How do we get to carbon negative?
If we are to realise the UK’s stated aim of reaching ‘net zero’ carbon emissions by 2050, we will actually need some industries to produce less than zero carbon.
The reason why is simple. Because it‘s going to be very hard to stop anything at all in the UK emitting carbon by 2050. To take just one example, in 2019 road transport was responsible for almost a quarter of our total emissions. No matter how fast newer and more efficient electric vehicles come on stream, or how soon the sale of new petrol and diesel cars is banned it’s going to be very difficult indeed to remove every single fossil-fuelled vehicle from our roads by this century’s half-way point.
Decarbonising the aviation and agriculture sectors — responsible for 8% and 9% respectively of the UK’s 2019 emissions — will also present a potentially impossible challenge. As a result, ‘residual emissions’ such as these are forecast to remain in the economy.
We cannot accurately calculate precisely how much carbon dioxide (CO2 ) the UK will emit as we decarbonise. As 2020 showed us, unexpected events such as the COVID-19 pandemic can cause dramatic and unpredictable changes. But at least one of the National Grid’s Future Energy Scenarios envisages a situation entitled ‘Steady Progress’, where decarbonisation is gradual and restricted to the sectors of power and transport. This scenario anticipates that the UK will still be emitting 258 megatonnes of CO2 in 2050.
In order to reach net zero CO2 in such a situation — or in any of the rosier scenarios, the UK would have to go further than just deploying carbon capture use and storage (CCUS) technology on fossil fuel-based infrastructure. Negative emissions that remove the thegreenhouse gas from the atmosphere are required.
How can we achieve negative emissions?
A growing technology called direct air capture (DAC) can even help remove CO2 from ambient air. It works in the same sort of way as CCUS, by harnessing methods including amines, sorbents or membranes.
One of the major challenges faced by DAC — especially when compared with CCUS — is the fact that there is so very little CO2 in the air around us. With concentrations of just 0.04%, the amines or solvents DAC relies on are effectively seeking a needle in a haystack compared to those used in CCUS, which can interact with a much more concentrated stream of CO2 from processes such as thermal electricity generation.
One of the leading technologies with the potential to enable us to reach negative emissions is bioenergy with carbon capture and storage (BECCS). This can remove CO2 from the atmosphere and store it permanently underground at the same time as generating renewable energy. Many consider BECCS an essential part of the journey to net zero.
According to the National Grid’s report on Future Energy Scenarios, in the UK alone BECCS has the potential to generate 62 million tonnes of negative carbon emissions every year by 2050.
It’s clear that there are scientifically proven technologies available already that can help us achieve negative emissions. Now the challenge we face is to develop a sufficient economic model — accompanied by robust government policy — that supports the investment required to build this new infrastructure and to deploy it at the scale needed to tackle the climate crisis.