Governments across Europe are under pressure to improve waste management practices and reduce landfilling. One option is to co-fire high-grade refuse-derived fuel in coal fired power stations.

Siân Green

“In the UK, there is a huge waste problem,” states Andy Biffen, engineering director of UK renewable energy group ReEnergy. “We send a lot of waste to landfill and are way behind many other EU countries in terms of recycling and the recovery of energy from residual waste.”

European targets for recycling and the reduction of landfill represent a considerable challenge for the UK waste industry, says Biffen, but it is not alone. Countries such as Ireland, Greece and Portugal are in a similar position to the UK, landfilling at least 70 per cent of municipal solid waste (MSW).

By 2020, European Union (EU) countries must reduce the amount of MSW that is sent to landfill by 35 per cent over 1995 levels. The UK currently produces around 35 million t of MSW each year, three-quarters of which is landfilled. The volume of MSW production has been increasing at around three per cent per annum – slightly above GDP levels – and is forecast to double from 1995 levels by 2020. Just 17 per cent of household waste is recycled or composted.

Figure 1. The UK, Ireland and Portugal are among countries that need to drastically reduce landfilling levels
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Some radical changes to waste management practices are therefore required in the UK – and other countries – in order to increase levels of recycling, composting and energy recovery. But while countries such as Denmark and Sweden have embraced incineration, planning requirements and public opposition in the UK mean that it is likely that new energy from waste plants will continue to struggle against delays during the planning and development stages while facing continued uncertainty of ever being given the go-ahead.

But with every challenge comes opportunity, and Italian environmental company Pirelli Ambiente has developed a technology that could help the UK and its neighbours overcome their waste management problems. The company has developed a patented process that converts MSW into high-grade refuse derived fuel (RDF) that can be used as a substitute for coal in industrial boilers such as coal fired power plants. It is a sustainable solution that will help to divert waste away from landfill, says Pirelli. The company is already using the technology in Italy, and is now targeting the UK market through a license agreement with London-based ReEnergy.

Recognising the opportunities offered by the UK market for its technology, Pirelli Ambiente signed an agreement with ReEnergy in November 2005 allowing ReEnergy to produce and sell the patented RDF throughout the UK. Under the agreement, Pirelli will provide technical assistance to ReEnergy as it negotiates to secure waste streams and develop high-grade RDF plants in the UK.

Figure 2. High-grade RDF production process
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In their analysis of the UK market, Pirelli Ambiente and ReEnergy believe that they could secure up to half of the UK’s annual MSW waste production stream and convert it into high-grade RDF for use in coal fired power plants and other industrial settings such as cement kilns. This would lead to the production of 9.6 TWh per year, as well as 12.3 million t/year of avoided landfill carbon dioxide (CO2) emissions.

“Although most of the market drivers for this technology come from the waste management side, one of the key advantages of using high-grade RDF in power plants is the avoidance of CO2 emissions from landfill,” says Biffen. “With rising gas prices and increasingly stringent emissions legislation, coal fired power plants are under more and more pressure to perform, and co-firing RDF could help them achieve their goals.

“Using 1 t of high-grade RDF results in an estimated 1.42 t saving in CO2, which gives the fuel value in the current market. In Italy, the fuel is further classified for green certificates, and we hope that it will achieve the same status in the UK.”

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In fact ReEnergy is lobbying hard to get the patented RDF fuel the status that it believes is deserves, but this is just one of several barriers that the company faces in its attempts to get the high-grade RDF technology off the ground in the UK.

One of the main barriers to the uptake of the fuel is the fact that power plants are now covered by the European Waste Incineration Directive (WID), which aims to limit the risks that waste incineration poses to the environment and human health. It means that unless power plants meet strict requirements for emissions of sulphur dioxide (SO2) and nitrous oxides (NOx), they cannot co-fire any sort of waste stream.

“These requirements came into effect for power plants at the end of last year but will eventually be lifted as the requirements of the WID and the Large Combustion Plant Directive (LCPD) coincide in 2016,” notes Biffen. “Some plants in Germany already meet the requirements and so are able to continue burning waste.”

Many coal fired power plants in Europe are just embarking on projects to meet LCPD requirements by installing flue gas desulphurization (FGD) and other control technologies, however, and so in the mean time, ReEnergy is lobbying the UK government to try to have the Pirelli RDF reclassified as “fuel” rather than “waste”.

“It may be derived from waste but the high-grade RDF is a fuel with similar calorific values to that of coal,” states Biffen. “In Italy it is already classified as such.”

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Pirelli’s technology has been used for over two years in a project in Cuneo, north-west Italy, where the fuel from the MSW stream of a consortium of 54 local municipalities is converted in a 25 000 t/year production facility. The high-grade RDF produced is used as a substitute for coal and petcoke in the main burners of a local cement kiln.

The patented high-grade RDF is produced from the dry fraction of residual waste, obtained after the MSW has had recyclables removed and undergone a process known as mechanical biological treatment (MBT). Rubber and non-chlorinated plastics are added to increase the calorific value of the fuel, which must be shredded and blended to ensure that it is suitable for co-firing in the main burners of pulverized coal boilers.

In addition to being examined by the operator of a major UK coal fired power plant, the fuel has been certified by boiler makers such as Ansaldo and ABB, and has also been certified by the Italian Agency for Energy and Environment. A key advantage that the fuel has over other types of RDF fuels is its low chlorine content, which allows it to be used in boilers with high-pressure parts without the risk of parts corrosion. “We believe that this fuel could be up to ten per cent co-fired without any mechanical damage or loss of performance,” says Biffen. ReEnergy also believes that the fuel has no adverse impact on ashes produced.

ReEnergy’s vision for the UK is to secure waste streams under long-term contracts and to construct high-grade RDF production plants, ideally located at power plants in close proximity to the source of the waste. The company was aiming to carry out a demonstration test of the fuel at a UK coal fired power plant last year but was thwarted by legislation that prevents the movement of waste across international borders (it required 100 t of Pirelli’s RDF fuel from Italy), and now the WID legislation prevents it from carrying out these trials altogether.

“In the future we will have to take potential clients to Italy to see the fuel in action, and there is always the possibility of using a coal fired test rig to demonstrate the fuel,” says Biffen.