Review of carbon removals by direct ocean carbon capture and storage (EU CRCF)

/in ,

Direct ocean carbon capture and storage (DOCCS) is a carbon dioxide removal method in which the pH of seawater is manipulated to extract carbon which can then be stored (e.g. through geological CCS). The seawater experiences a carbon deficit and draws CO2 out of the atmosphere. Typically, electrochemistry is used to separate seawater or brine into acid and base parts; the acid part is used to acidify seawater drives off CO2 for capture, and the base part is then mixed back in to restore alkalinity. This technical review presents the underlying chemistry, technologies, efficiency impacts, and sustainability implications of DOCCS.

The review was led by Martin Johnson (Ecodiversity), with key contributions from Cerulogy and Zara Popstoyanova (ICF). Its findings were presented alongside evidence from external experts and from the CRCF Expert Group on Permanent Carbon Removals at a European Commission workshop.

Download the report from the EU publications portal

Review of carbon removals through mineral carbonation (EU CRCF)

/in ,

This technical review concerns the sequestration of CO2 in the form of solid carbonate minerals, a process referred to as mineral carbonation. We focus in particular on cement-based building materials, but also consider alkaline industrial by-products such as metallurgical slags that contain calcium oxide or calcium hydroxide, and mine tailings containing silicates and other alkaline compounds. These materials carbonate naturally when exposed to atmospheric CO2 and moisture; ‘enhanced carbonation’ is where the process is sped up by active intervention, and this could be a candidate for recognition under the CRCF. The review covers the underlying chemistry of carbonation, the environmental factors that influence its rate, and the critical challenge of quantifying the natural carbonation baseline.

The review was conducted by Cerulogy, and was presented alongside evidence from external experts and from the CRCF Expert Group on Permanent Carbon Removals at a European Commission workshop.

Download from the EU publications portal
A stick and ball representation of a bicarbonate ion

Review of carbon removal by ocean alkalinity enhancement (EU CRCF)

/in ,

Ocean alkalinity enhancement (OAE) is a carbon dioxide removal method utilising carbonate chemistry to store CO2 as dissolved inorganic carbon (DIC) in the ocean. The ocean already durably stores a huge quantity of DIC due to its high alkalinity, driven by natural rock weathering. However, quantification and certification for engineered OAE activities present challenges due to the large spatial and temporal scales on which CO2 uptake from the atmosphere occur, the need for modelling to quantify removals, and the need for research and monitoring of ecological side-effects. This technical review for the European Commission explores these issues.

The review was led by Martin Johnson (Ecodiversity), with key contributions from Cerulogy and from Zara Popstoyanova (ICF). It was presented alongside contributions from experts in the field at a European Commission carbon removals workshop on ERW and OAE.

Download the report from the EU publications portal

Review of carbon removals through enhanced rock weathering (EU CRCF)

/in , ,

Enhanced rock weathering (ERW) seeks to sequester carbon dioxide as dissolved inorganic carbon (DIC) by accelerating the dissolution of alkaline minerals on the Earth’s surface. This technical review explores ERW in the context of the EU’s Carbon Removals and Carbon Farming Regulation (CRCF), and covers the theoretical underpinnings in geochemistry and soil science, implementation challenges, quantification & baselining issues, and sustainability safeguards that would have to be considered if an ERW methodology were to be developed for the CRCF.

The review was led by Cerulogy, with key contributions from Zara Popstoyanova (ICF) and Martin Johnson (Ecodiversity). It was presented alongside evidence from experts in the field at a European Commission carbon removals workshop on ERW and OAE.

Download the report from the EU publications portal

European Commission carbon removals workshop: DOCCS and mineral carbonation

/in ,

Cerulogy delivered a European Commission workshop on two carbon removal activities, in partnership with ICF and Ecodiversity. Direct ocean carbon capture and storage (DOCCS) encompasses a number of technologies that extract carbon dioxide from seawater for eventual geological storage. Mineral carbonation involves the absorption and permanent binding of carbon dioxide into materials (concrete and alkaline industrial wastes) in the form of solid carbonates.

The one-day workshop took place on 09th February 2026 with the goal of gathering input from experts and stakeholders to inform the CRCF process. Cerulogy and Ecodiversity presented technical reports that provided an overview of how the carbon removal pathways work, challenges in implementation, issues around quantification and baselining, and potential sustainability impacts. Experts from academia and industry presented on specific topics, and participated in discussions.

Presentations and workshop recording

Review paper on DOCCS

Review paper on mineral carbonation

A stick and ball representation of a bicarbonate ion

European Commission carbon removals workshop: ERW and OAE

/in ,

Cerulogy delivered a European Commission workshop on two carbon removal technologies, in partnership with ICF and Ecodiversity. The ocean is the Earth’s largest reservoir of carbon (in the form of dissolved inorganic carbon, or DIC): by adding alkalinity to the Earth’s surface, watercourses and/or oceans, enhanced rock weathering (ERW) and ocean alkalinity enhancement (OAE) seek to augment this reservoir and stimulate net draw-down of carbon dioxide from the atmosphere.

The one-day workshop took place on 25th September 2025 with the goal of gathering input from experts and stakeholders to inform the CRCF process. Cerulogy and Ecodiversity presented technical reports that provided an overview of how the carbon removal pathways work, challenges in implementation, thorny issues around quantification and baselining, and potential sustainability impacts. Ten ERW/OAE experts from academia and industry presented on specific topics, and participated in discussions.

