Enhanced rock weathering (ERW) is a promising solution for durable carbon dioxide removal (CDR) which involves spreading finely ground alkaline rocks (such as basalt and other silicate rocks) over land. Scientists posit that the alkaline materials will react with carbon dioxide in the air, sequestering it in mineral or aqueous form, potentially for tens of thousands of years. ERW is most commonly proposed in agricultural fields by spreading crushed rock onto agricultural soils, building on the longstanding approach of applying pulverized rock (such as limestone) to soil to manage its pH.
In theory, ERW provides a number of advantages as compared to other CDR methods. When applied on agricultural fields, it can utilize existing infrastructure to apply the crushed rock, making the process relatively quick and cheap. In addition to sequestering carbon dioxide, ERW can also improve soil health and thereby increase crop yields and may have other co-benefits, such as mitigating ocean acidification. However, ERW poses certain environmental and human health risks, such as soil and water contamination, and could be harmful to some crops. Before ERW can be deployed at scale, further research is required to resolve key uncertainties surrounding the process, and better understand the risks it might present. Field trials have been conducted to explore the efficacy of ERW, such as in the U.S., India and Brazil. Due to its pre-existing quarrying infrastructure co-located with basalt reserves, the viability of ERW projects in Minnesota has been explored, through initial field trials and modeling. Any field trials, and any potential subsequent deployment, must satisfy applicable legal requirements and obtain the relevant permits.
In a recently published white paper by the Sabin Center, we build on previous research into the application of federal laws governing ERW, and analyze the application of both federal and state laws to ERW projects in Minnesota.
In Minnesota, there are no state or federal laws that specifically address ERW. However, there are a number of general environmental laws that could apply to ERW projects. The extent to which, and how, these laws apply will depend on various factors, such as the location in which any given project is conducted and its environmental and health impacts.
This white paper specifically examines five groups of laws:
- land laws, which may impose restrictions on the spreading of alkaline material depending, in part, on who owns the land in question, i.e., whether the land is privately owned, state owned, or federally owned, as well as the type of material used;
- air pollution laws, such as the Clean Air Act, which may place restrictions on dust pollution that could be caused by spreading crushed alkaline rock;
- water pollution laws, such as the Clean Water Act, which may place additional requirements and permitting obligations depending on whether the project can cause water pollution;
- waste management laws, such as the Resource Conservation and Recovery Act, which may place additional federal and state requirements depending on the material used and its source; and
- environmental review laws, such as the National Environmental Policy Act, which may require review from government agencies for ERW projects that affect the environment.
The white paper also provides recommendations on legal reforms that could be implemented to address gaps and other shortcomings in the existing framework. The white paper is part of a series published by the Sabin Center on state-level regulation of CDR. Our other white papers, such as on ocean alkalinity and on seaweed cultivation, have highlighted similar legal reform needs. Taken collectively, the papers reveal opportunities for legal development that could help overcome barriers to CDR research and support the responsible development of CDR projects, if their benefits are proven and they are shown not to pose undue risks to the environment or communities.
Read the white paper, “The Legal Framework for Enhanced Rock Weathering in Minnesota” here.
Ashwin Murthy
Ashwin Murthy is the Negative Emissions Fellow at the Sabin Center for Climate Change Law.
