Biogas Combustion

In principal, biogas can be used like other fuel gas. When produced in household-level biogas reactors, it is most suitable for cooking. Additionally, electricity generation is a valuable option with the biogas produced in large anaerobic digesters.

Household energy demand varies greatly and is influenced by cooking and eating habits (i.e., hard grains and maize may require substantial cooking times, and, therefore, more energy compared to cooking fresh vegetables and meat). Biogas has an average methane content of 55-75%, which implies an energy content of 6-6.5 kWh/m3


Design Considerations

Gas demand can be defined on the basis of energy previously consumed. For example, 1 kg firewood roughly corresponds to 200 L biogas, 1 kg dried cow dung corresponds to 100 L biogas and 1 kg charcoal corresponds to 500 L biogas.

Gas consumption for cooking per person and per meal is between 150 and 300 L biogas. Approximately 30-40 L biogas is required to cook one litre of water, 120-140 L for 0.5 kg rice and 160-190 L for 0.5 kg vegetables.

Tests in Nepal and Tanzania have shown that the consumption rate of a household biogas stove is about 300-400 L/h. However, this depends on the stove design and the methane content of the biogas.

The following consumption rates in litres per hour (L/h) can be assumed for the use of biogas:

  • household burners: 200-450 L/h
  • industrial burners: 1000-3000 L/h
  • refrigerator (100 L) depending on outside temperature: 30-75 L/h
  • gas lamp, equivalent to a 60 W bulb: 120-150 L/h
  • biogas/dieselengine per bhp: 420 L/h
  • generation of 1 kWh of electricity with biogas/diesel mixture: 700 L/h
  • plastics moulding press (15 g, 100 units) with biogas/diesel mixture: 140 L/h

Compared to other gases, biogas needs less air for combustion. Therefore, conventional gas appliances need to be modified when they are used for biogas combustion (e.g., larger gas jets and burner holes).

The distance through which the gas must travel should be minimized since losses and leakages may occur. Drip valves should be installed for the drainage of condensed water, which accumulates at the lowest points of the gas pipe.

Appropriateness

The calorific efficiency of using biogas is 55% in stoves, 24% in engines, but only 3% in lamps. A biogas lamp is only half as efficient as a kerosene lamp. The most efficient way of using biogas is in a heat-power combination where 88% efficiency can be reached. But this is only valid for larger installations and under the condition that the exhaust heat is profitably used. For household application, the best way to use biogas is cooking.

Health Aspects/Acceptance

                    

In general, users enjoy cooking with biogas as it can immediately be switched on and off (as compared to wood and coal). Also, it burns without smoke, and, thus, does not lead to indoor air pollution. Biogas generated from faeces may not be appropriate in all cultural contexts. Assuming that the biogas plant is well-constructed, operated and maintained (e.g. water is drained), the risk of leaks, explosions or any other threats to human health is negligible.

Operation & Maintenance

Biogas is usually fully saturated with water vapour, which leads to condensation. To prevent blocking and corrosion, the accumulated water has to be periodically emptied from the installed water traps. The gas pipelines, fittings and appliances must be regularly monitored by trained personnel.

When using biogas for an engine, it is necessary to first reduce the hydrogen sulphide because it forms corrosive acids when combined with condensing water.

The reduction of the carbon-dioxide content requires additional operational and financial efforts. As CO2 "scrubbing" is not necessary when biogas is used for cooking, it is rarely advisable in developing countries.

References

Further Readings

  • Cover image of a reference book or miscellany.

    TILLEY, E.; ULRICH, L.; LUETHI, C.; REYMOND, P.; SCHERTENLEIB, R.; ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies (Arabic). 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag). PDF

    This is the Arabic version of the Compendium of Sanitation Systems and Technologies. The Compendium gives a systematic overview on different sanitation systems and technologies and describes a wide range of available low-cost sanitation technologies.

  • Cover image of a reference book or miscellany.

    DEKELVER, G.; RUZIGANA, S.; LAM, J. (2005): Report on the Feasibility Study for a Biogas Support Programme in the Republic of Rwanda. Netherlands Development Organisation (SNV) . URL [Accessed: 09.04.2010]. PDF

    This report presents the findings of a study conducted by Ministry of Agriculture (MININFRA) and SNV to assess the feasibility to set-up and implement a national programme on domestic biogas in Rwanda.

  • Cover image of a reference book or miscellany.

