Opportunity fuels are derived from biomass that might otherwise be disposed of as waste.
Types of opportunity fuels include:
- Biogas – which is primarily composed of methane, the by-product of the natural anaerobic decomposition of organic matter. Systems such as anaerobic digesters or gas collectors can collect and store the emitted biogas, which is then used for power or heat. Some sources of biogas are:
- Waste Water Treatment Plants (WWTP) – the effluent taken from the waste water can be processed through an anaerobic digester and used as an energy source. A 2004 report issued by the U.S. Environmental Protection Agency (EPA) Combined Heat and Power Partnership said there are 544 WWTP anaerobic digesters in use in municipal areas. Yet only 106 of these facilities used anaerobic digester to produce electrical or thermal energy. Maximizing the full potential of all 544 facilities could generate an estimated 340 megawatts of electrical power.
- Animal Feeding Operations – these have a better track record according to the EPA’s AgSTAR program, where according to a 2009 study, 113 of 125 operators have used bioenergy from the production of biogas for electricity for their on-farm usage. The annual estimated production is about 244,000 megawatts. The other 12 systems used the bioenergy to fuel boilers, return the fuel to the natural gas lines, or for odor emission control. The study selected dairy operations with more than 500 head or operations with more than 2000 swine to be the best candidates for capturing methane from the anaerobic digestion of manure.
- Landfills – the result of the decomposition of the organic waste found in landfills is a combination of carbon dioxide and methane. Usable bioenergy for the production of electricity can be stored through the use of gas recovery systems. This application can offset the use of fossil fuels, used in the production of liquid fuels, or upgrade to a higher quality pipeline gas. The EPA’s Landfill Methane Outreach Program estimated in 2009 that there are 445 landfills currently using landfill gas (LFG) to produce energy, and more than 535 additional landfills are good candidates to implement the technology for the gas-to-energy projects.
- Biosolids – which are the result of sewage sludge from WWTPs. Their use is for boilers as a heating source by drying and burning the waste in place of fossil fuels such as coal. Another use of biosolids is to convert them into biogas, then into bioenergy. The greatest current challenge in implementing this technology is the high water content of biosolids, posing a problem for reliable combustion and thus requiring the drying process noted above.