The Drax power station, Britain’s largest CO2 emitter, is launching a trial of “negative emissions” technology.
Drax has six power-generating units. Until 2013, they all burned coal but three of them have since been converted to burn wood. The switch-up came after the UK government’s big crackdown on coal power, after the 2008 Climate Change Act legally committed the country to steeply reduce its emissions.
Burning wood also produces carbon dioxide, but, according to policy set by the European Union, of which the UK remains a part of still, the process is considered carbon neutral. The reasoning is that the carbon dioxide produced in burning wood is the same amount that was captured when the tree was growing. So, in principle, if the wood is sourced from a forest that is grown sustainably—replacing each tree that gets chopped down to be burned—then the total emissions from the process will be zero.
The carbon dioxide released by burning trees, some experts say, is not recaptured back by new trees for many years. In that period, the greenhouse gases released will have contributed to heating up the planet—a process that cannot be negated by the new trees. In addition, felling a tree tends to release carbon that’s been trapped by the soil surrounding the plant.
Regardless of the debate on wood’s carbon neutrality, the new technology Drax is trialing could be a big win for the environment. Simply put, negative-emissions technology is a way to pull carbon dioxide from the air—that is, reducing the amount of carbon dioxide that already exists and thus negating some of its impact on warming the planet.
But to understand Drax’s negative-emissions claim requires mental arithmetic. Drax considers burning wood carbon neutral—aka zero emissions. Thus capturing any emissions from the process and then burying it underground will, in theory, remove carbon dioxide from the air—aka negative emissions. Climate scientists call this technology bioenergy with carbon capture and storage (BECCS). If we are to hit climate goals set under the Paris climate agreement, most climate models require the use of BECCS at large-scale.
To start with, Drax is investing £400,000 ($530,000) in the technology. It is working with C-Capture, a University of Leeds spin-off, led by Christopher Rayner, professor in the department of chemistry. Rayner told Quartz that the details of the technology are proprietary, but it is similar to those offered by large companies such as Cansolv, owned by Royal Dutch Shell, except C-Capture’s technology uses new chemistry and is more energy-efficient.
Here’s how it works: Exhaust gases from burning wood are passed through a mixture of specially designed chemicals (C-Capture solvent) in what’s called an adsorption tower. During the process, these chemicals selectively react with carbon dioxide and let other non-greenhouse gases such as nitrogen to pass through to the atmosphere. In a separate chamber, the chemical is then heated to release carbon dioxide, which can then be compressed and stored underground, in depleted oil and gas fields for example, or used for industrial purposes, such as in beverages or making plastics.
Drax will start studies by exposing the exhaust gas to see if C-Capture’s solvent is stable. If it is, then later this year, perhaps in September, Drax and C-Capture will build a demonstration plant that can capture up to 1 metric ton of carbon dioxide per day.
If the technology works, it could be a win-win for Drax. The power station currently has three large adsorption towers sitting unused. They were installed to capture sulfur emissions from burning coal, but since being converted to burning wood, which produces very little sulfur, they’ve been sitting idle. The plan is to see if those towers can be re-used to capture carbon emissions instead, which would save money while providing emissions reductions.
“But a lot will be driven by politics, rather than technology,” Rayner says. The UK government is looking to restart its efforts to build carbon capture and storage (CCS) technology in the country. That Drax is committing some money towards the technology already makes it more likely to capture some of the subsidies that might become available in the near future. And, as it did when it converted its coal units to burn wood, Drax will certainly need government money to scale up carbon-capture technology, which can cost hundreds of millions of dollars to build.
If Drax succeeds, it would have built Europe’s first BECCS plant. But the title of the first “negative-emissions plant” belongs to a smaller project in Iceland. There a startup called Climeworks is capturing carbon dioxide directly from the air, but at present it only puts away about 50 metric tons in a year—about the same as the emissions of one US household or 10 Indian households.