    DRESCHER, S.; ZURBRUEGG, C.; ENAYETULLAH, I.; SINGHA, M.A.D. (2006): Decentralised Composting for Cities of Low- and Middle-Income Countries – A User’s Manual. Dhaka: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC) and Waste Concern. URL [Accessed: 16.08.2010]. PDF

    This book describes approaches and methods of composting on neighbourhood level in small-and middle-scale plants. It considers issues of waste collection, composting technologies, management systems, occupational health concerns, product quality, marketing and end-user demands.

  • Cover image of a reference journal article.

    ITODO, I. N.; AGYO, G. E.; YUSUF, P. (2007): Performance evaluation of a biogas stove for cooking in Nigeria. In: Journal of Energy in Southern Africa 18, 14.URL [Accessed: 09.04.2010]. PDF

    Journal article on a biogas digester, which was designed, constructed and its performance evaluated using a 3m3 continuous flow Indian type biogas plant at the Teaching and Research Farm, University of Agriculture, Makurdi, Nigeria. Various technical drafts and mathematical and chemical formulas are shown.

  • Cover image of a reference book or miscellany.

    KOSSMANN, W.; POENITZ, U.; HABERMEHL, S.; HOERZ, T.; KRAEMER, P.; KLINGLER, B.; KELLNER, C.; WITTUR, T.; VON KLOPOTEK, F.; KRIEG, A.; EULER, H. (1999): Biogas Digest Volume II. Biogas - Application and Product Development. Eschborn: GTZ. URL [Accessed: 09.05.2014]. PDF

    This information service on biogas technology has been developed and produced on the order of the GTZ project Information and Advisory Service on Appropriate Technology (ISAT). It contains information on the application of biogas and product development.

  • Cover image of a reference book or miscellany.

    LOHRI (2009): Research on Anaerobic Digestion of Organic Solid Waste at Household Level in Dar es Salaam, Tanzania. Zurich University of Applied Sciences (ZHAW). URL [Accessed: 05.05.2010]. PDF

    Decentralized anaerobic digestion is a promising technology to handle the large organic fraction of the municipal solid waste (e.g. kitchen waste) with the additional benefit of producing biogas as well as fertilizer. This paper evaluates the suitability of the ARTI Compact biogas system as a decentralised low-tech treatment option for the organic fraction of household waste in Dar es Salaam, Tanzania.

  • Cover image of a reference book or miscellany.

    NES, W.J.; BOERS, W. van; UL-ISLAM, K. (2005): Feasibility of a national programme on domestic biogas in Bangladesh. Final report. Netherlands Development Organisation (SNV). URL [Accessed: 23.04.2010]. PDF

    This report presents the finding of a study conducted by the Netherlands Development Organisation (SNV) to assess the feasibility to set up and implement a national programme on domestic biogas in Bangladesh.

  • Cover image of a reference book or miscellany.

    NWP (Editor) (2006): Smart Sanitation Solutions. Examples of innovative, low-cost technologies for toilets, collection, transportation, treatment and use of sanitation products. Amsterdam: Netherlands Water Partnership (NWP). URL [Accessed: 13.04.2010]. PDF

    Smart Sanitation Solutions presents examples of low-cost household and community-based sanitation solutions that have proven effective and affordable. A wide range of innovative technologies for toilets, collection, transportation, treatment and use of sanitation products that have already helped thousands of poor families to improve their lives is illustrated.

  • Cover image of a reference book or miscellany.

    PACE Project (Editor) (n.y.): Biogas. The Pan African Conservation Education Project (PACE Project). URL [Accessed: 20.04.2010]. PDF

    Factsheet on biogas and how it can be produced at farm level.

  • Cover image of a reference book or miscellany.

    PBPO (Editor) (2006): Support Project to the Biogas Programme for the Animal Husbandry Sector in some Provinces of Vietnam. Hanoi: Provincial Biogas Project Office Hanoi . URL [Accessed: 13.04.2010]. PDF

    The Vietnamese and Netherlands Governments signed a Memorandum of Understanding for the implementation of a domestic biogas dissemination project in 10 provinces of Vietnam in January 2003. The project supports the agricultural sector in several provinces in Vietnam and uniquely joined Vietnams technical knowledge on fixed dome plant design and construction with Netherlands experience with large-scale dissemination of domestic biogas.

  • Cover image of a reference book or miscellany.

    SINHA, S.; KAZAGLIS, A. (n.y.): BIOGAS and DEWATS, a perfect match?. Bremen: Bremen Overseas Research and Development Agency (BORDA). URL [Accessed: 13.04.2010]. PDF

    The resources gained from DEWATS-linked biogas digesters (gas for cooking), when combined with adequate social interventions, have resulted in increased acceptance of the DEWATS installations by communities and institutions. Two case studies in Bangalore, India illustrate this approach of the Bremen Overseas Research and Development Association (BORDA).

