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How to Take One Man’s Trash and Create Useful Material and Energy for Others

No! You don’t need a genie and a lamp, and yes, it is possible. In fact, more and more people are doing it all the time.

Waste from one source becomes the raw material and energy for others when you use a process called Anaerobic Digestion. Waste treatment in this fashion uses the same process as that which naturally occurs in landfills. In an oxygen free environment it reduces organic waste to a relatively stable solid residue (digestate) similar to compost, and a gas containing about 60% of methane which is known as biogas.

Biogas is rapidly becoming one of Europe’s most important biofuels, with the sector scaling up to produce the alternative to natural gas on an industrial scale. Last year, hundreds of plants produced an estimated 5.3 million tonnes of oil equivalent energy from biogas.

Biogas upgraded to bio-methane to natural gas standards is included as an eligible renewable source. This gas (and natural/ propane gas) comes in at half the price of diesel in Europe (which currently around 1.25 GBPound or 2.50 $US/litre), and is very clean in emissions. Also, biogas in Europe gives direct financial returns when used to generate electricity, plus the value from payments made to the generator in renewable obligation certificates (ROCs), which further increases these returns.

Now, to tell you more about the process; Anaerobic digestion is a natural process which takes place in the absence of oxygen. Organic material is digested by bacteria in a closed reactor vessel and biogas is produced. In other words, Anaerobic Digestion is the degradation of organic wastes in the absence of oxygen and has been used for many years for the treatment of agricultural and sewage sludges. Although, generally more expensive than composting, the process has the great advantage of producing gas for energy recovery in addition to a usable end product.

Material is retained in an enclosed reactor at temperatures of 35-55 degrees Centigrade for a period of 10-30 days. Around 50% of the organic matter is degraded into biogas during this process.

Biogas is one of the least environmentally harmful fuels economically available today. Because it is based on biologically produced substances it is part of the normal natural recirculation of carbon which is always taking place, and does not contribute to the CO2 content in the atmosphere.

Biogas is such a green fuel because it is said to be carbon neutral. This is precisely because the carbon dioxide that is given off in the process was taken out of the atmosphere when the plants that it was made from grew. By growing another crop and digesting that you repeat the process. No extra carbon dioxide is produced, the carbon simply continually recirculates.

The production of this gas is also on development agendas as a poverty reduction and job-creation strategy. It is a very real alternative to petrol and diesel. Biogas is usually stored in the reactor under a pressure of up to 1000 mm WG (water gauge) and is immediately available for use at any time.

Biogas is also gradually gaining popularity, in Africa where the lack of clean and sustainable energy sources represents a danger to the environment and its people. There are several initiatives in progress in developing nations where the vision is to establish market-oriented bio-energy partnerships between governments, the private sector, civil society and international development partners.

Households with biogas plants have a greatly reduced need for burning fuel-wood, making significant savings on carbon emissions. Locally produced biogas will help further reduce carbon-dioxide emission to the environment, where they plan to achieve carbon neutral economies. Nepal for example has a scheme where use of the installed AD plants remains above 97 per cent.

Finally, I would like to point out that sewage gas is also biogas produced by the digestion of sewage sludge. Sewage plants use anaerobic digestion to reduce the volume of solid wastes and reduce the smell. In recent years, many UK water companies have recognised the potential of the gas produced and generate electricity from it to use on-site or sell to the national power grid.