Biogas

Turning waste into fuel

Biogas is a gas produced by the breakdown of organic matter. It is obtained through a process called anaerobic digestion of a wide variety of biodegradable materials, including manure, landfill and sewage waste, municipal waste, agricultural waste and plant waste.

Biogas is a renewable and flexible source of energy, is easily stored on-site in storage tanks and can be used for cooking, heating, the production of electricity, as a transport fuel or upgraded to natural gas quality for injection into a gas grid. It is a particularly suitable fuel for rural areas that are not connected to the mains gas grid. In these areas it may provide people and businesses with an environmentally friendly alternative compated to LPG, and especially compared to the use of coal, heating oil or diesel. In combination with energy efficient conversion technologies such as condensing boilers and micro-CHP systems, further carbon and energy savings can be established.

Usually the production costs of biogas are higher than those for natural gas. Subsidies for the production of biomass are available in many European countries.

In rural areas, however, animal and organic waste is usually available plentiful and often considered as having little value. The production of biogas can make such residue streams of value and may provide economic opportunities for the agricultural and forestry sector in rural areas. In those situations, biogas plants may be profitable without support. Additional earnings can be obtained from waste treatment, emission reduction credits or fertiliser production. The economics of installations also depend on the availability and the type of biomass or feedstock that is used to produce the biogas.

General Info

What is it?

Biogas is a gas produced by the breakdown of organic matter. It is obtained through a process called anaerobic digestion with micro-organisms of biodegradable materials such as manure, landfill and sewage waste, municipal waste, agricultural waste and plant waste.

Biogas can be the energy source for the production of electricity, heat (and the cogeneration of heat and power, CHP), be used as a transport fuel or upgraded to natural gas quality for injection into the natural gas grid.

What are the benefits?

Flexible: biogas can be used as fuel for the production of electricity, heat and transportation fuel.

The input material as well as the biogas itself can be stored and used when needed (e.g. for demand driven electricity and/or heat production, in a vehicle). Biogas can also be upgraded to natural gas quality and injected into the natural gas grid. Such purified biogas is very similar to natural gas (as this is also mostly methane) so that it can be used with common household appliances and industrial processes,

 

Locally available: In rural areas, materials that can be fed into a biogas digester are mostly readily and locally available: agricultural residues, manure, crops, etc. Industrial residues such as from beverage, beer and food production are locally or regionally available and often perceived as waste. Also wastes from landfills or sewer treatment facilities) can be used as input materials to produce biogas from.

Low-carbon and renewable: the materials used to produce biogas are natural and organic waste streams or residues that are often locally or regionally sourced. Associated greenhouse gas (GHG) emissions are low compared to other fuels such as natural gas (see more in the section environmental impacts). Biogas is a renewable fuel.

Additional benefits:

  • The biogas process offers the production of an effective organic fertiliser (and by this the substitution of mineral fertiliser).
  • The methane emissions of stored manure are captured and avoided, which would otherwise end up in the atmosphere. Methane is a very potent greenhouse gas.
  • Some seeds (from weed) are deactivated thus less weed control is needed.

How does it work?

Biogas is commonly produced through a process called anaerobic digestion with micro-organisms (bacteria and archaea) of organic materials such as manure, landfill and sewage waste, municipal waste, agricultural waste (from for example crops) and plant waste.

Organic materials are fed into an air thigh reactor (also called digester). In this digester, anaerobic bacteria and archaea are producing the biogas. Typically this digester is stirred and heated to provide optimal living conditions for the microorganisms, thereby optimising the digestion process. After these processes, the biogas is stored and becomes a flexible fuel. For some applications, biogas is further refined or blended with natural gas or LPG to increase its caloric value.

Upgrading biogas to natural gas quality is also increasingly done. Once upgraded the biogas becomes so-called bio methane. Once compressed, bio methane can be used as transportation fuel and is already used in cars, trains and ships – as is (compressed) natural gas.

The effluent of biogas plants (called digestates) is typically spread as fertilizer on arable land. It could be separated into concentrated fertiliser, humus and water.

