Economics of Anaerobic Digesters for Processing Animal Manure

Digesters are of interest with regards to climate changeenergyair 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.

The Environmental Protection Agency’s AgSTAR program has a website http://www.epa.gov/agstar/ with information to assist livestock producers who are considering installation of a digester.  The website contains a database of farm digesters that are operating in the United States or that have operated in the past.  It also provides a spreadsheet-based screening tool to help assess the potential feasibility of a project based on factors such as the feedstock, onsite conditions, the system type and size, and the planned biogas use.

What does a digester cost to install?  Costs will vary widely depending on the situation, but the two sources discussed below show what some recent dairy farm digester installations have cost. The reports are the 2015 article by Manning and Hadrich, and the annual reports of the California Department of Food and Agriculture’s Dairy Digester Research and Development Program (CDFA).

The CDFA funded 117 dairy farm projects between 2015 and 2021.  All but one of them were covered lagoon digesters (see the fact sheet by Hamilton for a discussion of digester types).  Those funded in 2015 generated electricity, but most of those funded in 2017 and later have renewable natural gas (RNG) as the end-use of the biogas.  The AgSTAR database lists the herd sizes for 19 of these digester projects that are producing RNG.  For those projects, the average herd size was 7,479 cows and the average project cost was $947/cow or $4,384,479 total before deducting the CDFA grant.  For the entire group of 117 projects, the CDFA grant funds covered 33 percent of the total cost.

The total cost of the greenhouse gas reductions achieved by these 117 projects was $30.94 per 1 metric ton of carbon dioxide equivalent including both the CDFA grants and the matching funds, or $9.88/1 metric ton considering only the CDFA grant funding.  Those greenhouse gas reductions are calculated using methodology developed by the California Air Resources Board.

Manning and Hadrich report on 12 California dairy operations that had installed digesters and were using the biogas to generate electricity.  They found that in 2014 the average initial cost of a lagoon system was $1.1 million ($869/cow with an average herd size of 2,496 cows) while a plug-flow system was $ 1.5 million ($1,114/cow and 1,620 cows).  Subsidies covered around half of the initial investment on average.

The 12 Manning-Hadrich digesters included seven covered lagoon digesters and five plug-flow digesters.  Seven of the digesters were providing benefits to the operations that exceeded their costs after subsidies.  The other five were not operating profitably, including three of the plug-flows and two of the lagoon systems.  Three of the unprofitable plug-flow digesters had ceased operation at the time of the study while the others were all operating.  The seven profitable digesters had average annual operating costs of $0.98/cow while the five unprofitable ones averaged $2.72/cow.

Author: William F. Lazarus, University of Minnesota

Related:

Dairy Digester Research and Development Program (2022). Report of Funded Projects (2015-2022) 2022: Report to the Joint Legislative Budget Committee, California Department of Food and Agriculture, from https://www.cdfa.ca.gov/oefi/ddrdp/docs/2022_DDRDP_Legislative_Report.pdf.

Hamilton, D. (2019). “Types of Anaerobic Digesters.”   Retrieved 8/4/22, 2022 from https://lpelc.org/types-of-anaerobic-digesters/.

Manning, D. T. and J. C. Hadrich (2015). “An evaluation of the social and private efficiency of adoption:  Anaerobic digesters and greenhouse gas mitigation.” Journal of Environmental Management 154: 70-77.

U.S. AgSTAR. “AgSTAR:  Biogas Recovery in the Agriculture Sector.”   Retrieved 8/3/22, from http://www.epa.gov/agstar/.

