energy. Hang et al. carried out a batch study on fruit and
vegetable methanization for a period of 10 to 28 days to
optimize the maximum CH 4 yield. FVW are a rich source of
several valuable ingredients, but the high salts and cations
contents may impede the digestion process. In addition, the
rich source of organic and nitrogen content in feedstocks
releases a high concentration of free ammonia that may
possibly be toxic to methanogens (Chen et al. 2008).
Co-digestion of waste containing less nitrogen and lipid
content is preferably used to manage these problems.
Alvarez and Lidén reported different compositions of FVW
under mesophilic anaerobic conditions for biogas production. The use of organic components for the processing of
biomethane enhances the cleaner environment and provides
a quality life in rural areas and diminishes the risk of water
contamination (Fidelis 2018).
2.3.4 Bioelectricity
Organic components in FVW can be converted into electricity using microorganisms. Microbial fuel cells (MFCs) are
effective electrochemical technologies for waste treatment by
supplying renewable energy. The key benefits of MFC for
wastewater treatment include the safe, clean, productive, and
direct production of electricity, along with the elimination of
organic wastewater components. The MFC consists of a
partition of anode and cathode chambers by an active proton
exchange membrane. Bacteria oxidized organic components
and release a number of electrons and protons. The electrons
are passed through the external circuit and protons move to
the proton exchange membrane. Mediator-less MFCs were
constructed for the bioconversion of orange peel to bioelectricity and up to 0.59 V can be produced under optimized
conditions (Miran et al. 2016). Jia et al. investigated the
production of bioelectricity from FVW using MFC. This
study revealed that the rate of FVW loading has a major
impact on MFC output (Jia et al. 2013). Microbial population
research confirmed that fermentative bacteroides and exoelectrogenic Geobacter are the leading species that promote
the transformation of organic FVW to bioelectricity. Rikame
et al. reported the production of electricity from acidic FVW
leachate with the aid of a dual chamber mediator MFC. The
maximum yield of the power density of 15 W/m3 was
observed under optimized conditions with an open circuit
voltage of 12 V, and 90% COD elimination was also
observed (Rikame et al. 2012). Goud et al. used
canteen-based FVW composite as a proper substrate for the
generation of bioelectricity using MFCs. The energy conversion rate was improved with an irregular loading due to
the efficient usage of the substrate (Goud et al. 2011).
2.4 Biocontrol Agents
Biocontrol agents help to preserve and balance plant species
together with their natural enemies. These are environmentally friendly, easy to use, effective throughout the season,
and do not cause any side effects. This helps reduce the use of
chemicals and other pesticides. Microbial biocontrol agents
can be developed and used in one of three ways, depending
on the type and number of applications needed. Strategies are
classified into a classical approach consisting of a single,
inoculative introduction; an incremental approach consisting
of regular releases; and an inundative or biopesticide strategy. The epidemiological, density-dependent relationship
between the biological control target and the biological
control agent can be used to identify and differentiate these
strategies (Charudattan 1999).
2.4.1 Biofertilizer
FVW can be easily composted with up to 6–22% nitrogen
recovery and utilized as a substitute for a large proportion of
nitrogen fertilizer. Plots fertilized with biocompost provide
considerable yields compared to chemical fertilizers.
Long-term applications of FVW compost will result in carbon accumulation at the topsoil and improve soil nitrogen
levels over the years. Sarkar et al. used two amylolytic and
three cellulolytic thermophilic bacteria (Geobacillus strains)
for the composting of vegetable waste. A major reduction in
the C/N ratio was recorded after 10 days of incubation.
Vermicompost is a rich source of beneficial microorganisms
and nutrients and is used as a soil conditioner or fertilizer.
This includes the bio-oxidation and stabilization of organic
matter by the collective activity of earthworms and
microorganisms under aerobic and mesophilic conditions.
Aerobic treatment can be successfully integrated with the
implementation of legislative measures and technical and
managerial support for the management of vegetable waste
(Wadhwa et al. 2015). The aerobic thermophilic treatment
has been suggested to turn sewage sludge, agricultural
waste, or FVW into biofertilizer. This process involves the
treatment of organic wastes under controlled aeration at 60 °
C with stirring at neutral pH. In order to preserve neutral pH
for bioconversion, 5% of the total organic waste was added
to CaCO 3 at the beginning. By adding artificial or natural
bulking agents, the bioconversion and stability of the final
products can be improved. The addition of starter bacterial
culture like Bacillus thermoamylovorans enhances the bioconversion of the sewage sludge, but there is no need of
starter culture for aerobic bioconversion of FVW to organic
fertilizer. The end products included stable organic matter,
188
R. Reshmy et al.
vegetable methanization for a period of 10 to 28 days to
optimize the maximum CH 4 yield. FVW are a rich source of
several valuable ingredients, but the high salts and cations
contents may impede the digestion process. In addition, the
rich source of organic and nitrogen content in feedstocks
releases a high concentration of free ammonia that may
possibly be toxic to methanogens (Chen et al. 2008).
