Inside the Allerton waste 'incinerator'

FROM the A168 and A1(M) west of York, the huge new incinerator at Allerton Park - which went operational this week - looms large: a gleaming metallic structure with a stack that towers almost 230 feet tall. It would appear even taller - but the plant was built at the bottom of a former gravel quarry to try to minimise the impact.

The sight of such a gleaming modern plant plonked down in the Yorkshire countryside (albeit next to a landfill site and on a former quarry) was one of the many things objectors to this £361 million project - touted as the final solution to York and North Yorkshire's rubbish disposal problem - complained about.

They also worried that it would be noisy and dirty (it does, after all, burn plastic amongst other things), that it was too expensive - and that the technology used was already out of date.

Some of these concerns, at least, appeared to be belied when the UK Green Investment Bank (GIB) stepped in in late 2014 to put £33 million into the scheme. "This innovative project is a best-in-class example of how local authorities can improve recycling and generate significant amounts of renewable power from household waste," said GIB chief executive Shaun Kingsbury at the time.

The Allerton Waste Recovery Park seen from the road

But many Green campaigners remain unconvinced. Burning rubbish is an inefficient way of generating energy, says York Green councillor Andy D'Agorne. And because the city council and North Yorkshire County Council are each locked into a 25-year contract with Amey, which operates the plant, it locks us into process of burning rubbish some of which, in future, might be recyclable.

So what is the truth about this huge new plant?

It was built by infrastructure firm Amey, which will operate it under contract to City of York Council and North Yorkshire County Council for the next 25 years. Each year, the two councils between them will send 320,000 tonnes of 'black bag' rubbish to the plant for processing - rubbish that would otherwise have ended up in landfill.

There it will be sorted and separated. Paper, wood and various types of metals will be recycled. Food waste will be put through an anaerobic 'digester' (essentially a giant mechanical gut) where microbes will process it and turn it into methane gas, which will be burned to generate electricity.

The rest of the rubbish (including non-recyclable plastics) will then be effectively used as fuel - burned at very high temperatures to produce steam which will drive a steam turbine and generate more power. Between them, the aerobic digester and the incinerator are expected to generate about 30 MW of power - enough to power between 40,000 and 60,000 homes. "If you have a source of fuel - rubbish - you might as well use it to generate power," says Cllr Andrew Lee, North Yorkshire County Council's cabinet member for waste management. "It is better than putting it in a hole in the ground."

But is the plant clean clean? And does it represent good value for money?

The first thing you notice when you drive up - apart from the sheer, intimidating size of the plant - is how quiet it is. The next thing is that it doesn't give off any smell. That's because the plant is maintained at a 'negative pressure', says general manager Mark James: the pressure inside is slightly lower than the air pressure outside, so bad smells from the rubbish being processed don't escape.

There were also no streams of oily black smoke pouring from the tip of the stack when The Press visited.

There never will be, says Cllr Lee. Carbon and other emissions are scrubbed and filtered out so that what emerges from the top of the stack is only steam. That steam will sometimes look black - but that's because it behaves like a cloud, which changes colour depending on the weather conditions.

It isn't quite true to say that what comes out is only steam - the plant is allowed to emit small amounts of carbon dioxide and other gases, but only within strict European limits (more of which later). But it is mainly steam emerging from the top of that stack.

Conveyor belts in the mechanical treatment and separation plant

The plant itself (it isn't fair to call it an incinerator, Cllr Lee says, since incineration is only part of what goes on here) is effectively three plants in one.

Rubbish brought into the plant goes first to a mechanical treatment and separation unit, where as much recyclable material as possible is separated out. It's a huge room, filled with conveyor belts moving at all angles. Bags of rubbish are first shredded, then spilled onto the moving belts.

There are no fewer than 220 items of equipment in here dedicated to sorting recyclable rubbish out from the rest, says Mark James. As it passes along the belts, rubbish is sized and separated. Magnets pull out ferrous metals; infrared cameras identify recyclable polymers; and the remaining rubbish is checked over by human operators who can do a final sort by hand.

Up to 20,000 tonnes of recyclable material will be separated out every year at this stage. Metal, card and recyclable plastic is sent off for recycling. Food waste goes to the anaerobic digester, where it is coveted into methane which is burned to generate power. And the rest of the rubbish goes into the incinerator - or, to give it its official name, the 'energy from waste' plant.

Here, it is tipped into one of two giant incinerators, where it is burned over rollers at temperatures exceeding 850 degrees. That's important, says Mark James - such high temperatures mean that harmful dioxins are unable to form, so there is no danger of dioxin pollution being released.

Up to 40 per cent of the weight of the rubbish burned is water. This is given off as steam. Ash left over after the burning is sent off for recycling into aggregates. The potentially polluting gases - carbon dioxide and carbon monoxide, oxides of nitrogen, and other gases - are then subjected to complex processes of filtering and scrubbing. Lime is added to reduce acid levels, a urea spray is used to remove nitrogen oxides, and filters remove carbon and heavy metals. The resulting 'slag' of toxic particulates (carbon and heavy metals) is sent off to a 'hazardous waste' landfill in Teesside. But it is only about 8,000 tonnes a year, says Mark James, out of a total of 320,000 tonnes a year of black bag rubbish being processed.

As a result of the rigorous filtering and scrubbing processes, the emissions coming out from the plant's stack are mainly steam. Under the terms of its environmental licence, however the plant is allowed to emit small, 'safe' levels of carbon, carbon monoxide, sulphur dioxide, nitrogen oxides and particulates - but these levels are strictly regulated according to EU standards, Mark James says. Emissions are monitored on a 24-hour bases, any infringements have to be reported to the Environment Agency - and the plant would be quickly closed down under the terms of its licence if it consistently infringed emissions levels.

General manager Mark James at the Allerton plant

So how confident can we be that the plant is clean, and that it won't be pumping pollutants into the atmosphere?

Very, says Cllr Andrew Waller, York's executive member for the environment. "This is the same technology as used across the continent on a large number of facilities," he says. "It is carefully managed to limit the emissions to safe levels, and the environmental impact is less than that produced by land-filling the waste."

And what about the finances? Do they stack up?

York and North Yorkshire contributed nothing towards the construction costs of the plant. However, they are paying a lot of money to Amey to operate it on their behalf. The county council will be paying Amey £22 million a year over the next 25 years, while City of York will be paying £6 million a year.

That sounds like a lot. But compared to the costs of continuing to send rubbish to landfill, the plant represents good value for money, both councils insist. Landfill taxes are expected to climb quickly in the years ahead. North Yorkshire council estimates that, by using the Allerton plant t, it will save £256 million of council tax-payers money over the next 25 years. York estimates that it will save £53 million. At the end of the 25 year contract, ownership of the plant - which should have at least another five years of operating life - will pass to the two councils.

York's Green councillor Andy D'Agorne remains unconvinced about the plant, however.

Because of the effort needed to minimise toxic emissions, the technology is actually very expensive, he says. And there's another problem, he believes: the contract with Amey could end up forcing the two councils to send material for incineration that could otherwise have been recycled.

"Under the contract we are committed to supply a minimum volume of combustible waste," he says. "That undermines the market for plastic recycling."

Who do you believe? You pays your money and you takes your choice...