Life cycle assessment of enzyme-induced carbonate precipitation columns for ground improvement

Abstract We conducted a prospective life cycle assessment (LCA) of enzyme-induced carbonate precipitation (EICP) columns as a ground improvement technique for building foundation support. EICP is a recently developed bio-mediated biogeotechnology that can improve the strength and stiffness of soil by cementing soil particles together. EICP can be employed in a non-disruptive manner under existing facilities and has the potential to have lower environmental impacts than traditional ground improvement methods, which rely on high cement volumes to stabilize soils. We compared EICP against microfine cement permeation grouting (PG), an incumbent geotechnology. We followed a recently introduced framework, geotechnical whole LCA (Geo-WLCA), to conduct our LCA. Our assessment assumed the EICP columns were installed using tube-a-manchette (TAM) technology at a hypothetical site in Tempe, Arizona. Using a functional unit combining treatment area and target treatment strength, we found that, across all categories except eutrophication, the environmental impacts of EICP are less than half of those of PG. Except for eutrophication, EICP impacts are mostly due to equipment operation for TAM well installation and EICP solution injection. If not managed, ammonium chloride emissions from the EICP process contribute significantly to EICP eutrophication impacts. We highlight the importance of future work to further understanding and development of ammonium chloride impact mitigation. This LCA demonstrates that EICP columns may reduce the environmental impacts of ground improvement for foundation support. The approach used here can be reproduced for additional analyses of EICP for ground improvement and other applications.