Drax’s domes: where biomass is stored
IT IS the dream scenario for fighting climate change: a power station that delivers negative emissions. And it could be coming to the UK, helped along by the growth of forests in the American South and some handy holes beneath the North Sea.
The giant coal power station at Drax in Yorkshire, with its 12 cooling towers, is one of the world’s largest greenhouse gas emitters. It sends some 23 million tonnes of carbon dioxide up its stacks each year, while supplying up to a tenth of the UK’s power.
Its owners are now planning to replace coal with wood pellets and bury the emissions. Combined with growing trees to replace all those burned, the mega-polluter could one day be transformed into the world’s largest industrial absorber of CO2.
“This is a very exciting new technology,” says Jeremy Tomkinson of the National Non-Food Crops Centre, a consultancy that promotes bioenergy. “It means we can actually reduce the volume of CO2 in the atmosphere.”
The biomass side of the transformation is already under way. “Since the beginning of July, half of Drax’s electricity has been generated by burning biomass, mostly from pine forests in the American Deep South,” Drax’s vice-president for sustainability, Richard Peberdy, told me during a tour of those forests in Mississippi. The fourth of its six generators converts to biomass next year.
To feed the furnaces, the Drax company recently opened mills in Louisiana and Mississippi that turn logs cut from local pine forests into dried and compressed pellets, and a port at Baton Rouge, Louisiana, to ship them. It also buys hardwood pellets from elsewhere in the South, as well as Canadian sawdust, and will soon start burning wood from Brazil.
All told, 7 million tonnes of pellets will cross the Atlantic next year. Only about 5 per cent of Drax’s biomass comes from the UK, mostly straw and miscanthus.
Next up is carbon capture and storage (CCS). Later this year, the UK government is expected to give the go-ahead for the £500-million White Rose project at Drax, which from 2020 could capture 2 million tonnes of CO2 annually from a new power plant burning coal and biomass, sending it down a 165-kilometre pipeline for burial under the North Sea.
With CO2 burial up and running, the White Rose project will make electricity carbon-negative for the equivalent of around 600,000 homes. The pipeline will be big enough to take most of the rest of the CO2 produced at Drax if it were captured in future.
The UN Intergovernmental Panel on Climate Change sees such measures as vital to curbing global warming. Its most recent report, published last year, concluded that widespread use of biomass with CCS would be needed to keep warming below 2 °C.
“To arrest climate change we need negative carbon emissions. At the moment sustainable biomass with CCS is the leading technology to achieve this,” says Peter Emery, a Drax director and chairman of Capture Power, the consortium behind White Rose.
The most pressing question for now is the cost in CO2 emissions of producing the biomass. Drax says the energy needed to harvest, process and transport the wood will produce emissions just 14 per cent of those from burning coal. It also claims that all the carbon emitted by burning the wood can be recaptured by planting new trees.
However, Timothy Searchinger, an environmental analyst at Princeton University, says the time lag while new trees grow and soak up CO2 will increase the rate of global warming for several decades. And once trees have been felled, the land could be converted to other uses. A study last year for the UK’s Department of Energy and Climate Change found that in the worst case, in which cut forests are replaced by cotton farms, burning biomass at Drax might end up emitting three times as much CO2 as burning coal does.
What’s the catch?
But Drax is creating an economic incentive for planting and better forest management, Peberdy says. By providing a market, its plan could increase the carbon content of the forests. “We believe forests are growing [in area] faster than they would be if we weren’t here.”
Better than coal?
Dale Greene, dean of forestry at the University of Georgia, agrees. He says markets for timber products are the reason that southern forests have been growing in extent for decades. Mississippi has added 400,000 hectares, many on former cotton fields. “The effect of Drax’s arrival has been to help keep the South forested. If we harvest more, we plant more and there is more carbon in the forest,” he says.
Even so, trees would have to be planted on a vast amount of land to have any effect on climate change, says John Lanchbery of the RSPB. “This would be land which is currently used for something else, like wildlife or farming,” he adds.
Such land may be less diverse than the original forests. Scot Quaranda of the Dogwood Alliance, an environmental NGO, says that the more intensive forestry encouraged by Drax’s presence is replacing naturally regenerated diverse pine forests with uniform ranks of planted yellow pine.
Thomas Gasser of the Climate and Environmental Sciences Laboratory in Gif-sur-Yvette, France, backs the development of negative-emissions technologies, but adds that much more action is needed. “Drax is not a miraculous solution that spares us from shifting to a less carbon-based energy mix, and of reducing overall energy demand.”