Biogas production from anaerobic co-digestion of fallen teak leaves () and microalgae () were investigated. In this study, teak leaves and algae mixtures with or without pretreatment were used as the substrates and digested in 1-L of anaerobic fermenter, then optimal conditions were performed in 6-L fermenter. Pretreatment was performed using sodium hydroxide (NaOH) solution (w/v) at different conditions (0, 2, 3 and 4%), with different total solid (TS) ratios (10, 15 and 20%). The digesters were placed in an incubator at 34-36 °C for 45 days. The results showed that the co-digestion of pretreated (10% TS with 2% NaOH) of teak leaves and algae was significantly higher in terms of biodegradability of TS, VS, COD along with biogas yield, methane potential and highest yield was achieved 71.90% than those obtained by mono-digestion. Thus, results demonstrated that anaerobic fermentation of teak leaves and microalgae in digester system could get as high methane yield.

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In the suspension culture, the sharp structure of some nano-metals may destroy the cells and cause metal washout from the system, causing secondary pollution. A novel method of combination of nano-metals addition and immobilized dark fermentation microorganism can overcome this problem. In this study, the co-immobilization approach, nano-metal and the dark-fermented bacteria were incubated together within PVA-boric acid gel granule, could prevent washout of hydrogen producing microorganism as well as the added nano-metals. The results showed when 400 mg/L nano-metal nickel (NP-Ni) and 400 mg/L nano-metal iron (NP-Fe) were added within the immobilized cell, both the maximum H 2 production yield (HPY) and H 2 production rate (HPR) were improved to be 1.28 mol H 2 /mol glucose, 3.13 H 2 L/L/day and 1.19 mol H 2 /mol glucose, 1.90 H 2 L/L/day, respectively. The method is expected not only to allow microorganisms to have higher environmental tolerance but also increase hydrogen production.

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