Your choices:
1 Transport; 2 Fuel: liquid; 3 Residual oils/fats etc
| 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 | Process heat (> 1000 °C) |
| Wind | Local cooling (ind. house) | 1 Transport |
| 3 Residual oils/fats etc | Local heating (ind. house) |
Fatty acid methyl esters are 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 advantages with the upgrading process are mainly three:
- First it serves to homogenise the properties of the fuel so that the very inhomogeneous feedstock becomes a standardised fuel within narrow quality limits.
- Second it serves to make the fuel storable. The raw oil qualities will slowly oxidise and solidify unless contaminants and unsaturated fatty acids are removed or neutralised and this is achieved by the upgrading.
- Third the fuel produced attains sufficient quality for the immediate use in the transport sector. Not only is this one of the few processes that can yield a diesel oil substitute from waste fractions but the transport sector is also one where the willingness to pay is the highest, so this is a sector where the upgrading process may be paid for by the added value.
The feedstock needs to be filtered and free from solid impurities and water prior to the process, so the collection and handling needs be such as to provide a reasonably clean feed. Basically, the process is to add OH-groups to the fatty acid and thus transform it into an ester. This is achieved by the addition of an alcohol, typically ethanol or methanol in the presence of a catalyst, typically at low process temperatures. As compared to the raw vegetable oils, esters have favourable properties with respect to storage (they are more stable).