Your choices:
1 Process heat/steam (50 - 150 °C); 2 Fuel: gaseous; 3 Biomass (solid)
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| Biomass (digestible sludge) | District cooling | Comfortable indoor climate |
| Biomass (fermentable sludge) | District heating | Electricity |
| 3 Biomass (solid) | Electricity | Process cooling (< 0 °C) |
| Geothermal | 2 Fuel: Gaseous | 1 Process heat/steam (50 - 150 °C) |
| Sunshine | Fuel: Liquid | Process heat (150 - 1000 °C) |
| Water | Fuel: Solid | Process heat (> 1000 °C) |
| Wind | Local cooling (ind. house) | Transport |
| Residual oils/fats etc | Local heating (ind. house) |
Thermal gasification of solid biomass is an expensive and complicated process yielding a gas consisting of carbon monoxide, hydrogen and methane. For air-blown gasifiers the gas would typically contain 10-15% carbon monoxide and similar amounts of hydrogen and the methane content would be about 5% on a dry gas basis.
Using pure oxygen instead of air to run the process so that nitrogen no longer dilutes the gas will raise the gas quality significantly but the price will be the cost for oxygen. The losses in the process will amount to, depending on the system layout, anything from 10 to more than 30%.
There will also be a number of heavy hydrocarbons ("tar") together with hydrogen sulphide, hydrochloric acid and a number of nitrogen compounds. Finally, part of the inorganic ash will be evaporated and found in gas phase in the hot gas. The gasifier gas will leave the gasifier at the process temperature and as long as the gas is maintained at that temperature, gaseous contaminants and ashes remain gaseous, but the moment the temperature drops, tars as well as ashes will start condensing.
Performing this process only to obtain low-temperature (i.e. low-exergy) heat will not be feasible but in case there is a side process or a valuable side product the situation might become different.