Q4 2023: Carbon Dioxide Removal: getting back to Net Zero

The Planning Inspectorate has recently given consent to Drax Power (publisher of this report) to install carbon capture equipment at two of its biomass-burning generators in Yorkshire.  This would turn them into the world’s first large-scale power station capable of removing carbon dioxide (CO₂) from the atmosphere. But what are ‘carbon dioxide removal’ and ‘negative emissions’ technologies, and why are they needed?

Net Zero Emissions

At present, the UK and other countries are trying to reduce emissions of CO₂ and other greenhouse gases to slow the rate of global warming.  With more greenhouse gases in the atmosphere, more energy gets trapped within it, which causes temperatures to rise.  To stop further increases in the earth’s temperature, we must completely stop adding greenhouse gases to the atmosphere.  We can do so either by reducing emissions all the way to zero, or by reducing them most of the way and then offsetting any remaining emissions using carbon dioxide removal.  This approach is known as reaching ‘Net Zero’ emissions.

For some activities, such as long-haul air travel and heavy industry, the technological solutions for decarbonising may prove impractical or prohibitively expensive.  The Net Zero approach lets us still emit some greenhouse gases from these activities, so long as they are offset by removing an equivalent amount from the atmosphere. 

Some worry that technologies like carbon capture and storage (CCS) are a distraction from the task of reducing emissions from burning fossil fuels.  Efforts to avoid and reduce emissions first should indeed take priority – but we are now at the point where “keeping to 1.5 °C is simply not possible without the use of carbon capture and storage”.

The Climate Change Committee’s scenarios for the UK envisage our power system eliminating almost all its remaining emissions in the next decade using a combination of CCS, nuclear and renewable generation.  Their approach decarbonises electricity fastest and furthest – going beyond zero into net negative emissions ten years from now.  This is because it is much easier to replace or retrofit a relatively small number of stationary power stations than millions of widely dispersed heating systems and motor vehicles, for technological, organisational and (sometimes) political reasons.

Scenarios for the development of biomass electricity generation over the coming decade, with and without CCS. 
Left shows the central pathway from the Climate Change Committee’s 6^th Carbon Budget. 
Right shows the median pathway across National Grid’s Future Energy Scenarios.

Carbon Dioxide Removal

Carbon dioxide removal can take many different forms.  Some approaches aim to increase the amount of CO₂ taken up by the earth’s natural carbon sinks, often by growing (or re-growing) forests.  Others increase carbon take-up in the soil (such as adding biochar to it), or more controversially ‘seeding’ the oceans with nutrients to increase the amount of CO₂ that plant life there can absorb.  

The Drax plan to combine Biomass Energy with Carbon Capture and Storage (known as BECCS) is a technological approach to carbon dioxide removal. Another is Direct Air Capture (DAC), which sucks CO₂ directly out of the atmosphere using CCS technology.  However, because CO₂ concentrations are so much lower in the atmosphere than in a power station exhaust flue, it is more difficult to separate, and so the cost is likely to be significantly higher.

CCS technology applied to a power station stops 95–98% of its CO₂ emissions reaching the atmosphere.  CCS can turn a gas-fired power station into a low-emission power source, but adding CCS to a biomass power station turns it into a carbon-negative power source.  As the CO₂ absorbed by growing the fuel becomes permanently sequestered, this reduces the amount of atmospheric CO₂ over the life cycle of the biomass, resulting in the overall process being net carbon negative while producing renewable electricity.

Electricity from Biomass

Electricity generated by burning sustainably-sourced biomass is deemed low carbon by the UK government and international carbon accounting rules.  Although CO₂ is released from combustion in current biomass power stations, those carbon molecules were (relatively) recently in the earth’s atmosphere before being stored in growing biomass.  This type of carbon is part of the ‘biogenic’ carbon cycle: the natural process of plants absorbing CO₂ via photosynthesis and releasing it via respiration.  This is also known as the ‘fast’ carbon cycle, as carbon circulates through it relatively quickly.  This contrasts with emissions from burning fossil fuels, which unlocks carbon that was last in the atmosphere millions of years ago.

In addition to biogenic carbon, there are emissions from the harvesting, processing and transportation of biomass.  For Electric Insights, we follow UK legislation in assuming these electric creation activities put the carbon intensity of biomass electricity at 121 gCO₂/kWh – 70% lower than from natural gas and 87% lower than from coal.

Companies which generate electricity from biomass and BECCS, such as Drax and Ørsted, must follow strict sustainability guidelines for the use of biomass.  The Government’s Biomass Strategy outlines a priority use framework that evaluates where biomass would be most sustainably and efficiently used across sectors, accounting for the four principles of sustainability, air quality, the circular economy and resource efficiency, and ability to support the UK’s 2050 Net Zero target.

Global need for BECCS

Large-scale carbon removal, including from BECCS, is widely regarded as being critical to stabilising the global climate.  The Intergovernmental Panel on Climate Change (IPCC) suggests that the world will need to remove between 0.5 and 9.5 billion tonnes of carbon dioxide annually via BECCS by 2050 to stay on course to limit global warming to below 1.5°C target.

Governments around the world have been increasingly adopting policies which are supportive of carbon dioxide removals and BECCS.  These include the US Inflation Reduction Act, the EU Renewable Energy Directive and the UK’s ‘Powering Up Britain’ energy security, Net Zero strategy, and Biomass Strategy.

Both biomass combustion and carbon capture are mature technologies, but the combination of these together would be a world first.  This means that building the world’s first large-scale BECCS power station will require hefty up-front investment – estimated at around £2 billion.  It will also increase ongoing operating costs as the energy cost to capture CO₂ reduces the amount of electricity it can send to the grid.  This has led to criticism of the plans to go ahead with BECCS, suggesting it will add to consumer bills. 

However, if the UK is to meet its legally-binding commitment to Net Zero emissions, the cost of BECCS should not be compared to renewable electricity, which reduces but does not actively remove carbon emissions.  Instead, it will need to be compared to the wider alternatives, such as eliminating emissions from the most difficult sectors, such as aviation and heavy industry.

Given the catastrophic costs of allowing climate change to escalate, and the difficulty of eliminating emissions across the entire economy, carbon dioxide removal could prove a very wise investment.

IPCC scenarios for global warming and the role of BECCS over the next fifty years.
Data from the IPCC, IIASA, and Our World in Data.  The coloured lines represent four of the many scenarios modelled by the IPCC, which consider a range of ‘shared socioeconomic pathways’ (SSPs) and levels of radiative forcings from 1.9 to 7.0 W/m².