There are numerous alternative energy options including bioenergy, wind, geothermal, solar and ocean; sustainably produced bioenergy is an important part of any renewable energy portfolio. Bioenergy includes heat, electricity and/or power derived from biomass. Residential examples can use combution of wood fuel or pellets in small boilers and stoves. Larger applications include burning biomass for use in district heating systems, CHP (combined heat and power), power plants, or co-firing of biomass with fossil-based resources such as coal or natural gas.
Biofuels are liquid fuels derived from biomass, and are used as an alternative to fossil fuel based liquid transportation fuels such as gasoline, diesel and aviation fuels. In 2008, biofuels provided 1.8% of the world’s transport fuels. Some organizations use the term biofuels to mean solids, liquids, and gases used in the production of bioenergy. However, due to the numerous bioenergy forms and purposes, the IEA Bioenergy implementation agreement, Task 39 uses the more specific definition of (liquid transportation) biofuels.
A biorefinery is a facility that integrates the biomass conversion processes and equipment to produce fuels, power, heat and value-added chemicals. Similar to a petroleum-based refinery, by producing multiple products, a biorefinery takes advantage of the various components in biomass and their intermediates, therefore maximizing the value derived from the biomass feedstock. A biorefinery can generate several high-value, low volume products such as chemicals or nutraceuticals as well as low-value, high-volume liquid transportation fuels such as biodiesel and bioethanol. Material bioproducts include traditional products such as lumber, pulp and paper, as well as alternative products such as bioplastics and biochemicals.
Conventional biofuels have reached technological and market maturity and are commercially available; however, advancements in feedstock generation and processing can further reduce costs and achieve greater environmental performance. Typical conventional biofuels include sugarcane ethanol, starch-based or ‘corn’ ethanol, biodiesel and Pure Plant Oil (PPO). Feedstock used in the production of conventional biofuels can consist of sugars, starches, oil bearing crops, and animal fats – in some cases these can be used as food or animal feed. Conventional biofuels are characterized either by their ability to be blended with petroleum-based fuels, combusted in existing internal combustion engines, and distributed through existing infrastructure, or by the use in existing alternative vehicle technology like FFVs (“Flexible Fuel Vehicle”) or natural gas vehicles. There are also other niche biofuels, such as biogas which have been derived by anaerobic treatment of manure and other biomass materials. However, the volumes of biogas used for transportation are relatively small today.
Advanced biofuels use pre-commercial technologies using non-food crops, agricultural and forest residues. These materials are composed of 3 primary building blocks: cellulose, hemicellulose or lignin. Advanced biofuels can either be blended with petroleum-based fuels, combusted in existing internal combustion engines, and distributed through existing infrastructure or is dedicated for the use in slightly adapted vehicles with internal combustion engines (e.g. vehicles for DME). Advanced fuels can be produced from waste materials, stalks of wheat and corn, wood and dedicated energy crops. Many advanced biofuels are under development including cellulosic ethanol, biomethanol, DMF, Bio-DME, Fischer-Tropsch diesel, mixed alcohols and wood diesel. Some of these fuels are still in the early stages of development and can include algal biofuels and hydrogen from biomass.
Synthetic Biofuels are advanced and can be synthesized from gases made by thermal gasification of biomass, e.g.
* Fischer-Tropsch fuels: Fuels for compression-ignition (=Diesel) engines or spark ignition (gasoline) engines, also named BtL fuels (“Biomass to Liquid” fuels).
* SNG, synthetic natural gas produced by thermochemical processes.
* Dimethylether (DME), a gaseous fuel for compression-ignition engines.
Electro–fuels are generally biofuels which are based on electricity, in where an electrolyser splits water into hydrogen and oxygen. The hydrogen is then converted with carbon dioxide (and/or carbon monoxide) to a synthetic biofuel or used as is. The term is not defined clearly as concepts of biorefineries may include additional electricity to increase the yield in a process to biofuels. Ammonia and other non-carbon containing compounds which can be used in engines may also be defined as electro–fuels if electricity is used.