Farm-scale anaerobic digestion at Walford & North Shropshire College Jon Parry Director of Walford

Walford Farm 220 ha of ground 220 ha of ground 200 Holstein cows, averaging 7,800 l/cow/year 200 Holstein cows, averaging 7,800 l/cow/year 300 Lleyn ewes 300 Lleyn ewes 70 ha of cereal crops 70 ha of cereal crops 30 ha of forage maize 30 ha of forage maize 100 ha of grass 100 ha of grass 20 ha of woodland 20 ha of woodland A commercial unit required to produce annual profits but also serve as a teaching resource

The Walford Farm Digester Commissioned in 1994 and run every year since Commissioned in 1994 and run every year since “Fed” a diet of cow slurry throughout the winter period “Fed” a diet of cow slurry throughout the winter period 330 m 3 capacity, which equates to 15 days slurry production when all cows are housed 330 m 3 capacity, which equates to 15 days slurry production when all cows are housed Chopper pump lifts slurry from slatted channel directly in to the digester Chopper pump lifts slurry from slatted channel directly in to the digester Digester agitated via circulating gas from the top of the vessel through a series of pipes across the floor Digester agitated via circulating gas from the top of the vessel through a series of pipes across the floor Temperature increased to approx 38 oc by circulating water heated from burning harvested methane Temperature increased to approx 38 oc by circulating water heated from burning harvested methane

The Walford Farm Digester (cont) As gas quantity and quality improves CHP will produce heat that is re-circulated to maintain the temp As gas quantity and quality improves CHP will produce heat that is re-circulated to maintain the temp Digestate pumped from the bottom of the vessel over a separator Digestate pumped from the bottom of the vessel over a separator Solid waste is odourless and stored for use in gardens/fields Solid waste is odourless and stored for use in gardens/fields Liquor is stored in a glass enamel tower, and spread on farmland via irrigation system Liquor is stored in a glass enamel tower, and spread on farmland via irrigation system

Costings Where does slurry handling system stop and AD system start ? Best guestimate is £3,000 maintenance and £3,000 staff time per year Best guestimate is £3,000 maintenance and £3,000 staff time per year Electricity produced £10,000 - £8,000 per year Electricity produced £10,000 - £8,000 per year Double ROCs £5,000 - £4,000 per year Double ROCs £5,000 - £4,000 per year Improved nutrient availability £3,000 per year Improved nutrient availability £3,000 per year Compost sales £1,000 per year Compost sales £1,000 per year

What next ? Summer feedstock: Summer feedstock: –Green waste –Animal manures –Energy crops –Gate fees NVZ regulations NVZ regulations