Biomass has been identified as one of the major sources of fuel and materials that replace the ones based on fossil resources. The notable characteristics of biomass reside in its renewability. It has two aspects: sustainability and carbon neutrality. Both of the aspects originate from the same root: modern society’s excessive dependency on fossil resources and on fuels and materials derived from them. Fossil resources are apparently not sustainable. The classic prognostication by the Club of Rome in 1972 appears to have been realised early in the 21st century. Looming on the horizon, at the same time, is global warming and associated climate change, most likely caused by the extra CO2 emitted to the atmosphere through the combustion of fossil fuels, thereby enhancing the greenhouse effect on the earth’s surface. Biomass combustion itself will not increase the amount of atmospheric CO2 since the constituent carbon of biomass is the one that was fixed from CO2 in the atmosphere through photosynthesis, to begin with.