SELBY, Yorkshire, England -- Europe's second-biggest coal-fired power plant, the giant 4-gigawatt Drax Power Ltd., located about 200 miles north of London, will turn over a new leaf next month as it converts the first of its six boilers to pure biomass burning.
Over the next three years, the project will switch half the plant's capacity over to renewable sources. When the second boiler converts and starts operations next year, Drax will already be the biggest biomass power plant in Europe.
Once the third boiler has been converted, probably in 2015, the sprawling power plant -- the size of four large nuclear power plants -- will have halved its coal usage to 5 million metric tons a year. In its place, it will be burning about 7.5 million metric tons a year of imported biomass -- initially mostly wood pellets from managed forests in the United States and Canada.
"Biomass is here to stay," Drax Production Director Peter Emery said on a recent press tour of the plant to show off the major construction work underway to carry out the conversion. "It is a very attractive carbon footprint versus fossil fuels."
It is no idle undertaking. Drax is spending about £700 million ($1.06 billion) on the project, about half of it on site and the rest on expanded port handling facilities both in the United Kingdom and the United States, as well as custom-made train wagons designed to handle biomass and two new pelletizing plants in Louisiana and Mississippi.
By the end of next year, these two plants at Morehouse Parish, La., and Gloster, Miss., will be producing between them 1 million metric tons a year of wood pellets to be shipped by road and rail to expanded port facilities at Baton Rouge, La., where they will be shipped in 50,000-metric-ton loads across the Atlantic Ocean to three ports along the United Kingdom's east coast and taken by rail to Drax.
Much ado, but way smaller carbon footprint
"The bottom line is that we need to bring biomass to the U.K. at very low carbon footprint. If you put it in 50,000-tonne vessels, you can travel an awful long way and have an almost negligible carbon footprint per tonne of biomass," Emery said. Drax calculates that its total carbon footprint for burning pure biomass will be about one-tenth that of coal.
Dedicated trains, each carrying 1,500 metric tons of biomass, will arrive at the plant on two new rail lines and discharge their cargoes onto conveyors into a screening center to remove contaminants such as metals that could damage the boilers. From there, the biomass goes to either new storage domes or straight on via a sampling building to check quality and then into silos.
From these silos, the pellets will be blown by compressed air into giant grinders, where they will be pulverized to dust and injected into the boilers. There, they will be incinerated within two seconds of entry. For health and safety reasons, the whole system is enclosed.
When the biomass boilers are in full swing, it will take seven train loads a day to keep them fired up.
Biomass typically has about half the density of coal and two-thirds of its caloric value, so much more will have to be brought to the site for burning than if coal were to remain the main fuel source. That is why it is such a huge logistical operation, but one that Drax is publicly and commercially committed to.
"We are designing this as a base-load biomass plant," Emery said. "Within two or three years, it is quite possible that our coal units will not be operating all the year round as the carbon price rises."
Drax, fully operational since 1986, has been burning some biomass since 2010, but as a joint or co-firing fuel with coal and then only up to a maximum of 12.5 percent of the fuel mix.
It will be these supply lines that will be fueling the first boiler when it switches over next month to burning pure biomass.
While wood will make up the majority of the initial biomass supply, Drax is already burning fuels as diverse as straw, sunflower husks, sugar cane bagasse, olive pulp, peanut shells and bamboo as well as purpose-grown power crops.
A nonfossil rival to nuclear power?
All have different burning qualities and leave different residues. That is not a problem when co-firing with coal up to a maximum of 12.5 percent, but it presents other challenges when it is the sole fuel. Fast-growing plants in particular can contain high levels of sulfur and nitrates, which can cause problems in the boilers.
"So we are doing a lot of work in this area," Emery said. "We don't quite know how flexible we can be on changing biomass fuels." Drax is also investigating what to do with the new, pure biomass ash residue, with one possibility being as fertilizer.
Outside the United Kingdom, it has focused its biomass investment in the United States because it is an established and well-regulated market with forest owners, who previously supplied the pulp for lumber markets, searching for new outlets as traditional ones dwindle.
"We have been greeted there with open arms," Emery said. "In the U.S., the legal framework is very mature, so we can establish sustainability criteria and do audits, so it is a very good place to start. But it is important that we diversify our sources of supply."
Apart from the United States and Canada, Drax already gets biomass from as far afield as Russia, the Baltics and Africa. It is also looking at Latin America, where nutritionally depleted soils in deforested areas offer the opportunity for producing fuel crops. None of this would be possible without hefty U.K. government subsidies in the shape of Renewables Obligation Certificates, known as ROCs, that give biomass burning the same level of support as onshore wind power.
Under the electricity market reform bill now passing through Parliament, the ROC system will be phased out and replaced by feed-in tariffs supported by contracts for difference through which a government-backed agency guarantees the generators a set price. If the market price of electricity falls below that level, the agency tops it up, and if it rises above, then the generator has to refund the difference.
Each source of renewable power will attract a different guarantee or strike price.
Emery said he would be happy if the Drax biomass strike price were similar to the current ROC value. It is less than half the cost of the long-term government support being sought to support new French-built nuclear power plants under consideration.
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