Feedlot Air Emissions Treatment Cost Calculator

logoThere are several techniques that animal feeding operation owners and managers can use to manage odors and gas emissions. Each technique has different costs and benefits. The Feedlot Air Emissions Treatment Cost Calculator is a tool that can be used to compare alternative technologies and designs with different costs and benefits. The calculator has information on biofilters, covers, scrubbers, manure belts, vegetative buffer and anaerobic digesters.

This spreadsheet tool is intended to assist the operator of a livestock or poultry operation to calculate the costs and benefits of installing technologies to treat odors and gases that could be emitted from the facility.

Download the Air Emissions Treatment Cost Calculator

The tool requires Excel 2007 or later versions. Download the spreadsheet. Note: This is a spreadsheet with active macros. Depending on your security settings, you may have to tell your spreadsheet program that it is OK to open it. The four videos below provide instructions on how to use the decision tool.

Instructional Videos for the Air Emissions Treatment Cost Calculator

Four videos below describe the cost calculator and how to use it.


Biofilters and Covers

Scrubbers, Manure Belts, Buffers, Digesters

Benefits and Summary


Additional materials in this series (videos):

The Feedlot Air Emissions Treatment Cost Calculator was developed by Dr. Bill Lazarus (wlazraus@umn.edu) in the Applied Economics Department at the University of Minnesota for a multistate USDA funded research and Extension project. The calculator was suggested by stakeholders that included producers and managers of swine, poultry and dairy producing operations, equipment manufacturers and suppliers, human medicine, veterinary medicine, local and state regulators, local and county elected officials, Extension and NRCS.

Supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2010-85112-20520. If you have any questions about the project, contact Dr. Kevin Janni, University of Minnesota, kjanni@umn.edu

What Is Manure Worth Web Calculator

Livestock producers face uncertain markets and narrow margins

calculatorThis situation motivates growers to optimize production methods, utilizing all resources including manure. In addition, an increase in the price of commercial fertilizer experienced since 2009, has heightened interest in the use of manure for supplying crop nutrients and has significantly increased the value of manure as a nutrient source.

Estimates of the economic value of manure are important in comparing manure application rates and methods, valuing manure for off-farm sale, budgeting new facilities, and evaluating contract livestock production opportunities.

Free Manure Value Calculator

The University of Minnesota has developed a free calculator to rapidly estimate the value of manure for specific manure types, application methods, soil nutrient status, and crop need.

For more information, see the University of Minnesota’s page on Animal Waste/Manure Economics

The estimates are based on fertilizer replacement value and application costs. The manure economic value is calculated as shown below.

Net Economic Impact of Manure = Value of First-Year Fertilizer Replaced (N, P2O5, K2O, and micronutrients) & Fertilizer Application Costs Avoided + Residual Value in the Second Year or Later (if any, this relates to fertilizer nutrients that would have been purchased) +/- Non-NPK Yield Response (and possibly tillage impacts and weed control impacts)

Simple Steps to Evaluate Manure Value

In Step 1, enter current fertilizer (if using no manure) and N, P, K, and micronutrients needs for the crop.

In Step 2, choose the manure source, amount and nutrient content, and application method.

Step 3 considers some final adjustments such as second year benefits, tillage saving and yield boost impact.

Economics of Anaerobic Digesters for Processing Animal Manure

Digesters are of interest with regards to climate change, energy, air quality, and water quality. However, digesters are capital-intensive and difficult to maintain. Profitability of a farm-based digester usually requires utilizing the energy, carbon credits, tipping fees, and marketing other co-products such as manure solids that are separated out and composted.

Terminology and Types of Digesters

Anaerobic digestion is the process in which microbes in the absence of oxygen convert volatile acids in livestock manure into biogas consisting of methane, carbon dioxide, and small amounts of water and other compounds. The methane produced by this process can be burned to generate electricity and/or heat. Under favorable circumstances, there is also a potential for purifying the methane into a marketable, natural gas-grade biogas suitable for household and industrial use. For more information, see Processing_Biomass_Into_Biogas.

Rather than using the biogas to generate electricity, a few digester systems are beginning to upgrade the biogas to natural gas standards and trucking or piping it to off-site industrial users. One U.S. digester operator is following Sweden’s lead by powering milk trucks with compressed biogas. Digestion itself has little effect on the nutrient content of manure, but integrated nutrient removal systems have been proposed that would use digester energy to power other equipment that would divert nutrients away from land application to other uses. In addition to generating renewable energy, anaerobic digestion leads to reduced odor pollution, fewer pathogens, and reduced biochemical oxygen demand. Digestion stabilizes the volatile organic compounds that remain in the manure so that they can be land-applied with fewer objectionable odors; so many farm digesters have been installed to address neighbors’ complaints. There is little change in the nutrient value of the manure and organic matter that passes through the process, which can then be used as fertilizer. For more information, see Environmental Benefits of Anaerobic Digestion.

