Diet feeder experience sees bespoke AD mixer installed

Positive experiences with a Shelbourne Reynolds Powermix diet feeder for the business’s dairy herd meant that, when it was seeking a replacement mixer to feed its anaerobic digester, a Dorset estate chose to commission the manufacturer to design a high-capacity unit to fulfil its requirements.

At the Velcourt-managed Melbury Estate, Powermix diet feeders have been used to create a total mixed ration for the 700-strong milking herd for some years now, the current machine being a Pro 22 cu m unit. But the most recent Powermix addition to the farm’s equipment fleet contains similar design principles, yet is used for a very different purpose.

While a 25 cu m machine is the largest available in the standard Powermix range, good experiences with the estate’s own feeder led farm manage Allaster Dallas to approach Shelbourne Reynolds when he sought out a replacement for the mixer used to supply the farm’s anaerobic digester.

The farm installed its AD plant back in 2010, and it was equipped with a static mixer to supply the digester dome with the mixed material required to produce methane gas. However, by late 2016, this had already come to the end of its serviceable life due to premature wear and difficulties with service availability.

“The tub had rotted through, and we looked at a number of different replacement options, but many were simply too expensive or attracted little interest when we approached the suppliers about the prospect of installing a static machine,” says Allaster.

“Because we’d had good experiences with the Powermix models used for feeding the cows, I decided to approach Shelbourne to see if they could provide what we needed for the AD plant. Although the largest trailed model they offer is 25 cu m, and we were looking for something around double that size, we knew they had installed static mixers on other farms for AD use, and the company agreed to send a design engineer out to us to understand what it was we required. That was a big advantage in dealing with a UK-based firm, as our last machine had come from an overseas company. This time we had the opportunity to have designed exactly what we required, from the tub size to the gearbox strength.”

Installed in April 2017, the new 46 cu m Powermix Plus Bio 46 mixer blends wholecrop rye and grass silages, plus some slurry from the dairy unit to aid breakdown and methane formation once the mix has been transferred to the digester itself. The resulting methane powers a 750kW gas engine, feeding electricity into the local grid.


“Having a company prepared to work with us in this way meant we could ask them to build exactly what we wanted – it was the right way round to do things, rather than having to make an existing machine fit.


“Since installation it’s worked a treat, proving easy to load and producing an excellent mix that results in efficient gas production. And it looks to be robust enough to have a good life ahead of it.”