high pectin, cellulose, and hemicellulose are used as an
appropriate fermentation substrate. Among the various
wastes used for bioethanol processing, potato peels, apple
pomace and apple waste, banana peel and banana waste, beet
and beet pomace waste, kinnow mandarin (Citrus reticulata)
waste, and peach and peach waste have shown promising
results. Pineapple pulp contains large quantities of sucrose,
starch, and hemicellulose. These can also be used for the
production of bioethanol. Production of bioethanol
from pineapple, orange, and sweet lime fruit peels and
powdered avocado seed waste has also been reported. Shilpa
et al. reported that bioethanol yields for pineapple, banana,
orange, and pea peels were 8.34, 7.45, 3.98, and 2.58% after
seven days of fermentation. Among the four extracts of peel,
the highest bioethanol production was obtained from papaya
peel extract followed by banana and apple peel extracts
(5.90–4.94%) and the lowest yield was from turnip peel
extract (1.5%). On average, 20% of crop is grown, which
can be used for the production of bioethanol. Approximately
174 kg/ha or 220 l/ha of ethanol will be extracted from these
ground watermelons. Peach waste is used for the production
of brandy; 6 L of brandy with 43% alcohol can be obtained
from 100 kg of peach waste. Date extract was used as a
substrate for the production of ethanol using the brand
S. cerevisiae ATCC 36858 and S. cerevisiae STAR from
date waste using S. cerevisiae. Spoiled date fruit was used as
a substrate for methanol production using Clostridium acetobutylicum ATCC824 and B. subtilis DSM 4451 (Wadhwa
et al. 2015). The disposal of potato peel waste is a major
challenge in the vegetable processing sector and that also can
be utilized for the economical and environmental friendly
production of bioplastics (Devi et al. 2015).
Sugarcane bagasse was utilized for bioethanol production
via simultaneous saccharification followed by fermentation.
Bioethanol from the cultivation waste of cassava has been
reported by several researchers. It is significant to convert
complex carbohydrates into fermentable sugars before fermentation for the production of bioethanol from cassava
bagasse. Padmaja has demonstrated various pretreatment
methods followed by the use of a cellulolytic enzyme
complex to effectively break down complex carbohydrate
molecules of cassava waste to reduce sugars. Hydrothermal
treatments followed by microwave-assisted dilute acid
treatments were reported as an effective processing method
for breaking down the carbohydrate molecules. The alcohol
dehydrogenase gene acts primarily during the conversion of
acetaldehyde to ethanol in S. cerevisiae. Zhang et al. showed
a minimum energy consumption method for the extraction of
ethanol from uncooked fresh sweet potatoes. The enzymatic
fermentation of sweet potato produced about 14.4 g of
ethanol from 100 g of fresh roots (Zhang et al. 2013; Panda
et al. 2017).
2.3.2 Biodiesel
Biodiesel is a less volatile fatty acid that consist of
long-chain mono-alkyl esters linkages. In order to avoid
freezing at a very low temperature, B20 blending process is
used. Lee et al. developed a rapid synthesis of biodiesel
from pepper seed waste. The study found that the majority of
the lipids can be easily turned into biodiesel. Thushari and
Babel examined the use of waste palm oil and sulphonated
carbon acid catalysts extracted from coconut meal residues
for the production of biodiesel. Only a low-cost catalyst has
been used for the processing of biodiesel. The biodiesel
output from waste palm oil residues in the open reflux catalytic system is 92.7%. The fuel characteristics have been
concluded to be compatible for high scale production. In this
process, the catalyst used was very stable and was reusable
and recyclable for four more cycles. Hu et al. developed a
novel and effective technique for biodiesel production from
waste oils with high acid value using an ionic liquid catalyst
sulfobutylmethylimidazolium. Numerous process parameters namely reaction time, temperature, catalyst concentration and cycle of use, the molar ratio of conversion, etc. will
influence the production of biodiesel. Rattanapoltee and
Kaewkannetra reported biodiesel production from pineapple
peel and sugarcane bagasse as low-cost agricultural residues
for lipid accumulation. The study concluded that there would
be a 2.13-fold rise in lipid content during the sugarcane
bagasse bioconversion which reduces the cost of production.
So, agricultural wastes such as sugarcane bagasse are ideal
for the production of high-end biodiesel (Sindhu et al. 2019).
2.3.3 Biogas
This natural gas is a combination of carbon monoxide,
methane, hydrogen sulfide, and siloxane. It is formed by the
anaerobic digestion of the various wastes. When these gases
are oxidized, they can release energy and will work as fuels
(Panda et al. 2017). FVW are a significant problem, and
theiranaerobic processing for the production of biogas is an
emerging field of research. Deepanraj et al. examined that
the pretreatment of substrates had significant effects on the
production of biogas from FVW. Various pretreatments such
as autoclave, microwave, and ultrasound of waste have been
performed, and anaerobic digestion with compost has been
performed. Ultrasound pretreatment is used to maximize the
biogas production. Wu et al. reported an advanced method
for the manufacturing of biogas from FVW by co-digestion
with deoiled fat trap waste. The research was performed in a
variety of digesters such as mesophilic digester, anaerobic
temperature-phase digester, and anaerobic temperaturephase digester with recycling (Wu et al. 2015).
