Your choices:
1 Process heat (> 1000 °C); 2 Fuel: liquid; Residual oils/fats
| 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 |
| Biomass (solid) | Electricity | Process cooling (< 0 °C) |
| Geothermal | Fuel: Gaseous | Process heat/steam (50 - 150 °C) |
| Sunshine | 2 Fuel: Liquid | Process heat (150 - 1000 °C) |
| Water | Fuel: Solid | 1 Process heat (> 1000 °C) |
| Wind | Local cooling (ind. house) | Transport |
| Residual oils/fats etc | Local heating (ind. house) |
There are two liquid fuels produced from renewable energy sources on the market, namely ethanol and FAME or biodiesel, both primarily produced for and sold to the transport sector. In this material, methanol (commonly produced from fossil gas) and bio-oils from liquefaction processes are excluded.
For fundamental reasons (only materials where fermentable sugars are readily available for the enzymes and the yeast are naturally suitable for alcohol fermentation), todays' production of ethanol is to a significant extent based on dedicated energy crops. This raises the ethical question of large-scale use of agricultural land for energy purposes.
Biodiesel is produced using a low-temperature chemical conversion based on fatty acids. The raw material can be excess vegetable oil from agricultural production, rapeseed oil, soybean oil and alike but also residual cooking oils from – for example – restaurants or from food processing. The current production amounts to some 20 million m3 of FAME per annum, the main part of which is produced from palm oil, soy, rapeseed oil and waste oil/fat, where the latter resources is so far only minor. There may be reason to consider the palm oil extraction and its ecological and social effects prior to taking a decision to replace the use of fossil fuel oil with a large-scale use of FAME.
Though ethanol is not very corrosive to metals, gaskets, and seals it is still necessary to make sure that any container, transfer lines, and fittings are made from materials that are ethanol-compatible. Biodiesel is incompatible with certain rubbers and plastics, but not with metals. Nitrile rubber and polyurethane-based compounds deteriorate unacceptably by contact with biodiesel while other elastomers such as styrene-butadiene rubber (SBR), butadiene, isoprene, hypalon, silicon, and polysulphide are not resistant. Acceptable replacement materials include fluorine-rubber (Viton A) and polypropylene and polyethylene-based plastics.
Therefore, the selection of materials to avoid degradation of seals, fittings, and hoses are important for liquid biofuel applications. It is also necessary to take special precautions to ensure that liquid biofuel is transported or stored in containers and transfer lines that have been specifically selected for that purpose.
Though ethanol could technically be used to replace fossil oil in high-temperature processes there are a number of barriers including the attainable volumes if production is limited to ethically acceptable feedstock, problems with the materials in fuel feeding systems and the availability of suitable burners, so ethanol is not considered a suitable substitute for fossil oil.
Biodiesel, obviously only from socially and environmentally approved sources, can readily replace fossil oil for basically any high-temperature process.