Swine in a barn.

2022-23 Rapid Ag: Greenhouse Gas Sampling Approaches for Minnesota Livestock Farms

March 1, 2021

Project Leader

Erin Cortus, Department of Bioproducts and Biosystems Engineering

Team Members and Roles

  • Melissa Wilson, Department of Soil, Water and Climate, Co‐PI
  • Bo Hu, Department of Bioproducts and Biosystems Engineering, Co‐PI

Non-Technical Summary

We propose to develop a greenhouse gas measurement approach for livestock farms based on a mass balance of volatile solids and nitrogen – precursors to methane and nitrous oxide emissions, respectively. The approach uses manure and other product sampling (e.g., milk), to anchor greenhouse gas emissions for manure to specific farm practices. Ash analyses will confirm that manure (or other) flows are accurate. The mass balance approach will be undertaken in summer and winter conditions on 12 farms that span the range of swine, dairy and turkey production types and manure storage systems for Minnesota. On 4 select farms, the mass balance approach will coincide with continuous aerial emission monitoring of the main greenhouse gas source. The aerial monitoring will demonstrate the temporal variability in emissions, and provide an additional check of the mass balance approach. The mass balance and aerial emission monitoring approaches will be compared to greenhouse gas emission estimation methods currently in practice for Minnesota farms. The hypothesis of this research is that there are farm‐based measurements that can supplement and improve our greenhouse gas emissions estimates. In the process, we will identify production practices with potential to mitigate greenhouse gas emissions from manure.

Objectives and Goals

The overall goal of the project is to use manure and other product sampling (e.g., milk), to anchor greenhouse gas emission estimates for manure to on‐farm practices. The specific objectives are:

  1. To demonstrate mass balances of volatile solids and nitrogen on 12 Minnesota livestock farms
  2. To measure aerial greenhouse gas emission measurements for 4 manure storage systems in Minnesota
  3. Compare mass balance and continuous aerial measurements to current greenhouse gas estimation methods


"Conversations on climate and greenhouse gases are at a fever pitch in Minnesota due to a number of factors. We expect to be dealing with the science and accounting of greenhouse gases for at least the next decade as the jury is still out on what effect, if any, dairy has on our climate." – Minnesota Milk Producers, personal communication, 17 April 2020.

Producers are under pressure, both within their local communities and industries, to demonstrate and document environmental sustainability. A recent court decision prompted the Minnesota Pollution Control Agency to estimate greenhouse gas (GHG) emissions during environmental assessments while determining permit conditions for large concentrated animal feeding operations (MPCA, 2020).

Greenhouse gas estimation is also a key component to sustainability discussions within the livestock production and food supply chain (NPB, 2020; USDairy, 2020; Walmart, 2020). Greenhouse gas estimation methods are based on an estimate of the manure excretion by animals, the manure storage method and temperature conditions. This estimation approach does not account for all manure management systems, nor the variability in manure management between farms.

Responding to these pressures requires measurements to demonstrate GHG emissions and/or changes over time. Stored manure emissions are a critical piece of livestock agriculture’s contribution to GHG production. Cradle‐to‐gate carbon footprints (that consider GHG emissions from the full supply chain of resources used in production of pig or milk until it leaves the farmgate) estimate manure storage contributed 22.6% to US pig production’s 2015 carbon footprint (Thoma et al., 2018), and enteric and manure methane contributed 80% of dairy’s GHG emissions (Capper and Cady, 2020). Environmental sustainability analyses (i.e. Life Cycle Analyses) often draw on GHG estimation methods prescribed by IPCC (Dong et al., 2006), which are designed for national or regional scale application. Appuhamy et al. (2018) developed empirical models for improving volatile solids excretion estimates by dairy cows, with farm‐available data. A meta‐analysis comparison of GHG measurements from swine operations demonstrated the IPCC approach captured the average level but not the variability of methane and nitrous oxide emissions (Liu et al., 2013). Farm‐level emission measurements are costly and time intensive (Heber et al., 2001). Andersen et al. (2015) developed and validated a 3‐day assay for measuring methane emission from manure collected at deep pit swine manure storages. The emission estimates based on manure samples agreed well with the meta‐analysis (Liu et al., 2013), and also highlighted the variability behind this average and the need for more research to qualify the key factors contributing to variation (Andersen et al., 2015).

