The study was carried out on-site at a small pig farm in Chachoengsao
province, located about 100 km east of Bangkok. The
farm raises 170 breeder swines and 255 piglets, which yielded
about 2700 kg of fresh dung daily. Biogas was produced from
two fixed-dome digesters, each of which was 100 m3. The schematic
diagram of the fixed-dome digesters is illustrated in Fig. 1.
These digesters are of the Chinese design and are the most popularly
used for small-scale biogas plants in Thailand. The possible
sizes of fixed-dome digesters ranged from 5 to 200 m3. The biogas
is collected under a fixed concrete dome, displacing effluent sludge
as the gas pressure builds.