4 Biogas Production Process Steps

For Biogas to be produced from organic waste, there is a need for the Biogas Production Process Steps to be followed.

Biogas, commonly called biomethane or sometimes called marsh gas, sewer gas, compost gas, and swamp gas in the US is one of the renewable energy men have to turn to for sustainable energy as we run away from fossil fuel energy.

Other forms of renewable energy include; solar power, wind energy, hydroelectric power, nuclear energy, etc.

History has it that the Assyrians and the Persians used biogas for heating bath water in the 10th century BC and 16th century BC respectively. But, it was in the 17th century that Jan Baptista Van Helmont first discovered that flammable gases could evolve from decaying materials.

Also in 1776, Count Alessandro Volta deduced that there is a direct correlation between the amount of decaying organic matter and the amount of flammable gas being produced. Sir Humphry Davy in 1808 discovered that methane was present in the gases produced from cattle manure.

The developments in biogas continued with the first digestion plant built-in 1859 at a leper colony in Bombay, India, and biogas recovered from a “carefully designed” sewage treatment facility and used for the fueling of street lamps in Exeter, England in 1895. the design was based on a septic tank.

Biogas helps humans alleviate some problems faced globally like reducing our dependence on fossil fuel energy for the production of global energy and reducing the release of methane into the atmosphere which is a very dangerous gas to the ozone layer causing depletion of the ozone layer.

The product of biogas can be used as “all-natural” fertilizer. In the production of biogas, the organic materials decompose in a liquid environment with the nutrients of the organic matter dissolving in water and creating a nutrient-rich sludge that can be used as fertiliser for plants.

What is Biogas?

Biogas generally refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Biogas is often produced from raw materials like agrarian waste, manure, municipal waste, factory material, sewage, green waste or food waste.

Biogas is a clean sustainable, economically friendly source of energy.

Biogas is a renewable energy source and in numerous cases exerts a veritably small carbon footprint. Biogas can be produced by anaerobic digestion with anaerobic organisms which digest accouterments inside a restricted system or fermentation of biodegradable accoutrements.

Biogas is made up of methane, carbon dioxide, hydrogen sulfide and moisture and really you are taking organic matter running it through an anaerobic digester using anaerobic bacteria and in essence in you are using a fermentation process it is very similar to our stomach, you are taking the food using the bacteria.

The bacteria eat the food a din essence it burps methane gas, the methane gas is mainly biogas. Biogas is created from biodegradable materials utilising food waste streams, manure, sewage, municipal waste materials from plants and then it is also created naturally in landfills and that’s called landfill capture for collecting the gases.

Biogas is primarily methane (CH4) and carbon dioxide (CO2)and may have some quantities of hydrogen sulphide (H2S) moisture and selections. The gases methane, hydrogen and carbon monoxide (CO) are burned or oxidized with oxygen.

This energy released allows biogas to be used as a fuel it is often for any heating purpose like cooking, it also can be utilised in an internal combustion engine to convert the energy within the gas into electricity and heat.

Biogas is a gas that is very rich in methane and produced from the digestion of waste (agricultural, sewage and landfill) which is at a microbial level and can be used for power production. Biogas consists of mainly CO2 and H2S but can still contain other constituents that can be able to produce biogas.

When the CO2 concentration is high, the calorific value of the biogas is reduced so, CO2 separation is usually done before the biogas is used for power generation.

Importantly, this high CO2 content, as well as the smaller scale of biogas production makes this CO2 separation very attractive for membranes. As such, this field has been the focus of research endeavours recently.

Biogas is often compressed an equivalent way natural gas is compressed to Compressed Natural Gas (CNG) and used to power automobiles within the UK. For instance, biogas is estimated to have the eventuality of replacing around 17% of automobile fuel, it qualifies for renewable energy grants or subsidies in some parts of the planet.

Biogas can be cleaned and upgraded to natural gas norms when it becomes ‘Biomethane’. Biogas is taken into account to be a renewable resource because its production and use cycle are ceaseless.

It generates no net carbon dioxide organic material grows is converted and used and yet regrows in a continually repeating cycle from a carbon perspective as important carbon dioxide is absorbed from the atmosphere and therefore the growth of the primary bio-resources is released when the material is eventually converted to energy.

Although biogas is lighter than air, escaping biogas displaces air and is collected in shafts, rooms or cavities.

Biogas facilities are all very similar but they are also very unique, they all have different inputs as far as the feed, they all have a slightly different process and they all have different outputs. Some want to generate electricity, some want to generate heat and steam and some want to create gas just to be reused or to offset the natural gas.

