Page 376 - Refining Biomass Residues for Sustainable Energy and Bioproducts

340 Refining Biomass Residues for Sustainable Energy and Bioproducts

come from wheat, rice, and oilseeds crop. These bulks of agricultural wastes are
not only a trouble for collection and management but it also hampers the environ-
ment and health of the people. The major techniques followed by farmers today are
open dumping, burning of agro-wastes in open atmosphere in the field or in land
filling. Although methods adopted by farmers are cheap and easy, it leads to various
negative impacts on the agro-system as well as to the environmental climatic condi-
tions. It produces lots of smoke that cause air pollution, particulate matter, smog,
and disturbs soil physical, chemical, and biological structure including microbial
population and also releases greenhouse gases that lead to global warming
(Srivastava et al., 2015). It is the peak time to think on the situation and necessary
action to be taken for a better environment. In the present situation, India has
500 Mt of biomass production capacity of which 17,500 MW power can be
obtained (Kumar et al., 2015). The government is also promoting setting up of gasi-
fication plants for the generation of electricity.

15.3 Characteristics of agricultural wastes

The entire pathway (transportation and handling, pretreatment, conversion route,
and enrichment of products) for the utilization of biomass as renewable energy
source depends upon its type and physicochemical properties. These physical and
chemical properties play a vital role for the design and development of different
processes that convert the biomass to biofuel. The properties of the biomass vary
depending upon the location, climatic condition, inherent composition, etc., the dif-
ferent physical and chemical characteristics of agricultural wastes are summarized
in the following subsections.

15.3.1 Physical properties
Agricultural wastes are mostly the lignocellulosic biomass and their properties
include particle size, density (particle and bulk), grindability, and flowability.
Particle size—Biomass particles are of irregular shapes and nonuniform size (needle
shape, round, leaves shape, etc.) with different surface areas and it affects the feeding
rate, mixing and fluidizing conditions, heat and mass transfer behaviors, and also the stor-
age conditions. Variation in shape and size affects the conversion efficiency and energy
requirement. Aspect ratio (length/diameter) is a parameter that describes the particle size.
When a finely granulated particle converges to a spherical shape, aspect ratio reaches 1
(Shastri et al., 2014). Sieve shaker and digital imaging particle analysis are two known
methods for the characterization of particle size. Thus biomass should be comminuted to
convert the particle from as-received condition to desirable sizes for the user.
3
Density—Density is defined as mass of the substance divided by its volume (kg/m ). In
the field of bioenergy, two types of densities are considered. (1) Particle density and (2)
bulk density. The density of the biomass depends upon various parameters, such as mois-
ture content, shape and size of particle, and surface properties.