“Define Anaerobic Digestion”, said a student to me recently.
No doubt because I discovered anaerobic digestion back in the 1990s via my background of environmental biochemistry originally, I quoted the original Wikipedia definition. That one is all about breaking down organic material without oxygen present (ref: 1) and is all about the chemistry involved.
I thought There Was Only 1 Definition of Anaerobic Digestion! We Found 10!
To my amazement, she said she disagreed. She said, that I may have a point, but surely a definition should state the most important point of a thing. To her, on that basis, anaerobic digestion would be defined as the process that creates methane and carbon dioxide (ref: 2), she said. “Isn’t that what most people are interested in?”
Not wanting to be out-definitioned, I went online and found another website that used my definition (ref: 3). “Aha!”, I said, “Most people that know the definition of anaerobic digestion would agree with me. Look at [(ref: 3)], so I must be right!”
At that point, another student who had been listening, chipped in. He said, “No definition of anaerobic digestion could be right unless it centred on the ability of the AD process to “break down waste organic materials”. Wasn’t that ability, in the long term going be able to save the planet, by creating our future energy sustainably? We all agreed that its use in “decarbonising the planet” was probably more likely, what it would still be being used for in 1,000 years time. So, maybe that should be in any definition of it.
Sure enough. A few minutes of clicking on the internet provided us with a definition of AD based on its ability to “break down waste organic materials” (ref: 4).
It was becoming clear by this time that, the definition of anaerobic digestion was going to take many forms, and that the anaerobic digestion process meant different things to people according to their interests in the process. We continued for a few more minutes, and we had 10 different definitions for anaerobic digestion (see them all in or list below). The most commonly quoted were variations on the (old-fashioned?) chemistry based definition.
Which definition of anaerobic digestion did we like best though? Our favourite, mostly for the large number of ideas encapsulated in very few words, was: “Controlled anaerobic, or oxygen-free, digestion of animal manure is a way to treat manure to prevent foul odor production while generating a usable energy product.” (ref: 8).
Take a look at our Top 10 AD Process Definitions below:
1. Anaerobic digestion is a collection of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for … via Anaerobic digestion – Wikipedia, the free encyclopedia
2. Anaerobic Digestion. Anaerobic digestion is a biological process that produces a gas principally composed of methane (CH4) and carbon dioxide (CO 2) otherwise known … via Anaerobic Digestion – Waste to Energy & Biomass in California
3. What is Anaerobic Digestion? Anaerobic digestion is a series of biological processes in which microorganisms break down biodegradable material in the absence of oxygen. via American Biogas Council
4. Anaerobic digestion is a common technology in today’s agriculture, municipal waste, and brewing industries. It uses bacteria to break down waste organic materials … via Anaerobic Digestion Basics | Department of Energy
5. Anaerobic digestion (AD) is the process whereby bacteria break down organic material in the absence of air, yielding a biogas containing methane. via Anaerobic digestion – BIOMASS Energy Centre
6. Biogas production using anaerobic (oxygen free) digestion is a biological treatment process to reduce odor, produce energy and improve the storage and handling … via Biogas and Anaerobic Digestion — Penn State Extension
7. Anaerobic Digestion. Anaerobic digestion is a biological process in which bacteria digest biomass in an oxygen-free environment and produce a gas principally composed … via Anaerobic Digestion – Washington State
8. Controlled anaerobic, or oxygen-free, digestion of animal manure is a way to treat manure to prevent foul odor production while generating a usable energy product. via Anaerobic Digestion: Biogas Production and Odor Reduction …
9. Anaerobic digestion is a process in which microorganisms break down biodegradable material in the absence of oxygen. The products of this are biogas (a mixture of … via Anaerobic digestion – Appropedia: The sustainability wiki
10. Anaerobic digestion (AD) involves the break down of biodegradable material in the absence of oxygen by micro-organisms called methanogens. It is already widely used … via Anaerobic digestion | WRAP UK
Which definition do you think is the best? Please do take a moment to add a comment and give us your ideas!