Professor Kevin Anderson:

I thank the Deputy for her question. On carbon capture and storage, when it is applied to fossil fuel power stations, people typically talk about that nowadays more for gas than for coal. It is key that it is considered in the full life cycle emissions. That means from construction right through to things like getting the gas out of the ground and the leaks from the gas when that is done, through to the transport. When one looks at the full life cycle emissions, it is typically about 100 g to 300 g of CO2 equivalent in the estimates for gas with carbon capture and storage. To give some flavour of that, a good gas-fired power station without carbon capture and storage is probably about 400 g and a coal station is probably about 900 g. If one looked at offshore or onshore wind power generation, it is probably somewhere nearer 5 g to 25 g. When full life cycle carbon capture and storage is applied to fossil fuels in power generation, it is still far too high to bring emissions down in line with the Paris Agreement. It may have been appropriate 20 years ago but in 2020 it is too little too late. That is not to say that carbon capture and storage cannot be important for something like capturing the process emissions, that is the chemical emissions of CO2, from cement production, which is a significant proportion of global emissions or possibly from steel production as well. It may have a role there but it is inappropriate to consider it for energy generation because we cannot get the life cycle emissions down low enough.

When we apply carbon capture and storage to the combustion of biomass, we often get bio-energy with carbon storage, BECS. There, in theory at least, we will be removing the CO2 from the atmosphere because it is being absorbed through photosynthesis, the material is being burned and the CO2 is being captured and buried underground. From an engineering point of view, this is incredibly inefficient but overall, the concern is that if this is scaled up there will be major ecological impacts because the various biomass crops have to be grown, harvested, chipped and burned before the CO2 is sequestered. That process is incredibly inefficient and damaging from an ecological perspective, particularly if material is imported from other countries. In the UK, for example, we import timber from the US to burn in our Drax power station. That has a huge set of ecological implications. Playing to the global models, it looks incredibly damaging from the ecological perspective. That is not to say that some of these things may have a niche role here and there but we have to be careful about how they will be applied. We also have to be cautious about some of the other techniques such as reforestation and so forth. I am all for improved forestry management and some reforestation. Planting trees seems like an easy option but when trees are planted, the soil is changed and depending on what happens to the soil, more CO2 might be mobilised from the soil than is captured in the trees themselves. Afforestation can be problematic but forestry management may have a role to play.

My concern with all of these matters is they are used as substitutes for ongoing fossil fuel use. In Sweden, for instance, they are expanding Stockholm Arlanda Airport with the claim they will plant some more trees in the north of Sweden. That is completely inappropriate. We will need some negative emission technologies or forms of sequestration to compensate for some of the ongoing emissions of methane and nitrous oxide from agriculture that we simply cannot remove from the system, even if we all went vegan and never ate rice, which does not sound like a wonderful diet. Even if we did that, we would still have a lot of residual emissions from agriculture and therefore, we require some forms of negative emissions or CO2 removal to compensate for those emissions but we should not use it to compensate for emissions from energy, which need to be brought down to zero.