More than three million tonnes of RDF from mechanical-biological treatment plants could be in need of disposal by 2013 (ENDS Report 361, pp 25-28). There are currently few outlets for the material apart from cement kilns.
Shanks, which operates six plants in east London that will produce about 200,000 tonnes of RDF per year, is sending some to Castle Cement’s Ketton works in Lincolnshire. It also intends to send 90,000 tonnes a year to Novera’s planned gasification plant in nearby Dagenham (ENDS Report 381, p 18)
Power stations have not been considered an outlet because the material is classed as ‘waste’ under EU law. A power station would have to be refurbished to meet the emission and temperature requirements of the waste incineration Directive (WID) (ENDS Report 361, pp 25-28).
However, in February, Scottish and Southern wrote to the Environment Agency requesting clarification of the regulatory regime surrounding RDF. The definition of what counts as a "co-incineration plant" under the Directive is unclear, it says.
The company is looking into co-firing RDF at its coal-fired power plants in Ferrybridge, Yorkshire, and Fiddler’s Ferry, near Widnes.
"We’ve asked the Agency if we’d have to convert an entire 2GW facility to meet WID when we would only want to burn RDF in one boiler," said Samantha Fuller, the company’s research and analysis manager. "Can’t we simply make an individual boiler compliant?"
The company proposed such a strategy to Greater Manchester Waste Disposal Authority last year. The authority had tendered for the disposal of 270,000 tonnes of RDF from five MBT plants.
GMWDA has since chosen to negotiate a contract with a Viridor-led consortium (ENDS Report 385, p 22), but this has not dampened Scottish & Southern’s interest.
The company would prefer to convert an existing boiler rather than build a new plant due to the difficulties of the planning process, Ms Fuller said. Changing the boiler’s fuel supply would only require a variation to its PPC permit.
"We also need to consider the full life of a facility," Ms Fuller said. "We could not build a new plant just to take RDF unless we had a guarantee of obtaining the material for the plant’s 40-year life."
Amin Anjum, waste policy adviser at the Agency, said Scottish and Southern’s interpretation of WID is correct. "If you have a chemical company that burns waste in its boiler, the boiler becomes a co-incineration plant under WID - not the whole plant." The situation is "the same" for a power plant.
Scottish and Southern hopes to receive a formal statement of the Agency’s position this month. It will then ask engineers to look at the technical and economic feasibility of burning RDF.
It is widely believed that RDF could only make up 10-15% of a boiler’s feedstock as high chlorine levels would be corrosive. But Ms Fuller says it will be "more economical" to burn a high percentage of RDF and accept increased maintenance costs.
Scottish and Southern is unlikely to go ahead with the project unless there is also change to the Renewables Obligation. Currently, a power station can claim renewables obligation certificates (ROCs) from co-firing biomass, but it is not eligible for them in any particular month if it also co-fires waste.
The DTI issued proposals for changing the rules last October, as part of its plan to "band" the RO (ENDS Report 381, pp 42-43). Power stations will be able to co-fire any combination of materials as long as 90% of the average energy content is derived from biomass.
The Departments of Trade and Industry and Environment (DEFRA) are discussing other ways to encourage waste burning in power stations. "Quite simply if you look at the number of waste disposal authorities considering MBT to produce RDF, something needs to be done," said Melville Haggard of DEFRA’s waste implementation programme.
He would not rule out making the RO "neutral" to waste.
DEFRA intends to change fuel sampling requirements for combined heat and power plants. These can claim ROCs on the biomass content of any waste they burn, but the current sampling requirements are "impracticable," according to Mr Haggard.
In spite of this movement, Scottish and Southern is the only power company ENDS spoke to that says it is considering burning RDF.
Eon proposed a CHP plant in its tender for the GMWDA contract. But ENDS understands the project was only viable if Eon received a gate fee for the waste similar to landfill.
"If you have to reapply for a PPC permit, you might as well spend the time building a new plant," said one environment manager. "That’s the view of most companies apart from Scottish and Southern."