Landfill gas industry prepares for new controls

Shanks, a pioneer in landfill gas power projects, remains the leading player in the field. The company will soon have 72MWe of generating capacity.

Patrick Pointer, Shanks' technical manager, says that complying with the proposed limits will be tight. "But on a well-managed active site the engines will meet the requirements," he said.

"Post-combustion clean-up techniques should not be needed for new engines," he said. But there may be an issue for older engines and for older sites with failing gas supplies.

"If you've got some really crappy engines and it's impacting on air quality then one could expect the Agency to take a dim view of it," Mr Pointer said. But that does not necessarily mean having to install a completely new engine. Modifications can sometimes be made to engine management systems, for example.

The Agency's Chris Deed agrees that new clean-up technologies will typically not be required, beyond the existing practice of removing particulates and water from the raw gas. "At a general level we don't anticipate the need for the more complex clean-up technologies."

Dick Turner, waste-to-energy manager at Viridor, argues that the aims of the new regulatory controls are not yet fully clear - but, he acknowledged, "it is a step-change from basically no statutory emission controls."

Mr Turner is responsible for around 45 generating units, across 11 landfill sites, with a total capacity of 38MWe. He does not expect major problems for the industry in complying with the limits on NOx and CO for the newest plants.

But there are lingering concerns about the proposals on VOCs and non-methane VOCs. These emissions are caused by methane slippage - traces of unburned gas passing through the engine. Engines fuelled by natural gas do not face regulatory limits for these emissions, notes Mr Turner.

Efficient combustion
Meeting the new controls may mean modifying an engine's operating parameters, perhaps by reducing power output in order to cut VOC emissions. By contrast, schemes have historically been designed so as to maximise power output, with combustion efficiency being a secondary concern.

"Up until now engines have got free fuel," Mr Pointer explains. "If you've got free fuel you're not likely to worry about the efficiency."

The drawback is that reducing an engine's load will have a detrimental effect on revenue as less electricity is generated.

At Viridor, Mr Turner summed up the mood in the industry: "It's still very early days," he said. "I have a fear that it may lead the industry to incur additional costs in the future, but it's not clear that that is the case."

Some practitioners are arguing that the results remain preliminary. Mr Turner said that identical landfill gas engines can have differing emissions. The worst thing would be to set the limits too tight and have to relax them subsequently, he said.

"I'm not sure that enough samples have been taken yet to give a statistically reliable standard."

Another concern is whether engine manufacturers have been given sufficient lead time - with the new standards applying from November 2004 - to plan their way forward. "Does the technology exist that allows us to meet those limits without back-end equipment?" Mr Turner asked.

Viridor did once consider a gas clean-up system to remove organic contaminants from raw landfill gas, but it was found not to be cost-effective. Mr Turner notes that some pre-combustion clean-up techniques give rise to new problems, such as the requirement to dispose of by-products.

Activated carbon offers one means of removing some of the trace components. These tend to be more of a problem early in a landfill's life, when the more volatile substances are released. But, insists Mr Pointer, "there's no real indication that there's going to be a VOC problem."

Monitoring costs
Whether or not clean-up technologies have to be employed, the industry is in line for significant new costs stemming from the new requirement to monitor emissions. In many cases, plant will have to be modified to facilitate monitoring.

The ongoing costs of emissions monitoring are put at around £5,000 per engine per test, and large sites have several engines.

"It's adding a whole new layer of administration into running a renewable energy plant," Mr Turner said. "In any event utilisation must be better than simply wasting by flaring."

These new costs have potential to make significant inroads into the financial viability of some schemes. Conversely, they may assist some developers in their efforts to ditch unwanted NFFO contracts.

The Agency expects operators to undertake cost-benefit analysis to justify any decision not to use techniques to clean up landfill gas pre- or post-combustion.

An interesting question, therefore, is whether the additional revenue from the sale of ROCs will be taken into account in weighing the appropriateness of such investment.

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