Among the sources of energy for the production of biogas, FVW are the most relevant because of their abundance
and heterogeneous compositions having high contents of
Potential Utilisation of Fruit and Vegetable Waste: An Overview
187
appropriate fermentation substrate. Among the various
wastes used for bioethanol processing, potato peels, apple
pomace and apple waste, banana peel and banana waste, beet
and beet pomace waste, kinnow mandarin (Citrus reticulata)
waste, and peach and peach waste have shown promising
results. Pineapple pulp contains large quantities of sucrose,
starch, and hemicellulose. These can also be used for the
production of bioethanol. Production of bioethanol
from pineapple, orange, and sweet lime fruit peels and
powdered avocado seed waste has also been reported. Shilpa
et al. reported that bioethanol yields for pineapple, banana,
orange, and pea peels were 8.34, 7.45, 3.98, and 2.58% after
seven days of fermentation. Among the four extracts of peel,
the highest bioethanol production was obtained from papaya
peel extract followed by banana and apple peel extracts
(5.90–4.94%) and the lowest yield was from turnip peel
extract (1.5%). On average, 20% of crop is grown, which
can be used for the production of bioethanol. Approximately
174 kg/ha or 220 l/ha of ethanol will be extracted from these
ground watermelons. Peach waste is used for the production
of brandy; 6 L of brandy with 43% alcohol can be obtained
from 100 kg of peach waste. Date extract was used as a
substrate for the production of ethanol using the brand
S. cerevisiae ATCC 36858 and S. cerevisiae STAR from
date waste using S. cerevisiae. Spoiled date fruit was used as
a substrate for methanol production using Clostridium acetobutylicum ATCC824 and B. subtilis DSM 4451 (Wadhwa
et al. 2015). The disposal of potato peel waste is a major
challenge in the vegetable processing sector and that also can
be utilized for the economical and environmental friendly
production of bioplastics (Devi et al. 2015).
Sugarcane bagasse was utilized for bioethanol production
via simultaneous saccharification followed by fermentation.
Bioethanol from the cultivation waste of cassava has been
reported by several researchers. It is significant to convert
complex carbohydrates into fermentable sugars before fermentation for the production of bioethanol from cassava
bagasse. Padmaja has demonstrated various pretreatment
methods followed by the use of a cellulolytic enzyme
complex to effectively break down complex carbohydrate
molecules of cassava waste to reduce sugars. Hydrothermal
treatments followed by microwave-assisted dilute acid
treatments were reported as an effective processing method
for breaking down the carbohydrate molecules. The alcohol
dehydrogenase gene acts primarily during the conversion of
acetaldehyde to ethanol in S. cerevisiae. Zhang et al. showed
a minimum energy consumption method for the extraction of
ethanol from uncooked fresh sweet potatoes. The enzymatic
fermentation of sweet potato produced about 14.4 g of
ethanol from 100 g of fresh roots (Zhang et al. 2013; Panda
et al. 2017).
2.3.2 Biodiesel
Biodiesel is a less volatile fatty acid that consist of
long-chain mono-alkyl esters linkages. In order to avoid
freezing at a very low temperature, B20 blending process is
used. Lee et al. developed a rapid synthesis of biodiesel
from pepper seed waste. The study found that the majority of
the lipids can be easily turned into biodiesel. Thushari and
Babel examined the use of waste palm oil and sulphonated
carbon acid catalysts extracted from coconut meal residues
for the production of biodiesel. Only a low-cost catalyst has
been used for the processing of biodiesel. The biodiesel
output from waste palm oil residues in the open reflux catalytic system is 92.7%. The fuel characteristics have been
concluded to be compatible for high scale production. In this
process, the catalyst used was very stable and was reusable
and recyclable for four more cycles. Hu et al. developed a
novel and effective technique for biodiesel production from
waste oils with high acid value using an ionic liquid catalyst
sulfobutylmethylimidazolium. Numerous process parameters namely reaction time, temperature, catalyst concentration and cycle of use, the molar ratio of conversion, etc. will
influence the production of biodiesel. Rattanapoltee and
Kaewkannetra reported biodiesel production from pineapple
peel and sugarcane bagasse as low-cost agricultural residues
for lipid accumulation. The study concluded that there would
be a 2.13-fold rise in lipid content during the sugarcane
bagasse bioconversion which reduces the cost of production.
So, agricultural wastes such as sugarcane bagasse are ideal
for the production of high-end biodiesel (Sindhu et al. 2019).
2.3.3 Biogas
This natural gas is a combination of carbon monoxide,
methane, hydrogen sulfide, and siloxane. It is formed by the
anaerobic digestion of the various wastes. When these gases
are oxidized, they can release energy and will work as fuels
(Panda et al. 2017). FVW are a significant problem, and
theiranaerobic processing for the production of biogas is an
emerging field of research. Deepanraj et al. examined that
the pretreatment of substrates had significant effects on the
production of biogas from FVW. Various pretreatments such
as autoclave, microwave, and ultrasound of waste have been
performed, and anaerobic digestion with compost has been
performed. Ultrasound pretreatment is used to maximize the
biogas production. Wu et al. reported an advanced method
for the manufacturing of biogas from FVW by co-digestion
with deoiled fat trap waste. The research was performed in a
variety of digesters such as mesophilic digester, anaerobic
temperature-phase digester, and anaerobic temperaturephase digester with recycling (Wu et al. 2015).
Among the sources of energy for the production of biogas, FVW are the most relevant because of their abundance
and heterogeneous compositions having high contents of
Potential Utilisation of Fruit and Vegetable Waste: An Overview
187