Types of Methane Digesters

Broadly speaking there are basically there different types of digesters- batch-feed digesters, continuous-feed, and hybrids. Continuous-feed digesters can take a constant flow of waste every day, while batch-feed digesters take all of the waste at once. During the time of a batch-feed digester, no more waste can get accepted (House 140-142). At Sarah Lawrence, because there is a large amount of food waste being generated every day, it is pretty obvious that a continuous-feed digester will be the best type. There are however many different types of methane digesters. Some, such as the Upflow Anaerobic Sludge Blanket reactor (UASB), Expanded Granular Sludge Bed (EGSB) reactor, the Anaerobic Continuous Stirred Tank Reactor (CSTR), the Anaerobic Baffled Reactor (ABR), Plug-Flow Digesters, Covered Lagoons, Complete Mix, Fixed Film, a Temperature Phased Anaerobic Digester (TPAD), among others I have yet to learn about have been installed with success in numerous locations. Other types are in more of the planning stage and may either produce hydrogen, a gas with more energy than hydrocarbons and that burns much cleaner, or Methane; however, there are hurdles that still need to be overcome in order for these to meet commercial success.
     Most of the reactors I have read about so far are meant to digest waste water or waste in a very dilute form. Plug-flow digesters, so far, seem to be the only type that can function without the need for a large amount of water-handling cow manure at a consistency about as thick as ground-up food waste.

Works Cited

House, David The Complete Biogas Handbook. Alternative House Information, 2010.

Fang, Herbert H.P. Environmental Anaerobic Technology: Applications and New Developments. London: Imperial College Press, 2010. 113-136.