anaerobic digester – Livestock and Poultry Environmental Learning Community

April 4, 2025May 11, 2025

Training Development for On-Farm Anaerobic Digester Operators

Purpose

This presentation documents the development of a new training program to be offered by North Carolina Extension (NC Extension), or other qualified entities, to serve on-farm digester operators in the state. This program was developed in response to increased adoption of on-farm anaerobic digestion (AD) systems in North Carolina, particularly on swine farms. With proliferation of on-farm digesters and the accompanying methane purification and transfer infrastructure, the availability of adequate training and support to ensure their safe and sustainable operation was a growing concern.

In North Carolina, the Water Pollution Control System Operators Certification Commission (WPCSOCC) was established, by NC General Statutes 143B-300 and 143B-301, to oversee training and certification of water pollution control system operators. During their quarterly meetings, the commissioners discussed this need and engaged North Carolina State University (NC State University), the 1860 land-grant institution, to provide expertise and support over development and administration of this training program.

What Did We Do?

The training development proceeded over the following steps:

- Need-to-know (NTKs) compilation: A team of five members representing NC Extension (the authors), NC Department of Environmental Quality (NC DEQ), and WPCSOCC met at regular intervals (three meetings in total, each 1.5 to 2 hours) to summarize key learning objectives that need to be met by the training program. External stakeholders representing animal industry, digester installers, and farm inspectors were consulted for input and comment on NTKs list (two one-on-one meetings). The NTKs were grouped by topic and divided into five (5) modules. Once finalized, the NTKs were submitted for approval by WPCSOCC during their regular meetings.
- Training material development: Once the learning objectives were approved, NC Extension team started compiling resources (factsheets, PowerPoint slide decks) from existing NC Extension training materials on the topic, and resources made available by colleagues in peer institutions to prepare training content. Other training content delivered by land-grant and industry associations were consulted during this step. WPCSOCC and NC DEQ representatives also provided some input on content. The developed content was 3-hours in length.
- Test offering: Once training material was developed, a group of 10 county extension agents with livestock training responsibilities were invited for the first offering of the training. They were encouraged to document impressions, comments, and provide feedback. Changes were made to address gaps, adjust pacing, and include more accessible graphics and data.
- Official offering: Two sessions were held in September and October 2024 for the following audiences [1] NC DEQ inspectors and supervisors (28 attendees) in Raleigh, NC, and [2] animal producers/operators who operate AD systems, as well as those considering investing in AD systems in Kenansville, NC (36 attendees).
- Feedback and continued learning: Feedback and questions by attendees were addressed in both sessions. In the second session, a county extension director facilitated compiling questions and shared them with the training leader to address. An open Zoom session was coordinated to bring expertise from regulatory agencies, the swine production sector, and AD technology installers to address these questions collectively. The answers were compiled into a frequently asked questions (FAQs) list that was reviewed by attendees before distribution and publishing on NC Extension portal, NC Swine Newsletter, and relevant trade magazines.

What Have We Learned?

Feedback and interactions with trainees showed growing interest in adopting on-farm anaerobic digesters primarily driven by the monetary value of biomethane sale as a renewable natural gas (RNG). Some cost-share programs further lowered the barrier to entry for many producers. Primary concerns/disincentives include profitability for small and medium size farms, impacts on nutrient management planning, and compliance. The training described above provides an opportunity to engage project developers/installers during the program to provide examples of adoption models without disclosing proprietary information. Clear delineation of responsibilities for the AD system between farm manager, operators, and project team supervision continues to be a priority.

Future Plans

Twice per year offering of the training is planned. Experiential and peer learning through field tours and testimonials by operators of ADs are planned for future offerings. A homepage for AD related content was developed on NC Extension portal including an opportunity to ask questions on the topic. The FAQ list will be continuously updated to answer new and emerging questions.

Authors

Presenting & corresponding author

Mahmoud Sharara, Associate Professor and Extension Specialist, Biological and Agricultural Engineering Department, North Carolina State University, Raleigh, North Carolina, msharar@ncsu.edu

Additional author

Mark Rice, Extension Specialist (retired), Biological and Agricultural Engineering Department, North Carolina State University, jmrice@ncsu.edu

Additional Information

- Portal for Manure Anaerobic Digesters on NC Extension webpage: https://animalwaste.ces.ncsu.edu/digest/
- Frequently Asked Questions (FAQs) answered RE: on-farm ADs: https://animalwaste.ces.ncsu.edu/2024/11/ad_faqs/

Acknowledgements

The authors would like to acknowledge Dr. Bob Rubin, WPSOCC board member and retired NCSU faculty, Patrick Biggs (NC DEQ), Jeffrey Talbott (NC DEQ), Christine Lawson (NC DEQ), Gus Simmons (Cavanaugh and Associates) , and Smithfield Foods for feedback, assistance, and insights provided during training development.

