Carbon Business Council’s Roadmap for Enhanced Rock Weathering

As more industry players realize the importance of offsetting carbon dioxide (CO₂) emissions as part of the International Panel on Climate Change (IPCC) goal of achieving carbon net zero emissions by 2050, enhanced rock weathering (ERW) has emerged as a highly promising method of carbon removal.

In March 2024, the Carbon Business Council (CO2BC) published a policy primer addressing opportunities, key challenges, and proposed policy recommendations aimed at accelerating advancement, deployment, and scaling of ERW. The primer resulted from the collaboration of thought leaders in the ERW and carbon dioxide removal (CDR) industry, reflecting the most up-to-date information from companies including Isometric, Eion, Puro.earth, Mati, Lithos, InPlanet, and Undo.

“ERW is a promising CDR approach that builds on the longstanding agricultural practice of applying pulverized rock dust to working lands to manage soil acidity. ERW accelerates the natural carbonate-silicate cycle and durably removes CO₂ from the atmosphere via the spreading of finely ground rock dust on agricultural soil,” CO2BC notes in the policy primer’s introduction. “There is clear scientific consensus that, in addition to rapid and deep reduction of global greenhouse gas emissions, CDR will be required at an immense, multi-gigatonne annual scale by mid-century to meet the goals of the Paris Agreement.” 

Remineralize the Earth (RTE) favors a CDR model that includes ERW, and discussions among key stakeholders indicate that the industry seems to be moving toward an endorsement of this proposal. One illustration is current work on building a monitoring, reporting and verification (MRV) protocol for a whole-systems approach aligned with efforts toward standardization and setting best management practices for commercialization efforts.

A consensus on the form and substance of such a model requires the perspectives of economists, financiers, as well as government policymakers to parse the more subjective attributes of markets, economies, national politics, and geopolitical financial policy.

ERW opportunities

Perhaps ERW’s most compelling raison d’être is the business case for corporate entities in mining, agriculture, and other sectors. CO2BC projects CDR to become a $1 trillion sector in the latter half of the  21^st century. Developing ERW capabilities to meet their net-zero targets enables companies to position themselves as major carbon traders.

A number of companies are currently focused on developing ERW infrastructure and scaling proof-of-concept operations. For example, XPRIZE Carbon Removal winner Mati Carbon is building systems to deploy rock dust in smallholder farms across Global South countries including India, Tanzania, and Zambia. The growing number of commercial ERW endeavors speaks volumes about ERW’s potential to offer “high-quality, long-duration CDR with Gt annual global scale potential,” that could see prices decrease to under $100 per ton from the estimated $160–$180 per ton currently.

Compounding ERW’s potential cost reduction, its ability to leverage existing infrastructure further lowers the barriers for corporate entities seeking to enter the field. ERW benefits from utilizing existing byproducts generated during mining operation and transporting them to deployment sites through existing supply chains. Early estimates show that the total CO₂ emissions from the manufacture and transport of rock dust to application sites account for 0.5 – 3% of ERW’s potential carbon sequestration capability. However, this figure depends on the success of ERW companies at scaling rock dust production and deployment.

Aside from ERW’s potentially massive economic benefits, its use of existing infrastructure, and its ability to sequester CO₂, deploying rock dust on agricultural lands has several agronomic benefits. Applying crushed silicate rocks on agricultural lands helps balance soil pH, increasing the bioavailability of important crop nutrients – such as potassium, calcium,  and magnesium – and reduces the need for traditional nitrogen, phosphorus, and potassium chemical fertilizers, improving soil health and crop yields. Moreover, silicate rock dust contains key macro- and micronutrients such as iron, silicon, zinc, manganese, and molybdenum.

These factors work in concert to increase crop yields and nutrient density, which directly translate to increased revenue for farmers in Global South communities, who are often the least responsible for, but the most vulnerable to, climate change. The additional revenue generated presents opportunities to invest in higher quality soil amendments, farming implements, seeds, and builds resilience at the frontlines of climate change.

Pathways to Scaling Up ERW

Despite ERW’s promise as a CDR method, it lags behind other forms of novel CDR, including biochar, Direct Air Capture with Carbon Storage, and Bioenergy with Carbon Capture and Storage. The policy primer attributes this gap to ERW’s relative anonymity, especially among policymakers and the public. Engagement and education is essential to highlight ERW’s CDR abilities, agronomic potential, and socio-economic benefits, while building understanding of stakeholder needs and priorities and how ERW can benefit farmers who apply rock dust to their fields.

