Biopiles are a common treatment for the ex-situ remediation of contaminated soil. Much research has been carried out on understanding and modelling microbial degradation, but hitherto no study has attempted to model the effect on a biopile of its ambient surroundings. A hydraulics-based approach to simulating a biopile in the context of its ambient surroundings is presented, taking into account processes within the pile, external conditions of wind and temperature, the location of aeration pipes and the venting pressure, and considering the distribution of treatment over various regions within the pile. A system of add-ons to a commercial CFD code has been developed, and various example simulations have been carried out to examine the potential of the hydraulics approach for practical application. Results show that the model produces reasonable results. with biodegradation related to the temperature within the pile and the temperature in turn related to wind speed and aeration details. A number of counter-intuitive results are described, indicating that simulation of the type carried out will produce valuable insight into the practical design of biopiling systems. The simulation system also allows the total environmental footprint of biopiling to be considered, examining not just degradation of contaminant but also its removal via volatilization and the energy used in heating air for venting. (C) 2009 Elsevier B.V. All rights reserved.