A Mixed-Integer Linear Programming Model for Enhanced Weathering Networks Considering Logistical Emissions

[Geoengineering News]

https://www.cetjournal.it/index.php/cet/article/view/CET25120015

Authors: Migo-Sumagang, Maria Victoria, Aviso, Kathleen B., Foo, Dominic C. Y., Tan, Raymond R., Tan, Yin Ling

30 November 2025

Abstract

Carbon dioxide removal (CDR) must be deployed at the scale of multiple gigatons per year to achieve the mid-century carbon neutrality target. Among the available CDR techniques, enhanced rock weathering or simply, enhanced weathering (EW) relies on processes that are technologically mature and result in durable carbon removal. It relies on the engineered acceleration of geochemical reactions between alkaline minerals and carbonic acid in water to permanently sequester carbon as bicarbonate ions in runoff. Ex situ EW involves spreading pulverized rock on the ground and allowing it to slowly dissolve in rainwater; in practice, the extent of completion of the reaction is dependent on local conditions and affects the “stoichiometric efficiency” of CDR. The CDR rate of suitable rocks is between 0.3-1.1 Gt CO2 per Gt rock without considering yet the CO2 penalties from processing the rocks. Scaling up EW to the required annual gigaton scale presents a massive logistical challenge that involves quarrying suitable rocks, grinding them into a suitably fine powder, transporting the rock powder to application sites, and finally putting it in the soil at a rate calibrated to match local conditions. In this work, we develop a mixed-integer linear programming model to optimize EW networks to maximize CDR for a given set of sources (rock-crushing plants) and sinks (application sites). The model determines both topology (source-sink matches) and physical flow rates; alternative solutions can be explored using integer cut techniques. The model is demonstrated using an illustrative case study of three sources and seven sinks. The optimal results utilized 76 % of the total available rock. The CO2 footprint is mainly due to production (rock crushing activities) at 82 %, transportation at 16 %, and application at 2 %. The introduction of carbon footprint (CFP) from various steps reduces the total CDR by 45.62 % highlighting that the CDR potential of EW networks is affected not only by the CDR rate and stoichiometric efficiency but also the CO2 penalties throughout the supply chain, with rock production giving the highest CO2 footprint. The sensitivity analysis shows that it might be worthwhile to focus on improving the production CFP along with the source material CDR rate.

Source: Chemical Engineering Transactions