Central to the success of every ERW project is quantifying the amount of CO₂ removed from the atmosphere. Even though creating the high-quality Monitoring, Reporting, and Verification (MRV) protocols required is expensive and time consuming, these research and development costs are likely to decline as protocols mature. Project developers should prioritize selecting or developing appropriate MRVs to ensure that projects attain their fullest potential.

While there is an emerging scientific consensus around the efficacy of ERW as a high-quality, long-duration CDR solution, scientifically informed site selection and project design is crucial to avoiding deployments at unsuitable sites. However, the substantial diversity of deployment contexts complicates project design because rock weathering rates vary based on a range of factors, from feedstock characteristics to the physical, chemical, and biological properties of soil at application sites.

Even as ERW has begun to receive meaningful support from governments and corporate entities in recent years, investors remain hesitant to fund early-stage projects due to unique economic attributes of ERW deployments, which consists of operating expenses and credit revenue earned over time. Project financiers need a clear understanding of ERW’s revenue profile across the ERW value chain to develop the appropriate finance mechanisms to fund ERW research and early-stage projects to achieve the scales needed to meet the Paris Climate Agreement’s goals.

Policy recommendations

As ERW scales globally, it is important for ecosystem stakeholders to monitor and assess potential risks, paving the way for continued adoption of ERW as a viable and scalable CDR method. Stakeholders should create method-neutral frameworks for international carbon markets and extend resources globally, ensuring high-quality projects and equitable distribution of benefits to farmers with the goal of making ERW policies integral to national CDR portfolios.

Given the opportunity to deploy ERW at scale worldwide, policymakers should adopt a portfolio approach to achieve gigaton-scale CDR. They should seek to implement method-neutral, criteria-based policies to fund and support high-quality CDR. Early real-world examples of such a policy approach include the US DOE CDR Purchase Pilot Prize, and the $100M Carbon Negative Shot Pilot Funding Opportunity Announcement.

SR and ERW: The way forward

Current ERW models, as championed by CO2BC’s policy primer, prioritize investors, companies, corporations, and governments in an overly mechanistic and monetized ERW paradigm.

Soil remineralization, on the other hand, is a traditional approach to soil restoration and enrichment. It is considered a form of “geotherapy” and the philosophical antithesis of geoengineering, which emphasizes technological interventions at scale. Geotherapy practices work in accordance with natural systems to reinvigorate and rebalance biogeochemical and ecological processes, representing low-cost sustainable solutions.

“The difficulty in monetizing ERW lies in a model driven by profit-oriented activity through direct investments from private equity investors, corporate funds, academic and government research subsidies,” Rock Dust Local founder and RTE Board Advisor Tom Vanacore said in an email exchange. “What is needed is a nature-based approach that minimizes disturbance and removes or lessens the need for synthetic fertilizers, herbicides, and pesticides.”

This multidisciplinary approach is rooted in the development of biomineral fertilizers as synthetic fertilizer replacements using indigenous and native sources of microbial feedstocks, thus providing a pathway for a ERW framework that moves towards a true whole-of-system approach using improved agricultural practices.

A more holistic ERW-specific MRV protocol should embed environmental services and stack CDR negative methods including ERW, carbonate mineralization, pyrogenic carbon capture through biochar, and microbial mediated carbon sequestration, and increase water holding capacities by increasing soil organic matter production, while emphasizing the environmental and social benefits of this approach.

Most important of all is keeping sight of the proven and historical benefits of soil remineralization. The promise it holds through the interaction of native and indigenous microbiology, combined with the innovative spirit of grower-farmers and land managers, can solve the most vexing problems we face as a civilization, all while using local resources to feed a burgeoning global population and stabilizing the Earth’s climate.

Benjamin ZH Tan is a graduate of Northeastern University with a masters degree in Media Innovation and Data Communication. He writes about the intersection of business, policy, technology and climate, and is committed to raising public awareness of the science of soil remineralization and emerging CDR technologies. During his down time, he enjoys landscape photography, hiking, and cooking.