Whole farm assessment of nutrient extraction from dairy manure


While animal manure contains nutrients and organic material that are beneficial for crop production, the concentrations of those nutrients are typically too low to allow economically viable transportation of bulk manures over long distances to where crops are sometimes produced. Therefore, dairy manure tends to be applied to soils near where it is generated. Since phosphorous (P) is conserved during manure handling compared to nitrogen, P concentrations in soils where dairy manure is applied tend to exceed crop demands. Due to the implication that P runoff from agricultural operations plays an important role in the eutrophication of streams and other water bodies, farmers are experiencing increasing pressure and regulation to not apply animal manures to fields that are already overloaded with P.

A possible solution to P overloading is to remove some of the P from manure before it is applied. In testing the MAnure PHosphorus EXtraction (MAPHEX) System Church et al. (2016, 2017, 2018), found that by treating liquid dairy manure with a screw press followed by a decanter centrifuge, 38 – 60% of the P could be removed from the manures of a wide variety of farms. A benefit to this approach is that the P removed, is concentrated into a stackable solid (about 72% moisture) that can be more economically transported to distant fields where P may be in deficit. The remaining liquid and course solids, containing greater than 90% of the manure N, can be beneficially used nearer the source without loading those soils with P. A comprehensive farm-scale evaluation of manure nutrient extraction is needed which can be done using the Integrated Farm System Model (IFSM; USDA, 2022). The IFSM has been used to assess other manure handling strategies along with many farm-scale options for crop, animal and feeding management.

What Did We Do?

We evaluated the whole-farm performance, environmental effects, and potential economic benefit of extracting P from dairy manure using a decanter centrifuge (Rotz et al., 2022). A farm in Pennsylvania with distant cropland was simulated with the IFSM to evaluate the feasibility of extracting P to reduce transport requirements on-farm or to produce a concentrated P product for off-farm use. Three production systems were evaluated with and without the use of centrifuge extraction. The first was the current farm with manure collected by flushing, next was the same farm with manure collection by scraping and the last was a modified farm with scraped manure where only forage crops were produced and concentrate feeds were purchased. Collection by scraping greatly reduced the volume of manure handled by the centrifuge thus reducing operating time and electricity use. Reducing the crop land and removing grain production created an imbalance in nutrient utilization with potential accumulation of P in the farm soil. Under this constraint, use of the centrifuge provided a method for removing a portion of the manure P for export from the farm.

Farm simulations estimated all forms of nitrogen, P, and carbon losses. This included erosion of sediment and runoff of sediment-bound and dissolved P across the farm boundaries. Costs for owning and operating the manure handling systems were determined using the economic component in IFSM. All equipment and facilities were amortized over an economic life and the annualized cost was added to other operating costs to get a total. Manure handling costs included fixed and operating (repair and maintenance, fuel, and labor) costs of the rotary screen, screw presses, and centrifuge. Manure hauling was also an important cost in the assessment because the number of trucks required and hauling distance varied among systems. Hauling cost included the amortized initial cost of trucks and annual costs for truck repair and maintenance, fuel, and operator labor.

What Have We Learned?

On a large dairy farm of 2,000 cows and 3,450 acres of land where manure must be transported to distant cropland to obtain uniform distribution, P extraction with a centrifuge provided a better ratio of nitrogen and P contents in manure used on nearby cropland and reduced transport costs for nutrients applied to more distant cropland. Centrifuge extraction was found to be more practical and economical when used with manure scraped from the barn floor than with flushed manure. Use of the centrifuge was not economically justified with the flush system where large volumes of low concentration liquid manure were handled. When barn floors were scraped, the benefit received through reduced manure volume more than offset the increased costs of owning and operating the centrifuge. To avoid long-term accumulation of soil P on the farm with less land (2,000 cows and 2,720 acres) where concentrate feed (27% of total feed) was imported, centrifuge extraction provided a material with a high P concentration that could be exported from the farm for other uses. Extracting the P in excess of crop needs cost about $1.14/lb P. This was generally greater than the price of phosphate fertilizer, but the extract also included other nutrients and micronutrients of value to crops.

