Technical, economic and environmental assessment of household biogas digesters in developing countries

Abstract

This study was carried out in response to the growing interest on household biogas digesters in Latin America, particularly in rural Andean communities. The aim was to compare traditional and novel digester designs, in terms of biogas production, cost and environmental impact. Three household digesters were compared: 1) fixed dome – Chinese model; 2) fixed dome – Camartec model and 3) plastic tubular – Taiwanese model. Data concerning design and operational parameters, construction materials and costs were obtained from our previous results on plastic tubular digesters and from the literature on fixed dome digesters. The biogas production rate ranged around 0.07-0.5 m3 biogas m-3 digester d-1 in plastic tubular digesters and around 0.35-0.7 m3 biogas m-3 digester d-1 in fixed dome digesters. The novel design of the Camartec model reduced construction materials and capital cost by 27 % compared to the Chinese model. The cost of plastic tubular digesters was mainly attributed to the geomembrane. The life cycle assessment showed how the Camartec model caused the lowest impact, while the plastic tubular digester had the highest impact; which was mainly attributed to plastic materials (greenhouse and biogas reservoir) and geomembrane (digester). In the Chinese model, the main impact was caused by concrete and bricks, which were respectively 38 and 22 % higher than in the Camartec system. The highest impact of the tubular digester may be explained by the lifespan of construction materials. From an economic and environmental perspective, the Camartec model seems the best option; the main advantage of plastic tubular digesters being its ease of implementation and handling.