Small-scale biogas plants in central Vietnam and biogas appliances with a focus on a flue gas analysis of biogas cook stoves

The major objective of this paper is to fill the research gap regarding small-scale biogas appliances by performing a flue gas analysis of biogas cook stoves in Vietnam. The methods of data collection included a questionnaire survey of rural households (n = 93), discussions with local consultants (n = 6) and observations in central Vietnam. Furthermore, flue gas analyses of biogas cook stoves were performed (n = 93). As the most common appliances, biogas cook stoves were reported as a substitute for conventional cook stoves, eliminating indoor smoke pollution and related health risks. The majority (96%) of biogas cook stoves were two-flame burners that averaged 2.4 (±0.74) years of age and were in use for over 3 h per day. High concentrations of CO in its diluted (8705.35 ± 1790.01 mg m−3) and undiluted forms (24,758.2 ± 4860.2 mg m−3) were detected in biogas flue gas. The concentration of unavoidable produced NO averaged 0.064 (±0.12) mg·m−3, which is an acceptable value for the transformation of biodegradable wastes into biogas that is consequently burned. The study contributes to covering the data gap, as similar studies have not been conducted in Vietnam. The information and data gained are important for further evaluations of biogas technology in Vietnam and other developing countries.