A centrifuge provides a useful tool for extracting and concentrating manure P, but the economic benefit to the producer depends upon the value of the full array of nutrients contained, manure handling practices, and the end use of the extracted material. Although marketing this material for its P content alone may not be economical, the material may have other value and the reduction in long-term risk of surface water eutrophication has a less well-defined economic benefit to society.

Future Plans

The IFSM provides a tool for evaluating the performance, environmental impacts and economics of beef cattle and dairy production systems. The addition of the new component for modeling manure nutrient extraction technologies provides a tool for evaluating the whole farm costs and benefits of various technologies being developed or proposed for on-farm use. These can include manure processing based upon dissolved air floatation, evaporation, ultrafiltration, and the full MAPHEX system.


Alan Rotz, Agricultural Engineer, Agricultural Research Service, USDA

Corresponding author email address


Additional authors

Michael Reiner, Support Scientist, Agricultural Research Service, USDA; Sarah Fishel, Support Scientist, Agricultural Research Service, USDA; Clinton Church, Chemist, Agricultural Research Service, USDA

Additional Information

Church, C. D., Hristov, A., Bryant, R. B., Kleinman, P. J. A., & Fishel, S. K. 2016. A novel treatment system to remove phosphorus from liquid manure. Appl. Eng. Agric. 32: 103 – 112. doi:10.13031/aea.32.10999

Church, C. D., Hristov, A., Bryant, R. B., & Kleinman, P. J. A. 2017. Processes and treatment systems for treating high phosphorus containing fluids. US Patent 10,737958.

Church, C. D., Hristov, A. N., Kleinman, P. J. A., Fishel, S. K., Reiner, M. R., & Bryant, R. B. 2018. Versatility of the MAnure PHosphorus Extraction (MAPHEX) System in removing phosphorus, odor, microbes, and alkalinity from dairy manures: A four-farm case study. Appl. Eng. Agric. 34: 567 – 572. doi: 10.13031/aea12632

Rotz, C.A., Reiner, M., Fishel, S., & Church, C. 2022. Whole farm performance of centrifuge extraction of phosphorus from dairy manure. Appl. Eng. Agric. In press.

USDA-ARS. 2022. The Integrated Farm System Model, version 4.7. University Park, PA: USDA-ARS. Retrieved from https://www.ars.usda.gov/northeast-area/up-pa/pswmru/docs/integrated-farm-system-model


This work was supported by the U.S. Department of Agriculture, Agricultural Research Service.  USDA is an equal opportunity provider and employer. The authors thank the producer who contributed characteristics of their farm for this assessment.


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.

What Does Manure Collection and Storage Look Like?

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Farms collect and store manure in different ways. For the most part, manure is handled and stored as either solid, slurry, or liquid. The biggest differences are between systems designed for solid manure and those designed for liquid or slurry manure.

Solid Manure

Solid manure is approximately 80% (or less) moisture and 20% (or more) solids. It can be stacked into piles and handled with equipment like front-end loaders and box scrapers. Semi-solid manure (around 15% solids) is handled and stored the same as solid manure.

Common examples where farms handle manure as a solid:

  • Beef feedlots and dairy farms scrape manure from open earthen lots (Photo 1)
  • Broiler (meat chicken) litter is a mix of manure, feathers, and bedding (Photo 2)
  • Layer (egg-producing chicken) manure contains feathers but no bedding (Photo 3)

Less common examples where farms handle manure as a solid:

an open beef feedlot on left and dairy lot on right

Photo 1. (Above) Two examples of open earthen lots with beef cattle on the left and dairy cattle on the right.

broiler litter being cleaned out of a barn (left) and broiler chicks (right)

Photo 2: (Above) Broiler litter being cleaned out of a house (left) and what a similar house looks like when populated with chickens (right). Photos courtesy of Josh Payne, Oklahoma State University.

manure belt system for removing manure from layer hen house

Photo 3: (Above) Most layer hen houses built recently use belt systems to remove manure. Several cages are stacked on top of each other and a belt in between each tier catches the manure. The belts convey manure to a collection point; manure is taken from the collection point to a separate storage area. Photo courtesy of Robb Meinen, Pennsylvania State University.

