A Decision-Support Tool for The Design and Evaluation of Manure Management and Nutrient Reuse in Dairy and Swine Farm Facilities


The decision-support tool (DST) being developed facilitates the selection of manure treatment technology based on farm needs and nutrient balance requirements. A life cycle assessment (LCA) approach is used to determine and allocate among sources the whole-farm greenhouse gas (GHG) emissions and environmental impact of different manure management systems (MMS) to facilitate decision-making. The purpose of the tool is to help users identify the suite of technologies that could be used, given the farm’s unique set of preferences and constraints. The tool asks for an initial set of farm details and these values are cross-checked with predefined conditions before starting the simulation. This tool helps in the rapid quantification and assessment of treatment technology feasibility, GHG emissions, environmental, and economic impacts during the manure management decision-making process (Fig. 1). The decision algorithm operates based on user input for weightage priorities of criteria and sub-criteria related to environmental, economic, and technical components.

Figure 1. Graphical abstract

What Did We Do?

The DST is a Microsoft Excel-based tool with precalculated mass balance for a selected number of MMS alternatives representing current and emerging treatment technologies and practices. The MMS considered for the tool includes various handling systems, aerobic and anaerobic treatment systems, solid-liquid separation techniques, chemical processing units, etc. Modules were developed based on mass and energy balances, equipment capital & operating costs, unit process, and technology performance, respectively. The tool utilizes data specific to the country/region/farm where feasible and default values to calculate the overall economic and environmental performance of different MMS, providing results unitized per animal/day or per year.

Then, an LCA approach is used to evaluate the potential environmental footprints of each MMS considered. A life cycle impact assessment (LCIA) is comprised of detailed quantification of inputs and outputs of material flows in a specific treatment and/or conversion process. At the output level, it also defines and quantifies the main product, co-products, and emissions. The major focus on the treatment methods is quantifying the raw materials (manure, wash-water, bedding, etc.) that are to be handled in each MMS, thereby characterizing the properties of effluents (nutrients, gas emissions, etc.). The results include carbon, energy, water, land, nitrogen, and phosphorus footprints along with the effluent nitrogen, phosphorous, and potassium concentrations.

What Have We Learned?

Systematic selection of appropriate technology can provide environmental and economic benefits. Manure management systems vary in their design, due to individual farm settings, geography, and end-use applications of manure. However, the benefits of technological advancements in MMS provide manure management efficiencies and co-production of valuable products such as recycled water, fiber, sand bedding, and nutrient-rich bio-solids, among others. The handling efficiencies and environmental benefits provided by manure treatment technologies come with additional costs, however, so the tradeoffs between environmental benefits and implementation costs also need evaluation.

Future Plans

The next steps are to finalize the dairy module. We are refining the tool’s user interface and demonstrating to stakeholders to gather information regarding key assumptions, outputs, and the functionality of the tool. Further, we also plan to complete the swine module.


Sudharsan Varma Vempalli, Research Associate, University of Arkansas

Corresponding author email address


Additional authors

Sudharsan Varma Vempalli, Research Associate, University of Arkansas

Erin Scott, PhD Graduate Assistant, University of Arkansas

Jacob Allen Hickman, Project Staff, University of Arkansas

Timothy Canter, Extension Specialist, University of Missouri

Richard Stowell, Professor, University of Nebraska-Lincoln

Teng-Teeh Lim, Extension Professor, University of Missouri

Lauren Greenlee, Associate Professor, The Pennsylvania State University

Jennie Popp, Professor, University of Arkansas

Greg Thoma, Professor, University of Arkansas

Additional Information

Detailed economic impacts and tradeoffs expected with the implementation of certain MMS related to this tool is presented during the conference by Erin Scott et al., on the topic “Evaluating Costs and Benefits of Manure Management Systems for a Decision-Support Tool”.

Varma, V.S., Parajuli, R., Scott, E., Canter, T., Lim, T.T., Popp, J. and Thoma, G., 2021. Dairy and swine manure management–Challenges and perspectives for sustainable treatment technology. Science of The Total Environment, 778, p.146319. https://www.sciencedirect.com/science/article/pii/S0048969721013875


We acknowledge funding support from the United States Department of Agriculture (USDA) National Institute of Food and Agriculture (NIFA) grant award (# 2018-68011-28691). We would also like to thank our full project team and outside experts for their guidance on this project.


The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2022. Title of presentation. Waste to Worth. Oregon, OH. April 18-22, 2022. URL of this page. Accessed on: today’s date.

Evaluation of a Solid-Liquid Manure Separation Barn

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This paper documents an on-going evaluation of an existing, full-scale solid/liquid separator barn for the potential of improved manure nutrient conservation and management, water recycling, including cost and handling implications. The barn has V-shaped pit floor to drain liquid manure, and automated scrapers to collect solid manure frequently. The finishing barn was built to improve indoor air quality, and improve manure handling and land application of nutrients.

What did we do?

  1. Collected monthly manure samples (both solid and liquid manure samples) at the commercial barn starting in September, 2016. The collected samples were analyzed for important manure nutrients, pH, and moisture content.
  2. Monitored daily liquid manure production by measuring the water level fluctuation in the receiving pit, using a liquid pressure data logger (U20L-04, HOBO Water Level, Onset Computer Corporation, Bourne, MA). A new pressure gauge with two sensors was then added to allow simultaneous measurement of atmospheric pressure to improve accuracy.
  3. Monitored accumulation of solid manure, by measuring dimensions of the manure pile during each sampling event. A camera was purchased and installed at the storage shed to take hourly photos of the storage pile.
  4. Conducted filtration pilot tests using water and salty water and a bench-scale cross-flow treatment system, capable of various filtration options including reverse osmosis.
  5. Conducted settling/pre-treatment tests of the liquid manure samples, by storing liquid manure in individual jars and periodically characterizing settling of manure solids and duration needed before the high-pressure filtration.Figure 1. The V-shape pit with automated manure scraper and trough at center (Left), and gravity draining of liquid manure from the trough to the sump pit (Right).

What have we learned?

Battery-operated gauges were able to closely monitor the water level, liquid manure flow, and operation of the pump, and the dual-sensor gauge was much easier in data analysis and downloading. The daily liquid manure level fluctuated significantly during the first six months of monitoring, which could be due to differences in animal size and occurrence of barn washing. Solid manure samples collected in the current project had higher moisture contents than the four samples collected in 2014, meaning the solid/liquid separation barn was not as effective in separating solids and liquids as in 2014.  But, the settling tests suggest a settling basin could be designed to pre-treat the liquid manure stream before a water extraction process.

Figure 2. Daily liquid manure separated by the solid/liquid separation barn

Future Plan

A year’s worth of data will be collected, and manure nutrient flows of the solid and liquid portions will be quantified. The team will also characterize and compare the barn and management costs (relative to a typical deep-pit barn), practicality, and costs of the use of filtration and reverse osmosis. Will provide pork producers information on potential for the solid/liquid separation barn and filtration process to improve nutrient management, land application, and water conservation.

Corresponding author, title, and affiliation

Teng Lim, Associate Professor, Agricultural Systems Management, University of Missouri


Other authors

Joshua Brown, Graduate Research Assistant; and Joseph M. Zulovich, Assistant Professor; Agricultural Systems Management, University of Missouri.

Additional information

Teng Lim, limt@missouri.edu


The authors would like to thank the National Pork Board and University of Missouri Extension for financial support, and the farm management team for their help with the project.