Your choices:
1 Transport; 2 Residual oils/fats etc; Fuel: liquid
| 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 | 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) | 1 Transport |
| 2 Residual oils/fats etc | Local heating (ind. house) |
Biodiesel is produced by chemically reacting a vegetable oil or animal fat with an alcohol such as methanol or ethanol. Since methanol is a bulk chemical, readily available worldwide, methanol is today the most common. The product then becomes a fatty acid methyl ester (FAME). Using ethanol instead the product will become a fatty acid ethyl ester, FAEE, which will have similar properties. It is these esters that have come to be known as biodiesel. The reaction requires a catalyst, usually a strong base, such as sodium or potassium hydroxide.
Though most of the biodiesel produced today originates from palm oil or from dedicated soy plantations, the ecological and social effects of which is debatable, there will also be side products from sunflower oil production and similar processes that can be used as a raw material. Animal fats like tallow and other residues from slaughterhouses are also possible feedstocks. With such feeds, from waste streams rather than from dedicated crops, biodiesel is generally considered to be renewable. Since the carbon in the oil or fat originated mostly from carbon dioxide in the air, biodiesel is also, like any other biomass-base fuel, considered to contribute much less to global warming than fossil fuels. Diesel engines operated on biodiesel tend to have lower emissions of carbon monoxide, unburned hydrocarbons, particulate matter and air toxics than when operated on petroleum-based diesel fuel.
Special processes are required if the oil or fat contains significant amounts of free fatty acids (FFA). Used cooking oils typically contain 2-7% FFA, and animal fats contain from 5% to 30% FFA. Some very low quality feedstocks, such as trap grease, can approach 100% FFA.
If only the feedstock is properly clean, the rate of conversion is up to 95% of the fatty input. The by-product will be a slightly contaminated glycerol which will have to find use.
The biomass-derived ethyl or methyl esters can be blended with conventional diesel fuel or used as a neat fuel (100% biodiesel).
Neat (100%) biodiesel is incompatible with certain rubbers and plastics, but not with metals.
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.