لاله قفقازی

Dry anaerobic digestion is a cost-effective method to purify and recover agricultural waste. Agricultural production statistics (over 128 million tonnes in 2019-2020) and its consequent high waste production (38 million tonnes per year) indicate the need for optimal disposal of this biomass. The purpose of article is identification and compare dry anaerobic digesters for optimal management of agricultural waste disposal in Iran.

This article is the result of several internal and foreign online sources: Google Scholar, Science Direct, Research Gate, and publishers Elsevier, Springer, Frontiers, and Civilica with the keywords of agricultural waste, biogas, and dry anaerobic digestion.

The results of the study show that good performance, low-cost energy, and maintenance are the benefits of mesophilic temperature conditions in dry anaerobic plants. Hydraulic retention times varied from 20 to 35 days, with mean total solids above 15% and mean methane percent at 55%. Batch digesters are a relatively simple and acceptable technology for disposal of agricultural waste but sustainability of biogas supply can be easier with continuous reactors, despite the high need for maintenance and management.

This technology, for its efficiency and flexibility, is essential for the high utilization of agricultural waste, and sustainable development of biogas. Appropriate technology to increase biogas productivity is suggested, by considering geographical features, production tonnage, and characteristics of agricultural waste. The batch anaerobic process in provinces of Iran that have smaller-scale agricultural activities is more effective than continuous digestion.

One of the most important emerging pollutants in human health, food safety, and environmental protection challenges is phthalate esters. Among these, the contamination of agricultural soils with the endocrine-disrupting chemical Di (2-ethylhexyl) phthalate (DEHP) has been confirmed globally. In this research, the DEHP-absorption potential of compost enriched with Fe3O4 NPs was identified. The effects of the sorbent dose in the range of 2–5 g.L-1, 3–11 pH, and DEHP concentration at 5–10 mg.L-1 on absorption efficiency (%) were optimized via response surface methodology in design expert software. The kinetic equilibrium experiment results showed a two-step process, requiring 6 hours of equilibrium time for the exothermic adsorption process at 25ºC. The adsorption process of DEHP fitted best to the pseudo-second-order kinetic (R2 = 0.9932) and the linear form of the Freundlich isotherm models. In the central composite design, the significant quadratic model was validated and used to predict the interaction of variables (P-value <0.0001, adjusted R2 = 0.9753). The optimum conditions of absorption efficiency (74.173%) were obtained at a sorbent dosage of 4.157 g.L-1, pH 5.85, and a DEHP concentration of 4.88 mg.L-1 with a desirability of 0.987. The comparison of FTIR absorption spectra confirmed the active participation of O-H bands (functional groups of phenol, alcohol, and carboxyl) and primary amine (N-H) in the DEHP absorption through interaction with the oxygen atom of the phthalate ester group (C=O). As a result of its successful and acceptable efficiency, using compost/Fe3O4 NP absorbent based on organic wastes is a low-cost and eco-friendly technique for DEHP removal from sensitive ecosystems and also to improve the efficiency of bioremediation in agricultural soils amended by compost.

Providing sustainable sources of energy, global warming, and maintaining soil health are the main challenges of the 21st century. Biochar has great potential in addressing these global issues and can be effective in achieving sustainable development goals. Biochar obtained from waste biomass (plant residues, urban and rural wastes) is a catalyst for the anaerobic digestion process and increases bioenergy production due to its mineral content and buffering capacity. This article is the result of reviewing valid online papers from Google Scholar, Science Direct, Research Gate, Elsevier, and Springer. The Results showed high advantages of biochar for using in the production of renewable energy and reducing greenhouse gases. Biochar potentially increases methane and hydrogen productions in anaerobic digestion and is efficient in on-site biogas enrichment, leading to biomethane production with a purity of more than 90%. On the other hand, it can be a cheap and potential replacement for the electrode of microbial fuel cells and reduce the cost of ion-based batteries. The application of biochar in the agricultural ecosystem increases carbon sequestration in soil and reduces methane and nitrogen oxide emission. The structural characteristics such as high surface area, optimal pore distribution, surface reactivity, hydrophobicity, and many functional groups make this adsorbent a suitable choice for the remediation of heavy metals from aqueous solutions. The potential of sustainable use of biochar in biological energy production (biogas and biohydrogen), reduction of greenhouse gases, carbon sequestration and soil health, and wastewater treatment along with its future challenges and perspectives is necessary with the Nexus approach of energy, water, and agriculture.