Merits of Manure Content Library

Purpose

The right amount of animal manure in the right location can benefit crops, soil, and water resources.  However, too much manure or manure in the wrong place is an environmental concern.  A recent survey of attitudes from farmers and their advisors on the benefits and barriers for manure use indicates that there is widespread knowledge of manure value for cropping systems, but logistical and community barriers remain. The survey also found that all respondents rated peer-to-peer interactions as the most influential on their decision-making for these topics. Thus, more extension efforts should be focused in assisting AFO managers and advisors to communicate messages on the value of manure and strategies for overcoming barriers, among their specific networks. For example, knowledge of the relationship of manure and soil health benefits is low among some segments. Farmers and their advisors all have very low opinions and understanding of manure’s benefits to environmental quality. Helping farmers, educators, and advisors articulate among themselves and to their rural communities the water quality benefits of organic fertilizers when applied to only meet agronomic needs of the crop may need expanded investments. With these needs in mind a team from the Universities of Nebraska, Minnesota, and Iowa State, and the assistance of the North Central Region Sustainable Agricultural Research and Education program developed a library to provide educators and advisors with access to recommended resources that will assist in the discussion of manure’s benefits and challenges.

What Did We Do?

Consultation among the team identified the following categories of interest for readily accessible educational or outreach materials for manure impacts on:

    1. Soil health and soil quality
    2. Economics of production and yield
    3. Crop fertility
    4. Water quality
    5. On-farm research

And guidance to navigating barriers such as:

    1. Direct costs associated with manure use
    2. Odor and other community issues
    3. Agronomic challenges (such as imbalance nutrients)
    4. Regulations
    5. Logistical issues of application
    6. Using manure in specialty systems (such as organic production)

With the categories for materials established, the team conducted an initial survey of extant educational and outreach materials via general internet searches and review of content available through the Livestock and Poultry Environmental Learning Community. The types of content thus assembled were varied: social media content, video, summaries of research, published extension and scientific journal articles, websites, and other content such as podcasts and decision support tools. All were included since it was intended that these resources be helpful for educators, producers, or others to converse with their own networks easily and confidently on the manure topics identified. The team anticipated that users could use the library to expand their social media activity, and thus their communication networks, or to prepare more confidently to discuss manure via a local radio presentation or discussion with a county board. Or even to add an article to local print media or a blog or personal website. All items included in the library were free to repurpose (with attribution) in local outlets or personal sites.

After consultation, the library was built using Airtable ™, a platform to create low-code databases, tools, or other apps. This platform allows the team to internally build a flexible database of content which can be sorted easily into pre-set categories (for example, topics of specific seasonal relevant), and arrange content into easily perused views to improve the user experience on a platform that could be easily embedded into existing team sites, such as lpelc.org (Figure 1).

Figure 1. The user interface for the merits of manure library, several such sorted views are embedded on the LPELC website for audience exploration by topic, media type, or seasonal relevance. Within each view individual entries can be further searched or sorted to further narrow exploration.

Each entry (Figure 2) in the library has an individual entry card, which includes keywords and text descriptions to improve searchability as well as a downloadable file, or links to the resource where appropriate, and a short example of how this material could be shared in the user’s social media network (recommended twitter text). The team intended to provide library users with not only the educational content, but also the means to improve their own in-network communication on manure topics. Accordingly, when posting to social media, hashtags, mentions and links to other content help (a) reach users who are following a specific topic (e.g., #manure), (b) recognize someone related to the post (e.g., @TheManureLady) and (c) direct users to more content related to the graphic (e.g., URL to online article). For our content library, each item is accompanied by recommended text that can be copied and pasted into the post of a social media engine if desired.

Figure 2. A single-entry page for the library.

What Have We Learned?

Since its launch in 2021 the library has had 343 unique users, average time that each user spends interacting with the library is 129 seconds, a solid interaction time for a website – industry standard is 120-180 seconds. However, we do not have any measure for how time spent on the library page is transformed into use of the library content. It is evident that more work is needed to improve awareness of the tool among audiences of interest. To this end, the team decided to develop a recognizable brand for library materials which might help other potential users to find their way to the site (Figure 3).

Figure 3. Library logo.

Future Plans

Library administrators continue to look for ways to improve the library content, user experience, and awareness of the tool among potential users. An overview of content, accessibility, re-purposing, and submission of relevant material will be shared to publicize the resource, encourage utilization of available materials, and invite submissions of new content relevant to the manure management community.

