Energy from waste: a wasted opportunity?

Paul Boughton

Waste is a huge problem in the UK. The country produces over 300 million tonnes of waste per year, enough to fill the Royal Albert Hall every two hours but the love affair with landfills could soon be coming to an end as we run out of space - and time. So what next?

A report launched today (4 December) outlines a five-pronged action plan devised by the Institution of Mechanical Engineers (IMechE) urging government to listen and stop 'covering up' a problem no-one wants to be 'dumped' with.

'A Wasted Opportunity' offers a series of measures and advanced technologies which, if adopted across the UK, could help us reach our targets of an 80 per cent reduction in CO2 emissions by 2050 and producing a third of UK electricity from renewable sources by 2020.

In the past the UK has adopted the policy of burying all waste, but following legislation in 2002 (UK and England) we must reduce this by 25 per cent by 2010 and 50 per cent by 2013.

The report states 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 such as paper and plastics are being shipped off to other destinations with their future unknown - and this still counts towards UK and local targets. The report also focuses on the benefits of the UK creating an Energy-from-Waste network which would help power the nation and reduce the need for landfill but the following five action points listed in thereport must be adopted if change is to happen.

An energy from waste (EfW) plant works by taking waste and converting it into usable energy - the main forms of which are electricity, heating and transport fuels, in the same way that coal, oil and gas are used as fuels in fossil-fired power stations. Pictured is an EfW plant on the Isle of Man.

Sewage, domestic, commercial, industrial, construction and demolition (which currently accounts for 36  per cent of our household waste) waste can all be used in the processes - as long as they are combustible and/or biodegradable. The IMechE is concerned that EfW plants should not be seen as a waste treatment plant but more accurately as a power station or even a Combined Heat and Power (CHP) station.

A thermal EfW plant, in particular, '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 erroneously and dogmatically focused on EfW as waste treatment rather than as energy production, and has attempted to deal with an EfW plant as if it were an incinerator, rather than a power station. In fact, the pollution caused by an EfW plant is as likely to be as damaging as throwing a sugar lump into Loch Ness.

The approach is very different in most other parts of Europe, where recycling and EfW are both used to their optimum potential, and, as a result, landfilling is successfully minimised.

The report states there is a massive public and Government misunderstanding about EfW which tends to conjure up images of huge incineration plants.

IMechE says the issue here is that the UK Government is itself veryunclear on this! Defra, constantly refers to EfW plants as 'incinerators' and despite huge widespread public consultation ... has ignored the feedback."

There are four main processes which are used in EfW plants:

Combustion is the most common and well-proven thermal process using a wide variety of fuels. The combustion process is that used in all the large coal-fired power stations in the UK, for example, and follows aprocess known as the Rankine Gasification is where oxygen in the form of air, steam or pure oxygen is reacted at high temperature with the available carbon in the waste to produce a gas, ash or slag and a tar product. The major 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 also a thermal process and involves the thermal degradation of organic waste in the absence of oxygen to produce a carbonaceous char, oils and combustible gases. Although pyrolysis is an age-old technology, its application to biomass and waste materials is a recentdevelopment.

Anaerobic Digestion (AD) is a biological process which is a method mostcommonly used with liquid and semi-liquid slurries such as animal waste. It is also used for obtaining gas from human sewage. The main advantage of AD is that it deals well with 'wet' waste, which is a real problem for all other forms. 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 notoriously hard to come by in the UK, but latest figures show we generate 307 million tonnes of wasteannually or 'enough to fill the Albert Hall every two hours'. Of that, Defra estimates that 46.4 million tonnes of 'household and similar ‘waste' were produced in the UK with 60 per cent of this landfilled, 34per cent 'recycled' and 6 per cent 'incinerated'.

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

"In a climate where we currently have over a million people classed as being in fuel poverty, the IMechE believes this is simply unacceptable," Ian Arbon, IMechE.

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.

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