Solid Manure Storage

Solid manure is typically stacked or piled in storage areas that may be covered (Photos 4 and 6, below) or uncovered (Photo 5, below) depending on the amount of rainfall or snowmelt an area receives. Farms in arid areas are more likely to manage solid manure storage areas without a roof or cover.

Roofs or covers prevent rain or snowmelt from entering the storage area, but are more expensive to build. If precipitation causes runoff from uncovered solid manure storage areas, the runoff needs to be captured and contained to prevent it from reaching streams, lakes, or other surface water.

manure storage area in the lower level of a high-rise layer hen house

Photo 4. (Above) Solid layer hen manure is stored on the ground level of this high-rise layer house. The hens are housed in the upper level and manure falls through slats in the floor. High-rise houses used to be the most common system for layer hens but are gradually being replaced by manure belt systems. Image courtesy of the United Egg Producers.

a beef feedlot manure storage area showing equipment used to stack the manure

Photo 5. (Above) The solid manure storage area and handling equipment for a beef feedlot.

a covered solid manure storage facility on a poultry farm

Photo 6. (Above) A covered manure storage structure on a poultry farm. Photo courtesy of David Schmidt, University of Minnesota.

Slurry Manure

Slurry manure is approximately 10-15% solids. It is a very thick liquid that requires pumps for collection and handling. Equipment and structures for handling slurry manure need to be engineered for materials of this consistency.

Common examples where farm collect and handle manure as a slurry:

  • Pig manure in deep pit barns
  • Dairy manure in scrape (Photo 8, below) or vacuum systems in free stall barns

Less common examples where farms collect and handle manure as a slurry:

  • Layer hen farms with scrape systems
  • Slatted floor beef buildings with a manure pit

a slatted floor in a pig barn

Photo 7. (Above) A slatted floor in a small-scale swine research barn. Slatted floors are part of both slurry and liquid manure collection systems, especially on pig farms. If a deep pit for long-term storage is beneath this floor, the farm handles manure as a slurry. If manure is flushed from beneath the slats to an external storage structure, the farm likely handles manure as a liquid. Photo courtesy of Rick Ulrich, University of Arkansas.

scrape system for collecting slurry manure in a dairy barn

Photo 8: (Above) An automated scraper collecting slurry manure in a freestall dairy barn. Slurry manure can also be collected from barns or feed pads using vacuum tankers. Photo courtesy of Karl Vandevender, University of Arkansas.

Liquid Manure

Liquid manure has only a small amount of solids (less than 5%). It is very dilute in terms of nutrient content and cannot be hauled long distances because of the cost of hauling large amounts of water. Liquid manure is collected and handled with gravity flow or pumps and is stored in structures called ponds or lagoons.

Common examples where farms handle manure as a liquid:

  • Runoff holding ponds for open earthen lots (beef or dairy)
  • Pull-plug or flush systems in pig barns
  • Flush systems in dairy barns

Less common examples where farms handle manure as a liquid:

  • Layer hen farms with flush systems

Slurry and Liquid Manure Storage

Slurry and liquid manure can be stored in earthen pits (Photo 9, below), holding ponds, or treatment lagoons. They can also be stored in above-ground tanks (Photo 10, below) or in concrete structures (Photo 11, below).

an earthen liquid manure storage structure

Photo 9. (Above) An earthen liquid manure storage structure on a pig farm. Photo courtesy of USDA NRCS.

an above ground slurry manure storage tank

Photo 10. (Above) The orange arrow points to an above-ground steel manure storage tank.

a concrete manure storage structure on a dairy farm

Photo 11. (Above) The manure storage structure on this dairy farm includes a concrete wall near the barn and ramp for access when removing manure. Photo courtesy of David Schmidt, University of Minnesota.

The video below, produced by the University of Wisconsin, introduces systems for handling and storing liquid and slurry manure. It also discusses safety precautions for these systems and structure. The final section covers the importance of agitation, or mixing, when preparing manure for land application.

