Why every village, town and community should have its own biogas facility!
Biogas technology is very advanced in scientific and engineering terms in Europe. It bears little resemblence to domestic biogas for cooking in rural India and is far more advanced and efficient than the failed US biogas industry of the 1970’s. It is a gas but is not recovered by drilling as with oil and natural gas. Biogas is not the same as and is far more efficient than incenerator, steam boiler type technologies and unlike them, does not pollute. It is much more efficient (about 85% when electricity and heat are co-generated) than wind turbine technology (about 30%) and enjoys a “capacity factor” in excess of 80% which is over 3 times that of wind energy. Biogas technology should not be confused with ethanol or biodiesel technologies and while crops, grasses and trees can be specifically grown to feed a biogas plant, it can also use and nutralise slurries, sewage, municipal waste, paper, whey and general biomass, (e.g. crop waste, bagass, forest residue, algae, silage, seaweeds), e.t.c. About 5,900 biogas plants with an installed electrical capacity of 2,300 MW are operational in Europe and 3,000 new biogas plants with an electricity generating capacity of more than 1,700 MW will be completed by 2013. In Germany alone there are over 4,500 commercial biogas plants with 1,650MW capacity. Germany is the World leader in biogas technology and in electricity produced by biogas fermentation. German biogas companies directly employ over 10,000 people. It is German Government strategy to generate up to 20% of its electricity requirement from biogas by 2020. The average EU biogas plant capacity is about 500kW. Biogas is conservatively estimated to be capable of generating 530MW electricity and over 1,500MW of heat in Ireland and can create lasting jobs and enterprise on Ireland’s farms, in its villages, towns and cities.
The process of anaerobic digestion (biogas fermentation) involves the breakdown of organic waste by bacteria in an anaerobic (i.e. without air) environment, leading to biogas production. This can occur naturally, in bogs, landfills, in lakes, swamps, oceans or in the stomachs of animals. Biogas consists of methane (50% to 75%), carbon dioxide (25% to 45%), water (2% to 7%) and trace gases (sulphur, oxygen, nitrogen, ammonia and hydrogen). Uncontrolled biogas release (e.g. by the melting of tundra permafrost or the excavation of bogs to e.g. build foundations for wind turbines) will release these gases to the atmosphere and will add to Global emissions of greenhouse gases. Methane, the dominant component of biogas is considered to be 21 times more global warming than carbon dioxide. Both are released by uncontrolled anaerobic digestion.
Farm, municipal or industrial anaerobic digestion plants ferment waste material to produce biogas. Organic waste feedstock is pumped into a closed vessel or tank (digester) with biogas generating bacteria. Anaerobic conditions are maintained in the vessel and the temperature is held at a value which varies depending on the bacteria used and the stage of fermentation. Biogas is usually combusted on site to generate electricity and heat. The biogas can be upgraded to pure methane gas for use in transport, by stripping out the CO2.
The methane content of biogas is the most energetic component of the gas. A cubic metre (m3) of methane has an energy content of 9.97 kilowatt hours (kWh) or 36 Megajoules (MJ). A cubic metre of biogas with a methane content of 55% contains about 21 MJ and in an engine generator will generate 2 kWh electricity. Recent technological developments promise to increase generation output. A cubic metre of biogas has approximately the energy of 0.55 litres of heating oil. Co-products (heat and fertiliser) add value to biogas production. Certified Emission Reduction (CER) credits, premium in the case of methane destruction, help to defray capital costs. But, biogas benefits go beyond financial returns.
Biogas production directly offsets the use of non-renewable resources (e.g. coal, oil, and fossil fuel-derived natural gas), with corresponding emissions reduction and energy security benefits. It consumes waste organic materials thereby cleaning the environment and reducing odours. It directly reduces greenhouse gas emissions by preventing methane release to the atmosphere. Biogas has a high “capacity factor” and a facility can operate as a reliable, standalone, diversified energy supply for towns, villages, communities and urban areas. Gas can be stored to increase electricity production at peak demand. Biogas production creates jobs and benefits the local economy. The residue slurry is a high quality, nutrient rich, inert, fertiliser.
Methane is a renewable transport fuel. In Europe some 1.3 million vehicles can run on methane fuel. It is relatively simple to adapt a vehicle to run on methane. Today methane can be carried on board vehicles as fuel in pressurised tanks. Research is ongoing to develop low cost gas separation systems and low pressure storage (e.g. nanosponge) for methane powered vehicles. It can be more profitable for a biogas plant to produce purified methane for transport vehicles, than generate electricity. However, in the Developing and Under Developed Worlds, the provision of electrical energy is a basic societal requirement.
