Characteristics of the studied site
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.
The gas analysis showed that the produced biogas was composed
of 60% CH4, 30% CO2 and about 10% N2. The N2 concentration
is considered as high, even when compared to that reported for
biogas in Thailand, i.e., 2–7% N2 [14]. This is also likely that the
air could leak in during biogas sampling for analysis. The estimated
heating value of the biogas was 21 MJ/Nm3. The H2S concentration
averaged during the study (Oct 2005 – Feb 2006) was about
2400 ppm. The potential biogas production from the system was
estimated at about 86 m3 per day, as shown in Table 1. The value
is found in good agreement with the average biogas production
rate from pig manure estimated by the Energy Planning and Policy
Office (EPPO) [16].
Characteristics of the studied site
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.
The gas analysis showed that the produced biogas was composed
of 60% CH4, 30% CO2 and about 10% N2. The N2 concentration
is considered as high, even when compared to that reported for
biogas in Thailand, i.e., 2–7% N2 [14]. This is also likely that the
air could leak in during biogas sampling for analysis. The estimated
heating value of the biogas was 21 MJ/Nm3. The H2S concentration
averaged during the study (Oct 2005 – Feb 2006) was about
2400 ppm. The potential biogas production from the system was
estimated at about 86 m3 per day, as shown in Table 1. The value
is found in good agreement with the average biogas production
rate from pig manure estimated by the Energy Planning and Policy
Office (EPPO) [16].
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