Types of biogas systems

[edit] Introduction

Biogas is a wide-ranging technology in that its use applications can extend from small units that provide fuel from organic waste for a single household to large agricultural systems that can provide systems

[edit] Applications

Biogas is commonly used in rural areas as a cost effective cooking gas, to reduce reliance on other fuels such as timber cuttings and help manage waste issues. It can also be used for the production of electricity in larger plants and community systems. It can also be used in MEP systems for water and space heating as well as stored in the compressed for used for vehicle engines, when converted.

[edit] Scale

Biogas systems can range dramatically in size, scale and use. Individual or micro biogas systems can be made to produce small cooking facilities for individual house holds, larger systems can incorporate larger a number of homes or compounds. Community systems may often be linked to agricultural small holdings in the geographical vicinity whilst larger industrial plants can be used effectively as power plants producing heat and electrical energy.

[edit] Types

[edit] Fixed Dome Biogas Plants

Fixed-dome plants are made with a sealed dome-shaped digester and displacement pit. Gas is stored in the upper part of the digester. As the production of gas starts, it rises to the top of the dome and the remaining slurry is pushed into the displacement pit. As the amount of gas collected increases so does the pressure and vice versa.

[edit] Floating Dome Plants

Floating dome plants normally have a dome shaped gas holder made of steel to collect the gas, this is not fixed but floats over the slurry in the digester tank.

[edit] Tube Digesters

Tube bio-digesters are typically some of the most simple to create, with a polyethylene tube, raised inlet trough, long, flexible fermenting reservoir, a gas vent tube, and a slurry output.

[edit] Balloon Plants

Balloon plants are made up ofa heat-sealed plastic rubber balloon, with the combined digester and gas-holder. The gas rests in the upper part of the balloon, with the inlet and outlet attached directly to the skin of the balloon, pressure can be adjusted by placing weights on or off the balloon.

[edit] Horizontal Plants

Horizontal biogas plants are often larger plants, processing waste generated from larger communities in larger elongated steel tanks and stored in balloons to be circulated to the community.

[edit] Continuous plants

Continuous biogas plants are often used industrially to maximise production, being fed and emptied continuously. The system of filling usually automatically causes a portion of emptying through overflows, the advantage is generally a constant flow of gas as opposed to batch plants.

[edit] Batch / Semi batch plants

Batch and Semi batch plants are used for set periods, in the case of batch plants they are emptied regularly, in the case of semi-batch plants certain materials are used on a slower cycle than other materials. For example straw is a slow digesting material so is replaced on a very slow cycle and mixed with dung which is filled and replaced more regularly.

[edit] Dry Fermentation Plants

Dry fermentation or Solid-State Anaerobic Digestion (SSAD) in a biogas plant involves the fermentation of organic feed stocks to produce biogas under anaerobic conditions (ie without atmospheric oxygen). Dry fermentation plants contain solids content which is around 15 and 35% as opposed to most of the above which are wet fermentation processes characterised by a higher liquid content and a lower solid content, normally around 10%. Related articles on Designing Buildings

[edit] Related articles on Designing Buildings

• Biogas
• Anaerobic digestion.
• Conventional liquid biofuel.
• Gas Goes Green.
• Liquefied petroleum gas (LPG).
• Mains gas.
• Natural gas.
• Oil - a global perspective.
• Peak oil.
• Renewable energy.
• Renewable heat incentive.
• Shale gas.
• Types of fuel.
• Water vapour.
• Zero carbon homes.
• Zero carbon non-domestic buildings.