A biogas facility can cost up to €2,500 per kW nameplate capacity, though the host economy dictates infrastructural, structural and construction costs, i.e. roads, concrete, steel, land, silos, labour, e.t.c. Taking capacity factor into account, capital costs compare favourably with wind turbines, the poster children of the alternative energy sector. A biogas plant usually must exceed 100kW in size to achieve economy of scale. It requires a constant supply of feedstock. A 500kW biogas plant will consume between 8,000MT and 15,000MT substrate per annum, depending on the energy content of substrate used. A well managed biogas facility will account for this and will vary substrates and make provision for silos. European biogas systems usually produce electricity at a cost of about €0.08 per kilowatt hour (kWh).
Methane is explosive and odourless, consequently safety precautions are essential.
Electricity production is limited by engine inefficiencies. The best biogas engines are about 40% efficient but secondary electricity can be generated by harnessing engine heat to increase overall electrical efficiency.
Bacteria can only access the sugars and starches which are relatively unprotected by the plant. Even after passing through the stomach and intestines of an animal, much of the energy in plantlife remains inaccesble. Plants are protected by lignin, a tough fibre which blocks predator access. Scientific research continues into ways and means to weaken lignin integrity and open more biomas sugars and starches to the bacteria.
Unlike wind, hydro, photovoltaic and fuel cell technologies, biogas has a range of useful co-products. In addition to electricity, an average biogas plant will produce a large volume of thermal energy which can be used in greenhouses, dwellings, public buildings, hospitals, schools, swimming pools, milking parlours, workshops, etc. Carbon Dioxide (CO2) is also produced. CO2 is often piped into greenhouses to raise air CO2 content by about 10% boosting plant growth and discouraging pests and vermin, obviating the requirement for pesticides. CO2 can also be frozen and used as a sandblaster (without the sand) to strip paint from ships, large vehicles, steel bridges e.t.c. and grime from stone buildings, statues, pavements, CSP panels, e.t.c.
The residue of the fermentation process is inert fertiliser, which can be spread on farmland or dried and sold as fertiliser to market gardening enterprises. The biogas process actually destroys pathogens in farm biomass and slurry. It also destroys seeds and spores so that unwanted plants will not grow when the fertiliser is spread on land. Biogas fertiliser enriches the soil with protein, cellulose and lignin, not normally delivered by inorganic fertilisers. Humic matter and humic acids present in the residue help reduce soil erosion (by rain or wind) and increase nutrient supply and soil hygroscopicity. Humic soil content is essential to low-humus soils often found in tropical regions. Properly managed, biogas effluent reduces the risk of surface or groundwater contamination.
A biogas process can form part of a co-generation facility. Even fossil power plants can co-generate with biogas and reduce their emissions.
Biogas systems reduce the growth of landfill volumes by diverting all organic materials to biogas fermentation. The residues are then used as fertiliser not filling up landfills. Landfill gas comprises an uncontrolled combination of gases which, in addition to methane and CO2, contain toxic chemicals (benzene, toluene, chloroform, vinyl chloride, carbon tetrachloride and 1,1,1 trichloroethane). Many are halogenated compounds (i.e. they contain chlorine, fluorine, or bromine) which when burned in the presence of hydrocarbons, can recombine into highly toxic compounds (e.g. dioxins, a carcinogen with no safe exposure level and furans) some of the most toxic chemicals identified. Tritium and mercury which cannot be destroyed by combustion, have been found in landfill outflows.
Sometimes, biogas recovery systems are installed into existing landfills. Even in a well managed landfill gas recovery system, over 50% of landfill gases will never be recovered. The International Panel on Climate Change calculates that, on average, only 20% of gas in landfills is actually collected. A landfill’s gas recovery lifetime is limited unless the landfill is continuously being filled, something we do not recommend. Once the readily available gas is depleted, the biogas machinery becomes redundant, electricity is no longer generated and must be sourced elsewhere. The facility is then usually shut down. However, a closed landfill will continue to generate gases and contaminants long after the gas recovery process is abandoned.
The costs of recovery and capture of secondary landfill gases and chemicals is a drag on profits and it may be tempting to simply release these gases to the air and put chemicals back to the landfill or into the engines. Regulation and control of exact landfill gas and chemical content and volume is difficult as, by its nature, a landfill contains an unknown volume and variety of gases, liquids, solids, chemicals, metals, e.t.c.
In contrast, a biogas facility can continue indefinitely, with no undisposable residue, landfill material, noxious smells, pollution or uncontrolled gas release. It will help to clean up the surrounding environment, provide valuable electricity, heat and fertiliser.
In summary, biogas fermentation is a holistic environmental technology which supports socio-environmental cohesion. It offers benefits to most sectors of society, environmental protection, energy, fuel, project contracts, enterprise opportunity, direct and indirect labour, farm and gardening fertiliser. Biogas should form an important part of every plan to develop villages, towns, communities and cities in harmony with their environment.
Note: Terraintegra is working with BioBit GmbH a Bavarian leading biogas expert company, partnering academia with commerce, to bring biogas technology, electricity and “quality of life” to villages in Africa and Asia.