Co-digestion of waste containing less nitrogen and lipid
content is preferably used to manage these problems.
Alvarez and Lidén reported different compositions of FVW
under mesophilic anaerobic conditions for biogas production. The use of organic components for the processing of
biomethane enhances the cleaner environment and provides
a quality life in rural areas and diminishes the risk of water
contamination (Fidelis 2018).
2.3.4 Bioelectricity
Organic components in FVW can be converted into electricity using microorganisms. Microbial fuel cells (MFCs) are
effective electrochemical technologies for waste treatment by
supplying renewable energy. The key benefits of MFC for
wastewater treatment include the safe, clean, productive, and
direct production of electricity, along with the elimination of
organic wastewater components. The MFC consists of a
partition of anode and cathode chambers by an active proton
exchange membrane. Bacteria oxidized organic components
and release a number of electrons and protons. The electrons
are passed through the external circuit and protons move to
the proton exchange membrane. Mediator-less MFCs were
constructed for the bioconversion of orange peel to bioelectricity and up to 0.59 V can be produced under optimized
conditions (Miran et al. 2016). Jia et al. investigated the
production of bioelectricity from FVW using MFC. This
study revealed that the rate of FVW loading has a major
impact on MFC output (Jia et al. 2013). Microbial population
research confirmed that fermentative bacteroides and exoelectrogenic Geobacter are the leading species that promote
the transformation of organic FVW to bioelectricity. Rikame
et al. reported the production of electricity from acidic FVW
leachate with the aid of a dual chamber mediator MFC. The
maximum yield of the power density of 15 W/m3 was
observed under optimized conditions with an open circuit
voltage of 12 V, and 90% COD elimination was also
observed (Rikame et al. 2012). Goud et al. used
canteen-based FVW composite as a proper substrate for the
generation of bioelectricity using MFCs. The energy conversion rate was improved with an irregular loading due to
the efficient usage of the substrate (Goud et al. 2011).
2.4 Biocontrol Agents
Biocontrol agents help to preserve and balance plant species
together with their natural enemies. These are environmentally friendly, easy to use, effective throughout the season,
and do not cause any side effects. This helps reduce the use of
chemicals and other pesticides. Microbial biocontrol agents
can be developed and used in one of three ways, depending
on the type and number of applications needed. Strategies are
classified into a classical approach consisting of a single,
inoculative introduction; an incremental approach consisting
of regular releases; and an inundative or biopesticide strategy. The epidemiological, density-dependent relationship
between the biological control target and the biological
control agent can be used to identify and differentiate these
strategies (Charudattan 1999).
2.4.1 Biofertilizer
FVW can be easily composted with up to 6–22% nitrogen
recovery and utilized as a substitute for a large proportion of
nitrogen fertilizer. Plots fertilized with biocompost provide
considerable yields compared to chemical fertilizers.
Long-term applications of FVW compost will result in carbon accumulation at the topsoil and improve soil nitrogen
levels over the years. Sarkar et al. used two amylolytic and
three cellulolytic thermophilic bacteria (Geobacillus strains)
for the composting of vegetable waste. A major reduction in
the C/N ratio was recorded after 10 days of incubation.
Vermicompost is a rich source of beneficial microorganisms
and nutrients and is used as a soil conditioner or fertilizer.
This includes the bio-oxidation and stabilization of organic
matter by the collective activity of earthworms and
microorganisms under aerobic and mesophilic conditions.
Aerobic treatment can be successfully integrated with the
implementation of legislative measures and technical and
managerial support for the management of vegetable waste
(Wadhwa et al. 2015). The aerobic thermophilic treatment
has been suggested to turn sewage sludge, agricultural
waste, or FVW into biofertilizer. This process involves the
treatment of organic wastes under controlled aeration at 60 °
C with stirring at neutral pH. In order to preserve neutral pH
for bioconversion, 5% of the total organic waste was added
to CaCO 3 at the beginning. By adding artificial or natural
bulking agents, the bioconversion and stability of the final
products can be improved. The addition of starter bacterial
culture like Bacillus thermoamylovorans enhances the bioconversion of the sewage sludge, but there is no need of
starter culture for aerobic bioconversion of FVW to organic
fertilizer. The end products included stable organic matter,
188
R. Reshmy et al.