Page 400 - Refining Biomass Residues for Sustainable Energy and Bioproducts

Agroindustry wastes: biofuels and biomaterials feedstocks for sustainable rural development 363

residues such as bagasse, leaves, husk, stalk, stem, peel, hull, stem, pulp, shells, and
stubbles are good feedstocks for agroindustries (Oyeleke and Jibrin, 2009). Forest
residues such as leaves, branches, old stands, pulp and timbers are also used for the
energy production. Wood wastes generated in wood processing industries such as
sawmill, plywood, and furniture factories are good feedsock for agroindustries mak-
ing biochar and wood chips (Clark, 2007). Growing willow and poplar as short rota-
tion coppice with 2 5 years cycle can be another sustainable option of feedstocks
for the bioethanol industry (Rae et al., 2004).
Microalgae (both sea and freshwater), cyanobacteria, and aquatic plants are
another group of feedstocks used in agroindustries. Wider adaptability, higher bio-
mass, and oil yield offer more advantage to use this feedstock in agroindustries.
Furthermore, lesser competition with agricultural land provides sustainability to
them as the feedstocks for third-generation biofuel, including jet fuel, ethanol, and
biodiesel (Naik et al., 2010).
Feedstocks used in agroindustries are of different characteristics. Collection,
transportation, and handling of such biomass are a challenge. Existing controversy
regarding the use of food crops as feedstocks and deterioration of soil health due
to growing of energy crops urges the importance of agricultural residues and
microalgae as feedstocks. Moreover, to obtain maximum yield of these feedstocks,
appropriate technologies have to be developed.

16.2.1 Products and wastes produced in agroindustries
Agroindustrial wastes have drawn attention of research community recently because
of their high nutritional compositions. Food and agroindustries are on the rise to
cater to the need of growing population in the World. These industries generate
waste residues in huge volume, and it has been a matter of concern for environmen-
tal pollution. Since wastes generated from different industries have different charac-
teristics and have wide array of use, a classification of these residues will give a
clear understanding. One of the categorizations in terms of the source of residue
generation is presented in Fig. 16.1. Agroindustrial wastes are broadly classified as
agricultural residues and industrial residues. Agricultural resides are further catego-
rized into field residues and process residues. Field residues are those which are left
behind in the field after harvesting of crops. These are mostly the stems, stalks, dry
leaves, and seed pods of the crops. The field residue volume is so large that unless
managed properly, they cause environmental impact and problems for next
cropping practices.
The crops after processing to valuable resources are also left behind some resi-
dues, generally termed as process residue. For instance, in the process of making
rice from paddy, husk comes out as residue. Other process residues include seeds,
roots, bagasses, and molasses. These residues are extensively used as animal feed,
soil improvement, fertilizer manufacturing, and other processes (Sadh et al., 2018a).
Food industry is another sector that generates huge amount of organic residues
and related effluents. These organic residues can be harvested from different food
processing industries such as juice, meat, confectionery, dairy, and brewery. The