As for agricultural crops, biomass crops can be grown in intensive production systems (external inputs such as pesticides and artificial fertilisers) or extensive systems with few external inputs. The choice between an intensive or extensive production system has consequences for yields. A method is presented to estimate biomass yields in intensive and/or extensive production systems. This method is applied to a poplar coppice production system. Results of the method are used to evaluate several intensive and extensive production systems with respect to bioenergy yield and fossil fuel use efficiency. The energy yield (GJ/ha) of the intensive systems was highest, while the extensive systems show the better fossil fuel use efficiency (GJ output/GJ fossil energy input).