Abstract
•Across four climates, MICP treatment of geothermal pavements increases energy output.•Dry, low thermal conductivity soils benefit most from MICP treatment.•A tool to estimate MICP-treated pavements’ thermal potential is introduced.•In Mediterranean regions (Fig. 12), annual heat rose 64% with 4.1 wt% carbonate.•Economic viability centres on material price; best cases cut costs by A$300/m.
As demand for low-carbon heating and cooling solutions grows, shallow geothermal energy systems integrated within pavements offer a promising approach for sustainable infrastructure. This study evaluates the technical and economic feasibility of microbial induced calcium carbonate precipitation (MICP)-treated geothermal pavements using a validated finite element (FE) model. Thermal performance of the embedded ground heat exchanger (GHE) system was examined across representative climates, subbase saturation levels, and subgrade thermal conductivities. Results show MICP treatment significantly enhances performance in dry conditions, particularly when subgrade conductivity is low (0.3 W/(m·K)). In a Mediterranean climate scenario, applying 4.1 wt% CaCO₃ increased annual thermal output from 177 to 290 kWh/m (64%). However, benefits diminish with higher subbase saturation or naturally high subgrade conductivity. The subbase-to-subgrade conductivity ratio emerges as a critical design parameter, with higher ratios generally improving thermal output but limiting the marginal gains from MICP. Economically, under optimal dry soil conditions, MICP treatment yields a net present value (NPVT) exceeding 300 AUD/m, offsetting over 70% of typical road construction costs. Sensitivity analysis shows MICP material cost as the dominant factor affecting NPVT. These findings emphasise the importance of balancing technical gains with economic considerations to optimise the application of MICP in geothermal pavements.