Generating electricity and heat energy from landfill destined waste

Posted: March 17, 2009 in environment, science & technology
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Photo: Verus Energy Ltd. Co-Founders Tim Jervis and David Diracles

Verus Energy is a development company focused on creating renewable power plants that use waste as the feedstock. Waste has been used to make heat or electricity on a commercial scale for quite some time, at least for the past 75 years. However, until recently the primary method of extracting energy from waste was incineration. The drawback of incineration is that it produces undesirable emissions which are difficult and expensive to get rid of. In addition, incineration plants often distribute electricity only, as opposed to electricity and heat, because they are too large to be located near commercial heat customers or district heating schemes. In such cases approximately 2/3 of the energy in the waste is lost as heat emitted to the atmosphere.

Verus is taking a very different approach. Instead of large scale mass burn incinerators, we are developing small scale, community based solutions that use advanced technologies such as anaerobic digestion and pyrolysis. Because these technologies can be deployed on a small scale, the facilities can be located next to a large heat user. For example if a plant were located next to a factory, the waste heat from the electricity generation process could be used by the factory. Typically this would displace the factory’s reliance on natural gas or other fossil fuels used to fire an on-site boiler.

Both anaerobic digestion and pyrolysis produce very clean emissions. The US and the UK have very tight limitations on power plant emissions and both of these technologies fall well below the allowed rates. With anaerobic digestion, waste is converted into biogas via the age old process of decomposing organic matter with bacterial digestion. As the bacteria digest the waste, they naturally produce biogas. The pyrolysis process also decomposes waste but instead of a biological process, it relies on the application of high heat. Waste is exposed to high heat in the absence of oxygen. Because oxygen is not present, the material does not burn. The high temperature environment converts the waste into a synthetic gas. The biogas and synthetic gases created in anaerobic digestion and pyrolysis can then be combusted in much the same way that natural gas is combusted to produce electricity and heat.

In addition to the clean exhaust in these processes, they allow large amounts of waste to be diverted from landfill. This reduces the leachate problems and methane, a green house gas 21 times as potent as CO2, associated with landfill.

How much energy could be generated from waste? The UK for example sends about 50 million tones of municipal, commercial, and industrial waste to landfill each year. If the UK could change its waste patterns so that 25 million tones was used to create energy, approximately 25 million MWhs of electricity and 50 million MWhs of heat could be produced. This roughly translates into enough electricity to power 2 million homes. While it’s definitely not enough to power the UK, it would make a meaningful and valuable contribution to the countries renewable energy targets and divert a vast amount of waste from being dumped in landfills.

For more information about Verus Energy, check out their website.

This is an edited version of an interview done by Green Is Sexy with the founders of Verus Energy

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