Abated vs. Unabated Emissions: Why They Matter for Achieving Net Zero

The word "abated" is the focus of much debate in the context of carbon dioxide emissions. World leaders have this year been underlining their commitment to phase out the use of unabated fossil fuels: that is, where emissions from their combustion are not mitigated through offsets or carbon capture technologies.

The final text of the COP28 statement called for "abatement, and removal technologies, such as carbon capture and utilisation and storage, particularly in hard-to-abate sectors." Meanwhile the G7 group of nations last year called for "a global effort to accelerate the phase-out of unabated fossil fuels to achieve net zero in energy systems by 2050." Such commitments are important in the race to decarbonize traditional energy sources, but they raise an important question: How exactly should we define "abated" emissions?

Currently, there is no widespread agreement on the answer, specifically on how much carbon dioxide should be removed for emissions to be classed as "abated". Some scientists argue this lack of definition risks hampering decarbonization efforts. "The term 'unabated', if left unchecked and poorly defined, could leave the interpretation of the commitment wide open," said a 2023 working paper by a group of scientists at Columbia University cited by Reuters.

What are abated and unabated emissions?

Unabated GHG emissions describe greenhouse gases which are released into the atmosphere from fossil fuels without any offsetting or removal, contributing to global warming in the process. Abated emissions describe those which have been reduced through technologies such as carbon capture and storage. But there is no consensus on the specific percentage of emissions that need to be captured to constitute abatement. The EU, for example, aims to be "predominantly free of fossil fuels well ahead of 2050," but the question of what "predominantly" means in the context of abatement has not been defined.

Attempts are being made to define the term. The latest IPCC report - where the definition of abatement is discussed only in a footnote - defines unabated fossil fuels as those "produced and used without interventions that substantially reduce the amount of GHG emitted throughout the life cycle; for example, capturing 90% or more from power plants, or 50-80% of fugitive methane emissions from energy supply."

Phasing out unabated emissions

While there is a lack of clarity around exactly what constitutes abatement, there is widespread consensus on the need to phase out sources of entirely unabated emissions. Doing so will not, however, be a straightforward process. Tackling emissions in heavy industry and other hard-to-abate sectors will be a particular challenge because they often rely heavily on fossil fuels, and presently have few viable alternatives that do not require significant investment. A successful transition will require the continued development of innovative emissions reduction technologies, as well as government policies which incentivize both carbon reduction and lower-carbon energy production.

Carbon capture and storage is one of the most promising of these technologies. Norway's Longship Project, which includes the Northern Lights transportation and storage consortium, provides a compelling example of how CCUS infrastructure can be developed to support the wider region's climate goals. The project aims to capture at least 1.5 million tonnes of CO2 per year initially - with plans to increase that amount over time - and store it in deep geological formations beneath the sea, where it can safely remain for thousands of years.

Carbon capture is currently relatively expensive, as early-stage technologies often tend to be, which partly explains why there are currently less than 50 operational CCUS projects globally - although that figure is rising rapidly, with more than 250 projects currently in the pipeline. Deploying CCUS technology at the scale required to meet the goals of the Paris Agreement - from 44Mt CO2 to 5.6Gt by 2050 - will require significant investment. The Global CCS Institute estimates that capital investment in CCUS capacity will need to reach between US$665 billion to $1.280 trillion by 2050 to meet the IEA's Sustainable Development Scenario, a framework which outlines a path to global sustainability goals.

Finding new ways to reduce emissions in carbon-intensive industries

Improving energy efficiency will also play a critical part in reaching net zero. According to the IEA, energy efficiency represents more than 40% of emissions abatement needed by 2040, and it can play a particularly important role in hard-to-abate industries.

Recapturing heat produced in industrial processes is one promising way of increasing efficiency, through processes including heat pumps and district energy systems. Such systems have significant untapped potential. In the EU alone, a recent report found that excess heat produced by heavy industry amounted to more than 250 TWh a year - more than the combined heat generation of Germany, Poland, and Sweden in 2021.

The cost of decarbonizing these industries - including cement, steel, ammonia, and ethylene - is estimated to be around $21 trillion by 2050, illustrating the scale of the challenge, although the figure could fall quickly if low-carbon electricity prices continue to fall. Nonetheless, such investment will be critical.