Your choices:
1 Biomass (digestible sludge); 2 Comfortable indoor climate; 3 Fuel: Gaseous
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| 1 Biomass (digestible sludge) | District cooling | 2 Comfortable indoor climate |
| Biomass (fermentable sludge) | District heating | Electricity |
| Biomass (solid) | Electricity | Process cooling (< 0 °C) |
| Geothermal | 3 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) |
When biogas is to be used more-or-less directly for comfort heating, one must consider the fact that the raw biogas is combustible but it is not a high-quality fuel gas. The raw biogas may be safely used in an IC-engine from which the cooling water is then used to provide comfort heating. The reason for this is that the ignition of the gas is then forced by the engine. This will only be viable for single-household or farm-scale applications.
The raw biogas is not advisable to be used in commercial boilers without a continuous pilot flame and such solutions will in most cases be too expensive to be viable for the individual household. Also the transport of raw biogas will demand separate pipelines.
Upgraded biogas, bio-methane, will have combustion characteristics similar to those of fossil gas and can be used in commercial fossil-gas boilers and combustion systems. Thus, to supply the customer with comfort heat from digestible biomass, the optimal solution is to upgrade the gas to fossil gas quality, inject it to the gas grid and then let the customer extract it at their site for direct combustion in commercial fossil gas boilers.