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A10 Use of acid air scrubbers in pig housing

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A10 Use of acid air scrubbers in pig housing

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Sector

Livestock farming

Net Effect

1

NH3

1

N2O

2

NO2

2

Nr to water

3

N2

3

Reliability

Robust

Tech. rqmts.

High

Overview

The removal of ammonia from exhaust air can be effectively achieved using filters or scrubbers, such as those employing water or acid, particularly in mechanically ventilated barns (Ndegwa et al., 2008; Sutton et al., 2022). The utilisation of acid scrubbers (Figure 1), primarily employing sulphuric acid, has demonstrated practical and effective results for managing exhaust air in large-scale livestock operations across Denmark, France, Germany, and the Netherlands (Melse and Ogink, 2005; Guingand, 2009). While most economically viable when integrated into new housing structures, these systems have exhibited ammonia removal efficiencies exceeding 90% based on their pH-set values. The potential contribution of this approach to curtailing nitrogen dioxide and nitrogen oxide emissions holds promise, however, more comprehensive research is required. 

The practical implementation of these purification techniques often encounters limitations. Their relatively high costs and technical challenges, compounded by issues related to dust, especially in poultry and pig housing, can constrain their broader applicability. This measure is regarded as robust in terms of nitrogen emissions reduction, but carries high technological requirements. 

An acid air scrubber connected to a livestock barn to manage ammonia and odour emissions. Picture source: https://www.frontiersin.org/articles/10.3389/fsufs.2018.00023/full

Figure 1. An acid air scrubber connected to a livestock barn to manage ammonia and odour emissions. Picture source: https://www.frontiersin.org/articles/10.3389/fsufs.2018.00023/full

Measure Efficiency

Acid scrubbers have been shown to lower ammonia emissions by varying amounts, ranging from 40% to 100%, with an average reduction of 96% (Melse and Ogink, 2005). In contrast, biological scrubbers, also known as biotrickling filters, are observed to reduce ammonia emissions by around 70% whilst also removing fine dust and odour (Ogink and Bosma, 2007). To deal with the high dust loads, multistage air-scrubbers with pre-filtering of coarse particles have been developed (Melse and Ogink, 2005; Ogink and Bosma, 2007).  

Melse and Ogink (2005) reported that odour removal through acid scrubbers ranged from 3% to 51%, averaging at 27%. On the other hand, biological air scrubbers exhibited a wider range of odour removal results, varying from -29% to +87%, with an average of 51%. In a pig housing study, Guingand (2009) demonstrated that acid scrubbers achieved approximately 75% reductions in both odour and particulate matter.  

How to implement

When installing acid air scrubbers in pig housing to control ammonia emissions, the following steps should be considered.  

  • Site Assessment: Evaluate the pig housing facility to determine the best location for installing the scrubber. Consider airflow patterns, accessibility, and proximity to ammonia emission sources. 
  • System Design: Work with experts or engineers to design a scrubber system tailored to the facility. Choose appropriate materials and components, considering factors like exhaust flow rates and pollutant concentrations. 
  • Equipment Procurement: Acquire the necessary equipment, including the scrubber unit, chemical storage tanks, pumps, fans, and control systems. 
  • Installation: Set up the scrubber unit and associated equipment as per the manufacturer's guidelines. Ensure proper connections to the exhaust source and exhaust stack. Install chemical storage tanks, delivery systems, and pumps to manage the scrubbing solution. 
  • Chemical Handling: Follow safety protocols for handling and storing chemicals used in the scrubbing process, such as sulfuric acid. Implement safety measures to prevent leaks, spills, and fumes. 
  • Piping and Ductwork: Install appropriate piping and ductwork to transport exhaust air to the scrubber and then to the exhaust stack. Ensure airtight connections to prevent leakage of pollutants. 
  • Fans and Airflow: Integrate fans to ensure proper airflow through the system. Fans help direct exhaust air into the scrubber and then expel it through the exhaust stack. 
  • Controls and Monitoring: Set up control systems to regulate factors like pH levels and chemical dosing. Implement monitoring systems to track ammonia levels, pH, and scrubber performance. 
  • Water Management: Design and implement water recirculation systems that deliver the scrubbing solution to the scrubber unit and manage the waste solution. 
  • Testing and Calibration: Test the scrubber system to ensure proper functioning, airflow, and chemical dosing. Calibrate control systems as needed. 
  • Training and Documentation: Train personnel responsible for operating and maintaining the system on safety procedures, maintenance tasks, and troubleshooting. Maintain thorough documentation of installation, equipment specifications, and maintenance procedures. 
  • Regular Maintenance: Schedule regular inspections, cleaning, and maintenance to ensure the system's optimal performance. Replace consumables like scrubbing solution and chemical reactants as needed. 

It's crucial to collaborate with experts in air quality management and engineering during the installation process. Proper installation and maintenance are essential to achieve effective ammonia reduction and ensure the safety of workers and the environment. 

Benefits

Installing acid air scrubbers in pig housing offers the following benefits: 

Each benefit depends on factors such as system design, operation, and local conditions, but collectively, they underscore the value of installing acid air scrubbers in pig housing. 

Costs

Captial Costs

Installing acid air scrubbers in pig housing entails various potential capital costs, including: 

    • It's important to note that these costs can vary widely based on factors such as the size of the facility, system complexity, local market conditions, and regulatory requirements. Careful planning and consultation with experts are essential to accurately estimate and manage these capital expenses. 

    Operational Costs

    Installing acid air scrubbers in pig housing involves several potential operational costs, including: 

    • These operational costs can vary based on factors like system size, usage intensity, local energy and chemical prices, and maintenance practices. Accurate budgeting and ongoing monitoring are crucial to effectively manage these costs over time. 

    Risks

    Installing acid air scrubbers in pig housing presents the following challenges and risks: 

    Assessing and addressing these challenges is essential to ensure successful implementation and operation of acid air scrubbers in pig housing. 

    References

     Guingand, N. 2009. Wet scrubber: one way to reduce ammonia and odours emitted by pig units. Pap. Present. sixtieth Meet. Eur. Assoc. Anim. Prod. Barcelona, Spain. 

    Melse, R.W., and N.W.M. Ogink. 2005. Air Scrubbing Techniques for Ammonia and odor reduction at livestock operations: Review of on-farm research in the Netherlands. Trans. ASAE 48(6): 2303–2313. doi: 10.13031/2013.20094. 

    Ndegwa, P.M., A.N. Hristov, J. Arogo, and R.E. Sheffield. 2008. A review of ammonia emission mitigation techniques for concentrated animal feeding operations. Biosyst. Eng. 100(4): 453–469. doi: 10.1016/j.biosystemseng.2008.05.010. 

    Ogink, N.W.M., and B.J.J. Bosma. 2007. Multi-phase airscrubbers for the combined abatement of ammonia, odor and particulate matter emissions. Proc. Int. Symp. Air Qual. Waste Manag. Agric. 

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

    Authors

    • Will Brownlie

      UK Centre for Ecology and Hydrology, Scotland