Presentations and workshop recording
Review paper on OAE
Review paper on ERW

 

Diverted harvest: Environmental Risk from Growth in International Biofuel Demand

/in , , , ,

In this report for Transport and Environment, we describe the biofuel policy frameworks and targets of the nine leading global producers and consumers: the USA, Brazil, the EU+UK, Indonesia, China, India, Argentina, Canada, and Thailand. The report links these countries’ biofuel feedstock demand to ecological risks, to the carbon opportunity cost of using extra land for agriculture, and to the greenhouse gas implications of relying on biofuels to displace fossil fuels.

We calculate that about 32 Mha of cropland is currently devoted to biofuel feedstock production after accounting for co-product allocation. The benefit of this, as conventionally calculated (i.e. ignoring ILUC), is a 233 MtCO2e/year emissions saving compared to an equivalent amount of fossil fuels. But returning this land to its natural state — and replenishing its above- and below-ground carbon — could provide a much larger carbon sink of 428 MtCO2e/year. While rewilding of agricultural land on this scale is not currently plausible, these numbers underscore the importance of thinking about land use in ways that aren’t readily captured by conventional lifecycle analysis.

Under present policy targets, biofuel consumption in the nine study countries is set to increase from 104 Mtoe in 2023 to 150 Mtoe in 2030. Given existing and future feedstock slates, and constraints on advanced and residual feedstock supply, we conclude that over 90% of this is likely to come from crops: that means an extra 20 Mha devoted to biofuels worldwide. Accounting for the range of crops grown in each country, we calculate that if ILUC is taken into account, biofuel policy in 2030 will increase emissions from transport fuels by 34 MtCO2e/year compared to 2023.

The EU+UK and Thailand are found to have adopted policies that are reducing biofuel-associated emissions down over time. The USA, India, and Indonesia, by contrast, are expected to expand use of high-ILUC palm and soybean oils, and so their biofuel policies are likely to be harming rather than benefitting the climate.

Download our report
Read the T&E briefing

A federal clean fuel standard (CFS) for the USA

/in , ,

Clean fuel standards (CFSs) are regulations which reward or penalise transport fuels based on their lifecycle greenhouse gas emissions — in particular, their emissions with respect to a ‘compliance standard’ which tightens each year. A number of CFSs are already in operation around the world.

Our paper published in the journal Energy Policy examines a hypothetical CFS covering the USA’s road and aviation segments. We model two transport decarbonisation scenarios: one with an emphasis on road electrification, and the other with an emphasis on next-generation liquid fuels and CCS. Both are designed to be consistent with a net-zero-2050 target for the USA’s economy as a whole, with road transport achieving a 87-94% carbon intensity cut and aviation ∼84% (excluding contrails). The electrification-heavy scenario offers faster and deeper emissions cuts, as well as being a significantly cheaper decarbonisation option.

The development and results of these scenarios provide context for considering CFS design issues: the ambition of targets, how to drive investment, and the need for restrictions on certain biofuel feedstocks.

Download the paper

Biochar and carbon accounting

/in ,

Biochar: accounting for carbon benefits of production and use

This report, commissioned by the International Council of Clean Transportation (ICCT), explores different pathways for crediting biochar in greenhouse gas lifecycle accounting frameworks. We focus on existing regulations such as the European Union’s Renewable Energy Directive (RED III) and the UK’s Renewable Transport Fuel Obligation (RTFO), which allow credit for soil carbon accumulation through improved agricultural management practices.

As biochar moves towards a mainstream role in agriculture and carbon markets, there is a clear need for robust accounting guidance. Through worked examples and policy analysis, the study unpacks key methodological questions around how biochar’s role, as both a soil amendment and a carbon removal product, may be fairly and accurately accounted in carbon crediting frameworks. We identify key safeguards, improvements to existing frameworks, and the need for measures to limit the risk of double crediting.

Download the report

Staying Aloft: Support Mechanisms for ‘Sustainable Aviation Fuels’ in the United Kingdom and European Union

/in , , , ,

The EU’s ReFuelEU Aviation and the UK’s SAF Mandate place requirements on fuel suppliers to bring alternative aviation fuels to market. In parallel, financial support for alternative fuels comes from the EU’s reimbursement scheme, which subsidises some fraction of the cost difference paid by airlines, and the UK’s guaranteed strike price (GSP), which shields SAF producers from variability in market prices.

This report examines the policy frameworks in the two regions and reviews their strengths and weaknesses. It finds that the structure and targeting of their complementary support mechanisms will deliver diverging outcomes. The EU’s reimbursement scheme will benefit airlines and reduce the costs to flyers, but will do little to motivate next-generation fuel producers. In contrast, the UK’s GSP delivers clear reassurance to fuel producers and is more likely to stimulate investment in the industry by facilitating finance availability and reducing the cost of capital.

The report presents illustrative model scenarios and concludes by distilling major challenges and recommendations for the two policy frameworks.

  • The EU’s mandate trajectory and its slightly obscure system of non-compliance penalties could be reviewed, and a joined-up approach adopted for targeting resources towards supporting investment in more sustainable alternative fuels.
  • For the UK, there are some important details to iron out about how price-setting works in the GSP; and a potentially vacillating balance of alternative fuel supply and demand from the EU may pose challenges for compliance and costs.
Download from the ICCT website