Authors

Amy Schmidt, Associate Professor, University of Nebraska

Corresponding author email address

aschmidt@unl.edu

Additional authors

Leslie Johnson, Associate Extension Educator, Mara Zelt, Schmidt Lab Project Director, Amber Patterson, Schmidt Lab Media Communications Specialist, and Rick Koelsch, Professor Emeritus, University of Nebraska-Lincoln; Erin Cortus, Associate Professor, and Melissa Wilson, Assistant Professor, University of Minnesota; and Dan Andersen, Associate Professor, Iowa State University

Additional Information

The full library is accessible at https://lpelc.org/value-of-manure-library/.

Acknowledgements

This product was assembled with financial assistance from the North Central Region Sustainable Agricultural Research and Education program.  NCR-SARE is one of four regional offices that run the USDA Sustainable Agriculture Research and Education (SARE) program, a nationwide grants and education program to advance sustainable innovation to American agriculture.

Value of Manure Library By Season

Winter

Spring

Summer

Fall

Authors/Sponsors

The project team assembling this product includes Amy Schmidt, Leslie Johnson, and Rick Koelsch, University of Nebraska-Lincoln; Erin Cortus and Melissa Wilson, University of Minnesota; and Dan Andersen, Iowa State University. These resources represent our recommendations for discussing the Value of Manure.

This product was assembled with financial assistance from the North Central Region Sustainable Agricultural Research and Education program. NCR-SARE is one of four regional offices that run the USDA Sustainable Agriculture Research and Education (SARE) program, a nationwide grants and education program to advance sustainable innovation to American agriculture.

Value of Manure Library By Media Type

Media types include social media, news articles, web pages, educational publications, decision support tools, and recommended research articles.

Authors/Sponsors

The project team assembling this product includes Amy Schmidt, Leslie Johnson, and Rick Koelsch, University of Nebraska-Lincoln; Erin Cortus and Melissa Wilson, University of Minnesota; and Dan Andersen, Iowa State University. These resources represent our recommendations for discussing the Value of Manure.

This product was assembled with financial assistance from the North Central Region Sustainable Agricultural Research and Education program. NCR-SARE is one of four regional offices that run the USDA Sustainable Agriculture Research and Education (SARE) program, a nationwide grants and education program to advance sustainable innovation to American agriculture.

Value of Manure Library By Topic Area

Topics include agronomics, economics and yield, soil health/quality, water quality, organic systems, neighbors, regulations and logistics.

Authors/Sponsors

The project team assembling this product includes Amy Schmidt, Leslie Johnson, and Rick Koelsch, University of Nebraska-Lincoln; Erin Cortus and Melissa Wilson, University of Minnesota; and Dan Andersen, Iowa State University. These resources represent our recommendations for discussing the Value of Manure.

This product was assembled with financial assistance from the North Central Region Sustainable Agricultural Research and Education program. NCR-SARE is one of four regional offices that run the USDA Sustainable Agriculture Research and Education (SARE) program, a nationwide grants and education program to advance sustainable innovation to American agriculture.

Value of Manure Library Grid View

Authors/Sponsors

The project team assembling this product includes Amy Schmidt, Leslie Johnson, and Rick Koelsch, University of Nebraska-Lincoln; Erin Cortus and Melissa Wilson, University of Minnesota; and Dan Andersen, Iowa State University. These resources represent our recommendations for discussing the Value of Manure.

This product was assembled with financial assistance from the North Central Region Sustainable Agricultural Research and Education program. NCR-SARE is one of four regional offices that run the USDA Sustainable Agriculture Research and Education (SARE) program, a nationwide grants and education program to advance sustainable innovation to American agriculture.

