Techno-economic and performance assessment of semi-continuous anaerobic digestion of domestic organic waste with digestate recirculation in the Dominican Republic

Abstract

Domestic organic waste (DOW) represents an abundant but underutilized biomass resource for renewable energy production, particularly in developing countries where waste management and energy access remain key challenges. This study assesses the technical, agronomic and techno-economic feasibility of producing biogas from DOW using a simplified anaerobic digestion approach based on pH monitoring and controlled digestate recirculation. A 0.1 m3 biodigester previously inoculated with rumen and cow dung was operated under mesophilic and tropical climate conditions, evaluating hydraulic retention times (HRT) of 30 and 60 days and a digestate recirculation ratio of approximately 16% to stabilize pH. Experimental results demonstrate that DOW can be effectively converted into biogas under low-technology operating conditions, achieving stable methane production without the need for advanced monitoring or strict control of multiple physicochemical variables. A HRT of 60 days showed improved performance compared to 30 days. Methane concentration averaged 56.3%, which, although lower than that of cow dung biogas, is sufficient for energy generation using commercially available engines. Digestate reuse promoted successful vitroplant acclimatization without the need for inorganic fertilization, highlighting its agronomic potential. By combining experimental operation with an empirical numerical model, this work provides practical indicators for assessing digestion performance under variable feedstock conditions typical of municipal food waste. Environmental assessment indicates avoided CO₂ emissions on the order of 600–3300 tCO₂·year−1 for a 1-MW plant, depending on operational assumptions and emission factors. Techno-economic analysis shows payback periods ranging from 4 to 9 years and 6–22 years; and internal rates of return between 10.8%–18.5% and 19%–31%, with plant factors of 33.3% and 60%. These results demonstrate that DOW-based biogas systems can support decentralized, low-cost waste-to-energy solutions with environmental and agricultural benefits, particularly in developing and emerging economies.

Highlights • Anaerobic digestion of domestic organic waste was experimentally evaluated under low-technology operating conditions. • The effects of hydraulic retention time, organic loading rate, and recirculation on methane concentration were analyzed. • A statistical model was developed to estimate methane content based on HRT, OLR, and pH. • Stable operating conditions yielded methane concentrations comparable to values reported in the literature. • The results support the potential of domestic organic waste for decentralized biogas production.