There were 151 digesters operating at commercial livestock farms in the United States as of May 2010, according to the U.S. AgSTAR website.

While the focus here is on manure, any organic matter (“digestate”) can be processed in a digester. Wastewater sludge, municipal solid waste, food industry wastes, grain industry and crop residues, and paper and pulp industry wastes are other materials that are processed in digesters. Addition of organic matter from off-farm sources to a farm digester is referred to as “co-digestion”. The additional material can increase biogas output and can also generate “tipping fees” paid by the off-farm source.

Digester Designs

The three main designs for farm-based digesters are the covered anaerobic lagoon, plug-flow, and complete mix (or continually stirred tank reactor). The solids content of the material to be digested is an important criterion in the choice of digester design. Plug-flow digesters work best at a solids content of 11–13 percent, so they work well with dairy manure from operations that collect it by scraping or other methods that do not add much additional water. Complete-mix digesters work at a wider range of 2–10 percent solids, which makes them suitable for a greater variety of materials including swine manure and processing wastes as well as dairy manure. Variations on these three basic designs have been developed to enhance biogas output and/or to deal with varying moisture levels and other digestate characteristics. For more information, see Types of Anaerobic Digesters.

Plug-Flow Digester

Complete Mix Digester

Covered Lagoon Digester

Digester Temperatures

The rate of digestion depends on temperature, so anaerobic digesters are also classified by working temperature. Mesophilic digesters work at temperatures between 95 and 105 degrees Fahrenheit. Those that work between 120 and 140 degrees are known as thermophilic. Covered lagoons operate at psycrophilic temperatures lower than 95 degrees. They are lower in cost and are commonly used where odor control is the main objective. However, in some warmer locations covered lagoon digesters are successfully used to produce energy.

Livestock Facilities Best Suited for Digesters

It is not practical to run the manure from all livestock through digesters. The potential for methane production from livestock waste depends on size of the farm operation, freshness of the waste, and concentration of digestible materials in the manure. Free-stall dairy operations with daily-scraped alleys work well with digesters because the manure does not get mixed with dirt or stones and is moved into the digester while fresh.

Other Digester Applications

Municipal sewage treatment plants tend to use digesters to reduce the volume of solids and minimize the land required for spreading sludge. For more dilute wastes such as those in municipal sewage treatment plants or flush manure systems, “fixed-film” or “filter” digesters are designed to retain the bacteria on some type of medium long enough to break down the waste rather than allowing it to be immediately flushed out of the system.

Europe faced energy reductions during and after World War II and is still more dependent on imports of oil and natural gas than the United States. Thus, it is not surprising that Europe has moved more aggressively to develop digesters, along with other renewable energy sources, than has the United States. Europeans call them “biogas plants”. Germany is considered the world leader in farm-based digesters with around 4,000 currently installed. Small digesters have long been used in rural areas of India, China, and other Asian countries as a source of cooking gas.

Reducing Greenhouse Gas Emissions and Getting Credit For It

Digesters reduce greenhouse gas emissions, as measured by warming potential. However, some people are confused by the fact that a digester doesn’t reduce CO2. The methane from a digester is destroyed through combustion in an engine, flare, or other device. Combustion actually produces CO2 and water (H2O). Methane (CH4) is considered to be around 23 times as powerful as CO2 in its effect on global warming, however, so the overall impact of converting CH4 to CO2 is considered beneficial.

Burning biogas reduces greenhouse gas emissions in two ways: first, when manure is stored in a conventional liquid handling system without a digester, it typically emits a certain amount of methane-containing biogas. When that methane is collected in a digester and burned, it then will not escape into the atmosphere and cause warming. Second, electricity generated from that digester biogas will typically replace fossil fuel-generated electricity. There will be a reduction in CO2 emissions from not burning that fossil fuel.

There are at least two ways that a farm digester operator can generate revenue by burning biogas that contains methane. One way is to sell carbon credits. Such sales are generally handled through a third-party intermediary aggregator firm that audits the digester initially to verify the methane quantity and aggregates those quantities into an account that is sold to a buyer who has committed to some level of greenhouse gas reduction. The aggregator then monitors performance over some agreed-upon contract period.

Another way of generating revenue is by marketing renewable energy credits (RECs) to an electrical utility that is under mandate to generate part of their electricity from renewable sources. In Minnesota, for example, utilities must obtain at least 25% from renewable sources by 2025. The REC value would typically be negotiated as part of the power purchase agreement between the utility and the digester operator. More stringent water quality regulations are also pressuring livestock operations to minimize nonpoint nutrient losses and in the future may also offer nutrient credit trading opportunities to generate additional revenue.

