Clearfleau, a British provider of on-site treatment solutions for the food and beverage sector, has commissioned its most complex plant to date, which feeds bio-methane into the gas grid in rural Cumbria. By feeding the bio-methane into the gas grid, the facility is claimed to produce over £3m per annum in cost savings and revenue, while supplying up to 25% of the creamery’s energy requirements.
 
 
Completed tanks at Lake District Biogas plant.
 
The plant has been designed and built for Lake District Biogas, which will operate the site for twenty years taking feedstock from First Milk’s Aspatria creamery site. This comprises all the low-strength wash waters from the creamery, such as process rinses, and are supplemented by whey permeate (cheese production residue after protein extraction for use in energy supplements).  Both feedstocks are pumped to the AD plant from the creamery.
 
Revenue benefits include 20-year index-linked, government-backed incentive payments, with about £2 million per annum in support through the government’s RHI scheme and a further £1 million through the sale of gas to the wholesale market and from the Feed in Tariff scheme for the power generated in the CHP engine.
 
Clearfleau’s process takes the dilute wash waters from the Aspatria creamery site and these are supplemented by whey permeate.  The liquid is then pumped into the AD plant from the creamery where the bugs convert the fats and sugars in the feedstock into biogas.  After the AD process (removing at least 95% of the COD load), the effluent is further tested prior to discharge to the river Ellen. 
 
This is the first on-site anaerobic digestion (AD) plant in the dairy industry in Europe to feed bio-methane to the gas grid, generated exclusively by digesting the creamery’s cheese making residues. When the plant is operating at full capacity, it will treat 1,650m3 per day of process effluent and whey and generate around 5MW of thermal energy.
 

3D drawing of new Clearfleau AD plant for Lake District Biogas.
 
Reducing phosphate
 
As an initial step, Clearfleau was required to refurbish the existing aerobic plant to enable First Milk to significantly reduce levels of phosphate in their effluent, which is discharged to the River Ellen.  Supported by the Environment Agency, this will ensure an early delivery of new tighter discharge standards, which are required by the Water Framework Directive. 
 
Clearfleau’s on-site AD technology is proven to reduce the chemical oxygen demand (COD) of the production residues by at least 95%.  Aerobic polishing will then remove residual COD and nutrients (nitrates and phosphates) to allow safe river discharge. 
 
The new plant will produce 1000m3 of biogas per hour, of which over 80% will be upgraded for injection into the national grid.  At least 60% of the bio-methane will be used in the creamery for steam generation, with the balance being used by local businesses and households in Aspatria.
 
It has taken over from the outdated aerobic plant. This has saved First Milk from having to upgrade the old inefficient plant, reducing their effluent treatment costs and carbon footprint, while cutting operational costs, which are borne by Lake District Biogas. Additional benefits from the deployment of on-site digestion in the dairy processing sector include reduced energy and off-site disposal costs.  
 
The biogas is stored in the gas dome before being upgraded to bio-methane - 80% of the biogas is fed to a membrane based upgrade unit that removes carbon di-oxide from the gas to produce bio-methane with a comparable thermal value to North Sea gas (some biogas is also fed to a CHP unit to provide power to run the treatment plant). 
 
Circular economy
 
The food industry is now realising the contribution production residues can make to the circular economy. After the recent Paris Climate Change Summit, CEO’s of global food companies including Unilever and Nestle stated: “We want the facilities where we make our products to be powered by renewable energy with nothing going to waste.”
 
Gordon Archer, Chairman of Lake District Biogas says: “Completion of this £10 million project on time, given the weather conditions in Cumbria this winter, has been a major achievement for the project team and Clearfleau. This is the largest AD plant on a dairy processing site in Europe dedicated to handling the residual materials from the cheese making process.”