Mulching protects plants from extreme heat, cold, and water stress. As water and nutrient availability in dryland crops and agricultural areas is influenced by the quantity of rainfall and soil water holding capacity. Thus, to improves agricultural productivity in these areas, different CR are used as mulch to protect crop plants to secure nutrients, water, and temperature of the soil. Different materials used as mulch are CR, like rice, wheat, maize, and sugarcane. Mulching proves best in terms of improving crop production, improved biomass production, and water use efficiency with high profit and the best-harvested monetary benefits. Therefore, crop residue mulching may be practiced using AW as effective means for protecting soil deterioration, improving soil water holding capacity in soils, sustaining agricultural productivity (Thu et al., 2016). Mulching is also considered a soil management technique used to enhance soil organic matter and carbon sequestration, but it varies with CR amount, crop, and soil type (Chen et al., 2018). This technique is also used as organic amendment to improve physical, chemical, and biological attributes of agricultural soils, improving soil organic matter contents, soil moisture retention, enhanced nutrient cycling, and decreased soil loss, among other environmental and soil health benefits (Tunnel et al., 2015; Ranaivoson et al., 2018).
BURIAL OF CROP RESIDUES (CR)
Burial of AW in fields is an ancient practice which involves plowing of the CR after the harvesting and burial of these AW contributes to crop needs of nitrogen for next crop (Jahanzad et al., 2016) and called crop residue recycling intensively applied to enhance the utilization of resources in agricultural systems. The CR recycling shows that the crop residue of sugar cane and mung bean can improve the growth and the production of sugarcane and enhance the accumulation of diy matter, nitrogen, phosphorus, and potassium in the aboveground part of sugarcane and then availability in soil (He et al., 2018). CR burial is a good source of reducing weed seed dispersal and infestation (Mohler et al., 2018). It improves soil aggregation, microbial diversity, nutrient storage, and supply as well as water-holding capacity in combination with soil carbon sequestration (Singh et al., 2015).
USE AS BIOSORBENT
There is an emerging trend of using crop CR and other AW as biosorption of different heavy metals and other harmful contaminants of water (Sadeek et al., 2015). Heavy metals, especially carcinogens like arsenic and cadmium, pose serious human health risks by contaminating groundwater reservoirs and food crops by bioaccumulating in edible parts. Over 170 million people have been affected by these metals due to the uptake of contaminated water and food grains. Different methods are employed to remove these metals from water and food, but these are costly reverse osmosis, ion exchange, and electrodialysis. However, the cost-effective method was developed fr om different AW like sugarcane bagasse, peels of various fruits, and wheat straw and used as biosorbents, offering an environment-friendly solution for the toxic metals (Shakoor et al., 2016). Industrial effluents containing azo dyes are also treated with these cost-effective and environmentally friendly processes of biosorption using AW-derived biosorbents (Lee et al., 2016; Tran et al., 2017).
Biochar emerged as the solution to all the major soil problems ranging from nutrient deficiency, organic matter loss, carbon sequestration, carbon source, slow-releasing nutrient reservoir, and remedial measure to soil contaminants like heavy metals and pesticides. These biochars are derived or made from CR like com and rice stalks, cattle pigs, and PMs (Liu et al., 2015). The biochar is used as a nutrient source and known as the carbon source supply and sequestering source as it stores carbon in it for longer periods and releases it extremely slow. It is also used as biosorbent material for capturing heavy metals and pesticides residues in the contaminated soil and binding them to it for longer times for safe food grains production (Zhao et al., 2018; Igalavithana et al., 2017). There are other advanced biochar types like magnetic biochar derived from various types of AW exhibiting a good magnetic property and larger surface area. These magnetic biochars showed a remarkable application as an adsorbent for various wastewater treatments (Thines et al., 2017).
BIOFUEL PRODUCTION (WASTE TO ENERGY)
With the increase in global energy demand and decreasing the fossil fuels, there has been increasing demand for energy sources with cheap and continuous supply. Developing countries have increased their fuel consumption due to industrial development. This increased consumption of energy sources can lead to early end of fossil fuels. The bioenergy produced from the AW biomass is being a sustainable alternate energy source which received high acceptance in various sectors includes public, industries, and government policies. Hence an economic and efficient production process is essential to commercialize AW biomass-based biofuels (Gaurav et al., 2017). The bioethanol, biogas, and electricity from rice husk are used for commercial production and production costs of biofuels are 0.27-0.82 USD/ kg and it is possible to take advantage of AW as energy source in biorefmery to produce biofuels as source of energy to supply to demands in this country
- (Daza Serna et al., 2016). Iran produces 520,400 tons of pistachio wastes/yr from 500,000 ha total area of production under it. By optimum use of this pistachio waste, more than 400,000 tons of biofuel can be generated in which
- 103.5 million cubic meters of biogas and 47.6 million liters of ethanol can be produced (Taghizadeh-Alisaraei et al., 2017).
The production of biofuels from AW to blend with gasoline is another practice being done worldwide supporting the development of rural technology with knowledge-based jobs and mitigating greenhouse gas emissions. Today, engineering for plant construction is accessible and new processes using AW have reached a good degree of maturity and high conversion yields of nearly 90%. The growth of biofuel production is expected to be growing exponentially and it is necessary to move on ahead from its very early stages to a more mature consolidated technology (Valdivia et al., 2016).