Value of Manure Library for Educators and Advisors

Purpose

Manure is a resource that comes with many benefits and challenges.  This library is designed to provide educators and advisors with access to recommended resources that will assist you in your discussion of manure’s benefits and challenges.  Educators, please feel free to share and re-purpose educational products in this library with local audiences. Advisors, the library’s resources shall provide you with decision tools and educational products for enriching your discussions with clientele and rural community residents.

How to find materials

For those seeking specific resources, materials are organized visually by topic area and type of media. For those that would rather search materials more linearly, there is a grid version available.

In all views, there is a search button in the top right corner that looks like a magnifying glass and an expansion button that looks like two outward pointing arrows to view in full screen.

By Topic Area

Preview of manure value library database sorted by topic.
    • Manure as a fertilizer
    • Manure economics
    • Soil quality/health effects
    • Water quality effects
    • Use in organic systems
    • Neighbors
    • Regulatory concerns
    • Logistics

By Media Type:

Preview of manure value library database sorted by purpose.
    • Social media
    • Short news articles and web pages
    • Educational publications
    • Decision support tools
    • Recommended research articles

 

Instructions for Re-purposing Educational Content

Our team encourages and welcomes educators and advisors re-purposing of many of the social media and web page/news article resources found in this library.  Would these resources be helpful to you for Tweeting to your followers? Assembling talking points for a local radio presentation or discussion with a county board?  Or adding an article to local print media or your blog?

Example of social media graphic to be re-purposed.
    • Twitter Posts:  A broad range of Twitter posts, graphics with an educational message and short text introduction, are included for use with your social media connections.  Please re-purpose these for your local use. We ask that you maintain the “N Extension” and “WSA” logos in your re-purposed post.  You may replace the “Manure Happens. Take Credit” caption and the “Learn more at: http:// ________”  with an appropriate recognition of your organization and/or a web page that you would like to promote.
    • Web Page/News Articles:  Many of these library products can be repurposed for a variety of local uses.  News articles and web pages may be revised to add local information with the new authors name included if the original authors continue to be listed.
    • Any Educational Products:  Any of the Library resources may be used as talking points for a local radio broadcast or community group presentations. Please recognize the original authors and resource title in your presentation.

 

Is something missing from our library?

We welcome your suggestions of resources that you have found beneficial in your educational or advisory role.  Please email any of the project team members with your suggestions or submit them via our google form for our consideration.

Authors/Sponsors

The project team assembling this product includes Amy Schmidt, Leslie Johnson, and Rick Koelsch, University of Nebraska-Lincoln; Erin Cortus and Melissa Wilson, University of Minnesota; and Dan Andersen, Iowa State University.  These resources represent our recommendations for discussing the Value of Manure.

This product was assembled with financial assistance from the North Central Region Sustainable Agricultural Research and Education program.  NCR-SARE is one of four regional offices that run the USDA Sustainable Agriculture Research and Education (SARE) program, a nationwide grants and education program to advance sustainable innovation to American agriculture.

Performance and Payback of a Solid-Liquid Separation Finishing Barn

A 1200-hd solid-liquid separation finishing barn was built in Missouri for improved manure management and air quality. The facility has a wide V-shaped gutter below slatted flooring (Figure 1), which continuously drains away liquids.  A scraper is used to collect the solids, which are then managed separately. Field sampling and research were conducted to evaluate the performance of the solid-liquid separation finishing barn in improving manure nutrient management, potential nutrient/water recycling based on filtration, and barn construction and operating costs.

What did we do?

The barn (built in 2010) was closely monitored for manure production and nutrient content, and operating costs. Laboratory-scale pretreatments and filtrations were conducted to evaluate the practicality of nutrient/water recycling from the separated liquid manure.

What we have learned?

The daily liquid manure production averaged 885 gallons and daily solid manure production averaged 299 gallons (about ¼ of the total manure volume). The separation system removed 61.7%, 41.7%, 74.8%, and 46.2% of the total manure nitrogen, ammonium, phosphorous, and potassium, respectively, with the collected solids. The filtration results indicate that the microfiltration and reverse osmosis were time and energy intensive, which was probably constrained by the relatively small-scale unit (inefficient compared with larger units), small filter surface area, and high concentration of dissolved nutrients.

