Your choices:
1 Fuel: gaseous; 2 Biomass (digestible sludge); 3 Process heat
| What is your resource? | What do you want to deliver? | What is the service the customer wants? |
| 2 Biomass (digestible sludge) | District cooling | Comfortable indoor climate |
| Biomass (fermentable sludge) | District heating | Electricity |
| Biomass (solid) | Electricity | Process cooling (< 0 °C) |
| Geothermal | 1 Fuel: Gaseous | 3 Process heat/steam (50 - 150 °C) |
| Sunshine | Fuel: Liquid | 3 Process heat (150 - 1000 °C) |
| Water | Fuel: Solid | 3 Process heat (> 1000 °C) |
| Wind | Local cooling (ind. house) | Transport |
| Residual oils/fats etc | Local heating (ind. house) |
Especially at such industries where the process itself gives rise to digestible waste – and this is the situation with many different types of processes – may the internal use of a digester transform a waste problem to an energy- and cost-saving measure.
The digester works best of it can be kept at a reasonably constant load. Hence also the gas production will be relatively constant and in case of an intermittent industrial process this may cause problems with the gas storage. In such cases, it may be worthwhile to consider gas upgrading so as to make the commercial sale of surplus gas viable. The gas may be sold locally as a car fuel or it can be injected into the European gas grid.
If the process demand for heat is relatively constant, though, the raw biogas may be directly burnt in a hot-water or steam boiler or in a furnace to provide process heat.