Design and Design choice parameter of

medium sized biogas plants

Prakash Lamichhane BSP-Nepal

Feeding Material for Biogas Production

– All the biodegradable material

– Cattle dung

– Kitchen waste

– Human excreta

– Municipal waste

– Chicken droppings

– Green grasses

– Agricultural residues

– Other animal waste

Linkage of Technology, User and Resources

BIOGAS Technology

Technology

User

ResourcesCompatibility

Necessary Parameters

Resource

Biogas Technology

User

Technical parameters

Climatic Conditions

Time and movement

Family Size/Generator capacity

Food HabitsCooking Habits

Income level

Habits

Fuel and Cooking Device Preferences

Necessary Technical parameter for Biogas Production

Biogas

Anaerobic

Condtion

pH

Temperature

C/N ratioAgitation

Loading Rate

Retention Time

Necessary Conditions for Biogas Production (Contd….)

Biogas

Anaerobic

Condition

pH

Temperature

C/N ratioAgitation

Loading Rate

Retention Time

pH level

Optimum gas production – pH of inputmixture is 6-7

Temperature

The activity of bacteria largely dependsupon temperature.

Appropriate Temp. – 150C to 350C

The methanogenes are inactive inextreme high and low temperature.

Loading rate• Amount of raw material fed to the

digester per day per unit volume of digester capacity

• Incase of cow dung digester, the thumb rule is to put 6-8 kg of fresh dung for 1 m3 size of bio-digester.

• Correct rate of loading is essential for efficient gas production

• If plant is over fed, acidity will accumulate and methane production will be reduced.

• If loading rate is low, gas production will be reduced.

Biogas

Anaerobic

Condition

pH

Temperature

C/N ratioAgitation

Loading Rate

Retention Time

Necessary Conditions for Biogas Production (Contd….)

Retention Time• Average duration of time a simple

remains in the digester.

• For a cow dung plant, 40- 60 days is required, depending upon temperature.

• Volume of digester should be equal to 40 – 60 times the feed added daily.

• For a night soil digester, a longer retention time (70-90 days) is needed in order to kill the pathogens present in human faces.

daily added Feed of Volume

digester of volumeTotaltimeRetention

Biogas

Anaerobic

Condition

pH

Temperature

C/N ratioAgitation

Loading Rate

Retention Time

Necessary Conditions for Biogas Production (Contd….)

Carbon Nitrogen (C/N) ratio• For proper functioning of micro-

organism, both carbon andnitrogen is needed inside thedigester.

• C/N ratio – 20-30:1 is consideredbest for anaerobic digestion.

• If C/N is high – nitrogen will beconsumed rapidly leading todecrease in rate of reaction

• If C/N is low – nitrogen will beliberated and accumulated in theform of ammonia, which is toxic.

Biogas

Anaerobic

Condition

pH

Temperature

C/N ratioAgitation

Loading Rate

Retention Time

Necessary Conditions for Biogas Production (Contd….)

SN Raw Material C/N Ratio

1 Duck Dung 8

2 Human Excreta 8

3 Chicken dung 10

4 Goat dung 12

5 Sheep dung 19

6 Cow / Buffalo dung 24

7 Water hyacinth 25

438 Elephant dung

609 Straw (Maize)

10 Straw (Rice) 70

9011 Straw (wheat)

Above 20012 Saw dust

C/N ratio of some organic material

Biogas

Anaerobic

Condition

pH

Temperature

C/N ratioAgitation

Loading Rate

Retention Time

Necessary Conditions for Biogas Production (Contd….)

Dilution or Agitation• Before feeding the digester,

excreta such as fresh cowdung has to be mixedthoroughly with water.

• 1:1 on volume basis is used.

Anaerobic Condition• Digesters should be airtight

to maintain strictly anaerobiccondition

Biogas

Anaerobic

Condition

pH

Temperature

C/N ratioAgitation

Loading Rate

Retention Time

Necessary Conditions for Biogas Production (Contd….)

12

Case Study 1: Biogas Plants in Army Barrack

Improved Sanitation

13

Case Study 2: Biogas Plants in school Vajra Academy

14

Case Study 3: Biogas Plants in Maoists Cantonment

15

Case Study 4: Biogas Plants in Maoists Cantonment Contd…..

16

Case Study 5: Sunga Wastewater Treatment Plant, Thimi

17

Case Study 6: Dhulikhel Municipality (Drainage line)

18

Case Study 7:Chiken manure Biogas Plant

19

Case Study 8: Depending upon cattle shed inlet can be modified

4/15/2015

Case Study 9: Cattle urine collection

4/15/2015

Case Study 7: This is also design choice parameters

What about Biogas Generation from any organic substances?

S.N. Parameter Value

1 C/N Ratio 20 – 30

2 PH 6 – 7

3 Digestion temperature 20 – 35

4 Retention time (HRT) 40 –100 days

5 Biogas energy content 6 kWh/m3

6 One cow yield 9 – 15 kg dung/day

7 Gas production per kg of cow dung 0.023 – 0.04 m3

8 Gas production per kg of chicken dung 0.065 – 0.116 m3

9 Gas production per kg of human excreta 0.020 – 0.028 m3

10 Gas requirement for cooking 0.2 – 0.3 m3/person

11 Gas requirement for lighting one lamp 0.1 – 0.15 m3/hr

23

Schematic Layout of the Biogas System and its different components for Hotels/Institutional/Dairy farm/waste recovery

But For Piloting case just focus on 1:1 Dung water feeding in Pakistan

2009 - Namsaling

2010 – Gimehre Gaun – Kavre District

Thank You !!!!