A22 Segregation of urine and faeces in cattle houses
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| Measure | Sector | Net Effect | Impact | Reliability | Tech. rqmt. | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| NH3 | N2O | NOx | Nr to water | N2 | ||||||
A22 Segregation of urine and faeces in cattle houses  | Sector Livestock farming | Net Effect 2 | NH3 1 | N2O  | NO2 | Nr to water | N2 | Reliability Promising | Tech. rqmts. Medium |
Overview
Cattle are responsible for roughly 51% of the ammonia emissions in Europe and more than half of the 80% of total ammonia emissions originating from agricultural activities in the United States (Liu et al., 2017; CLRTAP, 2020). In the year 2014, cattle were accountable for about 44% of the total global production of nitrogen in manure (Zhang et al., 2017). In contrast, pig farming contributes to approximately 15% of worldwide livestock ammonia emissions (Philippe et al., 2011), whereas poultry production contributes around 13% of the global ammonia emissions (Crippa et al., 2016; Jiang et al., 2021).
The physical separation of faeces and urine within cattle housing presents a promising approach to enhance nitrogen management and reduce ammonia emissions. By segregating these waste components, the hydrolysis of urea, facilitated by urease in faeces, is diminished, resulting in decreased ammonia emissions both within the housing environment and during subsequent manure spreading (Sutton et al., 2022). Separating the manure into urine and faeces can be challenging, especially once urine and faeces have been mixed (e.g. see the measure for ‘Mechanical solid/liquid slurry separation’). The most common way of separating urine from faeces in cattle housing is through the use of slatted floors or grooved flooring systems (Figure 1). Slatted floors are designed with gaps or openings that allow urine to pass through while retaining solid faecal matter on the surface (Bittman et al., 2014). Some cattle housing systems use scraped manure alleys where solid manure is scraped regularly, and urine is allowed to flow through channels or gutters, further separating the two components (Bittman et al., 2014).
The separation of urine from faeces not only curtails ammonia release but also holds potential benefits during land-application. Specifically, as urine infiltrates soil more readily than mixed slurry, adopting solid-liquid separation minimises nitrogen loss during spreading. This integrated strategy offers a sustainable solution to optimise nitrogen utilisation, mitigate environmental impacts, and improve overall manure management practices within cattle housing systems.
Figure 1. A low-emission floor, with a sloped design and separate urine channel. The slope includes a urine gutter at a 1.5% incline, facilitating swift drainage to limit urine-feces contact and lower ammonia emissions. Image source: https://ahdb.org.uk/knowledge-library/how-cattle-house-flooring-can-reduce-ammonia-emissions
Measure Efficiency
Approximately 80% of the nitrogen intake in dairy cattle is expelled through urine and faeces. Urinary nitrogen is largely composed of about 75% urea, while faecal nitrogen is predominantly organic in nature. The conversion of urinary nitrogen (urea) into ammonia and subsequent volatilisation relies on the action of urease, an enzyme primarily present in faeces. Minimising the interaction between urine and faeces can help to mitigate urea hydrolysis and subsequent ammonia emissions.
Vaddella et al., (2010) compared the effectiveness of ammonia emissions reduction between the separation of urine and faeces during post-collection storage and the conventional method of handling manure, where urine and faeces are mixed together. Laboratory-scale experiments were conducted to assess ammonia emissions from simulated post-collection storage of three waste streams: (i) complete separation of urine and faeces (no contact between the two), (ii) realistic separation of urine and faeces (limited contact), and (iii) conventional scraped manure (control). Based on the study findings, the ranking of ammonia losses in descending order was as follows: combined realistically separated waste streams (3375 mg), combined idealistically separated urine and faeces (3047 mg), and scraped manure (2034 mg). Consequently, according to these results, the additional effort involved in separating the waste streams would not significantly enhance the reduction of ammonia losses during the post-collection storage of separated waste streams compared to the conventional method of collecting scrape manure. That withstanding, a range of studies (as reported in Vaddella et al., 2010) have demonstrated separation of urine and faeces within barn environments can deliver ammonia emissions reductions ranging from 5% to 99%.
However, the impact of this measure extends beyond housing systems. During land-application of manure, the separation of urine from solid waste becomes particularly advantageous. Urine, when isolated, has a higher potential to infiltrate the soil, effectively delivering nitrogen to the root zone where plants can readily utilise it. This not only enhances nitrogen uptake by crops but also minimises nitrogen losses through volatilisation, leaching, and runoff. The cumulative effect of reduced ammonia emissions within the housing system and improved nitrogen utilisation during land-spreading underscores the measure's effectiveness in reducing nitrogen emissions comprehensively. As a result, the practice contributes to sustainable agriculture by promoting more efficient nitrogen management and mitigating environmental impacts.
How to implement
It is important to consider the following steps when developing systems to separate urine and faeces in cattle houses to reduce ammonia emissions:
- Design of Housing System: Construct a cattle housing system with segregated areas for faeces and urine collection. Ensure separate channels or floors for urine drainage and faecal collection. Utilise slatted floors or other appropriate designs to facilitate separation.
- Urine Diversion Techniques: Implement techniques to divert urine away from faecal matter. Use sloped or grooved floors to guide urine into separate collection systems, such as troughs or pits.
