Alternative Backfill Materials for Sustainable District Heating Systems

District heating pipes are usually installed in open trenches that are refilled with backfill material. Special requirements were set for this material in standards and codes of practice and in the most cases natural sands were used in the past. Today natural sands are a scarce resource and must be protected. Furthermore, regulations of the circular economy challenge existing construction methods. In sustainable energy systems natural sands should only be used in exceptional cases. Against this background the general planning process and the significant calculation methods for district heating pipes were analysed and other material options and the hindrances for the use of alternative backfill were identified. Necessary modifications in the planning and calculation process were elaborated. It was shown, that the transition to a more circular economy approach in district heating systems is realistic, if conventional planning methods will be adjusted.