it must be purified before it’s used as fuel for vehicles or it’s injected into the gas pipeline network.
Water with specific pressure and temperature is poured into columns containing the gas in order to scrub it. This is after the gas is filtered. The carbon dioxide and sulfur compounds in the gas are absorbed by the water.

It can also be purified by passing it through activated carbon filters to remove impurities.

The resulting gas is at least 95% and 98% methane. Further separation is not cost-effective or sensible regarding the usability of the gas. To prevent condensation in subzero winter conditions, it is carefully dried before it is injected into the pipeline gas network.

Disposal of residuals

Residuals are the solids and liquids created in biogas production. These residuals are centrifuged to give enough water for the mixing of biowaste at the beginning of the production process. Residuals can be separated.

The liquid can be separated and used as fertilizers as it is rich in nutrients, especially nitrogen.

Solid residuals can be used as fertilizers in agriculture or in landscaping.


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