Geothermal heating impacts on BTEX biodegradation in various soils under cyclic fluctuating temperatures

Urban contamination of soil and groundwater by BTEX (benzene, toluene, ethylbenzene, xylene) compounds remains a widespread environmental concern that requires effective remediation strategies. Among available technologies, biological methods have gained significant attention for being both cost‑effective and environmentally sustainable. However, in‑situ bioremediation of BTEX is often limited by low subsurface temperatures (10–15 °C), which suppress microbial activity. Raising subsurface temperatures can stimulate microbial growth and accelerate contaminant degradation, but conventional heating methods can be costly. Geothermal heating offers a sustainable alternative by using shallow subsurface systems to extract heat in winter and inject excess heat in summer through ground‑source heat pumps. This excess thermal energy can serve as a heat source to enhance bioremediation processes.

This study investigates the effects of cyclic temperature fluctuations (5–40 °C) on BTEX biodegradation in contaminated soils at a small scale. Experiments using native microbial consortia across three soil types showed that cyclic heating significantly enhanced microbial metabolism and BTEX degradation compared with constant subsurface temperatures. Among the tested soils, silty loam exhibited the highest biodegradation under cyclic heating, outperforming sandy soil.

Overall, this research highlights the potential for leveraging geothermal heating systems to support more sustainable and efficient in‑situ remediation of BTEX‑contaminated subsurface environments.