8.1 Introduction
The continuing use of fossil fuels is responsible for many ecological concerns. This
necessitated a shift to focus from fossil fuels to more sustainable biofuels. Fossil
fuels are depleting and are responsible for environmental pollution. Moreover, about
88% of present-day energy requirements are being met by fossil fuels. As they are
depleting, research efforts are initiated for alternative fuels which are sustainable and
environment friendly (IEA 2015). Kothari et al. (2010) opined that biogas is best
suited for tropical climates as an environmental friendly and can aid in sustainable
development. It can be used for heart generation and electricity generation. It can
provide source of fuel to the rural population where there is less access to electric
power. It can be used as a substitute to firewood and charcoal. Anaerobic digestion is
a procedure where many diverse microbes transform organic waste to biogas. These
microorganisms can survive in anaerobic environments where the transformation of
organic matter to biofuel will take place. Wetlands generally are the most commonly
found areas where the presence of these microorganisms will be seen. Apart from
these freshwater sediments, digestive tracts of animals also host such environments
for the growth of the microorganism. This process is exploited for the production of
biogas using similar conditions where the necessary conditions for the growth of
anaerobic bacteria like pH, temperature, and anoxic conditions are maintained. A
part from this process is also used for the preparation of biofertilizers from agriculture and domestic waste. Anaerobic digestion is used for waste treatment and biogas
production (De Baere et al. 2010). It is a sequence of biological techniques that use a
different kind of bacteria to break down organic matter into biogas, mainly methane
and mixture of different gases (like carbon dioxide, hydrogen in anoxygenic conditions) (Antoni et al. 2007). A biogas unit consists of reception tank, digester, gas
holder, and an overflow tank. The improvement of reactor for anaerobic digestion
generation has undergone further advancements over the years. Ribas et al. (2009)
reported 70% COD elimination along with 70% methane content in biogas with the
aid of a mesophilic SBBR reactor while treating sugar cane-vinasse. Almeida et al.
(2017) studied configuration of different types of reactors. He observed that the
removal efficiency of COD increased by 97%. The effect of physicochemical
parameters on the biogas plant efficiency was also reported (Chen et al. 2017;
Hong and Haiyun 2010; Hussain et al. 2017; Liu et al. 2016). A thermophilic
digester functions at temperatures more than 50
C generating biogas. It has some
benefits such as that it does not need agitation and is quicker in fermentation than a
mesophilic digester. Vinasse produced at more than 70
C can be used for this kind
of biodigester. The main types of biogas production plants are fixed-dome plant and
floating-drum plants. In fixed dome type, the digester is fixed with a gas holder. The
costs incurred in operation are quite low, and the life span of these kinds of digesters
is generally about 20 years.
In conventional systems the major limitations are high space requirement, low
OLR/high HRT, low treatment efficiency, and biomass washout. Anaerobic digestion can be classified into two types, namely, wet digestion and dry digestion based
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R. Kumar et al.
The continuing use of fossil fuels is responsible for many ecological concerns. This
necessitated a shift to focus from fossil fuels to more sustainable biofuels. Fossil
fuels are depleting and are responsible for environmental pollution. Moreover, about
88% of present-day energy requirements are being met by fossil fuels. As they are
depleting, research efforts are initiated for alternative fuels which are sustainable and
environment friendly (IEA 2015). Kothari et al. (2010) opined that biogas is best
suited for tropical climates as an environmental friendly and can aid in sustainable
development. It can be used for heart generation and electricity generation. It can
provide source of fuel to the rural population where there is less access to electric
power. It can be used as a substitute to firewood and charcoal. Anaerobic digestion is
a procedure where many diverse microbes transform organic waste to biogas. These
microorganisms can survive in anaerobic environments where the transformation of
organic matter to biofuel will take place. Wetlands generally are the most commonly
found areas where the presence of these microorganisms will be seen. Apart from
these freshwater sediments, digestive tracts of animals also host such environments
for the growth of the microorganism. This process is exploited for the production of
biogas using similar conditions where the necessary conditions for the growth of
anaerobic bacteria like pH, temperature, and anoxic conditions are maintained. A
part from this process is also used for the preparation of biofertilizers from agriculture and domestic waste. Anaerobic digestion is used for waste treatment and biogas
production (De Baere et al. 2010). It is a sequence of biological techniques that use a
different kind of bacteria to break down organic matter into biogas, mainly methane
and mixture of different gases (like carbon dioxide, hydrogen in anoxygenic conditions) (Antoni et al. 2007). A biogas unit consists of reception tank, digester, gas
holder, and an overflow tank. The improvement of reactor for anaerobic digestion
generation has undergone further advancements over the years. Ribas et al. (2009)
reported 70% COD elimination along with 70% methane content in biogas with the
aid of a mesophilic SBBR reactor while treating sugar cane-vinasse. Almeida et al.
(2017) studied configuration of different types of reactors. He observed that the
removal efficiency of COD increased by 97%. The effect of physicochemical
parameters on the biogas plant efficiency was also reported (Chen et al. 2017;
Hong and Haiyun 2010; Hussain et al. 2017; Liu et al. 2016). A thermophilic
digester functions at temperatures more than 50
C generating biogas. It has some
benefits such as that it does not need agitation and is quicker in fermentation than a
mesophilic digester. Vinasse produced at more than 70
C can be used for this kind
of biodigester. The main types of biogas production plants are fixed-dome plant and
floating-drum plants. In fixed dome type, the digester is fixed with a gas holder. The
costs incurred in operation are quite low, and the life span of these kinds of digesters
is generally about 20 years.
In conventional systems the major limitations are high space requirement, low
OLR/high HRT, low treatment efficiency, and biomass washout. Anaerobic digestion can be classified into two types, namely, wet digestion and dry digestion based
226
R. Kumar et al.