Page 408 - Refining Biomass Residues for Sustainable Energy and Bioproducts

Agroindustry wastes: biofuels and biomaterials feedstocks for sustainable rural development 369

designing new products as well as food waste valorization. The characteristics of
the wastes that are commonly determined to judge the overall quality of the resi-
dues are listed in Table 16.5.
Fruit and vegetable wastes represent almost 20% 50% of total household
wastes. According to Raynal et al. (1998), the fruit and vegetable wastes are charac-
terized by 8% 18% total initial solid concentration and 87% volatile solids. The
organic compounds comprise 75% sugars and hemicellulose, 9% cellulose, and 5%
lignin. Fruit and vegetable wastes are mainly comprised proteins, fats, and carbohy-
drates, and the total moisture content varies between 80% and 90% (Grobe, 1994).
Fruit and vegetable wastewater is rich in antioxidant, pectin, fiber, carbohydrates,
minerals, food flavors and colorants. Generally, these wastes contain high value of
BOD, COD, and SS and are characterized by large variation in pH. Dairy whey is
another by-product having 30 50 g O 2 /L BOD and 60 80 g O 2 /L COD values.
The high value is contributed to the presence of lactose (4.5% 5% w/v) and solu-
ble protein (0.6% 0.8% w/v). The lack of affordable methods for the elimination
of COD in whey still forces milk-processing industries dump the by-product with-
out treatment, which causes a permanent hazard to environment (Rubio-Texeira,
2006). A significant amount of nutrients in the form of total nitrogen (14 830 mg/
L), phosphorous (9 280 mg/L) also present in dairy wastewater. The meat industry
in India has registered tremendous growth from 2.3 million tons in 11th five-year
plan to 7.0 million tons at the end of the 12th five-year plan. Approximately 55%
of the whole animal mass becomes the by-product. The meat industry possesses a
high risk to environment as the meat waste residue is a good substrate for harmful
microbial growth. The residues are rich in protein and can be used for biological
secondary treatments. Marine and seafood is another area where the by-products are
generated and are rich in components such as proteins, chitin, chitosan, and gelatin
(Ajila et al., 2011). The by-products of fish industries such as skin, bone, and fins
can be utilized as fish meal and fertilizer. Poultry processing requires 26.5 L of
water per bird for slaughter and other downstream operations. The poultry wastewa-
ter is rich in proteins, fats, and carbohydrates that are sourced from blood, skin, and
feather, and thus the wastewater has high BOD and COD values. Several studies
have been done on the biodegradability of wastewater using enzyme treatments.
Distillery wastewater known as stillage is the main by-product of distilleries.
The volume of stillage is B10 times that of the ethanol produced. The remaining
by-product after distillation of sugar-rich feedstock liquid, known as vinasse, is
characterized by high organic acid content and polyphenols. Due to this sugar-
based substrate, frequently the COD values exceed 100 g O 2 /L (Satyawali and
Balakrishnan, 2008). Due to low nutritive value, vinasse used as animal feed is lim-
ited; however, it has been used as fertilizer in some countries.

16.3 Utilization of the wastes

Although attempt has been made in many agrowaste industries to minimize genera-
tion of waste, it is inevitable that wastes are still generated. As discussed in the