What is net zero and how do we get there?
Reaching net zero emissions requires an overall balance between greenhouse gases being released into and removed from the atmosphere.
The UK net zero target covers all greenhouse gas emissions, not just CO2, but it’s worth noting that in the UK, CO2 is by far the biggest issue.
Greenhouse gas emissions could be reduced in several ways:
- Reducing the gross emissions produced to zero
- Using bioenergy so that emissions are offset by biomass growth
- Continuing to produce fossil emissions but capturing the greenhouse gases before they are released into the atmosphere
- Actively removing greenhouse gases from the atmosphere (negative emissions).
It’s likely that a combination of these approaches will be needed.
For sectors not to emit any greenhouse gases by 2050, they’d have to switch to using forms of energy that produce no greenhouse gas emissions at the point of consumption (such as electricity or hydrogen), and make sure that these fuels have also been produced via methods which produce no emissions.
Trees naturally pull CO2 out of the atmosphere (absorbing it during photosynthesis). This results in carbon being stored in forests, vegetation and in the soil. While the burning of fossil fuels releases carbon that has been ‘trapped’ underground for many millions of years, when we burn sustainably sourced wood or other bioenergy crops, the CO2 emitted can be offset by the CO2 they have absorbed over their life.
Another approach to minimising emissions is to capture the CO2 produced from fossil fuel combustion or other industrial processes before it’s released into the atmosphere. This is done via carbon capture. Capture rates are expected to range between 95 and 97 per cent across the FES 2020 scenarios. Therefore, using this approach results in low, but not zero, emissions.
The term ‘negative emissions’ refers to the removal of greenhouse gases from the atmosphere. But how is this achieved?
Planting more trees (afforestation) or restocking existing areas of forest or woodland (reforestation) is a natural way of achieving negative emissions.
Another approach is to combine CCS with the use of bioenergy, to store away recently absorbed CO2.
For example, if electricity is generated by burning biomass rather than coal or gas, with the resultant CO2 emissions being captured using CCS, this will result in negative emissions. This process is known as bioenergy with carbon capture and storage (BECCS).
New technology is under development to capture CO2 directly from the atmosphere. Direct air capture and storage (DACS) involves a chemical process which is used to absorb CO2 from a flow of air. This remains in the early stages of development; its downside being that it is a very energy intensive process.
Reaching a balance
The negative emissions options explored above offer opportunities to net off residual emissions from difficult to decarbonise sectors such as aviation, farming and certain industrial processes (steel, chemicals and cement production).
As long as enough greenhouse gases can be removed from the atmosphere to balance the residual amount emitted by certain sectors in 2050, net zero across the whole economy can be achieved.
How are emissions measured?
Because there are many different greenhouse gases, and they differ in how strongly they trap heat and in how long they stay in the atmosphere, it’s vital to have a consistent way of measuring them. For this reason, they are typically converted into a CO2 equivalent measure.
Each gas is recognised as having a different global warming potential (GWP100) which reflects the energy that a one-off emission of the gas would trap in the climate system over 100 years, compared to a one-off emission of carbon dioxide over 100 years. The CO2 equivalent (measured in tCO2e) multiplies one tonne of gas by its associated GWP100.
When we model energy supply and demand in FES we cover the geographical boundary of GB, not the UK. However, when calculating the impact of our modelling on decarbonisation targets, we will account for emissions across all sectors and the whole of the UK.
Although the production-based/territorial method of accounting reduces the risk of double-counting and gaps, we recognise there are times when considering the true carbon footprint of a product, and other forms of emissions accounting can be extremely important. For example, current accounting does not consider the international supply chain and changes in the UK can result in emissions being offshored (i.e. increasing reliance on imports).
Another weakness in current accounting relates to international aviation and shipping. With territorial accounting, it isn’t clear who accounts for emissions from planes/ships as they travel between countries. Currently, the UK targets include emissions resulting from domestic flights (i.e. those that both take-off and land in the UK), but not international ones (that take off in the UK, but land outside it).
The CCC recommendations in May 2019 made it clear that the net zero target must cover the whole economy, including international aviation and shipping. They suggest that these emissions should be based on the fuel taken on board planes and ships before they leave the UK (known as ‘bunker fuels’ methodology).
In FES, we’ll follow the standard UK methods of emissions accounting laid out above and align with the CCC recommendations on aviation and shipping to include emissions from bunker fuels. This is because consistency across the industry is essential.
Net zero is a whole system target
Reaching net zero requires a whole society approach. Energy system emissions are a subset of greenhouse gas emissions produced across the wider economy. Reducing emissions to zero by 2050 is a huge challenge; for some sectors it will be near impossible. Therefore, there will be some reliance on negative emissions for other sectors to achieve the overall net zero goal.
In our FES 2019 net zero sensitivity, we explored a target of 96% emissions reduction by 2050 with existing technologies, the remaining 4% being reliant upon speculative technologies. This aligned with the approach taken by the Committee on Climate Change (CCC) in their 2019 net zero report. This year our FES 2020 net zero target removes the ‘hiding place’ provided by speculative technologies and will present a number of scenarios that demonstrate 100 per cent emissions reduction by 2050 from 1990 levels. This is also aligned with the CCC’s latest approach for their 6th carbon budget analysis.
In order to develop our FES scenarios, we conduct deep analysis on the GB energy system. We also consult with stakeholders to understand the emission pathways for non-energy sectors (e.g. farming). We make sure our FES scenarios are credible and integrated with a whole-of-society net zero target for 2050.
Knowing the best assumptions to make for non-energy sectors enables us to more accurately model the scale of negative emissions required from the energy sector. Our FES 2020 scenarios will illustrate credible pathways to 100 per cent emission reduction by 2050, which clearly call out ‘what we must believe’ across the whole UK economy and society to enable this to happen.