The attempt to transition from a fossil-based to a bio-based economy is putting increased pressure on the limited amount of available biomass. Concentrating on biogenic waste matter that is currently not put to use, such as green waste, may be one way of tapping potential additional raw materials. Hydrothermal carbonization (HTC) processes are particularly well suited for converting this green waste into valuable energy sources. The results show that HTC coal can currently only compete economically with fossil energy sources in an ideal context. However, there is potential for cost reduction. Additionally, there is a clear potential for reducing greenhouse gas (GHG) emissions compared with fossil fuels and the GHG mitigation costs are within the standard range of other biogenic means of supplying heat.