A single smouldering waste treatment could lock away more carbon dioxide than it releases—potentially sequestering up to 7 kg of CO₂ per kg of waste, compared to the 0.1–2 kg emitted by current systems. This matters because waste management is a major source of hard-to-abate emissions. Over 2 billion tonnes of municipal solid waste are generated globally each year, and traditional treatment contributes roughly 5% of global CO₂ emissions. By 2050, waste generation is projected to reach 3.4 billion tonnes annually, with associated emissions of 2.6 gigatonnes of CO₂-equivalent. Existing technologies struggle to reduce these numbers. The project fills a knowledge gap: no one has yet combined smouldering combustion with thermal activation of ultramafic rocks to both treat waste and permanently mineralise CO₂. If successful, carbon-negative smouldering could transform waste infrastructure—turning treatment plants from net emitters into carbon sinks. It would also support the UK’s net-zero targets by 2050 and offer a scalable solution for off-grid sanitation and hazardous waste in remote areas. The team will use experiments and modelling to address geochemistry, heat transfer, and economic viability, aiming to move from proof-of-concept toward field demonstrations.
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Carbon-negative innovations are urgently needed to improve the sustainability of global waste management systems. This project will provide the scientific basis needed to scale-up carbon-negative smouldering, a new carbon-negative waste treatment technology that integrates smouldering combustion with carbon sequestration via thermal activation of ultramafic rock. This integration will directly harness energy from waste to drive carbon sequestration. Current waste management systems release 0.1 to 2 kg CO2-equivalent per kg waste. In contrast, our proof-of-concept research suggests that carbon-negative smouldering may sequester up to 7 kg CO2 per kg waste. Given the novel state of this technology, key knowledge gaps related to geochemistry, heat and mass transfer dynamics, and economic and sustainability success factors must be addressed to advance from proof-of-concept to large-scale operation. Tarek Rashwan, Phil Renforth, Christine Switzer, José Torero, and Katherine Dobson will address these knowledge gaps alongside an international team of industry partners. Carbon-intensive waste management is a major societal challenge. Globally, over 2 billion tonnes of municipal solid waste are generated annually, and traditional waste management systems currently output ~5% of global CO2 emissions. These emissions are tough to abate. By 2050, global waste generation is projected to increase to 3.4 billion tonnes per year and will require management systems that output 2.6 GT CO2-equivalent annually. In the UK, major national commitments recognise waste management challenges and aim to maximise resource circularity and minimise environmental pollution, while also pursuing low-carbon solutions needed to reach net zero targets by 2050. Carbon-negative smouldering can improve waste treatment systems, addressing global waste management challenges and contributing positively to the UK’s environmental goals and net zero agenda. Applied smouldering has recently emerged as a scalable, energy-efficient, and sustainable thermal technology. It has been applied to treat hazardous materials and recover energy and resources from challenging wastes, e.g., faeces within off-grid systems in low-income regions and hazardous waste liquids in remote locations worldwide. Smouldering is therefore highly compatible with a circular economy. However, as waste is combusted to CO2, carbon emissions remain a key sustainability limitation. Carbon mineralisation in ultramafic rocks has the potential to sequester 1-10 GT CO2 annually. However, this mineralisation is often limited to 3-10% of total CO2 mineralisation potential due to inhibiting compounds. Thermal activation prior to carbon mineralisation can release these compounds and address this limitation. Carbon-negative smouldering systems can harness energy from wastes to thermally activate ultramafic rocks. Through combining expertise in smouldering, geosciences, and carbon solutions, this project will use experimental and modelling tools to advance carbon-negative smouldering beyond proof-of-concept towards large-scale operation. This project will: Evaluate thermal activation experimentally across smouldering and ultramafic rock conditions, which is needed to quantify the potential for carbon-negative waste treatment. Integrate thermal activation geochemistry processes into an existing smouldering numerical model, which is needed to forecast dynamics in large-scale systems. Identify economic and sustainability factors that govern carbon-negative smouldering scale-up success through a techno-economic analysis and life cycle assessment. Altogether, this project is poised to unlock follow-on opportunities on an accelerated path to carbon-negative smouldering application, including scale-up experiments and field demonstrations. Alongside an international team of partners, our project will open a new field that aims to improve waste sustainability worldwide.
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