Process Wastewater

Process wastewater is water used by farms, often for cleaning, which comes in contact with animals, manure, or feed. It may also contain chemicals for sanitizing or cleaning a product or surface. This is not considered to be manure, but must be captured and contained and can be stored in the liquid manure storage structure or a separate structure.

Common types of process wastewater generated on animal farms:

  • Egg wash water
  • Milking center wash water

Covered Manure Storage

In recent years, the use of covers on manure storage structures has increased. This is especially true for pig farms. Covers are primarily used to address odor concerns, but can also be part of an anaerobic digestion system. Photo 12, below, shows a covered manure storage structure.

a small manure storage structure with a cover installed

Photo 12: (Above) A very small earthen manure storage structure with a cover installed. Most covered manure storage structures are larger than this but look very similar.

Is There Enough Manure Storage Capacity?

The main purpose of manure storage is to contain manure, process wastewater, and contaminated runoff until it can be safely and appropriately applied to crop fields or be used in an alternative manner. Good stewardship of manure storage involves two important steps:

  1. Designing the facility so it has enough capacity to store manure and process wastewater generated by the farm plus precipitation plus freeboard (margin of safety) during time periods when land application is not possible or appropriate.
  2. Operating and maintaining the manure storage or treatment facility so that problems can be identified and prevented or corrected before they cause overflows or failures.

There are several considerations when calculating the amount of capacity needed in the manure storage or treatment structure and planning for its operation and maintenance.

Regulatory requirements. For some farms, the minimum amount of storage capacity and freeboard as well as frequency of inspections is prescribed by regulation. Keeping records on design and construction, inspections and findings, maintenance activities, corrections made, and amount of manure or process wastewater in the storage structure is essential to prove the requirements are met.

Cropping system. Manure is not usually applied to fields between planting and harvest for cultivated crops. The amount of time fields are unavailable during the growing season should be factored into the planning for manure storage structures. Hay or pasture fields add some flexibility because manure can be applied more often. But, as with cultivated crops, hay or pasture fields should not have more manure nutrients applied than is agronomically indicated in the nutrient management plan. Farmers who rely on off-site manure transfers to neighboring farms or for other uses should also consider the cropping system or other timing needs of manure recipients and plan their storage period appropriately.

Climate. The design capacity of manure storage will be influenced by the amount of time that manure must be stored during extended time periods that are undesirable for land application. Those include times when soils are frozen, snow-covered, or saturated. Design capacity for uncovered manure storage structures also needs to consider how much rain or snow melt may add to manure levels.

two examples of liquid manure depth markers

Photo 13. (Above) This collage shows two depth markers in manure storage structures. The concrete structure on the left includes a simple rope (see orange arrow) marked at regular intervals as a way to monitor manure levels. The marker on the right is more elaborate and includes (recommended) a “start pumping” mark (yellow bar extending to the left). The especially important levels a farm manager should know are “start pumping” when the level reaches design capacity and, for some structures, “stop pumping” when it reaches a lower limit. It is also important to know the level to which manure should be pumped/emptied before entering a season where land application is not possible. If a state bans manure application from December 15 until April 1 for example, a farm should know which mark manure levels should be below to ensure enough storage capacity going into that season. Concrete structure image courtesy of Robb Meinen, Pennsylvania State University and metal depth marker image courtesy of Leslie Johnson, University of Nebraska.

Future plans. What are the chances a farm will add more animals in the future? Expanding to 1,500 animals when the manure storage is designed for 1,000 means the structure will fill up faster than originally intended, making unlawful spills or inappropriate land application practices more likely.


Figure 1. A schematic of the different categories of waste and the related volumes that the storage design must accommodate. More than just manure, process wastewater, or open lot runoff needs to be factored into the designed capacity. Anaerobic lagoons require a minimum volume at all times so that the bacteria treating the manure remain present and active. Some minimum storage level also helps keep the bottom sealed by preventing drying and cracking. Storage or treatment structures that do not have a roof or cover also need to hold typical rainfall or snowmelt for the area. Every storage structure storage should be designed and managed to maintain a margin of safety, or freeboard, so that it is never filled to the top. Figure courtesy of University of Missouri Extension via Dr. Charles Fulhage.

