The document discusses the design of digesters, focusing on size calculations based on energy production and end user requirements. It outlines various factors such as biodegradability, concentration of feed, and health criteria that influence digester design, including gas production rates for different types of animal manure. Two design approaches are presented, emphasizing the importance of end-use requirements in determining the most effective digester specifications.

1. Design of Digester – Size based on
Energy – Based on end user
requirements

2. Design of Digester
• Type of digester used
• Purpose for which the digester is used
• Size based on health criteria
- reduction of possible transmission of diseases
- temperature & retention time
• Size based on production of soil conditioner
- breakdown, stabilization, storage of organics &
nutrients
• Size based on energy
- gas production

3. Size based on Energy
• Biodegradability of the materials
(Pretreatment)
• Concentration of the feed
• Kinetic constants
• Retention time
• Temperature (digester)
• Design – gas production rate per unit volume
V = (B0 S0/HRT)
μm = 0.013 (T) – 0.129 (T = 20-60°C)

4. Ultimate methane yield
• Beef manure on grain ration concrete lot = 0.37 m3
• Beef manure on grain ration dirt lot = 0.25 m3
• Dairy cattle = 0.20 m3
• Pigs = 0.50 m3
KCH = 0.8 + 0.0016 e0.06S0 (cattle manure)
KCH = 0.5 + 0.0043 e0.091S0 (pig manure)

5. Design Based End Use Requirements

6. Design Based End Use Requirements

7. Approach A

8. Approach A – Contd.,

9. Approach – B
(C/N ratio)

10. Approach – B (Contd.,)