Content – Other fuels
Definition of biofuel.
The most common definition of “biofuel” is; a fuel that is produced or derived from biological matter, from recently living plants or organisms different from the geological processes of forming fossil fuels from prehistoric biological matter.
Biofuels are produced in solid, liquid or gaseous form.
There are different categories of biofuel for use in gasoline, diesel and natural gas engines, some types can easily be used without any problems, others will require more testing before they can be used and possibly would require modifications to be made to the engines before safely used.
The main categories of biofuel are:
- Various types of biodiesel
- Ethanol which is the main substitute for gasoline
- Biogas, mainly methane but also some butane and propane produced from biomass as substitutes for fossil natural gas.
Bio-ethanol is mainly produced from sugarcanes and residues from the pulp industry, while most first generation biodiesel is produced from food crops such as soybeans, canola and palm oil plants.
Second generation biodiesel often called HVO, advanced, green, synthetic or renewable diesel is produced from waste containing vegetable oils or animal fats or residue from forestry. This is a biodiesel with similar composition as fossil diesel but without any smell, taste or harmful contaminations.
HVO is an abbrevation for hydrogenated vegetable oil.
Biogas is generated through biological digestion of various organic materials from animal farming, sewage and landfills.
Since the car or engine manufacturers do not yet fully approve liquid biofuels as adequate replacement for fossil fuel, liquid biofuel in most cases is only used as an additive that is mixed into the fossil fuel.
The exception being second-generation biodiesel such as HVO that is approved by most truck manufacturers.
However, since the availability is scarce and the price is high the use so far is very limited.
5 – 10% biodiesel or bioethanol may normally be blended into petroleum based diesel or gasoline without harming the engines.
There are some exceptions to this; in particular some older fuel injection engines are sensitive to biofuel.
Emissions from biofuel
Combustion of biofuels emits CO2 and depending on the fuel and the use, may also emit other harmful substances such as carbon particulates, carbon monoxide and NOx (various nitrous gases).
However biofuels are considered less harmful to the environment than the traditional fossil fuels since the emission of greenhouse gases from biofuels is not seen as increasing the net amount of greenhouse gases in the atmosphere.
The reason for this is that the biofuels are produced from renewable sources that take part in the “short term” carbon cycle.
Also the emissions of carbon particulates, carbon monoxide, NOx and sulphur compounds in some cases are reduced or can be reduced compared to burning fossil fuels.
- The amount of greenhouse gases released from the combustion of biofuel would have been released through natural decomposition of the biological material if it had not been converted and used as biofuel.
- The trees, algae and other green plants that forms the biomass, the basis for the biofuel have already absorbed a similar amount of CO2 through the photosynthesis as what is emitted through the combustion process.
- If trees, algae and other green plants are replanted they will absorb a similar amount of CO2 through the photosynthesis as what is emitted through the combustion process.
As already pointed out, there are various forms of biofuel, some may be used in existing infrastructure and equipment others will require modifications to engines and other infrastructure. 5% – 10% of biodiesel or bioethanol may be blended into petroleum based diesel or gasoline without harming the engine. Biogas may be used in engines already prepared for fossil gas as fuel.
The most common forms of biofuels are: Biomass, biogas, ethanol, methanol, and biodiesel.