Resources On Manure Storage Design and Sizing

a manure storage full and near overtopping

Photo 14. (Above) A manure storage structure about to overflow due to recent rainfall. This problem is most common when long winters or extended wet periods in the fall or spring make manure land application difficult or impossible. Managing this risk requires planning ahead as much as possible to prevent it.  In this photo, the farm is agitating the manure and getting ready to apply it to a field to lower the manure level in the storage structure. Favorable weather conditions allowed application when field soil conditions were acceptable, or no longer saturated.

Recommended Reading

Previous: Trends in Animal Ag & Manure | Next: Manure Nutrients and Land Application


These materials were developed by the Livestock and Poultry Environmental Learning Center (LPELC) with funding from the U.S. Environmental Protection Agency and with input from the Natural Resources Conservation Service, National Cattlemen’s Beef Association, National Milk Producers Federation, National Pork Board, United Egg Producers, and U.S. Poultry and Egg Association.

For questions on these materials, contact Jill Heemstra, jheemstra@unl.edu. All images in this module, unless indicated otherwise, were provided by Jill.

Reviewers: Tetra Tech, Inc.; Joe Harrison, Washington State University; Rick Koelsch, University of Nebraska; and Tom Hebert, Bayard Ridge Group

Cataloging and Evaluating Dairy Manure Treatment Technologies

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To provide a forum for the introduction and evaluation of technologies that can treat dairy manure to the dairy farming community and the vendors that provide these technologies.

What Did We Do?

Newtrient has developed an on-line catalog of technologies that includes information on over 150 technologies and the companies that produce them as well as the Newtrient 9-Point scoring system and specific comments on each technology by the Newtrient Technology Advancement Team.

What Have We Learned?

Our interaction with both dairy farmers and technology vendors has taught us that there is a need for accurate information on the technologies that exist, where they are used, where are they effective and how they can help the modern dairy farm address serious issues in an economical and environmentally sustainable way.

Future Plans

Future plans include expansion of the catalog to include the impact of the technology types on key environmental areas and expansion to make the application of the technologies on-farm easier to conceptualize.

Corresponding author name, title, affiliation  

Mark Stoermann & Newtrient Technology Advancement Team

Corresponding author email address  


Other Authors 

Garth Boyd, Context

Craig Frear, Regenis

Curt Gooch, Cornell University

Danna Kirk, Michigan State University

Mark Stoermann, Newtrient

Additional Information



All of the vendors and technology providers that have worked with us to make this effort a success need to be recognized for their sincere effort to help this to be a useful and informational resource.

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. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.

USDA-NRCS and the National Air Quality Site Assessment Tool (NAQSAT) for Livestock and Poultry Operations

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The National Air Quality Site Assessment Tool (NAQSAT) was developed as a first-of-its-kind tool to help producers and their advisors assess the impact of management on air emissions from livestock and poultry operations and identify areas for potential improvement related to those air emissions.

What did we do?

In 2007, several land-grant universities, with leadership from Michigan State University, began developing NAQSAT under a USDA-NRCS Conservation Innovation Grant (CIG). The initial tool included beef, dairy, swine, and poultry operations. A subsequent CIG project, with leadership from Colorado State University, made several enhancements to the tool, including adding horses to the species list. In 2015, USDA-NRCS officially adopted NAQSAT as an approved tool for evaluating air quality resource concerns at livestock and poultry operations. USDA-NRCS also contracted with Florida A&M University in 2015 to provide several regional training workshops on NAQSAT to NRCS employees. Six training workshops have been completed to date (Raleigh, NC; Modesto, CA; Elizabethtown, PA; Lincoln, NE; Richmond, VA; and Yakima, WA) with assistance from multiple NAQSAT development partners. Additionally, USDA-NRCS revised its comprehensive nutrient management plan (CNMP) policy in October 2015 to make the evaluation of air quality resource concerns mandatory as part of CNMP development.

