Modeling and optimization of laying hen manure drying process to reduce protein and ammonium-N losses by adding sodium bentonite and wheat straw

• Published in: Journal of environmental management Vol. 351; p. 119668
• Main Authors: Khademi, Sahar, Masoumi, Amin Allah, Sadeghi, Morteza, Riasi, Ahmad, Moheb, Ahmad
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2024
• Subjects: Additives; Ammonium Compounds; Ammonium-N; Animals; Bentonite; Box-Behnken design; Chickens; Crude protein; Dehydration; Environmental pollution; Female; Hot air drying; Manure; Sodium; Triticum; Additives; Ammonium-N; Environmental pollution; Box-Behnken design; Crude protein; Hot air drying
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2023.119668

Laying hen manure (LHM) is a major source of pollution due to its high nitrogen (N) and moisture content (MC). Therefore, reducing the MC of LHM is necessary to retain its recyclable value and reduce environmental pollution. One effective way is by incorporating sodium bentonite (SB) and wheat straw (WS) as amendments in the LHM. This work aimed to optimize the drying conditions of LHM and investigate the effect of SB and WS utilization on the dehydration rate, reduction of crude protein (CP), and reduction of ammonium-N (N H4+-N). The response surface methodology (RSM) was used to optimize these processes. For this purpose, two sets of experiments (drying of LHM with and without SB and Ws) were designed. The independent parameters were air temperature (70, 80, and 90 °C), air velocity (1, 1.5, and 2 m s−1), layer thickness (5, 10, and 15 mm), SB (2%, 4%, and 6%), and WS (3%, 7.5%, and 12%). The results indicated that temperature and WS had the most significant influence on all responses. To maximize the dehydration rate and minimize the reduction of CP and N H4+-N, the optimal conditions were a temperature of 78 °C, air velocity of 1 m s−1, and layer thickness of 5 mm in the first set of experiments, and a temperature of 80 °C, air velocity of 1.5 m s−1, layer thickness of 11 mm, 6% SB, and 12% WS in the second set of experiments. Under the optimum conditions, LHM treated with 6% SB and 12% WS retained 10% more CP and 58% more N H4+-N than untreated LHM. Therefore, according to the obtained results, SB and WS are recommended as additives to reduce the CP and N H4+-N losses of LHM during the drying process. •Laying hen manure (LHM) drying was optimized to reduce crude protein (CP) losses and microbial load.•The effect of sodium bentonite and wheat straw on CP and N H4+-N losses in LHM was evaluated.•Models were confirmed with experimental data to achieve the desired goal.•LHM treated with 6% SB and 12% WS retained 10% more CP and 58% more N H4+-N than untreated LHM.•Higher drying temperatures decreased the Salmonella colonies compared to lower temperatures.