Quantitative assessment of environmental indicators influencing enzyme induced carbonate precipitation (EICP) technique in soil: LCA based approach

Abstract

Enzyme induced carbonate precipitation (EICP) is an emerging sustainable technology in the field of geotechnical engineering. It involves the application of urease, a plant-based urease enzyme which mediates the precipitation of calcium carbonate (CaCO₃) via hydrolysis of urea. This results in biocementation and subsequent improvement of the strength of the soil. In purview of this developing bio-stabilization technique, Life cycle assessment (LCA) can be used as a promising tool for incorporating sustainability metrics to evaluate the environmental impacts related to EICP technique and assist in policy and decision making. In this present study, an attributional LCA is conducted to investigate and quantify the various environmental impacts associated with EICP concentrations as proposed by various researchers. The environmental impact indicators taken into consideration are global warming potential (GWP), eutrophication potential (EP), energy use potential (EUP) and freshwater ecotoxicity potential (FWP). The results revealed that chemical constituents of EICP i.e., urea (51.25–74.53%) and non-fat milk powder (52.82–87.11%) are the dominant contributors to GWP (max: 2146.95 kg CO₂ eq). Urea also contributes to EUP in the range between 69.58 and 92.6% (max: 14,279 MJ). However, NH₄Cl, the by-product (NH₄Cl) of EICP process, a water pollutant, is the major contributor to EP (max: 326.44 kg N eq) and FWP (max: 289.25 kg 1,4-DCB eq). This indicates that more focus should be bestowed on EP and FWP to better characterize and quantify the associated ecosystem response due to over-utilization of the chemicals, for any EICP stabilization technique. Thus, this analysis considers the aspect of sustainability inground modification technique, aiding the advancement of EICP research.

Graphical Abstract