Management of waste from different agricultural sources is a demand of the time, as without treatment, disposal of waste creates a lot of problems to the environment (Brunner and Rechberger, 2016). Waste from agriculture is disposed of in an unscientific manner in most of the countries of the world (Taiwo, 2011). It is important to consider the produced waste as a rich nutrient resource than only the impact of fertilizer can be minimized. OW by composting can be converted into manure, and using as manure in the field has positive effects on the soil as well as crop health (Jack and Thies, 2006). Improper disposal of agricultural waste can cause air (odor formation), water (eutrophication), and soil (decrease in microbial poll) pollution. Improper disposal also increases the incidence of diseases as waste becomes the nutrient source for various pathogens, which can cause several problems in living organisms. The demand for food is increasing with the rising population, which leads to a huge gap between production and demand as agricultural land is shrinking day-by-day (Nath et al., 2015). Thus it is important to recover nutrients from the waste material in order to sustain the growing nutrient demand. Recycling of the OW and using processed waste as a nutrient source is a viable and economical option to overcome the rising nutrient gap (Chew et al., 2019). It is important to devise a holistic approach in which all OW types can be managed in the proper way.
The effective method of converting agricultural waste into a nutrient-rich product is vennicomposting (Suthar, 2009). In vennicomposting, earthworms are used to decompose waste material from kitchens, food-processing units, agricultural fields into a form that can be easily used in the field as a potent nutrient source (Sharma et al., 2005). Earthworm species like Eisenia foetida, Eudrilus eugeniae, Perionyx excavates, and Decogester bolani are mostly used in India because of easy handling, short life span, the capability to tlnive in extreme weather conditions, high multiplication rate, as well as cost-effective (Dominguez, 2018). Vennicomposting is one of the easy methods available for the conversion of waste into a useful product (Shukla, 2018). Agriculture waste rich in organic material can be used efficiently in order to avoid wastage of useful nutrients from the crop residue (Cerda et al., 2018).
ADSORBENTS IN THE ELIMINATION OF HEAVY METALS
Industrialization and urbanization have resulted in an increase in the release of several heavy metals into the environment (Singh et al., 2011). Heavy metals are toxic as cannot be degraded into non-toxic forms, thus have a significant impact on flora and fauna living in the heavy metal contaminated environment (Duruibe et al., 2007). Currently, adsorption is used to remove heavy metals from the contaminated environment (Lakherwal, 2014). By using adsorption, different waste of agricultural origin can be used as an effective adsorbent for heavy metal removal from the contaminated ecosystem (Demirbas, 2008). Agriculture waste like sugarcane bagasse, horticulture waste, rice husk, sawdust has proven to be low-cost adsorbent of heavy metals and can remove heavy metals in an effective way (Saka et al., 2012).
Animal manure can be used as a nutrient source in the field that significantly helps to improve soil health (Timsina, 2018). Manure is not only the source of macronutrients (nitrogen, phosphorus, potassium) but also micronutrients, thereby help in maintaining the fertility of the soil in a cost-effective maimer. Manure application to the soil increases nutrient and moisture content of the soil as well as improves the health of the soil (Wang et al., 2016). Processed waste can be used as a soil amendment (composts, biosolids) and is known to increase the organic matter as well as the nutrient status of the soil (Cooper- band, 2002). The amount of nutrients contributed to the soil by amendment is totally dependent upon the composition of amendments. Waste material as soil amendments has tremendous advantages as waste material has good nutrient content and also can be used for reclamation projects (Sydnor and Redente, 2002). Using waste as soil amendments will reduce the burden of OW accumulation and also improves the soil health by retaining moisture and elevation of nutrient content (Fidelis and Rao, 2017). AW acts as a soil amendment (Parr and Homick, 1992).
Manure can be easily used for the production of methane gas in an economical way (Moller et al., 2004). Methane gas produced can be used as fuel for heating purposes. Methane production from manure occurs in anaerobic conditions in which waste is first converted into organic acids, and then methanogen uses organic acids and leads to the formation of methane gas (Li et al., 2011). Anaerobic digestion (AD) of waste is essential for the large-scale disposal of poultry, swine, and daily waste (Sakar et al., 2009). AD results in odor reduction, waste stabilization, and also retain the nutrient value of processed waste (Wilkie, 2005a, b). The different technologies for the degradation of organic waste for sustainable development are depicted in Figure 1.2.
FIGURE 1.2 Environmental sound technology for sustainable management of agricultural wastes.
Agro-industrial waste can be used to produce biofuel, thus providing alternative fuel sources compared to fossil fuel (Leiva-Candia et al., 2014). With the increasing burden on fossil fuels, biofuel production as an alternative energy source is also increasing to overcome dependence on fossil fuels. The utilization of agricultural waste as a substrate for biofuel can be economical as dependence on forest for biomass can be easily reduced (Mohammed et al., 2018). Crops are cultivated in less time and waste are also produced in large amount, thus increasing OW’s availability as a substrate for biofuel production (Lee et al., 2019). Vegetable waste is also an effective OW for biofuel production by fermentation technique using Saccharomyces cere- visioe (Hossain et al., 2017). In order to reduce the enormous quantity of OW generation, biofuel is produced from agricultural waste and can help to conserve the environment by increasing the production of eco-friendly fuel (Chandra et al., 2012). Weeds are also produced in large quantities and the crops and have shown biofuel producing potential, thus becoming the potent substrate due to fast growth and short life cycle (Chandel and Singh, 2011). The soil’s fertility and health are deteriorating at an alarming rate, but OW can help overcome these issues and enhance soil properties in an eco-friendly way.
Waste from agriculture industries is disposed in an unscientific manner in most of the countries of the world. Inadequate management of this waste put tremendous pressure on the quality of the environment (air, water, and soil). Furthermore, OW increases the incidence of diseases as waste becomes the nutrient source for various disease-spreading microbes. Thus, it is important to manage and recover essential constituents from AWs in a sustainable maimer. Therefore, it is important to devise holistic approaches in which all the types of OW can be managed in an adequate maimer. Recycling the OW and using processed waste as a nutrient source is a viable and economical option to overcome the rising nutrient gap.