Entec Bulletin
Energising the Waste Hierarchy
Energy from waste: Eureka or rubbish?
In the UK, we throw away 420 million tonnes of waste every year. Of this, a large proportion comes from agriculture, mining, construction and the sewage management industries. For most of us, the waste stream we see every day is 'municipal' solid waste (MSW). This comprises the rubbish in our dustbins, along with other wastes collected by our local councils. In the UK, we produce over 30 million tonnes of MSW every year, enough to cover a football pitch to a depth of around 10 miles!!
Historically, the UK has simply disposed of MSW to landfill sites. It is true that the engineering of landfills has improved substantially in recent years, and the control over their environmental impact has increased greatly, but landfill disposal still remains at the bottom of the hierarchy. Whilst this option still dominates the way in which we manage waste in this country (for instance, about 77% of England's MSW went to landfill in 2001/2), the UK's waste management industry is now moving up the hierarchy.
The main driver for this is the EU's Landfill Directive, including the requirement for local authorities to reduce the amount of biologically active MSW that goes to landfill. When this kind of waste is landfilled, it rots down and in doing so creates 'landfill gas', which contains a lot of methane, a very potent greenhouse gas.
Overall, we're continuing to produce more waste, but even if as individuals we step up reduction, composting and recycling, there will still be a large quantity of waste that needs to be handled, managed and disposed of - the 'residual' or 'post-recycling' waste.
About two-thirds of MSW is of recent biogenic origin such as food wastes, paper and card. To comply with the Landfill Directive, this potentially biodegradable waste needs to be removed, or made biologically stable, before being landfilled. But as well as being potentially biodegradable, MSW can be used as a fuel. Weight for weight, residual MSW contains about a third of the energy content of coal and when burnt, it releases energy in a similar way to any other fuel.
Of course it doesn't make sense to burn all our waste. We need to aim for the top of the hierarchy and do much more to reduce our production of waste and then to improve our reuse and recycling. But Energy from Waste (EfW) can work alongside as part of an integrated waste management scheme, as proved in Denmark, where in 1999, 24% of MSW was recycled, 23% was composted, and 41% went into Energy from Waste. Burning MSW also produces lower net emissions of CO2 than burning coal. Plus you're not going to create as much landfill gas, so EfW really can help reduce greenhouse gas emissions.
Energy production always brings with it some environmental impact, and EfW does produce solid residues such as ash alongside the gaseous products of combustion. We also need to carefully consider the possible environmental and human health impacts of construction and operation. But tightening regulations and substantial improvements in technology have greatly improved the environmental performance of EfW plants in recent years, and a recent DEFRA study* states that "risks to human health from incineration are small in comparison with other known risks. We must acknowledge the role of incineration with energy recovery as a sustainable waste management option…".
So what of the future? Waste management policies are rightly driving us towards better use of our resources. Meanwhile, energy policy drivers include the reduction of greenhouse gas emissions, and the need to maintain the security of our energy supplies. But they don't have to be incompatible. Within an integrated waste management scheme that firstly targets recycling opportunities, an Energy from Waste project can contribute substantially to the avoidance of landfill. And when you consider that using say 50% of our MSW for energy could potentially provide up to 10% of UK household electricity, it's clear that EfW could provide a useful contribution in keeping our energy supplies diverse, secure and affordable.
In recent years, the UK has seen the construction of a small number of new EfW schemes. Others are planned or in construction, using an ever-growing range of technologies - all with the same aim: to safely and economically recover useful energy from our waste, and to securely dispose of all residues. However, the rate of growth is much slower than many observers think is needed for us to achieve our Landfill Directive targets, and it would be a shame if we fail to realise the role Energy from Waste can play in meeting our need for more sustainable waste management solutions.
*Review of Environmental and Health Effects of Waste Management: Municipal Solid Waste and Similar Wastes, DEFRA, 2004
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