Below are some of the industries that can benefit from biogas;

  • Food processing facilities
  • Pulp and paper mills
  • Wastewater treatment plant facilities
  • Municipal waste
  • Landfills
  • Independent facilities with feedstock

What can I do with Biogas?

Biogas can veritably be useful to us in numerous ways. So if asked “what can I do with Biogas?” then my answer would be that Biogas is used readily in all applications designed for natural gas like direct combustion including absorption heating and cooling, cooking, space and water heating, drying, and gas turbines.

It may even be utilized in fueling internal combustion engines and fuel cells for the production of mechanical work and/or electricity.

I can use Biogas for the production of electricity and heat domestically. The electricity can be used in engines, microturbines and fuel cells.

With the production of biogas, I can help reduce the production of greenhouse gases like methane as efficient combustion replaces methane with carbon dioxide.

Methane is 21 times more efficient in trapping heat in the atmosphere than carbon dioxide, biogas combustion which releases methane and is used for other purposes would reduce greenhouse gas emissions.

With the help of biogas production, I can help reduce the odours, insects, and pathogens associated with manure stashes in farms because animal and plant wastes can be used to produce biogas.

They are processed in anaerobic digesters as a liquid or as a slurry mixed with water.

Anaerobic digesters are usually composed of a feedstock source holder, a digestion tank, a biogas recovery unit, and heat exchangers to keep up the temperature necessary for bacterial digestion.

Through catalytic chemical oxidation methane which is biogas can be utilised in the production of methanol production.

Biogas, if compressed for use as an alternative transportation fuel in light and heavy-duty vehicles, can use the same existing technique for fueling already being used for compressed natural gas vehicles.

In numerous countries, biogas is viewed as an environmentally attractive alternative to diesel and gasoline for operating buses and other local transit vehicles.

The sound level generated by methane-powdered engines is generally lower than that generated by diesel engines and the exhaust fume emissions are considered lower than the emission from diesel engines, and the emission of nitrogen oxides is veritably low.

How can Biogas Benefit my Organisation?

  • Biogas facilities can help organisations that have a waste problem they are looking to solve
  • It can help organisations that desire to be energy independent or reduce their reliance on external energy sources
  • It can also help organisations that desire to incorporate sustainability into their organisational culture.

Biogas Production Process Steps

Biogas production process steps consist of the process steps that are involved in the production of biogas.

Biogas is produced various types of organic waste through some processes. Microbes feeding on biomass play the biggest role in the production of biogas because the digestion that is carried out by these microbes produces methane.

This methane is used as biogas. It can also be upgraded to have natural gas qualities enabling it to be transported over long distances.

This results in not just the production of biogas but also organic nutrients which can be used for agricultural purposes.

The biogas production process steps include;

  • Solubilisation or hydrolysis
  • Acidogenesis
  • Acetogenesis
  • Methanogenesis

1. Solubilisation or Hydrolysis

Solubilisation or hydrolysis is one of the biogas production process steps and here fats, cellulose and proteins in insoluble forms are decomposed into soluble compounds.

Fats are decomposed by fat decomposing organisms, cellulose is decomposed by cellulose decomposing organisms, proteins are decomposed by protein decomposing organisms. All these are decomposed into soluble compounds. These decomposing organisms can be called microbes.

2. Acidogenesis

Acidogenesis is one of the biogas production process steps and here acidic bacteria converts the soluble compounds to organic acids like acetate and volatile fatty acids. if the process forms volatile fatty acids then, acetogenesis goes on next and if the process forms acetate, hydrogen molecule and carbon dioxide, the next process would be methanogenesis.

3. Acetogenesis

Though methanogenesis can also take place after acidogenesis, acetogenesis can also occur after acidogenesis. Acetogenesis is one of the biogas production process steps that volatile fatty acids form by acidogenesis converting them to acetate, hydrogen molecule and carbon dioxide.

4. Methanogenesis

Methanogenesis is one of the biogas production process steps and here the organic acids are converted to methane, carbon dioxide and water by methanogenic bacteria.

3 Biogas Production Process Steps

Fig. The Biogas Production Process Steps

The combination of the above processes can be termed Fermentation.

Biowaste or biomass is crushed into smaller pieces and mixed with an equivalent amount of water to create slurry preparing it for the anaerobic digestion process.

Before any other procedure is carried out in the biogas production process steps, sanitisation should be done. This is carried out by heating the slurry for one hour at a temperature of 70oC.

This enables the by-product which is not biogas (digestate) to be used as fertilisers on the farm. The temperature of the slurry should be around 37oC so the microbes or microorganisms could work very well.