Air and Water Quality

Digestion converts volatile organic compounds in manure to more stable forms that can be land-applied with fewer objectionable odors; so many farm digesters have been installed to address neighbors’ complaints.

Nutrients do not disappear in a digester, although some may settle out. Organic nitrogen is converted to ammonium during digestion, so the ammonium level in the digestate typically rises. This conversion may make the nitrogen more rapidly available to the crop once land applied, which may offer opportunities to change application rates and timing. Without a change in nutrient amounts, adding a digester is unlikely to have a large impact on water quality. Digesters are often included along with manure storage facilities, solids separators, and composting facilities in an improved overall system. Taken together, the system may offer great opportunities to improve water quality by transporting the manure nutrients to fields where they are most needed and applying them when the crops need them most.

Manure Fiber Utilization

Use of separated dairy manure fiber for bedding is common, despite concerns that it might increase mastitis problems. The concern is greatest in warm and moist conditions. Determining the impact on mastitis is complicated by a number of factors, including different ways of measuring the concentration of bacteria in bedding (by weight on a wet or dry basis or by volume); changes in bacterial levels in bedding during the time it sits in the stall; the relationship between bacteria in the bedding and on teat ends; and the impact of bacteria in bedding and on teat ends on the occurrence of mastitis and on milk quality. More research is needed to clarify the impact of bedding type on mastitis, in the context of the many other management factors on a typical dairy farm. The economic value of solids as an off-farm soil amendment appears to vary widely, depending on the seller’s marketing expertise and location.

Capital and Requirements and Operations and Maintenance Costs

The capital requirements to install a digester will vary widely depending on digester design chosen, size, and choice of equipment for utilization of the biogas and/or for separating out manure fiber. The current capital cost range for complete digester systems is estimated at $1,000 to $2,000 per cow depending on herd size, with the cost to maintain an engine-generator set at $0.015 to $0.02/kWh of electricity generated. An AgSTAR regression of investments made versus herd size at nineteen recent dairy farm plug-flow digesters gave a result of $566,006 + $617 per cow in 2009 dollars. Ancillary items that may be incurred are charges for connecting to the utility grid and equipment to remove hydrogen sulfide, which could add up to 20 percent to the base amount. Figuring the ancillary items at 10 percent, the investment works out to $1.2 million for a 700-cow dairy operation, going up to $2.7 million for 2,800 cows. A similar regression for thirteen mixed digesters gave $320,864 + $563 per cow. A solids separator would add up to another 12 percent to these amounts. There is considerable interest in digester designs that are economically feasible for smaller farms, but some digester components are difficult to scale down. A complete mix digester with separator installed on a 160-cow Minnesota dairy farm in 2008 cost $460,000, or $2,875/cow. Another recent study found that the electrical generation equipment made up on average 36 percent of total investment for a group of 36 digesters, suggesting that substantial cost savings may be possible in situations where the biogas can be used for heating rather than to produce electricity.

Public Incentives

The federal government and many states offer incentives for installing digesters. The 2008 Farm Bill included two grant and loan programs that cover digesters – the Rural Energy for America Program (REAP) and the Value-Added Producer Grant Program. REAP provides grants of up to 25 percent of project cost and loan guarantees of up to $25 million. Value-Added Producer Grants can provide planning costs and working capital. Utilities will also sometimes underwrite part of the cost of the electrical generating equipment.

Potential Challenges When Installing a Digester

While most farm-based digesters in the U.S. generate electricity with the biogas, negotiating an acceptable agreement with the local utility is often a challenge. Arranging financing and obtaining permits are other challenges that producers have noted.

A potential concern with accepting off-farm wastes is that on livestock farms with small land bases, the livestock manure alone may already have too much nitrogen and phosphorus for the cropland available. Imported nonfarm organic wastes would contain additional nutrients which could exacerbate the cropland nutrient imbalance. The tipping fees and added gas output need to be weighed against potentially greater manure hauling costs to take the effluent to more distant cropland where the nutrients can be utilized.

The Bottom Line

A digester is a major capital investment, and calls for a careful engineering and economic analysis of the particular situation. Consultants and computer decision tools are available to assist with the analysis. Published digester economic assessments tend to show that the most successful digesters are those that have generated added value from separated manure fiber, charged tipping fees from accepting off-farm food processing wastes, or had a nearby high-value use for the biogas or electricity. Pathogen reduction is another frequently-cited benefit of digestion. Electricity sales alone are not usually enough to cover costs. Even an unprofitable digester may be regarded as successful if it provides nonmonetary benefits such as odor control.

