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A new report titled ‘A Wasted Opportunity’ has outlined an action plan to prevent the UK turning into one big dumping ground.

The plan, devised by the Institution of Mechanical Engineers (IMechE) urges the government to adopt a series of measures and advanced technologies which, if adopted across the UK, could help reduce CO2 emissions by 80 per cent by 2050 and produce a third of UK electricity from renewable sources by 2020.

The UK previously adopted a policy of burying all waste, but 2002 legislation stated the UK must reduce this by 25 per cent by 2010 and 50 per cent by 2013.

The report said this cannot be achieved by recycling alone as there are too few recycling plants.

There is also the issue that large quantities of recyclable products are being shipped abroad to uncertain futures, but this still counts towards UK and local targets.

The report highlights the benefits of creating an energy-from-waste network, which would help power the nation and reduce the need for landfill.

An EfW plant converts waste into usable energy.

Sewage, domestic, commercial, industrial, construction and demolition waste (which currently accounts for 36 per cent of waste) can all be used in the processes, as long as they are combustible or biodegradable.

A thermal EfW plant treats waste in the same way that a coal-fired power station treats coal.

Any other benefit, such as volumetric reduction, is a useful by-product, but is not the primary purpose of an EfW plant.

Unfortunately, most legislation over recent years has focused on EfW as waste treatment rather than as energy production and has classified EfW plants as incinerators rather than power stations.

The approach is different to most parts of Europe, where recycling and EfW are used to their optimum potential, minimising landfill.

The report highlights massive public and government misunderstanding about EfW, which tends to conjure up images of huge incineration plants.

IMechE says the government is unclear about this and claims Defra refers to EfW plants as incinerators despite widespread public consultation.

Four main processes are used in EfW plants.

Combustion uses a variety of fuels and is used in all UK large coal-fired power stations and follows a process known as the Rankine Cycle.

Gasification is where oxygen in the form of air, steam or pure oxygen is reacted at high temperature with the carbon in waste to produce a gas, ash or slag and a tar product.

The benefit of gasification of bio-wastes is that the product-gas can be used directly, after significant cleaning, to fuel a gas turbine generator.

Pyrolysis is a thermal process that involves the thermal degradation of organic waste in the absence of oxygen to produce a carbonaceous char, oils and combustible gases.

Anaerobic Digestion (AD) is a biological process most commonly used with liquid and semi-liquid slurries such as animal waste.

AD efficiently processes wet-waste and can obtain gas from human sewage.

It is ideal for small-scale operations such as farms, where enough energy (electricity and heat) can be produced to run the farm (including fuelling some of the vehicles) from what is produced on the farm.

Accurate statistics for total waste are hard to come by in the UK, but latest figures show the country generates 307 million tonnes of waste annually, or enough to fill the Albert Hall every two hours.

Defra estimates 46.4 million tonnes of that was ‘household and similar waste’, with 60 per cent of this landfilled, 34 per cent recycled and six per cent incinerated.

According to statistics, none of this resource was used as fuel in EfW plants.

Ian Arbon of IMechE said: ‘It is extremely improbable that the UK’s legally binding renewable energy commitments can be reached unless EfW plants are established and become regarded as the best-proven, safe, clean energy recovery solution available to us.’

Institution of Mechanical Engineers

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