Page 312 - Refining Biomass Residues for Sustainable Energy and Bioproducts

Potentials of postharvest rice crop residues as a source of biofuel 281

benzene (Chandra and Sinha, 2016; Duarte-Davidson et al., 2001). It also further
leads to reduced red blood cell count in humans, thus deteriorating the oxygen car-
rying capacity of the blood. Animals are also severely affected. Animals have been
found to suffer from corneal irritation and temporary blindness and chronic bronchi-
tis. Pollution of the atmosphere due to rice crop residue burning is also responsible
for decreased milk yield in animals. A higher exposure level even sometimes leads
to the death of animals. The reason behind the deaths may be attributed to the trans-
formation of hemoglobin to carboxyhemoglobin due to higher concentration of car-
bon dioxide and carbon monoxide in the animal’s blood (Dikshit and Singh, 2010).
Crop friendly pests, essential microorganisms, and certain animals such as snakes,
frogs, earthworms residing in the soil thus lose their lives due to the mass burning
process (Kumar et al., 2015; Kaur and Rani, 2016). Plants are also greatly affected
due to the open burning of rice residues in situ. Small and average-sized plants near
the rice fields are also destroyed due to the burning process. Depletion in the num-
ber of plant species growing in such area contributes toward the loss of biodiversity
of that particular area (Mehta et al., 2013).
The rice crop residues are of high economic value; however, their improper dis-
posal via conventional methods leads to various environmental and health compli-
cations. Alternatives for burning of rice crop residues must be given priority at the
present scenario. Instead of wasting the residues by simply burning them off, efforts
should be taken toward production of biofuels such as biogas and ethanol from the
large masses of rice crop residues produced in a year during the postharvest period.
The efficient and green production of biofuels from rice residues may reduce the
dependency of humans on fossil fuels. This may further provide an efficient solu-
tion to the problem of fuel scarcity that the earth’s population is deemed to face in
the decades to come.

13.4 Transformation of postharvest rice crop residues
to biofuel

Biofuel production from renewable resources, mostly agricultural wastes, has been
an important topic of interest. Wood and agricultural crop residues that contain lig-
nocellulosic biomass are considered as a potential raw material for production of
bioethanol and biodiesel (Kaparaju et al., 2009). Biofuels produced from these raw
materials are a promising replacement for the fossil fuels that play a major role in
environmental pollution. Rice straw is one of the postharvest residue of the rice
crop and is an important renewable bioresource for the production of biofuels. It is
suggested that around 205 billion liter of ethanol per year can be produced globally
from rice straw accounting for approximately 5% of the total world’s consumption.
Rice straws contain carbohydrates in the form of glucose, xylose, arabinose, man-
nose, and galactose (Roberto et al., 2003; Yoswathana et al., 2010). Fig. 13.4 shows
the distribution of various carbohydrates present in the rice straws.