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A24 Rapid drying of poultry manure

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A24 Rapid drying of poultry manure

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Sector

Livestock farming

Net Effect

1

NH3

1

N2O

2

NO2

2

Nr to water

2

N2

2

Reliability

Robust

Tech. rqmts.

Medium

Overview

The rapid drying of poultry litter reduces hydrolysis of uric acid to ammonia, and can therefore reduce nitrogen emissions from poultry farming operations (Figure 1). Drying is typically achieved by installing appropriate ventilation systems in the manure pit to decrease moisture content, and/or by using manure removal belts to remove the manure to dry storage outside the building (Sutton et al., 2022). Both systems limit the conditions conducive for ammonia release, particularly if the manure has been dried on the belts through forced ventilation, thus resulting in reduced emissions and a positive contribution to environmental quality.  

While the primary goal of drying poultry litter is to reduce ammonia emissions, keeping excreted nitrogen in the form of uric acid can also be expected to reduce nitrous dioxide, nitrogen oxides and dintrogen emissions, since it will also reduce nitrification and denitrification. By reducing such nitrogen losses, dried poultry litter will have a higher fertiliser value for farmers, which should be compensated by using reduced doses during land application, as compared with decomposed poultry litter (Dróżdż et al., 2020). 

This measure is considered a robust strategy to reduce nitrogen emissions that has intermediate technological requirements. 

Poultry manure dying on manure belts before being transported to covered dry storage. Image source: https://www.vdlagrotech.com/en/products/dryingtechnology/manure-drying

Figure 1. Poultry manure dying on manure belts before being transported to covered dry storage. Image source: https://www.vdlagrotech.com/en/products/dryingtechnology/manure-drying

Measure Efficiency

Aviary systems with manure belts for frequent collection and removal of manure to closed storages reduce ammonia emission by more than 70% compared with the deep litter housing system. Keeping excreted nitrogen in the form of uric acid can also be expected to reduce nitrous dioxide, nitrogen oxides and dintrogen emissions, since it will also reduce nitrification and denitrification. By reducing such nitrogen losses, dried poultry litter will have a higher fertiliser value for farmers, which should be compensated by using reduced doses during land application, as compared with decomposed poultry litter (Dróżdż et al., 2020). 

The manure needs to undergo drying until it contains 60-70% dry matter to minimise the subsequent generation of ammonia (Sutton et al., 2022). When manure is collected from belts and placed into drying tunnels with intensive ventilation, either inside or outside the structure, it's possible to achieve a dry matter content of 60-80% in less than 48 hours (Sutton et al., 2022). However, this approach increases exposure to air, which raises the risk of elevated ammonia emissions. 

Shifting to a weekly removal process from the manure belts to covered storage facilities can result in a 50% reduction in ammonia emissions compared to a bi-weekly removal approach (Sutton et al., 2022). In a broader context, the emissions from laying hen houses equipped with manure belts will be influenced by several factors: 

(a) The duration for which the manure remains on the belts. 

(b) The specific drying systems employed. 

(c) The breed of poultry being raised. 

(d) The ventilation rate applied to the belt area, where a lower rate corresponds to higher emissions. 

(e) The composition of the feed given to the poultry.

How to implement

To implement rapid drying of poultry litter and mitigate nitrogen emissions, consider the following steps and considerations: 

  • Drying Methodology: Utilise an intensively ventilated drying system, such as drying tunnels with controlled airflow and temperature; arrange manure belts to ensure efficient collection of poultry manure for subsequent drying. 
  • Optimal Dry Matter Content: Aim to achieve a dry matter content of 60-70% in the dried poultry litter for effective reduction of nitrogen emissions. 
  • Drying Duration: Employ techniques that enable rapid drying within a timeframe of fewer than 48 hours. 
  • Ammonia Control: During drying, strike a balance between quick drying and preventing excessive exposure to air, which can lead to higher ammonia emissions; drying poultry litter to 60-70% dry matter content significantly decreases the subsequent formation of ammonia. 
  • Storage and Removal: Opt for a weekly schedule of removing dried manure from the manure belts to covered storage facilities; ensure that the storage areas are adequately covered to minimise nitrogen emissions. 
  • Factors Influencing Emissions: Manure residence time on belts affects emissions; shorter durations are preferable; choose efficient drying systems to minimise emissions; different poultry breeds might impact emissions, necessitating breed-specific considerations; adjust the ventilation rate at the belt area to balance drying speed and emission control; manage the composition of poultry feed to influence nitrogen content in the manure. 
  • Monitoring and Optimisation: Regularly monitor drying times, dry matter content, and emission levels; fine-tune drying and ventilation parameters based on monitoring results. 

By adhering to these guidelines, the rapid drying of poultry litter can be effectively implemented to reduce nitrogen emissions, contributing to more sustainable poultry farming practices. 

Benefits

Implementing a poultry litter drying system to mitigate nitrogen emissions offers several notable advantages: 

Overall, implementing the poultry litter drying system offers multifaceted benefits that encompass environmental, regulatory, economic, and operational aspects, contributing to a more sustainable and responsible poultry farming practice. 

Costs

Captial Costs

Implementing the described poultry litter drying system involves several key capital costs: 

    • It's important to conduct a comprehensive cost analysis that considers these factors to determine the total capital investment required for the implementation of the poultry litter drying system to reduce nitrogen emissions. 

    Operational Costs

    In addition to the initial capital investment, implementing the poultry litter drying system to mitigate nitrogen emissions involves ongoing operational costs. These may include: 

    • When assessing the financial viability of implementing the poultry litter drying system, it's crucial to factor in these ongoing operational costs alongside the initial capital investment. This comprehensive evaluation will provide a clearer understanding of the long-term financial commitment required for sustainable poultry farming practices. 

    Risks

    While the implementation of the poultry litter drying system offers several benefits, it also presents certain potential risks and challenges that need to be considered: 

    To effectively manage these risks, thorough planning, careful monitoring, ongoing training, and contingency strategies are essential. A comprehensive risk assessment should be conducted before implementing the poultry litter drying system to ensure that potential challenges are addressed and mitigated to the best extent possible. 

    References

    Dróżdż, D., K. Wystalska, K. Malińska, A. Grosser, A. Grobelak, et al. 2020. Management of poultry manure in Poland – Current state and future perspectives. J. Environ. Manage. 264: 110327. doi: 10.1016/j.jenvman.2020.110327. 

    Sutton, M.A., C.M. Howard, K.E. Mason, W.J. Brownlie, and C.M. d. Cordovil, editors. 2022. Nitrogen Opportunities for Agriculture, Food & Environment. UNECE Guidance Document on Integrated Sustainable Nitrogen Management. UK Centre for Ecology & Hydrology, Edinburgh, UK., Edinburgh, UK. 

    Authors

    • Will Brownlie

      UK Centre for Ecology and Hydrology, Scotland