Suitability/applicability

Biogas it is a particularly suitable fuel for rural areas that are not connected to the mains gas grid. In these areas it may provide people and businesses with an environmentally friendly alternative compated to LPG, and especially compared to the use of coal, heating oil or diesel. In combination with energy efficient conversion technologies such as condensing boilers and micro-CHP systems, further carbon and energy savings can be established.

A biogas' plant operation is much influenced by the used input material and its local availability. Common commercial biogas plants usually need several thousand tonnes of input material per year. This means that a certain scale (farms, industrial sites) is required to make the production of biogas profitable. Also, sufficient space is required to store and process the biomass.
Detailed Info

Costs, Savings, Earnings

Usually the production costs of biogas are higher than those for natural gas which has similar applications. Therefore biogas installations usually need support which is available in many European countries.

In rural areas, however, animal and organic waste is usually available plentiful and often considered as having little value. The production of biogas can make such residue streams of value and may provide economic opportunities for the agricultural and forestry sector in rural areas. In those situations, biogas plants may be profitable without support.

The economics of biogas installations depend not only the availability, but also on the type of biomass that is used to produce the biogas.

Additional earnings can be obtained from waste treatment, emission reduction credits or fertiliser production.

Environmental Impacts

Greenhouse gas (GHG) emissions associated to biogas are low. Biogas can potentially be carbon-neutral as the amount of carbon that is emitted during combustion of the biofuels is equal to the amount of carbon that was absorbed from the atmosphere during plant growth, hence creating a closed cycle. However, some greenhouse gas emissions also occur during the production, conversion and distribution of the biogas, which have to be allocated to the biogas in order to evaluate its benefits over the entire life-cycle (including the entire supply chain). Biogas is often produced from local or

regionally available residues that have lower associated GHG emissions and do not compete with other land-uses such as food production.

If manure is treated in a biogas plant there is a higher positive environmental effect due to manure treatment and methane emission reduction. Waste treatment or residue utilisation has in most cases positive environmental effects recycling of materials (like minerals) and renewable energy production). If energy crops are grown there are certain sustainability issues (e.g. food vs. fuel production, influence on biodiversity and water quality).

The environmental impact is further reduced when the following requirements are met:

  • Manure treatment: In cattle bearing there are high methane emissions by manure storage. Manure has an about 23 times higher greenhouse gas potency compared to CO2. If manure is treated in biogas plants these emissions are avoided. Due to avoided methane emissions manure treatment biogas plants offer energy production by negative CO2 emissions (reduced GHG effect).
  • Digestate substitutes mineral fertilizer.
  • The by-product heat is used usefully and efficiently.
  • Low leakage rates (methane losses)
Input material choice: Waste and residue processing offers biogas production with low emissions. If energy crops are grown the material has potential negative impact on sustainability (like all agricultural production).

Efficiency

As biogas is a fuel, its efficiency depends on the efficiency of the technology that converts the fuel into end-uses such as heating or power.

Commercial Maturity

Biogas production through digestion is considered a mature and reliable technology. There are over 10.000 biogas plants currently in operation in Europe with several decades of experience. Biogas is currently often more expensive to produce than fossil alternatives and therefore financial support is needed to make it commercially viable. This support is available in many European countries.

Level of Maintenance

Not applicable.

Technical Details

Biogas mainly consists of methane (50 – 75%), carbon dioxide (30 – 45%), water vapour and some other gas components (in traces). Purified biogas (bio methane) has similar properties as natural gas.

Typical capacities for commercial biogas plants range between 50 kWel and some MWel. Typical biogas installations at farms have digester volumes of 500 to 5000 cubic metres and require several tonnes of biomass input per year. Such installations usually produce more biogas than a single farm requires for meeting its energy needs. Domestic biogas installations are not very common in Europe, particularly because of the labour intensive nature of such installations, (particularly feeding and emptying the digester).

There are several biogas technologies available on the marked, which are adapted to the available biomass and specific application.

Regional variations

Biogas plants can be realised in all countries and regions in Europe. Local climate conditions have an influence on the specification of an installation (e.g. on the required production of heat to heat the biomass in a digester) and the type of (regionally) available biomass has an influence on a plant’s operation. Regional conditions therefore need to be taken into account when designing systems.

Trade associations

European Biomass Association

www.aebiom.org

European Biogas Association

www.european-biogas.eu