Tree-planting, restoring wetlands and use of chemicals to remove CO2 from air needed, as well as cutting new emissions, say scientists

Tree-planting, restoring wetlands and using chemicals to take carbon dioxide from the air will all be needed to reduce the UK’s greenhouse gases in line with government plans, scientists have said.

If these measures are taken urgently, they could make enough of a contribution to make the UK “net zero” in terms of carbon emissions by 2050. However, a major programme to bring them into effect would be needed as a matter of urgency.

“We will need to remove greenhouse gases from the atmosphere as well as work on ways to stop emitting so much in the first place,” said Nilay Shah, head of chemical engineering at Imperial College London, and a member of the working group on the report. “The very first thing we need to do is go to a very low number on emissions by 2050. If we work very hard on decarbonising energy and emissions from building and transport and industry, we can bring down emissions to 130m tonnes of carbon dioxide equivalent (MtCO2e) by 2050 compared with 450 MtCO2e today.”

That remaining 130m tonnes “is very difficult to get rid of”, said Shah, partly as it comes from activities such as agriculture and aviation, which are hard to decarbonise. This left a gap which could only be filled by removing greenhouse gases from the air.

In a joint report on greenhouse gas removal, the Royal Society and the Royal Academy of Engineering found that increasing the amount of forested land in the UK to 5% of land area could play a major role as trees act as a carbon sink. At the same time, farmers could be encouraged through incentives or subsidies to use their land to store carbon through better farming methods. Restoring natural features such as wetlands and marshes would also store more carbon.

Construction companies should also be given incentives to use wood, which is a natural store of carbon, and cement can be manufactured with waste carbon dioxide to offset the emissions from its production.

However, while these measures together would account for about a quarter of the carbon reductions needed, technology to remove carbon from the air would also be required, the scientists said.

Some of this could be done by capturing carbon emissions at source, such as at power plants. Using bioenergy, such as wood, plants and waste, while capturing the resulting carbon dioxide is technically possible and should be pursued, the scientists urged. But they said other methods, such as direct air capture, would also be needed.

Direct air capture usually involves chemical processes called “scrubbing”, which means using compounds that react with carbon dioxide in the air to form new chemicals that can be safely disposed of, locking in the carbon. While scrubbing is commonly used to clean up other emissions, such as coal-plant emissions containing sulphur, using it to remove carbon from the air is difficult and can be costly.

The report found that economically encouraging the use of direct air capture would require a price to be put on carbon dioxide, probably of as much as $100 a tonne.

Richard Black, director of the Energy and Climate Intelligence Unit, called the report “crucially important” for the UK’s low-carbon future. “It shows the UK can take its carbon emissions down to net zero by around mid-century and can do so affordably,” he said. “If anything, it has over-estimated the amount of negative emissions the UK will need, and yet still concludes that we can deliver.”

He pointed ahead to a major report coming from the Intergovernmental Panel on Climate Change next month, which is expected to find that the world must achieve net zero emissions by 2050 to meet the Paris agreement targets. After that report, the UK’s statutory government advisors, the Committee on Climate Change, will issue formal advice on how the UK can meet such a target.

Black said: “This report, showing it is possible [to achieve net zero emissions], could not have come at a more opportune time.”

Direct air capture of carbon dioxide is different from the forms of carbon capture and storage (CCS) attached to power plants, which have been targeted in the past. For most of the past decade, the UK was pursuing carbon capture and storage technologies focused on taking carbon emissions from fossil fuel power plants and storing them under the North Sea, with several companies working on the technology. However, the previous government pulled the plug on those plans and the UK no longer has any pilot projects for CCS from power plants, though other countries have moved ahead with pioneering projects.

Shah said CCS for power plants would also be needed, in addition to direct air capture, if the UK is to continue to use fossil fuels. Such plants could all share the same transport and storage infrastructure, bringing down costs.