Experimental research of efficiency of semi-continuous and periodic biogas production processes by using chicken...

Semi-continuous and periodic biogas production processes were investigated. Dry chicken manure containing 40.0 ± 0.5% volatile solids (VS) was used for the production of bioloading. Semi-continuous operation bioreactor and periodic bioreactor were used to implement research. Bioloading was additionally supplemented with newly prepared parts by removing 10% of decomposed mass and by adding the same amount of preheated mass every 7 days (semi-continuous process). The process was periodic when the mass was completely decomposed (after 45 days of the experiment) and fully removed (bioreactor was loaded with a new portion of raw material to 100% of the working volume again). Total duration of both experiments was 90 days. The results show that biogas production by semi-continuous process is more effective than periodic process due to higher total biogas yield (up to 39.7%) and higher methane yield (up to 33.5%). The maximum concentration of CH₄ was determined during the periodic biogas production process, but the difference was only up to 2.1% (68.9% and 66.8%, respectively). Since the produced biogas had quite high average CO₂ and H₂ S concentrations (<40.0% and 2.1 g/m³ , respectively), it is recommended to use filter-adsorbers or biofilters. According to the results, semi-continuous type bioreactor is more effective than periodic. PRACTITIONER POINTS: Maximum CH₄ concentration in biogas, produced during periodic process, is 2.1% higher than during the semi-continuous process. Average CH₄ concentration in biogas, produced during periodic and semi-continuous process, reaches 52.7% and 53.0%, respectively. Biogas and methane yield (during periodic process) is 39.7% and 33.5% lower than during the semi-continuous process. CH₄ concentration decreases (after supplement) about 6.0%-7.0% (during the semi-continuous process), but increases to the next cyclic bioloading supplement. Semi-continuous biogas production process is more efficient than periodic.