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This biogas basics article discusses designs, methods, and projects for biogas production to obtain useful renewable-energy methane gas for use as a fuel.

Our page top photo of the KIST biogas project in Rwanda, described by the Ashden Awards for sustainable energy program is from the Ashden awards program.

Watch out: Because sewer gas contains methane gas (CH₄) there is a risk of an explosion hazard or even fatal asphyxiation. and the chance that there are possible health hazards from sewer gas exposure, such as a bacterial infection we include here some safety warnings for people undertaking amateur biogas production projects. Also see METHANE GAS SOURCES.

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Biogas Plants: Using Septic Gas or Sewer Gas for Fuel

Various efforts have been made to use sewer gas or septic gas as a fuel for heating or lighting deriving methane from bacteria-powered manure or even human waste or food waste digesters in many countries.

What is Biogas and How Is It Used Around the World?

Bio-gas is a mixture of methane (CH4) and carbon dioxide (CO2) produced by the break-down or digestion of organic waste such as manure, vegetable matter, sewage, or even food waste. The gas produced is clean and burns clean, providing a more healthy fuel than some alternatives such as wood.

Because biogas is high in methane it can be used as a fuel for cooking, lighting, or even powering vehicles or other machines. And because bio gas can be produced from waste material its production is considered a potentially sustainable energy source.

Quoting below, we refer to Ashden's explanation of biogas:

Biogas systems use bacteria to break down wet organic matter like animal dung, human sewage or food waste. This produces biogas, which is a mixture of methane and carbon dioxide, and also a semi-solid residue. The biogas is used as a fuel for cooking, lighting or generating electricity. Using biogas can save the labour of gathering and using wood for cooking, minimise harmful smoke in homes, and cut deforestation and greenhouse gas emissions. Biogas plants can also improve sanitation, and the residue is useful as a fertiliser

How is Biogas Produced?

Key in biogas production is the construction of a proper container (an anaerobic biogas digester) that is air-tight (and safe). When organic materials such as dung, vegetable matter, or sewage break down in the absence of large amounts oxygen (where anaerobic bacteria cause the desired decomposition) the result is a production of useful quantities of methane (CH4) that can be used as a fuel, along with carbon dioxide, and lower amounts of hydrogen and other trace gases.

This biogas production process produces little heat and an end product higher in nitrogen than if the same process is attempted in the presence of oxygen and aerobic bacteria.

The decomposition of waste matter by anaerobic bacteria occurs in two phases: acidic anaerobic bacteria break down the organic waste into peptides, glycerol, alcohol, sugars that are then further converted by other anaerobic bacteria into methane and the other materials listed above.

In large or commercial biogas production systems such as using large amounts of manure, the waste is mixed with water to form a slurry that is fed continuously through the digester. In smaller home or farm biogas producing designs the waste is fed into the digester in batches, manually and water is also added manually as required. -- various sources.

Large Scale Biogas Production & Use Projects

While using sewage waste to produce methane involves both the explosion hazard cited just below, and the difficulty of dealing with a high percentage of liquid volume, some efforts to obtain usable methane fuel gases from sewage have been reported.

The New York Times reported (May 13, 2010) a successful 2005 prison project in Cyangugu, Rwanda using "beehive-shaped converters to house bacteria to ferment the waste." [Photo, left, from the Ashden award for this KIST designed program ]

Methane was collected for cooking and the residue was used as fertilizer. The project design was used in six other prisons, reported the Times who credit the sewage methane gas production system design to the Kigali Institute for Science and Technology (KIST). KIST received an Ashden Award for sustainable energy projects for this effort.

Productive sources of bio-gas (gobar gas in Pakistan and India) currently (to 2010) include landfill produced biogas (50% methane) and bio-digesters or advanced wastewater treatment systems (up to 75% methane) designed for methane gas production and capture.

Small Scale Biogas Production & Use - Home & Do-it-yourself Bio-gas Projects

Some readers have asked if they could just capture methane gas from their septic tank to use as a household fuel for heating, cooking, or gas lighting. And there are septic-tank-like systems designed for that purpose, but as we warn below, don't just try hooking up your septic tank to a gas burner.

While rural farmers and families have made use of manure (animal dung) as fertilizer and when dried, as fuel for eons, use of manure to produce biogas for local use is more recent.

Indeed biogas can be produced, captured, compressed (like natural gas) and used as a fuel, including powering vehicles, and on a smaller scale, it has been successfully produced in home-sized biogas projects, such as in India and Pakistan where Ashden describes a one cubic meter floating-dome (thus safer) home-scale biogas plant installed by BIOTECH in a home in South India. Manure from two to four cows or five to ten pigs can produce sufficient biogas to supply the cooking (and possibly lighting) needs for a single family.

Biogas plants in small scale projects produce methane or bio-gases from livestock manure mixed into a slurry using a system to which local toilets (producing human waste) may be connected. Low-cost brick-dome domestic biogas plants (properly constructed for safety?) can cost as little as $300 U.S. (Asia) to $1400. U.S. (Africa) and in addition to producing biogas for fuel, these systems can produce usable fertilizer.

Biogas and Methane Gas Safety Warnings

Watch out: We reported at SEWER GAS ODORS that because sewer gas contains methane gas (CH₄) there is a risk of an explosion hazard.

