Organic Waste Recycling

172 Organic waste recycling: technology and management

(b)

Figure 4.9 (a) Schematic of floating gas holder digester. (b) A floating gas holder
digester (GATE 2006)

Table 4.10 Comparison between Chinese and Indian designs of biogas digesters (Tam
and Thanh 1982)

Chinese design Indian design

Construction

material

Several different materials

Usually locally available

Masonry

May be brought from outside

village

Construction Closed, underground masonry

or concrete pit with adjacent

inlet and outlet

Requires skill to build dome,

careful lining to prevent gas

leaks

Usually self-help

Simply above-ground tank

Easy to build but hard to install

when drum cannot be made or

easily carried

Self-help possible, but gas holder

has to be produced in workshop

Gas storage In dome combined with

digestion chamber

Manometer indicates gas

volume

For use throughout digester

lifespan with occasional

linings

Keeping it gastight is a

problem; needs efficient

lining

In floating metal drum

Height of drum indicates gas

volume

Drum needs regular painting to

prevent corrosion

No problem in keeping gastight