The biogas is produced through anaerobic digestion which occurs in the tank for about three weeks. Then the gas can be purified by removing some impurities and carbon dioxide of which after this, the biogas can be ready for use.

Key components of a biogas system include:

  • Delivery system from feedstock
  • The anaerobic digester
  • An auxiliary heating system
  • The gas capture and cleanup system
  • The delivery system for the biogas to its end use

You can check a video that can give you a summary of Biogas production process steps.

Click Here.

Types of Biogas

The types of biogas are grouped according to the type of biogas plant used for its production. The types of biogas plant include;

  • The Fixed-Dome biogas
  • The Floating Gas Holder biogas.
  1. The Fixed-Dome Biogas

This type of biogas is produced in a fixed-dome biogas plant. The fixed-dome biogas plant is a brick and cement structure having the following sections:

  • Mixing tank: Located above the ground level
  • Inlet chamber: The mixing tank opens underground into a sloping inlet
  • Digester: The inlet chamber opens from below into the digester which is a huge tank with a dome-like ceiling. The ceiling of the digester has an outlet with a valve for the supply of biogas.
  • Outlet chamber: The digester opens from below into an outlet chamber.
  • Overflow Tank: The outlet camber opens from the top into a small overflow tank.

The biogas is produced through the following procedures:

  • The various forms of biomass are mixed with an equal quantity of water in the mixing tank. This forms the slurry.
  • The slurry is fed into the digester through the inlet chamber.
  • When the digester is partially filled with the slurry, the introduction of slurry is stopped and the plant is left unused for about two months.
  • During those two months, anaerobic bacteria present in the slurry ferments the biomass in the presence of water.
  • As a result of anaerobic fermentation, biogas is formed which starts collecting in the dome of the digester.
  • As more biogas is formed in the digester, the pressure exerted by the biogas forces the spent slurry into the outlet chamber.
  • From the outlet chamber, the spent slurry overflows into the overflow tank.
  • The spent slurry is manually removed from the overflow tank and used as manure for plants.
  • The gas valve connected to a system of pipelines is opened when a supply of biogas is required.
  • To obtain a continuous supply of biogas, a functioning plant can be fed continuously with the prepared slurry.
  1. The Floating Gas Holder Biogas.

This type of biogas is produced in a floating gas holder biogas plant. The floating gas holder biogas plant is a brick and cement structure having the following sections:

  • Mixing tank: Located above the ground level
  • Digester tank: This is a deep underground well-like structure. It is divided into two chambers by a partition wall in between.
  • It has two long cement pipes:
  1. Inlet pipe opening into the inlet chamber for the introduction of slurry.
  2. Outlet pipe opening into the overflow tank for removal of spent slurry.
  • Gasholder: An inverted steel drum resting above the digester. The drum floats over the digester. The gas holder has an outlet at the top which could be connected to gas stoves.
  • Overflow Tank: Present above the ground level.

The biogas is produced through the following procedures:

  • Slurry (mixture of equal quantities of biomass and water) is prepared in the mixing tank.
  • The prepared slurry is fed into the inlet chamber of the digester through the inlet pipe.
  • The plant is left unused for about two months and the introduction of more slurry is stopped.
  • During this period, anaerobic fermentation of biomass takes place in the presence of water and produces biogas in the digester.
  • Biogas being lighter rises up and starts collecting in the gasholder. The gas holder now starts moving up.
  • The gas holder cannot rise up beyond a certain level. As more biogas collects in the gas holder, pressure begins to be exerted on the slurry.
  • The spent slurry is now forced into the outlet chamber from the top of the inlet chamber.
  • When the outlet chamber gets filled with the spent slurry, the excess is forced out through the outlet pipe into the overflow tank. This is later used as manure for plants.
  • The gas valve of the gas outlet is opened to get a supply of biogas.
  • Once the production of biogas begins, a continuous supply of gas can be ensured by regular removal of spent slurry and the introduction of fresh slurry.

FAQs

Where can I buy Biogas?

You can purchase biogas from biogas and renewable energy distributors near you. You can also with the help of the internet source for biogas distributors near you. You can do that by just googling “Biogas distributors near me” and with your location on, you will be shown biogas distributors that are close to your location.

Does Biogas Explode?

Yes, biogas explodes and this happens biogas is because biogas composed of some gases that have the ability to cause an explosion.

Biogas is composed of approximately 60% of methane and methane is explosive when it mixes with air and so, if biogas is mixed with 10%-30% of air, it can cause an explosion. Also, hydrogen sulfide and ammonia which are also contained in biogas can also explosion.

That is why it is necessary as a precautionary measure not to allow flame or smoke near a biogas digester.

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