Muntons is finalizing a £5.4 million anaerobic digestion plant aimed at reducing CO2 emissions from 27,264 to 26,605 tonnes annually, while converting up to 80,000 tonnes of liquid malt waste into organic fertiliser. The closed-loop system not only enhances sustainability by replacing artificial fertilisers but also regenerates 25% of the site's electricity demand and reduces transportation by 3,000 tanker movements per year. The project utilizes HRS heat exchangers, significantly improving efficiency through energy recovery and ensuring high-quality digestate that meets stringent standards.

1. M
alted ingredients company
Muntons (Stowmarket,
Suffolk) is putting the
finishing touches to its £5.4
million on-site anaerobic
digestion (AD) plant which
will help reduce the firm’s
CO2
emissions from 27,264
to 26,605 tonnes per annum.
Integral to the success of the 499 kW facility is a three Tank Batch
Sludge Pasteuriser System with Energy Recovery from HRS
Heat Exchangers, which will help turn up to 80,000 tonnes of
Muntons’ liquid malt waste into quality organic fertiliser (known
as digestate). This will be used on local farmland, helping the
company’s network of growers to produce some of the 250,000
tonnes of barley needed to make Muntons’ malt, around 180,000
tonnes per annum.
Muntons is a company with sustainability at its core and this
project will create a closed loop system, exemplifying the circular
economy. The company became interested in AD after analysis
showed that 60 percent of the carbon footprint of its supply chain
came from the artificial fertiliser used by its barley growers. The
firm realised that using its liquid malt waste as feedstock for an
on-site AD plant would not only produce a high quality digestate
for its farmers to use instead of artificial fertiliser, it would also cut
3,000 tanker movements per year and generate 25 percent of the
site’s electricity demand.
The digestate will be pasteurised to meet stringent PAS 110
standards using the HRS Heat Exchangers three Tank Batch
system, ensuring that the final fertiliser is free from plant
pathogens or other biological contaminants. The beauty of the
closed-loop system is that the waste feedstock which is turned into
digestate during the AD process has come only from the processing
of barley. It is then applied to the next barley crops for use in the
factory.
As well as a comprehensive proposal, the Muntons’ team was
impressed by the HRS system, which can save up to 70 percent of
heat required, as well as its ability to run at a half flow rate, should
the volume of digestate stock reduce. Additionally, the equipment’s
monitoring feature enables Muntons to track every batch of
digestate back to the feedstock from which it was produced. “The
fact that the HRS system offers batch reporting was also a big
draw; traceability is very important to us,” remarks Lawrence
Howes, Project Engineer at Muntons.
Matt Hale, International Sales Manager at HRS: “For Muntons,
this whole project has been about maximising efficiency. Although
they have an abundance of heat, they still wanted to recapture what
they could - our heat exchangers will provide at least 40 percent
heat regeneration.”
The HRS system works on a three tank principle; while one tank
is being filled, the second tank holds the sludge at 70°C at the
same time as the third tank is being emptied (each process lasts
one hour). Waste cooling water from the CHP engine is used to
heat the sludge in corrugated tube-in-tube heat exchangers, which
Muntons is a company with
sustainability at its core and this
project will create a closed loop
system, exemplifying the circular
economy.
HRS Heat Exchangers
help Muntons close the
loop
F CASE STUDY
CASE STUDY
66 | December 2015 - Milling and Grain

2. is more efficient than heating an entire tank of digestate. HRS has
also incorporated an energy recovery section into the process to
make it even more efficient: energy is transferred from the hotter
(pasteurised) sludge to the colder (unpasteurised) sludge, reducing
energy consumption by up to 70 percent compared to normal
systems and using heat which would otherwise be wasted.
This means that the digestate is not the only circular part of the
process. Heat generated by the engine used to generate electricity
is used initially in the pasteurisation process, and then regenerated
for use elsewhere on site, for example to heat water for cleaning.
Lawrence comments on his equipment decision making process:
“We were already aware of the quality and reputation of HRS Heat
Exchangers in the food production industry – using their solution
enables us to make use of an abundance of waste hot water. Not
only does the corrugated tube-in-tube technique deliver improved
performance, they’re also more resistant to fouling, which means
less downtime and maintenance. In addition, we had a short
deadline – just 16 weeks – which HRS was able to meet easily.”
The AD plant is currently undergoing commissioning and will
become fully operational in late spring. For Muntons, the benefits
are clear – better waste management, a reduction in tanker
movements, energy generation, and, thanks to its PAS 110 quality
pasteurised digestate. All in all Muntons has significantly reduced
its carbon footprint saving 1159 tonnes of CO2
pa (from 27,264
to 26,605) – the emission equivalent of 300 average family cars
(approx.).
With our Heat Recovery Dryer you get the
lowest energy consumption on the market.
TORNUM Grain Coolers – The eco-friendly
way of preserving grain quality.
Up to 30%Energy Savings
Heat Recovery Dryer
TORNUM AB Box 100, SE-535 22 Kvänum, SwEdEn
Phone +46 (0)512–291 00 E-mail: info@tornum.com
www.tornum.com
Milling and Grain - December 2015 | 67