This document discusses a case study of an anaerobic digester installed on Walford Farm in Shropshire, England. It provides details on the farm operations, the installation of the digester in 1994 using funding from Life, and the benefits it provides. The digester processes farm waste through anaerobic digestion to produce biogas which is used in a CHP unit to generate electricity, while the digestate output has enhanced nutrients for use as fertilizer. The financial analysis shows the installation costs were recouped through annual income from electricity production and other benefits.

1. Anaerobic Digester’s
-A case study
Adrian Joynt
Farm Manager
Walford & North Shropshire College

2. ANAEROBIC DIGESTION
A simple process first developed by
the Chinese

3. Walford Farm
• 500 acres
• 220 dairy cows, 100 followers
• 300 Lleyn ewes
• 155 acres Cereals
• 75 acres Maize
• 215 acres grass
• 50 acres woodland
• Environmental Stewardship

5. The Walford Digester
• Life funding
• Set up and operation
• Problems
• Benefits

6. The AD Process

7. Why Install an AD Plant?
• Demonstrate the technology and the use of
AD in Farm Waste management
• Maximise potential benefits of AD within a
farm based system
• Maximise the use of the farm resources
• Evaluate the system and component parts
• Comment on costs, benefits and viability
• Reduces Methane emissions

8. The Installation
• Opportunity to apply for Life funding arose
in 1993
• Shropshire County Council helped with
grant application
• Planning Permission granted in 1993
• Site preparation and Anaerobic Digester
installation started February 1994, took 8
weeks
• CHP unit commissioned October 1994

9. The Process
• Intake of chopped waste
• Feedstock
• Retention time
• Temperature
• End Product utilisation

10. The 5 Golden Rules
• Temperature
• Good diet
• Temperature
• Good mixing
• Temperature

11. What Are The Benefits?
• Manageability of products
• Odour reduction
• Simple technology
• Small reduction in BOD
• Energy production
• Enhanced nutrient availability in separated
liquid

12. Drawbacks
• Maintenance
• Operator time
• Capital investment

13. Financial Implications
• Installation costs £132,500
• Annual running costs £3,500 (excluding
farm labour)
• Increased nutrient availability £2,000
• Electricity production £10,000
• Eligible for “Double” ROC’s £5,000
• Compost sales £2,500

14. Potential
• Finance (investment)
• Sales
• Energy production
• “Gate” fee on green waste
• Summer feed stocks
• NVZ regulations