Anaerobic Digestion and Biodigesters

May 19, 2013

3 minutes, 18 seconds read

Anaerobic Digestion and Biodigesters

Probably not.
That’s the conclusion of this independent research which compared the environmental impact and costs for deploying an anaerobic digester versus LFCs for a small community.

  • An anaerobic digester (AD) is usually a large commercial facility that converts organic waste to heat and electricity.
  • You can send your waste food to such a facility usually at no cost.
  • Alternatively, you can install an LFC in your facility which will digest your waste food and send the output down the drain.
  • Independent research was done to evaluate the costs and environmental impact of deploying LFCs versus constructing an AD.
  • The conclusion is that the LFC has lower costs, faster payback, and less environmental impact than AD.

What is Anaerobic Digestion?

AD is the process of breaking down organic material in the absence of oxygen. The output is methane (CH4) plus other gases.

Commercial anaerobic digesters (AD) take organic material from a variety of sources to produce the methane. That methane is then burned to produce heat and electricity. Where the organic material is waste food that would otherwise go to a landfill, one can initially presume that the generation of energy (heat and electricity) is free.

However, the cost of building a commercial AD facility and the cost and environmental impact of transporting the organic material to that facility make the energy not as free as initially presumed.


Should You Be Sending Your Waste Food to an AD?

If you are currently sending your waste food to a landfill, and for the same environmental impact (that is, it is transported a similar distance) you can send it to an AD, then your carbon footprint will be reduced.

Methane is a greenhouse gas that is 72 times worse for the atmosphere than carbon dioxide (CO2). When you send waste food to a landfill, it creates methane and that has a huge impact on your carbon footprint. When that methane is instead created in an AD, the energy is captured with less impact on the environment.

Is there an alternative?

The LFC biodigester from Power Knot is a machine that sits in your kitchen and digests the waste food aerobically. Aerobic digestion is the process of breaking down the organic material in the presence of oxygen. The output is water and carbon dioxide (CO2), so the process has no smells.

With the LFC biodigester, your waste food does not sit on your loading dock where it can smell, and it does not travel long distances. You put the waste food into the LFC biodigester as it is generated.

As well as reducing your carbon footprint and improving your operation, the LFC biodigester can save you significant money on the costs of the disposal of your waste. An LFC biodigester can have a payback period as short as six months.

Report from Brunel University, UK

Independent research was undertaken to determine the economic and environmental impact of treating waste food with AD or LFC biodigesters for small communities. The research considered:

  • the environmental impact using life cycle analysis (LCA) of LFC biodigesters versus an AD that produces biogas and digestate
  • the financial analysis of LFC biodigesters versus an AD

The report finds the payback for an LFC biodigester to be 23 to 39 months, but it is 12.9 years for the AD.
The report concludes that the LFC biodigester results in 73% fewer emissions than the AD.


Any organization that produces large quantities of waste food should not be sending it to a landfill because of the impact on the environment.

If your community has an AD that is close to your facility, sending your waste food to that facility (if collected at no charge to you) is probably a good thing. However, if your waste food has to travel long distances to an AD facility, if it is collected infrequently, or if you are charged for the service, deploying an LFC biodigester in your facility is likely to be a better solution.