Transcript BV Dairy: The AD Plant - South Wessex Waste Minimisation Group

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
31st jan
2nd feb
4th feb
10th feb
12th feb
14th feb
16th feb
18th feb
20th feb
22nd feb
24th feb
26th feb
28th feb
2nd Mar
4th Mar
6th Mar
8th Mar
10th Mar
14th Mar
16th Mar
18th Mar
20th Mar
22nd Mar
24th Mar
26th Mar
28th Mar
30th Mar
1st Apr
3rd April
5th April
7th April
9th April
11th April
13th April
15th April
17th April
19th April
21st April
24th April
26th April
28th April
30th April
02-May
04-May
06-May
08-May
27%
176
kWh Electricity Generation
3500
3000
2500
2000
1500
1000
500
0
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
5oC
30oC
15oC
85oC