Snippet from website of the National Air Quality Site Assessment Tool

Group photo of team in field

Zwicke in class lecturing

Zwicke and group in animal housing facility

What have we learned?

NAQSAT has proven to be a useful tool for bench-marking the air emissions impacts of current management on confinement-based livestock and poultry operations. In the training sessions, students have been able to complete NAQSAT runs on-site with the producer or producer representative via tablet or smartphone technologies. Further classroom discussion has helped to better understand the questions and answers and how the NAQSAT results can feed into the USDA-NRCS conservation planning process. Several needed enhancements and upgrades to the tool have been identified in order to more closely align the output of the tool to USDA-NRCS conservation planning needs. NAQSAT has also proven to be useful for evaluating the air quality resource concern status of an operation in relation to the CNMP development process.

Future Plans

It is anticipated that the identified needed enhancements and upgrades will be completed as funding for further NAQSAT development becomes available. Additionally, as use of NAQSAT by USDA-NRCS and our conservation planning and CNMP development partners expands, additional training and experience-building opportunities will be needed. The NAQSAT development team has great geographic coverage to assist in these additional opportunities.

Corresponding author, title, and affiliation

Greg Zwicke, Air Quality Engineer – Air Quality and Atmospheric Change Team, USDA-NRCS

Corresponding author email


Other authors

Greg Johnson, Air Quality and Atmospheric Change Team Leader, USDA-NRCS; Jeff Porter, Animal Nutrient and Manure Management Team Leader, USDA-NRCS; Sandy Means, Agricultural Engineer – Animal Nutrient and Manure Management Team, USDA-NRCS

Additional information





C.E. Meadows Endowment, Michigan State University

Colorado Livestock Association

Colorado State University

Florida A&M University

Iowa Turkey Federation

Iowa Pork Producers

Iowa Pork Industry Center

Iowa State University

Iowa State University Experiment Station

Kansas State University

Michigan Milk Producers Association

Michigan Pork Producers Association

Michigan State University

Michigan State University Extension

National Pork Board

Nebraska Environmental Trust

Oregon State University

Penn State University

Purdue University

Texas A&M University

University of California, Davis

University of Georgia

University of Georgia Department of Poultry Science

University of Idaho

University of Maryland

University of Maryland Department of Animal and Avian Sciences

University of Minnesota

University of Missouri

University of Nebraska


Virginia Tech University

Washington State University

Western United Dairymen

Whatcom County (WA) Conservation District

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. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.

Nitrogen and Phosphorus Cycling Efficiency in US Food Supply Chains – A National Mass-Balance Approach

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Assessing and improving the sustainability of livestock production systems is essential to secure future food production. Crop-livestock production systems continue to impact nitrogen (N) and phosphorus (P) cycles with repercussions for human health (e.g. secondary particle formation due to ammonia emission and drinking water contamination by nitrate) and the environment (e.g. eutrophication of lakes and coastal waters and exacerbation of hypoxic zones). Additionally, P is a limited resource, and sustaining an adequate P supply is a major emerging challenge. To develop strategies for a more sustainable use of N and P, it is essential to have a quantitative understanding of the flows and stocks of N and P within the society. In this study, we developed detailed national N and P budgets to assess nutrient cycling efficiency in US (livestock) food supply chains, to identify hotspots of nutrient loss and to indicate opportunities for improvement!

What did we do? 

1. National nutrient mass-balance

A mass-balance framework was developed to quantify nutrient flows within the US. In this framework, the national US system is represented by 9 major sectors are relevant in terms of nutrient flows: mining (relevant for P only), industrial production, agriculture, food & feed processing industry, retail, households and other consumers, energy and transport, humans, and waste treatment. These sectors can exist of several sub-sectors. For example, the agricultural sector consists of several secondary sub-systems including pasture, agricultural soil, livestock and manure management (WMS – waste management system).

