Pilot scale study of anaerobic treatment of food waste using ambient and solar heated digesters

ABSTRACT Food waste (FW) is high in nutrients and has gained global attention as an ideal substrate for bioenergy recovery through anaerobic digestion (AD). Ambient digesters have been widely used because of their ease of installation, low cost, and low energy input. However, to improve biogas production sustainably, there is a need to consider reactor heating using renewable energy such as solar. This study sought to apply psychrophilic and mesophilic biodigester temperatures for FW treatment. For ambient digestion, a complete-mix flexible biodigester, named STH-1000A, covered in a greenhouse structure was operated between 24 and 32 °C. A prototype complete-mix tank biodigester, named VUT-1000C, was designed and operated at mesophilic conditions of 37 °C through solar geyser heating. VUT-1000C produced 1200 L of biogas per day while STH-1000A 150 L/day. VUT-1000C and STH-1000A generated up to 1.8 and 0.4 kWh of electricity, respectively. The power balance showed that VUT-1000C used 68% of its power production and STH-1000A consumed 398%. Digester heating using solar geyser is a novel and promising technique for achieving mesophilic condition leading to improved biogas production.