Your choices:
1 Fuel: gaseous; 2 Biomass (digestible sludge); 3 Comfortable indoor climate
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| 2 Biomass (digestible sludge) | District cooling | 3 Comfortable indoor climate |
| Biomass (fermentable sludge) | District heating | Electricity |
| Biomass (solid) | Electricity | Process cooling (< 0 °C) |
| Geothermal | 1 Fuel: Gaseous | 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) |
A large number of anaerobic digesters of single-farm size have been installed during the last decade(-s), many of them in Germany. The majority of installations make use of the combination of a digester with an IC-engine to provide the farm itself with parts of its need of electricity and part of its need for comfort heating.
In case the digester is large-scale and it is not desired so upgrade the gas to natural gas or transport fuel quality, the gas is best used in the central boiler in the district heating system.
If the main aim with the digester is to produce gaseous fuel, then the gas should be upgraded and either be sold locally as a transportation fuel or injected into the gas grid. This will demand that the digester is not too small, i.e. that the plant is either municipal or industrial size.
Once the gas is injected into the common European gas grid, it can be extracted and used for any purpose.