Effect of harvesting age and performance evaluation on biogasification from Napier grass in separated stages process

Abstract

Napier grass is a potent source of biomass commonly grown throughout the tropics. Here the effects of harvesting age and performance evaluation on Napier grass biogasification were investigated. Three different harvesting ages of fresh Pakchong-1 Napier grass at 35, 45, and 55 days were digested. Two separated stages process, combining Completely Stirred Tank Reactor (CSTR) and Anaerobic Baffle Reactor (ABR), was then operated for acidification and methanation. The results depicted that the different grass harvesting ages promoted different characteristics of biomass feedstock in particular for total solid, lignin content, and C/N ratio. The different gases production potentials about 70.8–164.6 ml biogas/g VSadded and 32.9–84.5 ml CH4/g VSadded were then promoted. The acidification of 45 days harvesting age at 1.5–3.0% (VS) in CSTR generated the different acid production for 5.9–7.5 g/l. The selected solid load of 2.0% VS generated about 21.1 g CODtotal/l or 7.5 g TVA/g VSadded. This was solubilized for almost 50% and consisted of acetic acid for 77.2–82.2%. The gases production from this hydrolysate in ABR was stably operated and produced about 484.0 and 267.8 ml /g CODremoved for biogas and methane, respectively. This result depicted the possibility of biogas production from Pakchong-1 Napier grass employing two separated stages process.