Comparison of Biogas Productivity in Thermophilic and Mesophilic Anaerobic Digestion of Bioethanol Liquid Waste Nina Anggita Wardani (a), Nurul Afiqah (b), Muhammad Mufti Azis (a), Wiratni Budhijanto (a*)
a) Chemical Engineering Department, Gadjah Mada University Jalan Grafika no. 2, Sleman 55281, Daerah Istimewa Yogyakarta, Indonesia *wiratni[at]ugm.ac.id b) Chemical Engineering Department, University Technology Petronas Persiaran UTP, 32610 Seri Iskandar, Perak, Malaysia
Most of anaerobic digesters in Indonesia are run under mesophilic condition because Indonesian climate is sufficiently good to easily maintain mesophilic condition. On the other hand, thermophilic anaerobic digestion offers an advantage of much higher biogas production rate, although it needs more tedious control and energy supply to achieve the thermophilic temperature of 50-60°C. We run laboratory scale experiments to compare process performance of anaerobic digestion of bioethanol liquid waste (vinasse) at mesophilic and thermophilic conditions. Digested cow manure was used as inoculum. Start-up was conducted with only the inoculum inside the reactors. After the reactor passed through the starvation period, the vinasse feeding was started. The hydraulic retention time (HRT) was gradually decreased from 60, 42, until 30 days. Each step of HRT took 7 up to 14 days for stabilization. At the same HRT, thermophilic reactors produced biogas at the rate of four times faster than the mesophilic reactors. The methane concentration in the biogas for thermophilic process was relatively the same as the mesophilic one. With such higher rate of biogas production, the energy cost for thermophilic can be possibly better compensated.