Different livestock categories can have distinct environmental impacts and nutrient use efficiencies (e.g. (Hou et al. 2016), (Eshel et al. 2014), (Herrero et al. 2013)), we therefore distinguish six livestock categories (dairy cattle, beef cattle, poultry (meat), poultry (layers), sheep, hogs) and

 their associated food commodities (dairy products, beef from dairy cattle, beef, poultry, eggs, lamb, pork).

For each sub-system, we identify and quantify major flows to and from this compartment. All flows are expressed in a common unit, i.e. metric kiloton N per year (kt N/yr) for nitrogen and metric kiloton P per year (kt P/yr) for phosphorus. Quantified flows include nutrient related emissions to the environment and waste flows.

At present, the waste sectors and environmental compartment are outside the system boundaries, that is, we quantify flows to these compartments, but we do not attempt to balance these sectors. We do, however, keep track of the exact chemical species (e.g. emission of N2O-N to air instead of N to air) emitted as far as possible. The municipal waste treatment (MSW) and municipal waste water treatment (WWTP) are treated in more detail: major flows from and to these compartments are quantified. These sub-sectors are treated in more detail because of their role in nutrient recycling through e.g. sewage sludge application on agricultural soils.

Data were collected in priority from national statistics (e.g. USDA NASS for livestock population) and peer-reviewed literature, and were supplemented with information from industrial reports and extension files if needed. If available, data were collected for the years 2009 to 2012 and averaged, when unavailable, we collected data for the closest year.

2. Scenario analysis

In the scenario analysis, we test the opportunity for dairy livestock production systems to contribute to a more efficient nutrient use through anaerobic co-digestion of dairy manure and organic food waste. Recently, Informa Economics assessed the national

 market potential of anaerobic digester products for the dairy industry (Informa Economics 2013). Next to a reduction in greenhouse gas emissions, anaerobic co-digestion of dairy manure and organic food waste can contribute to improve nutrient cycling efficiency (Informa Economics 2013). Dairy manure contains high levels of nitrogen and phosphorus, which can be used as a natural crop fertilizer, if recuperated from manure. Presently, non-farm organic substrates such as food waste are typically disposed of in landfills, which causes greenhouse gas (GHG) emissions and also results in a permanent removal of valuable nutrients from the food supply chain (Informa Economics 2013). By anaerobic co-digestion, a part of the nutrien! ts contai ned in dairy manure and food waste can be recovered. These nutrients can be used to fertilize crops and substitute synthetic fertilizer application. In the scenario analysis, we test to what extent anaerobic co-digestion of dairy manure and food waste can contribute to improve nutrient cycling efficiency, particularly by substituting synthetic fertilizers. We develop the scenario based on data provided in the InformaEconomics report.

What have we learned? 

In general, our results show that livestock production is the least efficient part of the total food supply chain with large losses associated with manure management and manure and fertilizer application to crops. In absolute terms, the contribution of the household stage to total and N and P losses from the system is small, approximately 5 and 7% for N and P, respectively. However, households ‘waste’ a relatively large percentage of purchased products, (e.g. 16% and 18% of N and P in dairy products end up as food waste), which presents an opportunity for improvement. A scenario was developed to test to what extent anaerobic co-digestion of dairy manure and food waste can contribute to improving nutrient cycling efficiency on a national scale. Results suggest that 22% and 63% of N and P applied as synthetic fertilizer could potentially be avoided in dairy food supply chains by large scale implementation of anaerobic co-digestion o! f manure and food waste.

Future Plans     

Future research plans include a further development of scenarios that are known to reduce nutrient losses at the farm scale and to assess the impact of these scenarios on national nutrient flows and losses.

Corresponding author, title, and affiliation        

Karin Veltman, PhD, University of Michigan, Ann Arbor

Corresponding author email    


Other authors    

Carolyn Mattick, Phd, Olivier Jolliet, Prof., Andrew Henderson, PhD.

Additional information                

Additional information can be obtained from the corresponding author: Karin Veltman, veltmank@umich.edu


The authors wish to thank Ying Wang for her scientific support, particularly for her contribution in developing the anaerobic co-digestion scenario.

This work was financially supported by the US Dairy Research Institute.


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. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.