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. 2025. Title of presentation. Waste to Worth. Boise, ID. April 7-11, 2025. URL of this page. Accessed on: today’s date.

March 5, 2019July 15, 2020

White Meat-Green Farm: Case Study of Brinson Farms

Waste to Worth home | More proceedings….

Abstract

Comprehensive on-farm resource utilization and renewable energy generation at the farm scale are not new concepts. However, truly encompassing implementation of these ideals is lacking. Brinson Farms operates 10 commercial broiler houses. The farm generates heat for its houses using biomass boilers and litter anaerobic digestion to produce methane. Solar panels assist in heating process water for the boilers and digester. Biomass feedstock includes litter as well as municipal yard wastes. Liquid fertilizer is a product of the digester while residual solids are included in the farm’s composting operation. The operator has used a futuristic approach to not only attain energy independence for the farm, but also to comprehensively utilize byproducts of production and other local “wastes”, diverting them from local landfills. Considering the propane cost for a single winter flock has reached $66,000 and the annual electric bill may be $120,000, energy costs very much affect grower profitability. This approach decreases the uncertainty in energy costs. Brinson Farms provides a unique look into ensuring long-term farm sustainability in an environmentally friendly way and with a wide-ranging systems approach to management.

Purpose

The purpose of the renewable energy project was to implement an innovative, sustainable solution to manage poultry manure and other organic waste products using anaerobic digestion as well as to demonstrate the ability to effectively and economically reduce dependence on outside utilities.

What Did We Do?

Brinson Farms demonstrates comprehensive utilization of local resources that have historically been viewed as wastes. These organic materials (broiler litter, yard trimmings, storm damaged trees and waste vegetables) come from both the farm and the community. Broiler litter and waste vegetables are anaerobically digested to produce methane. The methane is then used in three ways: 1) to generate electricity for the farm; 2) in boilers to heat water used in the digestion process; and 3) in dual-fuel biomass boilers to heat water for heat exchange in the broiler houses when biomass sources are low. Two other significant products from the digester include liquid fertilizer (approximately 5-2-3) that is sold and residual solids that are incorporated into the farm’s composting facility. Solar panels assist in heating water for the biomass boilers and the digester. The simple payback period for the on-farm poultry litter digester system is approximately 5 years.

Brinson Farms anaerobic digester complex.

What Have We Learned?

Brinson Farms provides a unique system to ensure long-term farm sustainability in an environmentally beneficial manner. Attributes of the integrated system include: 1) bio-based energy production; 2) reduced utility costs; 3) comprehensive litter utilization; 4) no need to land apply poultry litter; 5) production of high quality, organic liquid fertilizer; 6) production of a marketable soil amendment (compost); and 7) diverting wastes from landfills. The farm/community interface is mutually advantageous. The farm uses yard trimmings and trees for energy and as a compost substrate; the community has a free repository to dispose of the biomass, where otherwise it would have to pay landfill fees.

Biomass storage and boiler to heat broiler houses

Future Plans

Future plans include developing economic evaluations for each of the system components so that farmers can choose the renewable energy/value added process(es) that will best fit their local resources as well as short and long term financial plans.

Authors

Dana M. Miles, Chemical Engineer, USDA-ARS Genetics & Precision Agriculture Research Unit, Mississippi State, MS, dana.miles@ars.usda.gov

Additional Information

John Logan: johnlogan1@windstream.net;

Jeff Breeden: jbreeden@egesystems.com;

Eagle Green Energy: http://eaglegreenenergyinc.com /;

Arora, S. 2011. Poultry Manure: The New Frontier for Anaerobic Digestion. http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1046769.pdf

Acknowledgements

The assistance of John Logan and Jeff Breeden to effectively describe the Brinson system is greatly appreciated.

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.

March 5, 2019March 26, 2019

Anaerobic Digestion of Finishing Cattle Manure

Waste to Worth home | More proceedings….

Purpose

The concept of utilizing feedlot manure in an anaerobic digester to power an ethanol plant, which then produces feed for cattle, has been called a closed loop system. In this system inputs are minimized and outputs are used by another component. This research looked at differences in manure quality within this system. Trial 1 considered incorporating distillers grains into the cattle diet and the effects on methane potential of the manure. For this system to be utilized by the feedlot industry in Nebraska, the manure collected for anaerobic digestion must be collected from soil-based open feedlot pens which account for over 95% of the feedlot cattle raised in Nebraska. Trial 2 addressed the methane potential of open-lot feedlot manure and its feasibility for anaerobic digestion.

An integrated biorefinery utilizes distillers grains for cattle feed and cattle manure for biogas generation to power an ethanol plant. This system has been referred to as a “closed loop” system due to energy recycling within the segments.

