The cultivation of energy crops on heavy metals contaminated (HMC) areas offer opportunities, which combine site remediation with energy recovery. Numerous tests have been conducted using phytoremediation in HMC soils with energy crop species. Sida hermaphrodita L. Rusby, has shown potential as an energy crop useful in the phytoextraction of HMs. The aim of the study was to investigate the efficiency of using S. hermaphrodita in energy crop production in HMs contaminated sites. The study investigated the impact of different fertiliser treatments on the composition of elements in cultivated biomass on HMC arable land and sewage sludge dewatering sites to determine its suitability for energy production in gasification processing. It was found that S. hermaphrodita is a species accumulating HMs mainly due to their bioavailability in soil (Cd r = 0.877, Zn r = 0.876). Calculated Cd and Zn bioaccumulation factors for plants cultivated on HMC arable land were 12-fold and 18-fold higher respectively, when compared to a sewage sludge dewatering site. Lower heating value of biomass was higher by about 7% for biomass cultivated on HMC arable land. Despite the presence of HMs in ash after the gasification process, some of it could be used as fertilizer, especially on heavy metal contaminated sites.