Biopiles

Biopiles are an ex situ bioremediation technology used to treat contaminated soils by piling the material into mounds and promoting microbial degradation of organic contaminants under aerobic conditions. The system relies on aeration, moisture control, nutrient addition, and sometimes inoculation to stimulate hydrocarbon-degrading microorganisms.

Typical configurations include a mound of excavated soil, an aeration network (perforated pipes for forced air or provisions for passive aeration), moisture and temperature monitoring, nutrient amendments (nitrogen, phosphorus), and sometimes a liner and leachate collection to protect groundwater. Materials such as compost, wood chips, or other organic amendments may be mixed with the soil to improve microbial activity and structure.

Operation involves excavating and screening soil, placing it in piles, applying moisture to maintain optimum water content, and delivering air to sustain aerobic conditions. Temperature and moisture are monitored to gauge biodegradation progress, and the process is adjusted by changing aeration rate, moisture, or nutrient inputs. Treatment times vary from several months to a few years depending on contaminant type, climate, and pile design.

Biopile degradation targets petroleum hydrocarbons, solvents, pesticides, and other biodegradable organics. Advantages include relatively low cost, simplicity, scalability, and suitability for treating large volumes of soil. Limitations include climate dependence, potential emissions of odors or volatile organic compounds, leachate management requirements, and reduced effectiveness for highly recalcitrant contaminants.

Applications are common at former gas stations, refineries, military sites, and other industrial locations where soils are excavated for treatment.