Last week it was announced that Ferrybridge power station will close, mainly because environmental legislation is about to make coal burning unsustainable. But, as MATT CLARK discovers, better news is being generated a few miles away.

IMAGINE trying to resurface the entire M1 without closing the road to traffic and you get some idea of the monumental task that has been facing engineers at Drax Power Station of late.

Now work is almost complete and the site is about to swap coal for biomass to fuel another of its generators. It’s the third to be converted since April 2013 and the biggest power station in the country is now home to the most significant decarbonisation project in Europe.

But it’s taken a while – and with good reason. Biomass was first suggested as an alternative to coal more than a decade ago. However, this was unknown technology and took years of research before engineers were happy to give the green light.

It would prove a portentous move. The current EU agreement is to reduce CO2 emissions by 40 per cent over the next 15 years and Drax is about to producing carbon savings of 12 million tonnes a year.

“That’s the equivalent of three million cars, ten per cent of the total number on the road,” says Andy Koss, chief executive of Drax Power. “Also, from a coal perspective, and where policy was going, it made a lot of economic sense to move to biomass.”

Drax is full of mind-blowing figures. The station produces four billion watts of power every day; each generator produces enough electricity to run a city the size of Leeds; the station supplies seven million homes and the Royal Albert Hall would fit comfortably inside each of its four new biomass storage domes.

Inside these industrial cathedrals air is forced out with nitrogen gas and a blanket of carbon dioxide descends to produce optimum conditions. But nothing is left to chance. Sonar pings across the walls, and sensors abound to pick up any slight heating in the material. If it is detected, more nitrogen will be fired to stabilise the pellets. As a last resort a water deluge system is in place.

Pauline Butler has been showing visitors round the power station for 20 years and says the domes arrived on the back of a small truck, rather like a tarpaulin, and were then inflated, insulated by polyurethane foam and sprayed with layer after layer of concrete.

“They’re like papier mache in reverse, she says. “The strength is on the inside.”

State-of-the-art too, but Pauline says in the early days of biomass, Drax’s R&D centre was anything but hi-tech.

“It may have been on the edge of Europe’s biggest power station, but there was no electricity,” she says. “So we started our research using portable generators.

“It was all about let’s give it a go. From smashing bits of wood with old farm machinery to where we are now is just phenomenal.”

Apart from reducing greenhouse emissions, biomass allows the power station to increase or reduce output in an instant. Something wind, gas and nuclear plants can’t do.

“It’s not just about producing power,” says Andy. “You have to control the voltage and frequency. We have a contract on one of the units where we can increase by ten megawatts in seconds if the National Grid calls us saying a wind farm has dropped off or Coronation Street has finished early, can you respond.”

Of 70 products trialled, wood proved to be the best, but Pauline insists forests are not being felled to burn at Drax. Instead the station uses by-products of the construction and paper industry.

It is delivered as pellets by seven trains a day, consisting of 200 new waggons designed to dispense material into hoppers beneath the tracks as the engine moves along, to reduce the problem of dust.

Because Drax has taken time to understand the vagaries of biomass, the site has not suffered some of the pitfalls encountered by other power stations, most notably Tilbury which caught fire spectacularly just months after converting. Now Drax is moving towards meeting ten per cent of the country’s renewable electricity target as one of the cheapest renewables on the system because all the infrastructure is already in place.

Andy says all they are doing is changing the fuel source, but in truth there has been a lot more to it than that.

“It was very bold and had never been done on this scale before,” he says. “The innovation and ingenuity of our team is unparalleled, I can’t imagine a bigger process engineering job in this country, during this century on the size, scale and complexity of what we have done and are doing here.”

Lee Ford who runs one of the biomass units calls it an “odd job”. “You need to know a lot but you don’t have to do it all the time,” he says. “Sometimes it runs smoothly and you have little input, sometimes it gets busy.

“We’re here in case it goes wrong.”

In the early days so called experts predicted the conversion would go very wrong, very often, if it even worked at all.

“At best, people told us we would lose 30 per cent of capacity, at worst that we would destroy the boiler,” says Andy. “Actually the biomass is running at the same level as a coal unit and in certain respects it is more responsive and less wearing on the mills.”

Converting to biomass is just the latest move by Drax’s to clean up its act. Global warming may hit the headlines these days, but during the 1980s we were more worried about acid rain. Back then, Drax became the first power station to invest in flue gas desulphurisation, which at the time made it the cleanest coal-fired power station in the UK.

“Now with biomass, every unit has 86 per cent less carbon associated with it,” says Andy. “Taking this power station entirely from coal to biomass would be good for the environment and we’d still very much like to convert the fourth.

“Is the fifth and sixth feasible? Yes with the right support, to allow us to make those long term investments.”