Title: Methane production from napier grass by two-stage anaerobic digestion

Authors: Nusara Sinbuathong; Yuwadee Sangsil; Suchat Leungprasert; Suriya Sawanon

Addresses: Scientific Equipment and Research Division, Kasetsart University Research and Development Institute (KURDI), Kasetsart University, Bangkok 10900, Thailand ' Department of Environmental Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900, Thailand ' Department of Environmental Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900, Thailand ' Department of Animal Science, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom 73140, Thailand

Abstract: Digestion of Napier grass was investigated in two-stage anaerobic reactors. The reactor volume was 4 and 5 litres for the acidogenic and methanogenic reactors, respectively. The acidogenic reactors were fed once daily at 100, 150, 200, 250, and 300 mL/day with a slurry of Napier grass. The organic loading rates (OLRs) were 0.60, 0.90, 1.20, 1.50 and 1.80 kg chemical oxygen demand (COD)/m3.day. Mixed ruminal microorganisms from cows were used as the inoculum. The pH was adjusted to 7.5 for all methanogenic reactors at the start-up period. The reactors were operated at 30°C. The maximum methane (CH4) yield was observed at an OLR of 1.20 kg COD/m3.day. The average pH in the acidogenic and methanogenic reactors was 5.3 and 7.4, respectively. At the maximum CH4 yield OLR, the CH4 production was 148 litres at STP/kg dry Napier grass added to the reactor, which indicated that 6.76 kg of dry Napier grass is needed to produce 1 m3 of pure CH4.

Keywords: methane production; anaerobic digestion; bioenergy; biogas; global warming; Napier grass; Pennisetum purpureum; elephant grass; acidogenic reactors; methanogenic reactors; ruminal microorganisms; cows; anaerobic reactors.

DOI: 10.1504/IJGW.2016.079774

International Journal of Global Warming, 2016 Vol.10 No.4, pp.423 - 436

Received: 17 Sep 2014
Accepted: 06 Feb 2015

Published online: 14 Oct 2016 *

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