A Year in the Life of BV Dairy’s AD Plant

AD Update• AD plant signed over March 2011

• All waste produced at the manufacturing plant is treated by the AD plant

• Award winning

kWh Electricity Generation176

27%

Challenges• Running at 45% capacity

• PAS 110 certification, and Biofertiliser properties

• Solids Separation Unit

What went wrong at the AD Plant??

After a night out on the town

We woke up to this

So, what was the cause?

What should happen:– Gas is stored within the dome– Once the dome reaches a

given level, gas is ejected to CHP engine, Flare or Boiler

– If gas pressure within dome increases, the gas will be emitted via the Pressure Relief Valve (PRV)

So, what was the cause?

What actually happen:– Sludge entered the gas line

blocking the path to the CHP/Flare

– The PRV failed– Gas was unable to exit the

dome which resulted in a pressure build up

The outcome of the AD Failure

• One word….EXPENSIVE– All waste/permeate produced from BV Dairy

had to be sent off-site– Digestate had to be removed as Hazardous

waste, as an instant reaction– Increase in waste water treatment– Loss of potential electricity generation– Increased OPRA Scores– Interestingly despite the initial gas release we

didn’t have a single complaint from our neighbours

The Repair

• Two new dome membranes had to be manufactured, which had a 1 ½ month lead time

• The PRV was replaced with an improved design

• Alarms are now in place to alert engineers of the presence of sludge within the catchment pot

Current Situation

• The digester coped with being dormant for two months, with methane being produced within two days of the repair

• Due to strong back up and understanding from the EA and Wessex water we managed to minimise damage to the environment

• Current issues with Digestate disposal and low volumes of incoming waste, The Government needs to look at positioning of AD Plants in the UK

What’s next?!RHI and water saving

85oC

5oC30oC

15oC