# Drying Characteristics of Chicken Manure Under a Variable Temperature Process  
[PERSON]  
1 College of Animal Science and Technology, Henan Agricultural University, Zhengzhou 450046, China; [EMAIL_ADDRESS] (C.L. ); [EMAIL_ADDRESS] (C.K. )1 College of Animal Science and Technology, Henan Agricultural University, Zhengzhou 450046, China; [EMAIL_ADDRESS] (C.L. )2  
[PERSON]  
1 College of Animal Science and Technology, Henan Agricultural University, Zhengzhou 450046, China; [EMAIL_ADDRESS] (C.L. )2  
[PERSON]  
2 Heman Engineering Research Center on Animal Healthy Environment and Intelligent Equipment, Henan University of Animal Husbandry and Economy, Zhengzhou 450046, China; [EMAIL_ADDRESS] (Q.D. )2  
[PERSON]  
2H. [PERSON]  
the drying process of other materials, requires significant energy consumption to remove moisture. In recent years, the technology involving utilizing residual heat from chicken house ventilation for drying chicken manure has been widely promoted worldwide. This method removes moisture from chicken manure by utilizing the heat from air exhausted from chicken houses, demonstrating a positive effect on reducing energy consumption [1,2]. However, several challenges have emerged during the application of this technology in China, particularly during extended periods of rainfall or when the relative humidity of the exhaust air exceeds 85%. These conditions can significantly reduce the dehydration rate of chicken manure [3]. In winter, low ventilation rates and low inlet air temperatures further complicate the drying process, resulting in an increase in time for the moisture content to drop to 30%. This, in turn, can lead to manure accumulation and increased ammonia emissions [4, 5, 6]. To address the issue of low drying rates caused by prolonged rainy weather or high relative humidity in the external environment, a method for drying chicken manure combining residual heat from chicken house ventilation with auxiliary heat sources has been developed in China. A schematic diagram of the manure drying system is shown in Figure 1. Two stages make up the drying process. In the early drying stage (first stage), residual heat from chicken house ventilation is used to pre-dry the chicken manure. In the late drying stage (second stage), auxiliary heat sources such as biomass-burning furnaces, hot blast stoves, or heat pumps are employed to dry the chicken manure at higher temperatures, accelerating the dehydration rate during the final drying phase [7,8]. Currently, this technology has been widely used, both domestically and overseas, due to its favorable treatment effects. However, there is a lack of theoretical research on the drying characteristics of chicken manure under variable temperature conditions. It remains unclear how drying temperatures can be set to optimize energy savings and how drying parameters can be adjusted to minimize nitrogen loss during the drying process. Previous studies regarding the drying characteristics of chicken manure have primarily focused on environmental conditions to elucidate their effects on drying rate and drying time. [PERSON] et al. [9] investigated the relationship between temperature, wind speed, and dehydration rate within a temperature range of 70 \({}^{\circ}\)C to 110 \({}^{\circ}\)C, developed a drying model for chicken manure, and determined the diffusion coefficient during the drying process. Similarly, [PERSON] et al. [10] examined the effects of temperature, wind speed, and sample thickness on the drying process within a temperature range of 40 \({}^{\circ}\)C to 60 \({}^{\circ}\)C, resulting in a water loss model for chicken manure. However, these studies were conducted under constant-temperature drying conditions, and their findings are mainly applicable to traditional drying methods, such as electric heating drying and coal-fired hot air drying. These traditional methods are associated with high energy consumption and significant nitrogen loss [11, 12, 13, 14].