Manure sample‐based estimates show promise for estimating methane production rates from stored manure, but deserve more extensive testing and comparison to farm‐level measurements. Diving into the causes for variability offer opportunity for more realistic and farm‐specific greenhouse gas emissions. Improved greenhouse gas measurements or estimates will more accurately predict current greenhouse gas emission levels, identify mitigation techniques, and focus resources where they are needed. This project offers an innovative approach to air quality improvement and strengthens engagement by the livestock sector in sustainability discussions.

The bottom line: manure is a critical piece for greenhouse gas emissions and carbon footprints for livestock and crop production systems. Estimation methods rarely incorporate farm‐based manure characteristics. The first desired outcome of the proposed work is that on‐farm sampling and measurement methods improve the accuracy for greenhouse gas emission estimates from the wide variety of manure management systems on Minnesota farms. This would lead to the second desired outcome; that enhanced techniques for on‐farm measurements identify hot spots for mitigating greenhouse gases using current and future manure management methods to reduce emissions.


  • Andersen, D., Van Weelden, M., Trabue, S., & Pepple, L. (2015). Lab‐assay for estimating methane emissions from deep‐pit swine manure storages. Journal of Environmental Management, 159, 18‐26. doi:http://dx.doi.org/10.1016/j.jenvman.2015.05.003
  • Appuhamy, J. A. D. R. N., Moraes, L. E., Wagner‐Riddle, C., Casper, D. P., & Kebreab, E. (2018). Predicting manure volatile solid output of lactating dairy cows. J Dairy Sci, 101(1), 820‐829. doi:10.3168/jds.2017‐12813
  • Capper, J. L., & Cady, R. A. (2020). The effects of improved performance in the US dairy cattle industry on environmental impacts between 2007 and 2017. J Anim Sci, 98(1), 1‐14. doi:https://doi.org/10.1093/jas/skz291
  • Dong, H., Mangino, J., McAllister, T. A., Hatfield, J., Johnson, D. W., Lassey, K. R., . . . Romanovskaya, A. (2006). Emissions from Livestock and Manure Management. In 2006 IPCC Guidelines for National Greenhouse Gas Inventories (Vol. 4: Agriculture, Forestry and Other Land Use). Paris, France: International Panel on Climate Change.
  • Heber, A. J., Ni, J. Q., Haymore, B. L., Duggirala, R. K., & Keener, K. M. (2001). Air quality and emission measurement methodology at swine finishing buildings. Trans ASAE, 44(6), 1765‐1778.
  • Keener, H. M., & Zhao, L. (2008). A modified mass balance method for predicting NH3 emissions from manure N for livestock and storage facilities. Biosyst Eng, 99(1), 81‐87. doi:DOI 10.1016/j.biosystemseng.2007.09.006
  • Liu, Z., Powers, W., & Liu, H. (2013). Greenhouse gas emissions from swine operations: Evaluation of the Intergovernmental Panel on Climate Change approaches through meta‐analysis1. J Anim Sci, 91(8), 4017‐4032. doi:10.2527/jas.2012‐6147 MPCA. (2020).
  • FAQs on greenhouse gas emissions in feedlot environmental assessment worksheets. Retrieved from https://www.pca.state.mn.us/water/faqs‐greenhouse‐gas‐emissions‐feedloteaw NPB. (2020).
  • Commit and Improve: Pig Farmers’ Approach to Sustainability. Retrieved from Des Moines, IA: https://www.porkcares.org/sustainability‐report/
  • Thoma, G., Putman, B., Bandekar, P., & Matlock, M. (2018). A retrospective assessment of US pork production: 1960 to 2015. Retrieved from Ames, IA: https://www.pork.org/wpcontent/ uploads/2016/10/16‐214‐THOMA‐final‐rpt.pdf USDairy. (2020).
  • Sustainability. Undeniably Dairy. Retrieved from https://www.usdairy.com/sustainability
  • Walmart. (2020). Sustainability: Enhancing sustainability of operations and global value chains. Retrieved from https://corporate.walmart.com/global‐responsibility/sustainability/