Outside Visit to Digester at Stoke Bardolph

9 May 2019Visit to Anaerobic Digester at Stoke Bardolph ‘The Concrete Cow’ – John Jackson, Farms manager and Plant Manager

Rob Gray organised a superb visit to this interesting site, where we were presented by John with a very informative video and slide performance followed by a tour of “The Concrete Cow”, as John referred to it.

The video was good background information on ‘Delivering the future of Water’, which put into perspective their main regulated water business and their ‘renewable Energy’ businesses of CHP and Severn Trent Green Power Ltd. John questioned the audience on their views as to whether ‘Climate Change’ is a real issue or just a business driven opportunity.  The majority convinced it is a real issue.  Currently the Anaerobic plant at Stoke Bardolph is fed from crops: 80% maize silage and 20% Rye silage, but in the future there will be a Government Driven strategy to use food waste. The history of this site was outlined going back to 1880, when it was compulsory purchased and used for dumping sewage for Nottinghamshire.  As the regulations were not as stringent as present times, over the years there has been extensive use of the farm land for the recycling of sewages the ‘business/industrial/ community, so no crops for ‘human consumption’ can be grown on this vast farming area due to elevated metal levels within the soils..  So the crops for feeding the anaerobic digester on this Severn Trent land at Stoke Bardolph are used to feed the concrete cow  and currently supplemented by about 36 local farmers. The crop feed goes through the 3 ‘stomachs’ over about 70 days at a temperature between 38 and 42 oC and 7.8 PH, allowing the ‘bugs’ to do their work to release 54% methane gas.  Some of which is used to go through the CHP engines to feed electricity into the grid and the rest is ‘upgraded’ to ‘town’ gas at 98% methane content, supplemented by some propane to produce the required calorific values demanded by Cadent and the gas grid.  The plant is manufactured by Schmack, a German company as they are the leaders in these systems with about 8000 operating in Germany, compared to 350 in the UK.  John shared their business plans with us with 15.2 GWh being generated in the first plan,, rising to 23GWh pa in 2013 to 2016 and currently targeting 44 GWh pa.

We were then transported by tractor trailer to tour the actual plant, which operates 24/7 mainly automatically, other than the diggers that feed the crop stock into the feed tank. A number of questions were put to John regarding costs, operation efficiency, crops for human consumption v crops for energy generation, all of which he handled effectively with great knowledge and professionalism, which was much appreciated by the 22 Rotarians present.

Rob provided a Vote of thanks and a ‘bottle’ and we all trooped off for our supper at The Earl of Chesterfield well prepared after this “appetiser” with its mouth-watering aromas!       AR