Waste to Energy

Extracting energy from our waste did not originate from a desire to produce electricity but rather to reduce the environmental damage of the waste stream. In the case of landfill, the focus of this article, the methane generated by buried rubbish was collected and burned off long before the potential to utilise this energy source was harnessed. Now, using the methane produced by landfill to generate electricity is commonplace, with most large landfill sites operating generators to power their own needs and feed excess into the grid. This energy source is on the decline however. With landfill containment improvements, and an increasing volume of the waste stream being diverted to reuse, recycling or other uses, landfill sites are producing significantly less methane.

Incineration of solid waste tends to be popular in clusters – some regions embrace the process, while others shun it.  High temperature combustion of sold waste remains controversial primarily because of the perceived risks associated with the emission of toxic by-products into the atmosphere. There is actually very little evidence that modern incinerators, with their advanced treatment of flue-gas, emit hazardous levels of pollutants. Reluctance is therefore predominantly driven by negative public sentiment, a legacy of older style incinerators which were responsible for distributing high levels of toxic pollutants. Incineration extracts energy from the waste stream and in doing so significantly reduces the volume of waste that is sent to landfill, minimising the environmental and social implications of landfill in the process.

The emergence of alternative waste technologies which incorporate anaerobic digestion, or a combination of aerobic and anaerobic digestion, to produce biogas is shaping up to become the most efficient way of converting waste to energy. The controlled digestion of organic waste is similar to the process that takes place in covered landfill to produce methane however the process is accelerated and controlled, resulting in less volume of waste to landfill and a greater rate of capture of the biogas. This technology is still evolving. To date it has been used to greatest effect to generate energy from sewage, farming and industrial effluent however treatments to digest municipal solid waste, such as the process developed by Australian company Anaeco, are nearing widespread commercial deployment.