Page 40 - 048

22

3.2 Introduction

Nowadays, higher energy demands used for transportation, industries, power plant and as
well as household which was achieved mostly from fossil fuels are comprehensive coal, oil and
natural gas. Nevertheless, global fossil fuels storage was gradually decrease which a contrary in
prices. Moreover, the extensive use of fossil fuel which is caused of global climate change due to
rapidly increasing concentrations of greenhouse gas especially carbon dioxide during the
combustion of fossil fuels. Due to the depletion of limited fossil fuels is inevitable, there is an
urgency to search for replacement source of energy. Among several options, biohydrogen and
biomethane generated from organic wastes mainly achieved from various industries by applying
a two-stage anaerobic digestion process is one of the promising routes that can contribute to
sustainable biofuel in a form of biohythane. Biohydrogen is clean energy; high energy content,
rapid burning speed, high-octane number and it is considered to be promising fuel since it can be
produced using renewable sources. Additionally, gas mixture blending of hydrogen at 10 – 60%
by volume with methane could be considered as an efficient fuel for the vehicles using an
internal combustion engine (Alavandi and Agrawal, 2008).

Thermophilic mixed cultures has been examined for their potential as biohydrogen
producers and they are able to utilize a wide range of organic wastes. In our previously research
using two-stage anaerobic digestion process of skim latex serum in batch experiments and it was
operated under thermophilic condition. Sole fermentation of skim latex serum in batch
experiments, satisfactory results in term of biohydrogen and biomethane yield of 1.57±0.06 L
H 2/L-SLS and 12.20±0.31 L CH 4/L-SLS were achieved, respectively with initial organic
concentration of 22.8 g-VS/L. However, less hydrogen and methane production yield achieved
from sole fermentation of SLS compared with sole fermentation of POME was 4.2 L H 2/L-
POME and 15.2 L CH 4/L-POME, respectively was obtained (Mamimin et al., 2012). The
possible reasons for less both hydrogen and methane production yield are: (i) relatively high
concentration of ammonia (rubber preservation) of 1213±81 mg/L which was significant factor
affecting on both hydrogen producing bacteria and methanogen archaea; (ii) relatively high
sulfate content (rubber coagulation) of 258±1 mg/L which has inhibitory effect on both hydrogen
and methane production.

Thus, to enhance in both hydrogen and methane production yield, co-digestion of SLS
which is nitrogen rich substrate with other carbon rich substrate such as palm oil mill effluent
(POME) and waste glycerol is simplest method and suitable approach. Beside rubber, palm oil is
one of the most agricultural crops cultivated in Southern Thailand. Moreover, there are many
researches were successfully achieved in both hydrogen and methane generations using POME
as substrate. To overcome overload the process and inhibitory effect on both hydrogen producing
bacteria and methanogenic archaea and as well as improved biogas yield, various mixing ratio of
SLS and POME has been investigated.