Muntons partners with ENER-G to reap sustainable benefits from anaerobic digestion

Muntons Anaerobic Digestion 130x130

In an article published in Bioenergy Insight Magazine, ENER-G's Head of Operations Heather Foster, discusses the environmental and cost saving benefits of an anaerobic digestion project for Suffolk-based malt producer Muntons Plc.

The anaerobic digestion (AD) facility is providing organic fertilizer from digestate to local farms to grow the barley used for malting, thus creating a local circular economy.

A high efficiency ENER-G 499kW combined heat and power (CHP) system is powering the anaerobic digestion facility, which began operation in April 2015. It is supplying 11% of the site's electrical baseload and heat for use in the AD process – resulting in significant cost and carbon savings.


Reasons for AD investment

Muntons decided to invest in the anaerobic digestion project as part of its 'Practical Sustainability' strategy. The key reasons for developing the plant were:

  1. To help decarbonise the site's energy supply by converting process waste residue into renewable biogas - to provide sustainable power and heat for on-site processes. 
  2. To achieve energy security and reduce reliance on the National Grid by becoming an independent on-site energy producer.
  3. To achieve energy cost savings from high efficiency on-site generation and create additional revenue from the government's Feed in Tariff.
  4. To avoid the cost and environmental impact of waste disposal of processing residue. Previously, Muntons was spending £750,000 every year paying for 3,000 truck-loads of residue from its processes to be removed from the site. Now this same residue is utilised in the AD plant to create a methane rich biogas and digestate.
  5. To help achieve zero landfill and reduce transport miles involved in disposal
  6. To create high quality bio-fertiliser as the digestate by-product of AD and create a useful resource for local farms to enrich fields used to grow cereals. These cereals are Muntons' prime raw material - hence the benefit is circular. Muntons also generates a revenue from this valuable product.
  7. To treat liquid waste from the production process and reduce the cost of wastewater disposal and reduce environmental impact. The high Chemical Oxygen Demand effluent isnow treated anaerobically in the digester and can be safely released to the local river.


The AD process

Following a full tendering process and technology trials to test the CHP system and associated AD equipment and prove that it would process barley as a feedstock, Muntons appointed ENER-G as its cogeneration partner to design, manufacture, install, commission and maintain the biogas CHP system.

The methane rich biogas created by the AD process powers a CHP engine that generates electricity and heat, which is used to pasteurise the sludge that comes off the reactor. The sludge is subsequently centrifuged to render it dry enough for spreading back onto farm land as an organic fertilizer.

The CHP provides the main factory with green electricity, and heat to supply the digester conditioning tank and pasteuriser with hot water.

Muntons Environment Manager Ryland Cairns said: “This state of the art plant was selected after extensive proving trials on pilot plants over many months. It was constructed to generate a significant amount of our electricity use on site, which is vital when we hear of potential electric shortages in the winter months. It is designed also to de-risk our business by providing high-spec wastewater treatment.”


Sustainable benefits

The carbon reduction from this project amounts to 400 tonnes per annum through the removal of 3000 truck journeys between the two Muntons sites in the UK. An additional carbon saving of 466 tonnes per year is achieved by displacement of energy from conventional fossil fuel sources.

The payback on investment is 4.6 years, which will reduce if Muntons is successful in gaining Renewable Heat Incentive payments (RHI) for the associated activities.

Around 3,000 tonnes of bio-fertiliser per year is produced in the AD plant and is supplied to local farmers who supply Muntons with its barley, helping them to thrive and become more sustainable. Muntons buys almost all its malting barley from within a 50 mile radius. This creates a virtuous and sustainable circle of recycling. As such, all products used in the AD plant are totally traceable and food safe.

The social benefits of the project are summed up by Nigel Davies, Muntons Manufacturing and Sustainability Director. He said: “The generation of highly nutritive fertiliser is a genuine cradle-to-cradle process by returning to our growers material generated solely from malting barley."

The AD process has helped Muntons malt to be classified as 100% sustainable, endorsed by the Sustainable Agriculture Platform Initiative.  

Muntons is keenly focused on sustainable production - focussing its efforts around carbon footprinting and taking the lead in promoting its ethos to both suppliers and customers. The biogas CHP system is helping Muntons in its aim to reduce they carbon footprint of farming cereals by at least 50%. Muntons is the first maltster to develop a bespoke farming carbon footprint calculator and the first to make the pledge that all of its malt will be low carbon within 5 years. This is part of an overarching objective to minimise the impact of its business activity on the environment wherever possible.

To get the most out of this investment, Muntons has also conducted a number of research projects. This included the dosing of a novel strain of sulfolobalus archea to reduce hydrogen sulphide in the biogas; digestate composition and efficacy trials with Lincoln University to demonstrate its effectiveness over artificial fertilisers. Muntons also participated in University College London’s ‘Swab and Send' project, which has discovered a source of bacteria that produces antibiotics that kill the multidrug resistant e.coli superbug..

This anaerobic digestion project is a perfect example of the circular economy and 360 degree sustainability in action - a powerful demonstration of Muntons’ mission of 'Practical Sustainability'.