News Release

The Final 25%: How to tackle hard-to-reach emissions

Three reports from Oxford University on reaching the Final 25% and achieving Net Zero

Reports and Proceedings

University of Oxford

The Final 25%: Hard-to reach emissions. Dr Katherine Collett

video: Dr Katherine Collett, University of Oxford, explains that our food system produces some of the hard-to-reach emissions in the Final 25%. view more 

Credit: University of Oxford

Electricity, transport, and heating account for a massive 80% of greenhouse gas emissions and are at the forefront of the battle to achieve Net Zero. However, reaching Net Zero means also dealing with the hard-to-reach 20% of emissions: agriculture, plastics, cement, and waste, and extracting at least 5% extra from the atmosphere to account for the emissions that we simply cannot get rid of. Together, this is known as the ‘Final 25%’. And Net Zero cannot be achieved without tackling this hard-to-reach wedge.

Made up of a range of greenhouse gas emitters, which are harder to spot than pollution-belching-carbon-burning power stations, these emissions cannot be overcome by flipping a switch or buying a new car. But, combined, they account for one-in-four tonnes of greenhouse gases.

To investigate the problems and suggest policy pathways for new innovation, Oxford’s Smith School of Enterprise and the Environment is today publishing findings from the ‘Final 25%’ project. The project called on the expertise of leading industry, investor, academic, civil society and policy minds to lay out roadmaps of investment to give us a fighting chance of meeting Net Zero with technology. These are contained in three keynote reports covering: the use of polymers; nature-based solutions for greenhouse gas removal; and alternative proteins.

Report author and the Director of Oxford's Smith School of Enterprise and the Environment, Professor Cameron Hepburn says, ‘The Final 25% emissions identified in our three reports must be tackled if we are to achieve Net Zero. Reducing or eliminating them is going to mean some real changes, though, and significant investment is needed in R&D to make sure these can happen. We can do this and the novel and imaginative solutions contained in these reports could get us there.’

The reports considers a host of imaginative and sometimes challenging ways to tackle the Final 25%, including:

  • Using semi-arid and saline land for plant growth either for product feedstocks or for greenhouse gas removal.
  • Using biomass and atmospheric CO2 to create sustainable polymers, and
  • Adopting alternative proteins, including plants, insects and algae, which would free-up land to be used for environmental services such as nature-based greenhouse gas removal.

Leading report author, Dr Katherine Collett, says, ‘Mitigating climate change demands more than a shift to renewable electricity generation; investment in harder-to-abate sectors is already required.

‘To reach Net Zero, intersections between plastics, proteins and plants, three seemingly unconnected systems, may hold the key. Our reports explore the potential of these systems in detail, pointing the way forward for research, policy development, regulation, and financing options.’

Brian O’Callaghan, Lead of Oxford’s Economic Recovery Project and another report author, explains, ‘In the shadow of COVID-19, government investment in green innovation can both help to constrain climate change and seed new industries to stand as powerhouses of economic growth in the long-term.’

Linking to past green investment programs, he continues, ‘The US invested big in renewable energy research and development during the global financial crisis. That investment has delivered many multiples. Governments could make similar progress in agriculture and industry today.’


The Final 25% reports - Embargoed until 00:01 BST, Thursday 5 August 2021.


Industrial need for carbon in products

There is considerable international awareness about the problem of plastics in the environment. The report highlights that the need for petrochemical-based materials including polymers (plastics), asphalt, carbon fibre, pharmaceuticals, lubricants, solvents, and fertilisers, is not disappearing anytime soon. They are indispensable in modern economic and social systems. To reach Net Zero, new approaches are needed.

In particular, solutions are urgently required for manufacturing sustainable plastics, which are overwhelmingly produced with oil as a feedstock.

The report explains that research into sustainable feedstock alternatives needs to be accelerated, along with considering what will happen to the product at the end of its life: will it be recycled, biodegrade, or be buried? The report recommends:

  • Using alternative sustainable feedstocks, such as biomass plants, and CO2 from the atmosphere to create plastics.
  • Increasing recycling rates, which have been less than 10% historically, by designing products to be recycled and investigating alternative recycling technologies.
  • Implementing policy to require sustainable polymer production to increase over time, allowing industry time to develop and transition to new products.


The Climate Impact of Alternative Proteins

Animal products account for 16% of total greenhouse gas emissions, and this number is expected to grow to 35% by 2050 with increases in demand for animal products, driven by increased consumer wealth in emerging economies such as India and China.

The report recommends accelerated use of alternative sources of protein, including traditional plant-based proteins (e.g. tofu, nuts, peas, beans), insects, mycoproteins (e.g. products produced by Quorn), algae (e.g. spirulina), protein derived from bacteria, and cultured meat.

As well as the potential to produce Nearly Zero emissions, use of these alternatives means grazing land can be ecologically restored and provide natural greenhouse gas removal.

According to the experts, if these emissions are to be reduced, urgent research is needed into:

  • Bacterial and cultured meat.
  • Novel plant feedstocks for mycoprotein and insects.
  • Green fertiliser, and
  • Mapping the potential of converting agricultural land to nature-based greenhouse gas removal.


Nature-based ‘sinks’ for CO2 and sources of carbon feedstocks

Nature can be used as a carbon sink, removing emissions from the atmosphere (often called greenhouse gas removal), and as a source of carbon-heavy feedstocks, in the form of plants. Three main options are explored to understand how nature can fulfil these two roles. But further research is needed for these to be scaled up:

  • Considering the use of agriculturally-unfavourable land, such as semi-arid regions and saline land, to grow crops. These can remove CO2 from the atmosphere and provide carbon feedstocks for products such as plastics.
  • As discussed in the report on alternative proteins, grazing land as well as other recently deforested regions can be released for reforestation – which provides another CO2 ‘sink’.
  • Also, soil carbon could be increased – to provide a further carbon sink and potentially increase crop yields.


The Smith School of Enterprise and the Environment

The Smith School of Enterprise and the Environment equips enterprise to achieve net zero emissions and the sustainable development goals, through world-leading research, teaching and partnerships.

True Planet: Oxford research for a changing world

The world is in a climate crisis, and Oxford researchers are at the forefront of trying to find solutions in adaptation and resilience, nature, energy transition, clean road transport and green finance.

Our researchers are working with partners in industry, government, the third sector and at other universities to address these challenges and to propose innovative approaches and solutions. Find out more about our True Planet campaign

The University of Oxford

Oxford University has been placed number one in the Times Higher Education World University Rankings for the fifth year running, and at the heart of this success is our ground-breaking research and innovation. Oxford is world-famous for research excellence and home to some of the most talented people from across the globe. Our work helps the lives of millions, solving real-world problems through a huge network of partnerships and collaborations. The breadth and interdisciplinary nature of our research sparks imaginative and inventive insights and solutions.





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