At SEPTIC & CESSPOOL SAFETY we explain that gases produced in a septic tank are dangerous, as a potential source of explosion and as a cause of death by asphyxiation if someone falls into or deliberately enters a septic tank.

Readers should also beware that because some waste contains other toxins including heavy metals, amateur attempts to collect and burn sewage-produced gases could produce dangerous levels of carcinogens or other contaminants.

Don't try just piping or pumping sewer gas out of a septic tank or sewer line (our photo at right) for fuel use. We do not recommend just "hooking up your septic tank" to obtain methane fuel gas.

Also for general advice about methane gas safety in buildings, see Building Drain & Sewer Line Odors for the full discussion of odors from building drains & drain piping. Also see Septic System or Sewer Piping for odors from septic systems and sewer lines.

See Plumbing Vent Defects for an explanation of sewer gas leaks from building drain vent piping.

Also see SEPTIC METHANE GAS for more sewer gas test advice and reference material. Also see Using the TIF 8800 Gas Detector.

Questions & Answers regarding this article

Questions & answers about biogas production and use systems as an energy source

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BIOGAS PRODUCTION & USE

ENERGY SAVINGS in buildings

GASES, EXPOSURE, TESTING
  Carbon Dioxide - CO₂
  Carbon Monoxide - CO
  METHANE GAS SOURCES
GAS MEASUREMENT TOOLS
GAS PIPING, VALVES, CONTROLS
HEATING SYSTEMS

METHANE GAS SOURCES

ODORS & SMELLS DIAGNOSIS & CURE
ODOR DIAGNOSIS CHECKLIST
PLUMBING SYSTEM INSPECT DIAGNOSE REPAIR
GAS MEASUREMENT TOOLS
SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SEPTIC & CESSPOOL SAFETY
  TANK, & CESSPOOL WARNINGS
  SPECIAL WARNINGS FOR HOME OWNERS
  SEPTIC METHANE GAS
SEPTIC SYSTEM ODORS
SEWER GAS ODORS
TOXIC GAS TEST PROCEDURES

• Large-scale biogas plants, Ashden Awards for sustainable energy, quoting from that website's KIST (see below) project and award to the KIST bio gas prison bio gas project. The Ashden Awards for Sustainable Energy Allington House, 150 Victoria Street, London, SW1E 5AE, Tel. +44 (0)20 7410 0330 - http://www.ashdenawards.org
  - original source: http://www.ashdenawards.org/winners/kist05. Also see the technical report on this Rwandan bio-gas project hosted at the Ashden website.

The Kigali Institute of Science, Technology and Management (KIST), has developed and installed large-scale biogas plants in prisons in Rwanda to treat toilet wastes and generate biogas for cooking. After the treatment, the bio-effluent is used as fertiliser for production of crops and fuelwood.

Large prisons, each housing typically 5,000 prisoners, are a legacy of the troubled past of Rwanda. Sewage disposal from such concentrated groups of people is a major health hazard for both the prison and the surrounding area. The prisons also use fuelwood for cooking, putting great pressure on local wood supplies.

Using biogas digesters to manage animal or human sewage is not a new idea, but in Rwanda has been applied on an enormous scale, and with great success. Each prison is supplied with a linked system of underground digesters, so the sight and smell of the sewage are removed. KIST staff manage the construction of the system, and provide on-the-job training to both civilian technicians and prisoners. The biogas is piped to the prison kitchens, and halves the use of fuelwood. The fertiliser benefits both crop production and fuelwood plantations.

The first prison biogas plant started operation in 2001, and has run with no problems since then. Biogas plants are now running in six prisons with a total population of 30,000 people, and KIST is expecting to install three more each year.

The Ashden judges were highly impressed with the scale of these biogas plants, and the benefits which they provide in a difficult environment - sanitation, fuel and new skills for prisoners. They also recognised the significant potential for using such systems in other institutions like schools, hospitals, and on dairy farms - work which KIST has started to undertake.

• "Q+A on Not Wasting Waste: "I've heard that cow manure, but not human waste, can be used for energy production. Is it possible?", The New York Times, 11 May 2010, p. D2.
• Kigali Institute for Science and Technology (KIST), Kigali, Rwanda, www.kist.ac.rw/ see biogas plants.
• "Biomethane fuelled vehicles – the carbon neutral option", (bio-methane or bio methane), John Baldwin, CNG Services LTD., Claverton Energy Conference, Bath UK, 24 November 2008
• Bio-Gas Technologies, Ltd., 2025 George St., Sandusky, Ohio 44870 Tel: 419.663.8000 - see http://www.biogastech.com/

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

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• Goodman Furnace High Temperature Plastic Vent HTPV safety recall US CPSC notice
• Home Heating System Should Be Checked [for proper venting and for CO Carbon Monoxide Hazards - DJF]
• Inspection Procedures for Oil-Fired Heating Systems Detailed step by step approaches for inspecting complex systems]
• Lennox Pulse Furnace Safety Inspection/Warranty Program: Carbon Monoxide Warning
• Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
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• Weil McLain Model GV Gas Boiler/gas valve CPSC recall/repair
• Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
• National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
• The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
• Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
• The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
• Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
• "Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• "Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• "Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
• Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
• Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
• Installation Guide for Residential Hydronic Heating Systems
• Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
• The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
• Links to our list of additional information on heating system inspection, repair, maintenance
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