What is a Biodigester?

A biodigester is a contained system in which feedstock (wastewater, food waste, manure, etc) is consumed by bacteria, breaking the feedstock down into smaller molecules and compounds, and often yielding useful products like semi-treated water and free electrons. It could be said that the earliest and simplest example of a biodigester is the humble compost heap – a sustainable agriculture favorite with roughly 12,000 years of evident use. While incomparable to today’s advanced biodigesters in terms of complexity, the composting process generally adheres to the same principles: feedstock (typically food waste like egg shells, used coffee grounds, or banana peels) is loaded into the heap or bin; latent bacteria set to work digesting and rendering the feedstock down to base chemical components, and the end result is a very useful product for humans as we are essentially transforming food waste into an agricultural aid to produce more food. Modern biodigesters usually work with fluid feedstock, rather than solid waste, and are often used to treat municipal wastewater.

What’s the Difference Between Aerobic and Anaerobic Digesters?

The word “aerobic” refers to utilizing oxygen in metabolic processes. Aerobic digesters typically require air to be pumped into the system to allow the bacteria to continue to digest around the clock, without variance in oxygen availability. Anaerobic systems do not require oxygen. In fact, introducing oxygen into anaerobic digesters can kill the anaerobic microbes, causing the system to fail. For this reason, anaerobic digesters are generally air-tight – and sometimes a pump of nitrogen gas is used to push out any other gasses present in the system before it is loaded with feedstock. Anaerobic reactors produce methane biogas, while aerobic reactors do not. Aerobic reactors are generally regarded as being more suitable for the food industry, as they are often smaller, easier to keep on-site, and usually require less upkeep or expert management. Anaerobic reactors are a good fit for agricultural businesses and wastewater treatment facilities as they are more worthwhile to operate at a large scale.

How Are Biodigesters Used and By Whom?

Both aerobic and anaerobic biodigesters break down organic waste, making them useful to a wide variety of industries. Any business that produces a large amount of organic waste could benefit from using biodigesters to not only reduce their carbon footprint, but also save cost on waste disposal solutions and even generate electricity in the case of large scale biodigesters. Businesses aren’t the only ones using biodigesters; digestion reactors have also become a staple of municipal wastewater treatment in the developed world. This technology can transform raw sewage and stormwater runoff into grey water that can be used for watering parks, golf courses, and can even be used in agriculture. Here’s a list of some real world examples of businesses that utilize biodigesters either as their primary business function, or as a supplementary function of their operations:

  • Seatech Energy produces anaerobic biodigesters using their patented four-stage “Anaerobic Sequential Up-flow Reactor” technology, which breaks down the anaerobic digestion process into four different chambers – Hydrolysis, Acidogenesis, Acetogenesis, and Methanogenesis. Their ASUR reactor technology yields more biogas than traditional anaerobic reactors, and with a higher methane content. They also manufacture seaweed cultivation solutions, in the form of an offshore pod. 
  • Vanguard Renewables offers waste management for all sorts of agricultural businesses, but their primary service is in outfitting farms and dairies with digesters to handle their manure and crop trimmings. The captured methane is frequently burnt on-site for electricity or heating. 
  • EKOGEA makes custom-tailored solutions for anaerobic digestion, providing for maximized biogas production or maximized breakdown of organics into simple minerals according to user need. Their systems are especially useful to municipal customers for wastewater treatment applications to produce useful grey water from raw sewage and stormwater runoff.
  • Yasasu focuses on developing systems for decentralized treatment of waste at the source, as well as municipal waste and recycling solutions. The biogas produced in their biodigesters is fed directly to power plants to produce electricity for lighting and biodigester processes. 

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