What Did We Do?

Seven continuously stirred anaerobic digesters were used to compare degradation of manure from 2 cattle diets (Trial 1) and 2 cattle housing methods (Trial 2). In Trial 1 manure was collected from confinement cattle on a control diet with 82.5% dry rolled corn or 40% of the corn was replaced with wet distillers grains plus solubles (WDGS), a byproduct of the ethanol industry. For Trial 2, manure was collected from cattle in complete confinement or soil-based open feedlot pens with all cattle on a similar byproduct diet. In both trials, organic matter (OM) degradation and methane production was measured for digesters on each treatment. In Trial 1, samples of effluent removed from the digesters were also used to identify differences in microbial community structure (Eubacterial and Archaeal) due to treatment.

What Have We Learned?

Trial 1. Organic matter degradation was slightly improved for manure from cattle fed WDGS (P = 0.10). Methane production was 0.137 L/g OM fed for WDGS manure and 0.116 L/g OM fed for the corn-based diet (P = 0.05). Microbial communities identified using 454-pyrosequencing revealed structuring of the microbial community based on diet (P < 0.001). This suggests that the microbial food chain that contributes to methane production is greatly influenced by the diet fed to cattle, and dietary manipulation may provide opportunities to increase or decrease methane production from cattle manure.

Trial 2. Manure collected from open-lot pens had an OM content of 26% compared to 88% for manure from complete confinement. This resulted in decreased methane production and OM degradation (P < 0.01) for digesters fed open-lot manure. However, methane was produced from open-lot manure suggesting that if ash buildup can be avoided open lot manure may be a viable feedstock for anaerobic digestion.

Future Plans

We are currently exploring new technologies that may enhance the use of open lot manure in anaerobic digestion. We are also identifying key microbes involved in methane production in order to better understand how things such as cattle diet affect methane production.

Authors

Andrea Watson, graduate student, University of Nebraska awatson3@unl.edu

Samodha Fernando, assistant professor, University of Nebraska

Galen Erickson, professor, University of Nebraska

Terry Klopfenstein, professor, University of Nebraska

Additional Information

A summary of these trials is available at beef.unl.edu/reports; 2013 Beef Report pg. 98-99.

Acknowledgements

Funding provided by Nebraska Center for Energy Sciences Research

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.

Anaerobic Digestion of Finishing Cattle Manure from LPE Learning Center

March 5, 2019March 6, 2019

Anaerobic Digester Operator Discussion Group

Waste to Worth home | More proceedings….

Why Is Peer-to-Peer Discussion Important?

The Anaerobic Digester Workforce Development Project is a project funded by the New York State Energy Research and Development Authority, aimed at developing and delivering high quality educational programs targeted to a range of workforces within the dairy farm-based anaerobic digestion (AD) sector of the clean energy field.

A goal of the project was to form a farmer driven discussion group among existing AD owners and operators. Farmers value and learn from the insights of fellow producers because they trust the experience and knowledge of others who are in situations similar to their own. This is especially true when adopting new technology. The purpose of this discussion group was to allow farmers an opportunity to learn from each other by sharing their real world experiences integrating and operating an anaerobic digester system into their farm business. Realizing that frequent, long-distance travel of all involved was a barrier to continued, dedicated involvement, the group opted to pursue a virtually-based discussion group platform. Farmers from across the state were linked via an online meeting site. This is an efficient method to allow farmers to interact with each other in a meaningful way without leaving their farm. The use of high definition video conferencing enhanced the interaction considerably. There have been many lessons learned from this challenging venture, as well as many successful communication strategies to share.

What Did We Do?

Realizing that frequent, long-distance travel of all involved was a barrier to continued, dedicated involvement, the group opted to pursue a virtually-based discussion group platform. Farmers from across the state were linked via an online meeting site. This is an efficient method to allow farmers to interact with each other in a meaningful way without leaving their farm.

What Have We Learned?

The focus of this presentation is to introduce the topic of forming and facilitating farmer based discussion groups with an emphasis on distance learning. By using online meeting and video conferencing farmers from across geographic areas can meet and engage in meaningful dialogue. This is especially useful when producers are implementing new technology in which they have no or limited experience. The opportunity to have an open dialogue with other farmers that have real world experience with the technology is invaluable. The experience and exchange of knowledge between farmers assists in the implementation and operation of the technology.

Future Plans

The virtual discussion group will continue to meet and develop. As we gain more experience and farmers become more comfortable with this method of interact we expect for the discussions to increase in value and effectiveness.

Authors

Kathryn Barrett, Sr. Extension Associate, Cornell University, ProDairy Program, Director of Dairy Profit Discussion Group Program. kfb3@cornell.edu

Acknowledgements

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.

Anaerobic Digester Operator Discussion Group from LPE Learning Center