The construction cost of the solid-liquid separation barn with solid manure storage was $323,000 ($269/pig-space, in 2010), 17% higher compared to the traditional deep-pit barn ($175 to $230/pig-space). It is likely that the solid-liquid separation barn will become less expensive when more barns of similar design are built, and the conveyor system can be improved and simplified for less maintenance and lower costs. Additional electricity cost was $331 per year for daily operation of the scraper and conveyor systems, and pumping the separated liquid manure fraction. The additional maintenance cost of the scraper system averaged $1,673/year. A net gain of $3,975/year was observed when considering the value of the separated manures, cost of land application, and annual maintenance cost.

A payback period of 15.1 years on the additional investment was estimated, when compared with the popular deep-pit operation. However, the payback period can be reduced by many factors, including improved conveyor system and growing popularity of the barn design in an area. When the distance to transport the slurry manure was increased from 5 miles to 7.5 and 10 miles, the payback periods became 12.7 and 11.3 years, respectively. The solid-liquid separation barn was shown to have better air quality when compared with deep-pit barns based on monthly measurements of ammonia and hydrogen sulfide concentrations.

Impacts/Implications of the Research.  

This study monitored the manure production of a commercial finishing barn utilizing a solid-liquid separation system. Overall, we can conclude that the final results obtained from monitoring the total manure production rate, air quality exiting the barn fans, and the pig growth rates made sense relative to other comparative sources. The overall results indicate that the barn design can attain some valuable benefits from separating the solid and liquid streams.  About a quarter of the manure volume was collected and managed as nutrient-dense solid manure (defined as ‘stackable’). The solid manure held 80% of the total solids and nearly 75% of the phosphorous.

Take Home Message

There are alternative barn designs and manure management systems (relative to lagoon and deep-pit operations) that should be considered when planning for a new operation or expansion. Considerations should include the need to better manage manure nutrients and improve air quality for human and animal occupants.

Future plans

Further consideration of the manure management, including work load and major- and micro-nutrients need to be furthered analyzed. Future research may look into application of a larger-scale crossflow system to see if nutrient removal and flow rates can be improved significantly. Future research may focus on improving manure filtrate flow, and determining the cost of installation and upkeep for a filtration unit that can operate at the level of a farm operation. Extrapolating the costs off of bench-scale model does not seem remotely indicative of the true cost, due to improved efficiency and power of larger unit.

Authors

Lim, Teng (Associate Professor and Extension Agricultural Engineer, Agricultural Systems Management, University of Missouri, limt@missouri.edu)

Brown, Joshua (University of Missouri); Zulovich, Joseph (University of Missouri); and Massey, Ray (University of Missouri).

Additional information

Please visit https://www.pork.org/research/sustainability-evaluation-solid-liquid-manure-separation-operation/ for the final report, and ASABE Paper No. 1801273 (St. Joseph, Mich.: ASABE. DOI: https://doi.org/10.13031/aim.201701558) for more information.

Acknowledgements

Funding for this research project was provided by the National Pork Checkoff and University of Missouri Extension.

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).
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).
Figure 2. The storage shed for solid manure to the north of the modified scraper barn (Left), and stored solid manure (Right).
Figure 2. The storage shed for solid manure to the north of the modified scraper barn (Left), and stored solid manure (Right).

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. 2019. Title of presentation. Waste to Worth. Minneapolis, MN. April 22-26, 2019. URL of this page. Accessed on: today’s date.

Cataloging and Evaluating Dairy Manure Treatment Technologies


Proceedings Home | W2W Home w2w17 logo

Purpose

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  

info@newtrient.com

Other Authors 

Garth Boyd, Context

Craig Frear, Regenis

Curt Gooch, Cornell University

Danna Kirk, Michigan State University

Mark Stoermann, Newtrient

Additional Information

http://www.newtrient.com/

Acknowledgements

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.