1. INTRODUCTION
We need green energy which could be a sustainable source for the power
supply to the environmental monitoring sensors such as temperature
sensors in the remote intertidal zone (tidal flats) in Japan and other
places. Depletion of energy reserves, global warming and the concern of
environmental pollution are inspiring the search for new environment
friendly and sustainable energy production methods all over the world.
Renewable bio-energy is viewed as one of the ways to alleviate fuel
needs of the future and to overcome the crisis of global warming.
Microbial Fuel Cell (MFC) is the bio-electrochemical device that
converts microbial reducing power into electrical energy which is a
green and safe source of bioelectricity (Logan & Regan, 2006; Hong et
al., 2009; Moqsud 2020). They use the existing substrates from renewable
sources and convert them into harmless by-products with simultaneous
production of bioelectricity (Habermann W. & Pommer, E.H., 1991). In
this way, bioelectricity production employing MFC has generated
considerable interest in both basic and applied research in recent
years. Moqsud et al., (2014) tried to get bioelectricity from various
organic wastes and also living plants by using MFC technology.
SMFCs are being considered for use as a potential power source for
aquatic water quality sensors such as pH, temperature, and dissolved
oxygen sensors (Moqsud 2020; Moqsud et al., 2017). SMFC can be a
potential source of remediation of this problem. The geo-bacteria (which
live in soil) break the organics in the soil and consequently generate
the bioelectricity. Abbas et al., (2017) found that SMFCs could be a
source of sustainable energy and heavy metal remediation. To change the
batteries from the environmental monitoring sensors of this contaminated
tidal flat is a serious problem and often the solar system is not
working due to the bad weather or other reasons.
The major objective of this study is to generate bioelectricity from a
contaminated sediment while improving its geoenvironmental condition in
the laboratory experiment and to compare it through field experiment of
SMFCs.
2. METHODS AND MATERIALS
2.1 SAMPLE COLLECTION
Four samples were collected for this experiment from Yamaguchi bay at
depths of 0-20 cm from tidal flat and the river areas during the ebb
tide. A ponar dredge sediment sampler was used to collect the samples.
Sample 1, 2 and 3 were collected near the intertidal zone of Yamaguchi
bay (33.93 N, 131.22 E), Ube city. Sample 4 was collected from the river
near that tidal flat area (33.93 N, 131.22 E) to compare the marine
sediments SMFCs and the river sediment SMFCs. The samples were collected
middle of May, the average ambient temperature is around
250C. The geoenvironmental condition of the Yamaguchi
bay tidal flat area is not good due to the various human activities. The
smell of the sediment was unpleasant and there is very small signs of
benthos in the sediment. The AVS value is more than suitable range in
different parts of the Yamaguchi bay and hence caused the declination of
catch of shell and decrease of the horseshoe crab has been observed
(Moqsud et al., 2017). This is a serious ecological problem and the
researchers are trying to solve this problem.
Table 1 summerises the basic physico-chemical properties of the four
sediments. From the grain size analysis of the four sediments, it was
observed that all the three sea sediments showed the similar trend,
however, the river sediment showed a different trend and the particle
size is larger than the sea sediments. It was seen that the loss on
ignition (LOI) which is the indicator of organic content was relatively
lower in sea sediments (sample 1, 2, 3) 12% than in the river sediment
14% (sample 4). The AVS value was also higher in the case of marine
sediments (more than safe limit , 0.2 mg/g-dry mud). Anaerobic bacteria
(sulfate reducing bacteria) reliably to generate AVS by converting the
sulfate to sulfide and is one of the major indicators for the
geoenvironmental condition (Rickard & Morse, 2005). In this study, the
AVS value will be taken as a key indicator of the geo-environmental
condition improvement. According to the Japanese fisheries research
association, the safe value for AVS is 0.2 mg/g dry mud for the benthos
living in the mud.