Case Studies

  • Cover image of a reference book or miscellany.

    ASHDEN (Editor) (2005): Biogas plants providing sanitation and cooking fuel in Rwanda. London: The Ashden Awards for Sustainable Energy. URL [Accessed: 13.04.2010]. PDF

    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 fuel wood.

  • Cover image of a reference book or miscellany.

    ASHDEN (Editor) (2007): Clean cooking and income generation from biogas plants in Karnataka. London: The Ashden Awards for Sustainable Energy. URL [Accessed: 14.03.2010]. PDF

    SKG Sangha (SKG S) is a non-profit organisation that supplies biogas plants to households in rural areas of South India. The ‘Deenbandu’ design plants are built on-site by local masons and labourers trained by SKGS, with very high quality standards. Plants produce biogas by digesting cow dung, replacing all the fuel wood used for cooking.

  • Cover image of a reference book or miscellany.

    VOEGELI, Y.; LOHRI, C.R.; GALLARDO, A.; DIENER, S.; ZURBRUEGG, C.; EAWAG (Editor) (2014): Anaerobic Digestion of Biowaste in Developing Countries. Practical Information and Case Studies. Duebendorf: Swiss Federal Institute of Aquatic Science and Technology (Eawag). URL [Accessed: 03.03.2013]. PDF

    This book published by Eawag/Sandec compiles existing and recently generated knowledge on anaerobic digestion of urban biowaste at small and medium scale with special consideration given to the conditions prevailing in developing countries. Written for actors working in the waste and renewable energy sector, the book is divided into two parts: Part 1 focuses on practical information related to the anaerobic digestion supply chain (substrate-, process-, and product chain), and Part 2 presents selected case studies from around the world.

  • Cover image of a reference book or miscellany.

    WAFLER, M. ; HEEB, J.; STAUB, A.; OLT, C. (2009): Pour-flush toilets with biogas plant at DSK Training Institute. Gujarat, India - Draft. Eschborn: Sustainable Sanitation Alliance (SuSanA). URL [Accessed: 25.04.2010]. PDF

    The project described aimed at avoiding manual scavenging of faecal products and at improving the sanitation situation at the Navsarjan Vocational Training Institute. Now greywater is separately treated and reused in the garden while the urine and faeces (blackwater) are directly introduced into a biogas plant. Digested sludge is dried on basic drying beds and used as compost for the garden. UDDTs were also installed. The concept was implemented and evaluated for its social and cultural acceptability, sustainable and hygienic safety.

  • Cover image of a reference book or miscellany.

    ZIMMERMANN, N.; WAFLER, M.; THAKUR, P. (2009): Decentralised Wastewater Management at Adarsh College Badlapur, Maharashtra, India. Eschborn: Sustainable Sanitation Alliance (SuSanA). URL [Accessed: 22.09.2010]. PDF

    This case study reports the development of an ecologically sound sanitation concept at the Adarsh Bidyaprasarak Sanstha's College of Arts & Commerce. In comprises separate urine collection and a DEWATS system for the treatment of black- and greywater consisting of biogas settler, an anaerobic baffled reactor, and anaerobic filter, a horizontal flow wetland and a polishing pond.

Awareness Material

  • Cover image of a reference book or miscellany.

    ASHDEN (Editor) (2007): SKG Sangha Film. London: The Ashden Awards for Sustainable Energy. URL [Accessed: 15.03.2011].

    Short film about SKG Sangha, a non-profit organisation that supplies biogas plants to households in rural areas of South India. The ‘Deenbandu’ design plants are built on-site by local masons and labourers trained by SKG Sangha, with very high quality standards. Plants produce biogas by digesting cow dung, replacing all the fuelwood used for cooking.

Important Weblinks

  • http://www.arti-india.org/ [Accessed: 09.04.2010]

    This webpage of the Appropriate Rural Technology Institute (ARTI) contains a report on an implemented biogas plant project in Maharashtra, India. The biogas is used for cooking.

  • http://akvo.org/ [Accessed: 09.04.2010]

    The sanitation portal of Akvopedia offers state of the art information on several sanitation technologies. It also mentions background knowledge on “Biogas as a source of energy”.

  • http://www.susana.org/ [Accessed: 09.04.2010]

    The webpage of Sustainable Sanitation Alliance working group 03 provides up to date information on the use of biogas and anaerobic biogas reactors. Technical drafts and links are also available.