- Collection and Storage: Directly collect urine and faeces in separate receptacles. Employ slurry stores or containers for each waste component, ensuring minimal mixing during collection and storage.
- Solid-Liquid Separation: Utilise mechanical separation methods, such as screens, filters, or centrifuges, to physically separate faeces and urine. This prevents the intermixing of the two waste components.
- Ammonia Inhibition: As faeces contain urease enzymes that catalyse urea hydrolysis into ammonia, separation minimises this enzymatic action, reducing ammonia formation.
- Application and Utilisation: When applying manure to fields, segregate application based on the waste components. Utilise urine-enriched liquid on soil, as it infiltrates more effectively, while solid faecal matter can be applied separately or composted for later use.
- Monitoring and Maintenance: Regularly inspect and maintain the separation systems to ensure effective operation. Monitor ammonia emissions, nutrient content, and application practices to optimise results.
- Adaptation to Herd Size: Scale the separation system according to herd size. Larger herds might require more sophisticated separation techniques and larger storage capacities.
- Employee Training: Train personnel in the correct implementation and maintenance of the separation system. This ensures proper operation and maximises the benefits of the practice.
- Environmental Considerations: Consider local environmental regulations and site-specific conditions when implementing the separation system. Ensure compliance with relevant laws and standards.
- Continuous Improvement: Continuously assess the efficiency and effectiveness of the separation system. Adjust operational practices as needed to optimise nitrogen management and minimise environmental impact.
By adhering to these scientific guidelines, the physical separation of faeces and urine in cattle housing can be effectively implemented to enhance nitrogen management and reduce ammonia emissions.
Benefits
Key benefits of adopting this measure:
In summary, the physical separation of faeces and urine in cattle housing offers multifaceted benefits, spanning improved air and water quality, nutrient management, animal welfare, and overall farm sustainability.
Costs
Captial Costs
The capital costs associated with implementing the physical separation of faeces and urine in cattle housing can vary based on several factors, including the scale of the operation, the specific techniques used, and local conditions. Potential cost may include the following:
It's important to note that these costs can vary widely based on regional differences, technological choices, and the specific circumstances of each operation. Conducting a thorough feasibility study, seeking multiple quotes from suppliers, and consulting with professionals can provide a more accurate estimate of the capital costs for implementing this measure.
Operational Costs
The operational costs associated with implementing the physical separation of faeces and urine in cattle housing will depend on various factors, including the size of the operation, the separation techniques used, and local conditions. Potential operational costs may include the following:
Operational costs can vary significantly depending on the specifics of the implementation. Conducting regular monitoring and cost analysis can help identify areas for cost-saving opportunities and operational improvement.
Risks
The risks associated with implementing this measure may include:
In conclusion, while separating urine and faeces in cattle housing has the potential to improve nitrogen sustainability and reduce environmental impacts, there are several risks and challenges that need to be carefully considered and managed. Proper planning, implementation, and ongoing management are essential to maximise the benefits of this approach while minimising potential negative outcomes.
References
Bittman, S., M. Dedina, C.M. Howard, O. Oenema, and M.A. Sutton, editors. 2014. Options for Ammonia Mitigation: Guidance from the UNECE Task Force on Reactive Nitrogen. Centre for Ecology and Hydrology, Edinburgh, UK.
CLRTAP. 2020. Assessment Report on Ammonia. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://unece.org/fileadmin/DAM/env/documents/2020/AIR/WGSR/Final_Assessment_Report_on_Ammonia_v2_20201126_b.pdf.
Crippa, M., G. Janssens-Maenhout, F. Dentener, D. Guizzardi, K. Sindelarova, et al. 2016. Forty years of improvements in European air quality: regional policy-industry interactions with global impacts. Atmos. Chem. Phys. 16(6): 3825–3841. doi: 10.5194/acp-16-3825-2016.
Jiang, J., D.S. Stevenson, A. Uwizeye, G. Tempio, and M.A. Sutton. 2021. A climate-dependent global model of ammonia emissions from chicken farming. Biogeosciences 18(1): 135–158. doi: 10.5194/bg-18-135-2021.
Liu, Z., Y. Liu, J. Murphy, and R. Maghirang. 2017. Ammonia and Methane Emission Factors from Cattle Operations Expressed as Losses of Dietary Nutrients or Energy. Agriculture 7(3): 16. doi: 10.3390/agriculture7030016.
Philippe, F.X., J.F. Cabaraux, and B. Nicks. 2011. Ammonia emissions from pig houses: Influencing factors and mitigation techniques. Agric. Ecosyst. Environ. 141(3–4): 245–260. doi: 10.1016/j.agee.2011.03.012.
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.
Vaddella, V.K., P.M. Ndegwa, H.S. Joo, and J.L. Ullman. 2010. Impact of Separating Dairy Cattle Excretions on Ammonia Emissions. J. Environ. Qual. 39(5): 1807–1812. doi: 10.2134/jeq2009.0266.
Zhang, B., H. Tian, C. Lu, S.R.S. Dangal, J. Yang, et al. 2017. Global manure nitrogen production and application in cropland during 1860–2014: a 5 arcmin gridded global dataset for Earth system modeling. Earth Syst. Sci. Data 9(2): 667–678. doi: 10.5194/essd-9-667-2017.
Authors
Will Brownlie
UK Centre for Ecology and Hydrology, Scotland