The document provides an overview of plant-based biofuels, emphasizing the potential of ethanol and biodiesel as renewable energy sources derived from crops like corn and sugarcane. It highlights production challenges, including high costs and competition with fossil fuels, while detailing current advancements in enzyme technology for biofuel production from lignocellulosic biomass. Additionally, it discusses India's biodiesel initiatives focusing on the jatropha plant and the potential for utilizing sweet sorghum for ethanol due to its drought resilience and cost advantages.

1. Plant Based Biofuel-Overview
DR.SREEREMYA
FACULTY IN BIOLOGY SCIENCE

2. • The source of energy captured by plants is the sun, which will be the
constant source of energy for the next few billion years. The carbon
released from the burning of biofuels is continually cycled rather than
being released from the ancient fixed carbon sources, as is the case for
fossil petroleum and natural gas. The problem is that the cost of the
production of fuels from lignocellulose and plant oils is high and this
nascent industry cannot compete with the oil prices. Current progress: For
the past two decades, ethanol has been synthesized primarily from
cornstarch and cane sugar. Fourteen billion gallons of ethanol were
synthesized in the USA from cornstarch in 2014. Approximately 40% of the
current USA corn crop is availed to produce ethanol and is not likely to
expand anymore, because the remainder of the crop is being availed for
animal feed and human food. Ethanol is produced from cane sugar in
Brazil at a level of 7.2 billion gallons in the year 2014. The renewable
energy source is the major terrain to be considered (Sreeremya, 2019).

3. • Together, Brazil and the USA produce more than 90% of the world’s supply of
ethanol. Biodiesel is a renewable fuel that has received considerable attention
recently because it is also non-polluting. It is carbon-neutral because the carbon
present in vehicle exhaust was recently fixed from the atmospheric carbon
(Kavalov, 2004). Biodiesel can be manufactured from numerous oils and fats
including virgin vegetable oils, such as canola, soybean, and camelina, from the
waste cooking oils, or from animal fats, such as the tallow or lard (Kaltschmitt et
al., 1997).
• Deconstruction and fuel production: A number of varying pretreatment regimes
have been explored in detail to be availed with various enzyme systems. Ammonia
fiber expansion (90–120°C; 250–400 psi) is highly effective on the grasses such as
corn stover and switchgrass but does not produce a lignin fraction that can be
availed for co-product manufacture. Lignin is desirable because its monomers can
be availed as a raw material for many more complex chemicals. Because the
ammonia can be much quantitatively recovered, it is relatively cost-effective.
Alkaline hydrogen peroxide is aviled in pulp-bleaching and is an effective
delignification agent (Kiel, 1994).

4. • However, the high concentration of the hydrogen peroxide made this
method cost-prohibitive. The addition of the small amount of copper ions
significantly improves the lignin extraction, thus making it highly effective
for the woody biomass pretreatment. These treatments usually are
followed by the treatment with enzyme mixtures to deconstruct the
cellulose and the hemicellulose from the cell walls, producing sugars for
fermentation, though in order for the enzymes to mainly function, the
biomass alkalinity must be neutralized, adding further cost to the
processing and also generating additional wastes (Kaltner et al., 2005).
• A promising new solvent for treating the biomass is γ-valerolactone or
GVL. It is derived from the biomass itself and appears to mainly pretreat
any type of biomass yielding sugar, lignin, and mineral salt streams that
can be mainly separated from the reaction mix. Ionic liquids (ILs) offer the
pretreatment strategy that has many advantages, including significant
enhancement in the rate of the enzyme hydrolysis of the cellulose
component of switchgrass

5. • Pretreated biomass is generally deconstructed with the enzymes,
whether these are mixtures isolated from fungal cultures, the
multifunctional enzymes isolated from microorganisms, or mixtures
isolated from the live bioprocessing organisms growing on the
biomass. To use enzymes cost-effectively for the biomass
conversion prior to fermentation, it is estimated that the enzymes'
cost should be approximately $0.10 per gallon of the ethanol. For
the past 15 years, intense research on enzyme production platforms
has yielded the fungal enzyme mixtures that do not meet these cost
requirements and, in fact, also require the huge infrastructure for
the production. Current research efforts are in the multifunctional
enzymes and combined bioprocessing organisms, the latter of
which can decompose the plant polymers as well as ferment them
into biofuels (Han et al., 2014).
• India has a very much rich biomass resource, which can be
converted into renewable energy.

6. • The Planning Commission of the government of India has launched quite an
ambitious National Mission on biodiesel to be implemented by the number of
government agencies and coordinated by the Ministry of Rural Development. The
mission focuses on the cultivation of the physic nut, the Jatropha curcas, and a
shrubby plant of the castor family. The seed contains 30 to 42% oil and can be
mixed with diesel after the transesterification (Luterbacher et al.,2015).
BIOETHANOL Ethanol is an alcohol-based fuel generated by fermenting plant
sugars. It can be made from many agricultural products and the food wastes if they
contain sugar, starch, or cellulose, which can then be mainly fermented and
distilled into ethanol. The technology for producing ethanol, at least from the
certain feedstocks, is generally well established (Bond et al., 2010) PLANT-BASED
BIOFUELS
• Ethanol is currently generated in many countries around the world, but current
efforts are underway mainly to mainly develop methods for producing ethanol
from lignocellulosic biomass, encompassing forest trimmings and agricultural
residues (cellulosic ethanol). Ethanol is generated mainly from sugar, as it is the
cheapest means. In Brazil, which is the largest ethanol producer, ethanol is
generated from sugarcane.

7. • India is one of the largest producers as well as the consumers of sugar;
hence, it is not envisaged to use sugarcane for the production of the
ethanol, at least in the near future. In India, molasses are the major raw
material for ethanol production, but it cannot fulfill the demand when
used for the automotive sector. Sweet sorghum competes with the
sugarcane for ethanol production. Sweet sorghum possesses some
advantages over sugarcane as it can be grown in very much dry condition,
requiring one-seventh the amount of the water required by sugarcane.
Though the feedstock's ethanol yield per unit weight is less, the lower
production cost from sweet sorghum compensates for the loss. Sweet
sorghum has a competitive cost advantage. The production cost of ethanol
from sweet sorghum and the sugarcane is about US$0.29 and 0.33 per
liter, respectively. Currently, efforts are being made to generate ethanol
from various agricultural products, encompassing trees, grasses, and
forestry residues, which are of considerable interest, as the lignocellulosic
materials are being mainly seen as the only foreseeable source of energy.

8. • The U.S. Departments of Energy (DOE) and Agriculture (USDA)
project that the more cellulosic ethanol will ultimately be produced
than corn ethanol because biocellulosic ethanol can be produced
from a variety of feedstocks, but more fundamental reductions in
the generation costs will be needed to make cellulosic ethanol
commercially viable (Garlock et al.,2012). The production of the
ethanol from cellulosic feedstocks is currently more costly than the
production of the corn ethanol because the cellulosic material must
first be broken down into the fermentable sugars that can be
converted into ethanol (Li et al., 2013). The production costs allied
with this additional processing would have to be reduced to make
the cellulosic ethanol cost-competitive with gasoline at today’s
prices. However, corn and the cellulosic ethanol are more corrosive
than gasoline. The widespread commercialization of these fuels
would typically require substantial retrofitting of the refueling
infrastructure—pipelines, the storage tanks, and the filling stations.