Domestic Anaerobic Digester

The Domestic Anaerobic Digester

We at UFL have been busy investigating the feasibility of a domestic anaerobic digester – now fondly referred to as the DAD.

Having been inspired by the micro anaerobic digester designed by James Murcott (Methanogen) below:-

Other micro AD plants and a validation that a domestic anaerobic digester is a viable concept can be found here.

We decided we would start from scratch and see what we could come up with. Our objective was to design a micro Anaerobic Digester that could replace a domestic sewage system or sceptic tank.

The design challenges that we identified are described below. We wanted a system that:-

  • is cheap to build so that cost would not be a deterrent
  • can be built from commonly available (off-the shelf) components
  • is energy efficient so that using the system gives a net energy contribution
  • is effective enough to produce safe digestate with negligible raw sewage content; the internal structure must ensure maximum retention time
  • will avoid the possibility of crust layers forming, so we had to design an energy-efficient system for mixing the contents
  • is capable of producing biogas with low hydrogen sulphide content so that it can be burned without damaging the device using the gas (cooker hob, boiler or engine) – we had to design a low cost hydrogen sulphide removal system
  • has a control system that is simple, reliable, understandable, low-cost and completely automated

We have successfully designed a low-cost Domestic Anaerobic Digester (the DAD) that meets all the above design criteria. It is based on an IBC (1 cubic meter liquid container).

Domestic Anaerobic Digester

IBC – the basis of our Domestic Anaerobic Digester

The DAD runs on 12vdc which can be supplied by a few solar PV panels and a car battery. A low-power heating system has been designed and a low-power mixer has also been implemented.

An automated control system has been developed which uses nothing more than thermostatic switches and automotive relays.

An optional low-cost hydrogen sulphide removal system has also been designed.

UFL are not in the business of manufacturing Anaerobic Digesters but we do want to promote their use and help society free itself from the utility companies. We are therefore offering our design to any interested parties who may be able to benefit from the ideas we’ve accumulated. We have spent a lot of time on this work so we are therefore asking a small fee of £20GBP for our design.
The purchase comes with a few conditions:- 1) that the design is not published nor transferred to any other parties; 2) the use of any of our design ideas is credited to UFL; and 3) changes/improvements to the design must be discussed with UFL (this is for intellectual satisfaction, and not that we want to compete with anyone else’s AD design – that’s not our business).

Having evaluated all the design choices and options, we have a good understanding of the problem space. We are therefore happy to discuss any aspect of our design with anyone wishing to use it.

The design has not yet been fully documented, but if you are interested in acquiring a copy, please register an interest by emailing The more people register an interest, the sooner we’ll finish the document.

Payment will need to be provided by PayPal. Once we have received a confirmation of payment from PayPal, the design document will be emailed immediately.

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