Additional Information

Author: William F. Lazarus, University of Minnesota

All Images: cc2.5 William F. Lazarus, University of Minnesota

Minnesota Watershed Nitrogen Reduction Planning Tool


Using the nitrogen reduction planning model involves three steps.  The first step is to select a watershed, enter hypothetical adoption rates for each BMP, and compare the effectiveness and cost of the individual BMPs.  The second step is to compare suites of the BMPs that would attain any given reduction in the N load at minimum cost.  The third step is to “drill down” to the details and assumptions behind the models of effectiveness and costs of any particular BMP and make any adjustments to reflect your particular situation.

Why Develop a Nitrogen Reduction Planning Tool?

A watershed-level nitrogen reduction planning tool (Excel spreadsheet) compares the effectiveness and cost of nine different “best management practices” (BMPs), alone and in combination, for reducing N loads leaving a Minnesota watershed.  The Minnesota Pollution Control Agency is developing a new set of standards for nitrate nitrogen in surface waters based on aquatic life toxicity.  The tool was developed to assist the agency and local resource managers to better understand the feasibility and cost of various “best management practices” to reduce N loading from Minnesota cropland.

What Did We Do?

The BMPs are:  reducing corn N fertilizer rates to extension recommended rates, changing fertilizer application timing, seeding cover crops, installing tile line bioreactors or controlled drainage, planting riparian buffers, or converting some corn and soybean acres to a perennial crop. The spreadsheet does its analysis for a watershed that the user selects.  However, the N loadings and crop economic calculations are done first by agroecoregion before aggregating the results into the watershed of interest.  Agroecoregions are units having relatively homogeneous climate, soil and landscapes, and land use/land cover.  The spreadsheet includes area data for the fifteen high-N HUC8 watersheds that make up roughly the southern half of the state, along with the state as a whole.  When the user selects a watershed for analysis, formulas retrieve results as an area-weighted average of the agroecoregions making up that watershed.  Each of the fifteen HUC8 watersheds includes between four and nine agroecoregions.

The N loadings from each agroecoregion are calculated in three categories:  drainage tile discharges, leaching from cropland, and runoff.  Nitrogen loading amounts modeled are “edge-of-field” measures that do not account for denitrification losses that occur beyond the edge of field as groundwater travels towards and is discharged to streams.  The BMPs consider only loading from cropland, but loading from forests and impervious urban and suburban land is also included in the totals.

What Have We Learned?

The EPA’s Science Advisory Board has said that a 45% reduction in both N and P is needed in the Mississippi River to reduce the size of the Gulf of Mexico hypoxic zone.  This tool suggests that the BMPs considered are not likely to achieve much more than half that reduction even at high adoption rates.  Reducing N fertilizer rates on corn down to extension-recommended levels and shifting from fall to spring or sidedressed applications tend to be among the cheaper BMPs to adopt, but the results vary across watersheds and weather scenarios.  Various other factors such as crop and fertilizer prices also affect the results, hence the need for a computer tool.

Future Plans

The tool and results of a larger project will be reviewed during the first half of 2013.  The tool may then play a role in implementation of the new N state standards in the state.


William F. Lazarus, Professor and Extension Economist, University of Minnesota wlazarus@umn.edu

Geoff Kramer, Research Fellow, Department of Biosystems and Bioproducts Engineering, University of Minnesota

David J. Mulla, Professor, Department of Soil, Water, and Climate, University of Minnesota

David Wall, Senior Hydrologist, Watershed Division, Minnesota Pollution Control Agency

Additional Information

The latest version of the tool and an overview paper are available at the author’s project page.

Davenport, M. A., and B. Olson. “Nitrogen Use and Determinants of Best Management Practices:  A Study of Rush River and Elm Creek Agricultural Producers Final Report, submitted to the Minnesota Pollution Control Agency  as part of a comprehensive report on nitrogen in Minnesota Surface Waters.” Department of Forest Resources, University of Minnesota, St. Paul, Minnesota, September 2012.

Fabrizzi, K., and D. Mulla. “Effectiveness of Best Management Practices for Reductions in Nitrate Losses to Surface Waters In Midwestern U.S. Agriculture.  Report submitted to the Minnesota Pollution Control Agency  as part of a comprehensive report on nitrogen in Minnesota Surface Waters.” September 2012.

Lazarus, W. F., et al. “Watershed Nitrogen Reduction Planning Tool (NBMP.xlsm) for Comparing the Economics of Practices to Reduce Watershed Nitrogen Loads.” December 11, 2012, http://wlazarus.cfans.umn.edu/.

Mulla, D. J., et al. “Nonpoint Source Nitrogen Loading, Sources and Pathways for Minnesota Surface Waters.  Report submitted to the Minnesota Pollution Control Agency  as part of a comprehensive report on nitrogen in Minnesota Surface Waters.” Department of Soil, Water & Climate, University of Minnesota, September 2012.


Partial support for this project was provided by the Minnesota Legislature.

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. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.