Dr. Lilong Chai, Assistant Professor & Poultry Engineering Specialist
Layer houses face the challenge of managing the copious amounts of manure generated by the hens. With 100,000 hens producing 1,500 to 2,000 tons of manure per year, it’s essential to reduce moisture levels before storage and land application. High moisture content in manure increases transportation costs, encourages the growth of bacteria and flies, and causes unpleasant odors. Moreover, excessive moisture leads to the loss of nitrogen and the emission of ammonia. Currently, layer farms employ various methods to dry fresh manure, including manure belt drying, manure drying tunnels, air duct heating, and in-house composting.
Key Takeaways
Manure Belt Drying System
A commonly used technique in conventional battery cage and cage-free houses is the manure belt drying system. This method involves running manure belts every 3-4 days, allowing fresh manure to dry within the house before being stored. During summer, the moisture content can be reduced from 75% to 20-30% within a 3-4 day period. However, drying manure is more challenging in winter due to reduced ventilation. Additionally, the feed formulation and the inclusion of salt can increase moisture levels in the manure.
Figure 1. Layer house manure belt system. (photos credit: Chai).
Manure Drying Tunnel or Drying Shed
To address the longer drying time required during winter, some layer farms utilize a manure drying tunnel. After removing the manure from the house, it is evenly distributed on a multi-tiered conveyor system. The manure passes through the tiers and is dried using the exhaust fans of the layer house or dedicated fans installed for the drying tunnel. The drying speed depends on factors such as the number of tiers, fans, and environmental conditions.
Figure 2. Manure drying tunnel on a layer farm. (photo credit: Ni et al., 2010; Chai et al., 2012; Big Dutchman).
In-House Air Duct Heating on Manure Belt
An alternative method to expedite manure drying is the use of air duct heating on the manure belt. In cage-free farms, where bird density is lower, additional heating is needed during winter. Warm air is introduced into the house through a duct above the manure belt, enabling the drying of manure to 10-20% moisture content within 3-4 days.
Figure 3. In-house air duct heating on manure belt (photo credit: Zhao et al., 2013).
Windrowing Under High-Rise Housing
Conventional high-rise layer houses feature A-frame cages with slanted boards behind them, allowing fresh manure to drop into a pit below. The accumulated manure in the pit is continually dried by exhaust fans. To further aid drying, some farms windrow the manure in the pit. This process involves continuously adding fresh manure without additional carbon sources. Depending on climatic conditions, windrowed manure in high-rise layer houses can have reduced moisture levels of about 20-30% when removed from the pit.
Figure 5. Windrowing of layer manure under a high-rise layer house. (Koenig et al., 2005).
Manure Drying on Bedded Floors of Cage-Free Houses
In cage-free houses, a percentage of fresh manure is dropped onto the floor while the remaining amount goes onto the manure belt. Moisture levels in the litter floor need to be carefully managed to prevent caked litter, which adversely affects bird health and welfare. Ventilation is the primary means of removing moisture from the litter floor, while periodic cleaning and the addition of fresh bedding materials help maintain dry and suitable conditions.
Figure 6. Caked litter on the floor of a cage-free house (photo credit: Chai).
These innovative manure drying methods ensure that layer houses effectively manage moisture levels in the manure, minimizing transportation costs and potential health hazards. As the poultry industry continues to strive for sustainable practices, it is crucial to explore and implement these drying techniques. Ames Farm Center is a leading provider of poultry equipment and supplies, offering a range of solutions to support the efficient management of layer houses.
To learn more about Ames Farm Center, visit their website: Ames Farm Center
Further readings:
- Aboltins, A., and Kic, P. 2015. Forced convection in drying of poultry manure. Agronomy Research. 13 (1)， 215-22.
- Chai, L., Ni, J.Q., Diehl, C.A., Kilic, I., Heber, A.J., Chen, Y., Cortus, E.L., Bogan, B.W., Lim, T.T., Ramirez-Dorronsoro, J.C. and Chen, L., 2012. Ventilation rates in large commercial layer hen houses with two-year continuous monitoring. British Poultry Science, 53(1), 19-31.
- Chai, L., Xin, H., Wang, Y., Oliveira, J., Wang, K., & Zhao, Y. 2019. Mitigating particulate matter generation in a commercial cage-free hen house. Transactions of the ASABE, 62(4), 877-886.
- Koenig, R., Miner, F.D., Miller, B. E, Palmer, M. D. 2005. In-house composting in high-rise, caged layer facilities. Fact Sheet. Sustainable Agriculture Research & Education. Read here
- Moore and Kaufman, 2017. Feathered creatures. UF/IFAS Extesnion Publication. Read here
- Ni, J. Q., Diehl, C. A., Chai, L. L., Bogan, B. W., Cortus, E. L., Lim, T. T., & Heber, A. J. 2010. National air emissions monitoring study: emissions data from two manure belt layer houses in Indiana-site IN2B. Final Report, Purdue University, West Lafayette, IN.
- Zhao, Y., Zhao, D., & Xin, H. 2013. Characterizing manure and litter properties and their carbon dioxide production in an aviary laying-hen housing system. In 2013 Kansas City, Missouri, July 21-24, 2013. American Society of Agricultural and Biological Engineers (ASABE).
