Wednesday, October 01, 2014

Rise in Biogas Plant Blockages Causes Financial Losses at Food Waste AD Plants

As governments and biogas plant operators have woken up to the amount of food waste that modern societies produce, there has been a trend for existing biogas plant operators to start accepting food waste as an additional feed source.

But, that has been causing big trouble for many biogas plant operators. It is causing many plant pumping failures, and big losses to these businesses due to time-consuming plant downtime while clogged pipework is dismantled and rebuilt.

There is a solution to this so read-on to find out what it is!

The Food Waste Problem

By "food waste", we mean all kinds of waste from food processing plants to out-of-date supermarket food packets, and this may also include restaurant and office canteen waste. These are wastes which until 20 years ago, in many countries would have been fed to pigs, or rendered down into various types of cattle feed.

Watch our video below, in which we explain the problem! (Please try not to get too emotional while watching!!)

(If this video does not display well on you device, it can also be wtached by clicking here: )

It was concern about the risks of infection spreading, such as "Foot and Mouth" and "BSE", that these types of wastes were deemed to cause if consumed as part of the food chain, which has lead to them becoming a "waste" and age-old practices for re-use of unwanted food, being banned. By preventing their consumption, the waste had to go somewhere, and has been resulting in huge tonnages which have been being landfilled to the detriment of landfills.

On the face of it, food waste should not be landfilled, and to do so is a huge waste of resources, because all the energy locked-up up in food makes it absolutely the best type of feedstock to use because it is the highest in calorific value. But, when an anaerobic digestion plant changes its feed material to food waste it also starts accepting a highly variable type of waste, and one which can vary greatly in viscosity and will almost always include a substantial amount of foreign matter, especially pieces of plastic and plastic film.

Existing Biogas Plant Pumps Are Often Not Suitable

Anaerobic Digestion plants built originally for manure and agricultural wastes/ energy crop digestion, and by some accounts also those designed by "experts" to accept food waste, are usually equipped with high solids passing centrifugal subtstrate pumping systems to deliver the feed into the digesters, and to remove it after digestion.

Such, "standard" pumps are being found inadequate and furthermore, as pipework starts to clog up, the flow rate from such pumps tends to drop, allowing yet more material to build-up within the pipework and eventually pumping stops when the pipe flow resistance overloads the pump system and all pumping ceases, until pipes and pumps are manually cleaned out.

To compound the problem, many AD Plants were never designed for the pipes to be dismantled and in such cases pipe replacement may be necessary.

The Solution

Pump experts recommend positive displacement pumps as the solution to this problem in combination with chopper or macerator pumps. An example is the Verderflex peristaltic pump series which when correctly installed is designed to reliably transport the chopped slurry from holding tanks and through the system to the digesters tank(s). This usually will be via a heat exchanger to raise the substrate’s temperature to a level suitable for efficient digestion, before it enters the AD plant digester tanks. The same type of pump may also be recommended for the outlet from the digester.

The Silver Lining Once Food Waste Problems are Solved!

With the right pump systems installed, biogas plants are capable of producing substantially more biogas from the higher calorific value food waste, so once upgraded pumping systems are working reliably, the pant operator can benefit from a significantly improved income from increased biogas energy sales.

For further information on peristaltic pumps and anaerobic digestion plant susbtrate/ digestate pumping, we sugest that you might do well to visit the Verder website at:

A case study pdf is also available on the Verder website, here:

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