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LAKE DISTRICT BIOGAS – GREEN GAS FROM CHEESE RESIDUES

Posted: 2016-11-21 17:26:02

LAKE DISTRICT BIOGAS – GREEN GAS FROM CHEESE RESIDUES

First Milk’s Lake District creamery produces award winning cheese under the Lake District brand.  It also has the largest on-site anaerobic digestion (AD) plant in the European dairy processing sector.  The bio-energy plant is supplying self-generated energy to the cheese-making process. 

Located in rural Cumbria, it is the first Digestion facility on a UK dairy processing site to feed bio-methane (upgraded biogas) into the gas grid that is generated entirely from its cheese process residues, without feeding any additional materials.   So how come this state of the art technology is being pioneered in rural Cumbria?  Richard Gueterbock of developers Clearfleau explains…

 

Like many European dairy businesses, First Milk’s creamery was under pressure to reduce costs, cut fossil fuel energy use and limit its impact on the local environment.  Due to falling milk prices affecting the entire European dairy sector, it also needed a funding partner for the project. 

Benefits or technical advantages of the approach taken

Digestion technology used for the Lake District Biogas (LDB) facility was developed specifically for the on-site digestion of food and beverage processing residues.  The design of the plant allows it to process a range of bio-degradable residues from sites like Lake District Creamery.  Residues are pumped from the creamery to balance tanks before being fed into the digester tanks on a continuous basis. 

 

Lake District Biogas (www.lakedistrictbiogas.com) commissioned Clearfleau to design and build the new on-site AD plant.  The bio-energy plant is a major boost for the creamery and the local community, who will have access to gas from the site.  The plant provides renewable bio-energy for cheese making, while reducing the creamery’s environmental impact and allowing cleansed water discharge to a nearby river.

There are three key elements phases to the on-site bio-energy project:

Aerobic Treatment: The existing effluent treatment plant needed re-investment.  The first phase of the project focused on refurbishing elements of the existing plant that are re-used to ‘polish’ the residual process waters (digestate) to allow discharge of cleansed water to the nearby river Ellen.  This was done in advance of the main build at the request of the Environment Agency (unwanted parts of the old plant will be decommissioned).  Modifications to the aerobic plant have made it more efficient to ensure that necessary protection is in place for discharge to the River Ellen.  This was achieved through improved aeration as well as the ability of the AD facility to reduce the treatable load by removing 95% of the COD load. 

Anaerobic Digestion: The high rate liquid digestion technology is designed to optimise biogas output from process residues.  It does this by optimising contact between the slow acting methanogenic bacteria and the bio-degradable material dissolved and suspended in the feedstock.  The AD plant is being fed with a combination of fatty wash waters and whey permeate (from production of cheese and high nutrition sports drinks).  

The process is able to treat fatty residues (unlike other high rate digestion systems) and efficiency is enhanced by extending the solids retention time in the digester to over 50 days, while reducing the liquid retention time to under 5 days.  Hence, the process is able to optimise biogas output (with over 95% COD removal) while minimising the load that is passed on to the aerobic plant.  By optimising biogas output we maximise energy output and project payback.    

Biogas Utilisation:  Biogas is stored in the gas dome before upgrading to bio-methane (some biogas is also fed to a CHP unit to provide power to run the entire plant).   Over 80% of the biogas is fed to a membrane based bio-methane upgrade unit that converts it into bio-methane that has a comparable thermal value to natural gas.  The up-grade system uses membranes to concentrate the gas and remove other gases like CO2.  It can then be fed into the grid with a comparable calorific value to natural gas.

 

 

Impact on biogas volumes and other performance issues

By blending the high and lower strength bio-degradable feedstocks with high rate mixing, the AD plant produces over 1,000 m3/hour of biogas, with a methane concentration of at least 55%.  When the CO2 is removed, the clean bio-methane can be fed into the grid where it is either used in the creamery boilers or by households and other factories in Aspatria.  As the entire system optimises biogas output and then allows it to be fed to the grid it is optimising the use of the renewable energy.

The technology is proven to get better feedstock degradation and COD removal than other less robust digestion systems.  The other feature of the AD system is that it has a low energy demand – hence the maximum quality of energy can be used in the production processes.  Also most of the process is sealed (and is a closed loop) and hence risks of odour are minimised and the wider impact of the creamery on the local environment (through odours or possible contamination of water courses) is significantly reduced.

Issues to be considered when specifying these plants

Each on-site plant has to be tailored to the feedstocks that are fed to it.  This will ensure that the plant maximises the energy output and minimises any impact on the environment.   Some of the issues that have to be addressed in the design phase include balance tank storage for the feedstocks, blending high and low strength materials, management of higher solid materials and minimising use of chemicals.

 

The on-site AD process converts over 95% of the bio-degradable material into biogas.   Each cubic metre of liquid feedstock fed into the AD plant generates about 14 cubic meters of gas.  Hence, the LDB plant will generate 1,000 cubic meters per hour of biogas or 16,000 cubic meters per day of bio-methane.

 

The new plant will provide significant treatment and disposal savings.  By feeding the up-graded bio-methane into the gas grid, the facility will produce over £3m per annum in cost savings and revenue, while supplying over 25% of the creamery’s energy requirements.  On-site digestion will also produce over £2m per annum in net revenue (after operating costs) from savings, incentives and gas sales.

 

The on-site facility treats all process residues from the creamery, transforming its operation by:

§  Generating 5.35 Megawatt hours (MWh) of renewable energy

§  Treating 1,650m3 per day of process effluent and whey

§  Producing around 1,000 Nm3/hour of biogas

§  Revenue for energy generated from FITs and RHI

§  Reducing costs by cutting fossil-based fuel purchase

 

The creamery’s state of the art digestion facility is handling its residues, while reducing costs and carbon emissions.  With funding supplied from outside the business and by outsourcing the plant’s operation and maintenance to Clearfleau, First Milk can now focus on its core cheese production activity. 

 

Replicability in the Dairy Industry

The technology can be used across the food sector on a range of liquid food process residues.  Like our AD plant at Nestle in Newcastle, the LDB plant will also be used to showcase the potential for on-site energy generation in the European dairy sector and we need also to demonstrate that this approach can be replicated on smaller dairy processing sites in the future.

 

ENDS

 

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For further information, please contact Gaye Spencer on 01635 569992 or gaye.spencer@gspr.uk

 

NOTES TO EDITORS

Clearfleau’s (www.clearfleau.com) award-winning innovative design sets it apart from other high-rate digestion technologies.   The robust anaerobic digestion process can handle load variations and the range of liquid co-products from the distillery sector.  It can also treat fatty materials from the food industry, diverting them away from sewer discharge.  The process has just three outputs: biogas for energy generation, residual bio-solids, a source of crop nutrition for local farms and clean water that can be discharged to a watercourse or re-used on site as grey water (in boiler feed or for non-food contact uses).