Can Enhanced Rock Weathering become a significant component of Urban Farming?

Enhanced Rock Weathering (ERW) has emerged as a promising climate mitigation strategy, with many studies recommending annual application rates of 40–50 tonnes per hectare to maintain high, observable weathering rates. However, our analysis of 23 ERW field deployments reveals that such substantial application volumes may not significantly improve net carbon dioxide removal efficiency and could pose potential ecological risks to farmland and aquatic ecosystems^1,2. As an alternative, we propose integrating ERW into urban farming systems as a sustainable carbon dioxide removal (CDR) technology.

Urban farming systems, such as hydroponic and vertical farms, increasingly considered in future food production, offer unique opportunities for ERW deployment³. With 68% of the global population projected to live in urban areas by 2050⁴, these systems are positioned to stabilise food security while supporting climate mitigation efforts. Incorporating ERW into these controlled environments offers several advantages. Unlike conventional field applications, the closed-loop cycling of carbon dioxide and water within urban farming systems enables precise monitoring and adjustment of key variables, including weathering products such as alkalinity and dissolved inorganic carbon (DIC) levels. These parameters can be efficiently tracked using cost-effective Monitoring, Reporting, and Verification (MRV) methods, potentially outperforming traditional field-based MRV methodologies in terms of accuracy and affordability.

This approach not only enhances the carbon dioxide removal efficiency of ERW but also aligns with the sustainable intensification of food production. By integrating ERW into urban farming systems, we propose a novel pathway for simultaneously mitigating climate change and addressing food security challenges.

References:

Calabrese, S. et al. (2022) ‘Nano- to Global-Scale Uncertainties in Terrestrial Enhanced Weathering’, Environmental Science and Technology. Available at: https://doi.org/10.1021/acs.est.2c03163.

Strefler, J. et al. (2018) ‘Potential and costs of carbon dioxide removal by enhanced weathering of rocks’, Environmental Research Letters, 13(3), p. 034010

United Nations(2018). 2018 Revision of World Urbanization Prospects 2018. https://www.un.org/en/desa/2018-revision-world-urbanization-prospects (Accessed: 2025/1/13)

Specht, K. et al. (2014) ‘Urban agriculture of the future: an overview of sustainability aspects of food production in and on buildings’, Agriculture and Human Values, 31(1), pp. 33–51. Available at: https://doi.org/10.1007/s10460-013-9448-4