What is biogas?

This is the gas or actually, a mixture of gases, produced during the anaerobic (oxygen-free) digestion of organic matter by various anaerobic bacteria. Biogas typically consists of 55 to 70% methane and 45 to 30% carbon dioxide with small amounts of hydrogen sulphide, water vapour and other impurities.

The combustible gas in biogas is methane which is the same as natural gas. One standard cubic metre of methane has an energy content of 35.8 Mj or 9.94 kWh. Biogas by itself can be used as fuel for boiling or heating purposes. In large quantities, it can be used to generate electricity using a gas engine generator or a gas turbine. For this purpose, hydrogen sulphide, which is corrosive, is first removed using certain desulphurization equipment. Similarly, water vapour can be removed by condensation equipment installed along the pipeline.  For other applications, such as fuel for NGV vehicles, biogas can be further upgraded to biomethane whereby carbon dioxide is also removed.

In a large landfill, or in a sewage or palm oil mill effluent pond, anaerobic conditions can exist whereby biogas is being produced and emitted into the atmosphere hence contributing to the global warming effect. This is because methane is a highly potent greenhouse gas (GHG), being 21 times more potent than carbon dioxide. 


What is a biogas plant?

A biogas plant is built to efficiently convert organic matter or biomass into energy (in the form of biogas) using the anaerobic digestion process. The substrate (that is, the input organic matter) used is usually organic waste material that would otherwise need to be disposed of. A biogas plant is designed to maximize the output of biogas from any organic material or biomass available in the shortest possible time. The residue, or digestate, can be processed into valuable organic fertilizer. Large biogas plants would include power generation equipment to convert the biogas to electricity which could be sold to the national grid.

A biogas plant is therefore a most effective system for biological recycling, besides contributing to a reduction in carbon emissions. As an investment, it is not only profitable but necessary in view of the inevitable depletion of fossil fuels. Unlike other methods of treating organic waste, a biogas plant has the further advantage of not causing any odour emission problem. This is because biogas plant digesters are completely sealed to ensure anaerobic conditions. Also, biogas plants can be designed to be as big or as small as required based on the quantity of substrate available. 

With the appropriate biogas plant technology, practically all kinds of organic waste or biomass can be used to produce biogas, and organic fertilizer. Such waste material therefore should not be regarded as waste but as stores of untapped renewable and sustainable energy. And biogas plant technology appears to be the best method to convert such organic waste into renewable energy.


In Malaysia, the palm oil industry generates the largest volume of organic waste in the form of empty fruit bunches (EFB), mesocarp fibres, palm kernel shells and also palm oil mill effluent (POME). Other major items of organic waste are the organic fraction of municipal solid waste (OFMSW), livestock farm manure, agro-industry processing wastes, sewage treatment plant sludge, etc. The biogas potential vary with different types of organic wastes.


Superior biogas technology 

Germany is the world leader in renewable energy and has the most advanced biogas technology. At SP Multitech Renewable Energy Sdn Bhd, we have a technology transfer agreement that enable us to build biogas plant with superior German technology but with Malaysian pricing.


Wet Fermentation

Anaerobic digestion biogas plants fall into two categories. The more common one is the wet fermentation plants which make use of steel or concrete tanks as digesters usually in a two-stage configuration. The first and smaller tank is for the initial hydrolysis stage followed by the acetogenesis and methanogenesis stages in the second and larger tank. It is a continuous process and the total tank capacity is sized according to the total daily input multiplied by the number of days of hydraulic retention time required. 


Dry Fermentation

The dry fermentation anaerobic digestion (DFAD) technology is a more recent development. This method is more energy and labour efficient, and is suitable for substrates with lower moisture content. This system consists of a number of digesters or bio-reactors equipped with special airtight doors, the number depending on the expected retention time required. Each digester is designed to accommodate one day’s supply of substrate which is fed each day into the digesters in sequence. Each digester is a batch processor but when operated in sequence, the system is a continuous process.

The DFAD biogas technology is particularly suitable for substrate with lower moisture such as OFMSW. This technology could revolutionize the management and disposal of MSW which is usually sent to the landfill. Such DFAD plants could be set up at landfill sites. Then the MSW received would  first sorted out with the organic portion going to the DFAD biogas plant to produce biogas and organic fertilizer. In the sorting process, recyclable items made of plastic, glass or metal could be taken out for sale to recycling companies. Then, only the inorganic, non-recyclable items need to go to the landfill, thereby helping to extend the lifespan of the landfill site. A big landfill that has up to 250 tonnes of OFMSW would have enough biogas to generate up to 3 MW of electrical output.

In both methods, it is important to monitor and  maintain optimum environment for the various types of bacteria, especially the methane-enhancing or methonogenic bacteria, to thrive on. This is where technological expertise and knowledge of such bacteria are required  to achieve good overall results. With technology support from our German partner, we are confident that our biogas plants would perform exceedingly well.


Global effort 

There is serious global concern about global warming caused by emission of GHGs and every country should contribute to the global effort to reverse the trend by promoting green or renewable energy. At SP Multitech Renewable Energy Sdn Bhd, we intend to play a significant role in this effort by building as many biogas plants as possible. We would consider it a service for the cause of global environmental protection.






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