Is energy from rubbish just a load of hot air?

Forget wind farms, solar power and hydro-electricity, the growth area in renewable energy is actually far closer to home: in our dustbins.

Mention renewable energy and most people think of solar, wind and wave power. But these generate only a fraction of the UK’s energy requirements. The fuel for the future is more likely to come from our dustbins.

Wind power may get the lion’s share of media coverage but, according to the DTI’s 2001 Energy Digest, energy from waste is the second-biggest source under the renewables heading. Ninety municipal solid-waste and general industrial energy-from-waste schemes have been approved, with 16 currently operational, generating 193MW of power. There are three that burn chicken waste, while the latest, a 2MW plant in north Devon that will burn gas from fermented dung from local farms, is awaiting approval from the Environment Agency to begin operating in the next few weeks.

Energy from waste is set to grow further, driven by an increasing shortage and the rising cost of landfill sites, plus forthcoming EU directives. However, obstacles also exist in the shape of public opposition to waste incinerators, while some question whether energy from waste should count as a renewable source at all.

A typical energy-from-waste plant generates electricity for 50,000 homes. Cities that have waste power plants are Coventry, Birmingham, Nottingham, Sheffield, Dundee and London. They burn waste to turn water into steam, to drive a turbine to generate electricity. Municipal solid waste includes everything from household refuse to scrap tyres, hospital waste, meal and bone, paper, cardboard, wood and plastics.

If you find these materials unlikely fuels, then chicken waste must seem preposterous. But there are three UK chicken litter power stations, in Eye and Thetford in East Anglia and Fife, Scotland. The Fife plant uses a fluidised-bed combustion process in which the waste burns in a container of air-suspended sand at very high temperatures. The others use mass grate technology, where waste is burnt on a grate with the remains scraped off afterwards to be used as fertiliser.

The heat value of these waste materials is about 30 per cent that of coal, 10 MJ/kg. This leads to one criticism of incineration: that its output-to-input ratio compares badly with other renewable energy technology, such as hydro-electricity. But incinerators can also burn refuse-derived fuel (RDF), processed waste from which all recyclable material has been removed, after which it is shredded and compacted into pellets. This more concentrated fuel has 60 per cent of the heat value of coal.

Andrew Limbrick, energy policy advisor for the Association of Electricity Producers, is currently writing standards for RDF. He says: ‘It’s more popular on the continent. It is hardly used in the UK. It involves sorting and screening the waste for materials that can be recycled.’

The rise of waste incineration here began with the Non Fossil Fuel Obligation, established during privatisation under the Electricity Act in 1989. Primarily intended to protect nuclear power, it also provided a guaranteed price and market for other non-fossil fuels. The government approved five NFFO orders between 1990 and 1998.

The burning question

Since February 2000 NFFO has been superseded by a new renewables policy, obliging all suppliers to provide a specific proportion of their electricity from ‘eligible renewables’. That policy also exempted renewables from the Climate Change Levy, and set up an expanded support programme with capital grants, and a bigger R&D programme, as well as including proposals for the development of a regional strategic approach to planning and targets for renewables.

EU directives, one promoting electricity generation from renewable energy sources and another intended to reduce the use of landfill, coupled with a landfill tax which rises by £1/tonne annually, will add to the momentum. Under the landfill directive it will be up to local authorities to develop alternative waste disposal strategies for organic waste, such as composting. Incineration will be an option, but the Department of the Environment, Food and Rural Affairs says small schemes designed to meet the needs of the immediate area will be favoured over bigger schemes.Despite this, Ian Fell, professor of energy conversion at the University of Newcastle-upon-Tyne, says problems with planning and the ‘not in my backyard’ mentality are holding the industry back. ‘We talk about plants but do little about it.

The planning system takes so long it becomes a disincentive to invest. The government has listed 60 to 120 sites and we need several [to go into operation]. We are running out of holes for landfill.’

Government plans for waste are unrealistic, he adds. ‘We get one per cent of our energy from waste. The EU average is six per cent. But there is no realistic strategy for using waste to generate energy. The activists say we should recycle but we’re bad at that.’

There is certainly plenty of scope to reduce landfill growth by increasing the use of incineration. According to ESA 90 per cent of municipal solid waste in the UK currently goes straight to landfill, with only a small percentage being recycled and just 10 per cent used for generating energy. Recovery rates in other European countries are generally 35-80 per cent.

After incineration only a relatively small quantity of ash remains to be disposed of. There are two main types: bottom ash, which is similar to coal ash, and flue ash, which can be used as a construction material, reducing the need to quarry new aggregates; in landfill sites, because it is inactive, it does not create the methane gas and leachate formed when organic materials decompose.

Poisonous emissions

Flue ash can, however, contain high levels of dioxins and needs to be buried in special landfill sites that have no groundwater. Even so, this is outweighed, says the energy-from-waste industry’s representative, the Environmental Services Agency, by the fact that incineration can reduce municipal waste in landfill by 90 per cent.

Fell accepts that people have been concerned about poisonous emissions, notably dioxins, from incinerators. He says: ‘There is no doubt that in the past incinerators have not been good and have put a lot of dioxins into the atmosphere. But now the rules are very strict and the latest technology can achieve an output less than parts per billion.’

There are also health concerns about landfill. A government-commissioned study by the Small Areas Statistics Unit at Imperial College recently found that babies born to parents living within 2km of landfill sites have a one per cent higher chance of a birth abnormality. And those living the same distance from sites containing hazardous waste have a seven per cent increased risk. The study was the largest undertaken, covering more than 9,500 British landfill sites.But despite government and European Union support for renewable energy their inclusion of waste power in that definition is opposed by environmental groups. Mark Johnston, energy campaigner for Friends of the Earth, does not classify incineration as a renewable. His organisation does not want any new power-from-waste plants. ‘Public money should only go to genuine renewable energy. It makes better sense to recycle or compost. With recycling you’re reducing energy consumption to produce more glass and other industrial products.’

This view is endorsed by the chief executive of the Environment Agency, Baroness Young, who says that using waste as an energy source sends the wrong message to manufacturers and consumers: that producing waste is OK.

Nonetheless, without a significant change in UK attitudes to recycling, it looks as though energy from waste will keep on growing – at least in the medium term.