Thermal-Chemical Conversion of Animal Manures – Another Tool for the Toolbox


How Can Thermo-Chemical Technologies Assist in Nutrient Management?

Livestock operations continue to expand and concentrate in certain parts of the country. This has created regional “hot spot” areas in which excess nutrients, particularly phosphorus, are produced. This nutrient issue has resulted in water quality concerns across the country and even lead to the necessity of a “watershed diet” for the Chesapeake Bay Watershed. To help address this nutrient concern some livestock producers are looking to manure gasification and other thermo-chemical processes. There are several thermo-chemical conversion configurations, and the one chosen for a particular livestock operation is dependent on the desired application and final by-products. Through these thermo-chemical processes manure Factory processingvolumes are significantly reduced. With the nutrients being concentrated, they are more easily handled and can be transported from areas of high nutrient loads to regions of low nutrient loads at a lower cost. This practice can also help to reduce the on-farm energy costs by providing supplemental energy and/or heat. Additional benefits include pathogen destruction and odor reduction. This presentation will provide an overview of several Conservation Innovation Grants (CIG) and other manure thermo-chemical conversion projects that are being demonstrated and/or in commercial operation. Information will cover nutrient fate, emission studies, by-product applications along with some of the positives and negatives related to thermo-chemical conversion systems.

Exterior of factory processingWhat did we do? 

Several farm-scale manure-to-energy demonstration projects are underway within the Chesapeake Bay Watershed. Many of these receive funding through the USDA-NRCS Conservation Innovation Grant program. These projects, located on poultry farms, are being evaluated for the performance of on-farm thermal conversion technologies. Monitoring data is being collected for each project which includes: technical performance, operation and maintenance, air emissions, and by-product uses and potential markets. Performance of manure gasification systems for non-poultry operations have also been reviewed and evaluated. A clearinghouse website for thermal manure-to-energy processes has been developed.

What have we learned? 

The projects have shown that poultry litter can be used as a fuel source, but operation and maintenance issues can impact the performance and longevity of a thermal conversion system. These systems are still in the early stages of commercialization and modifications are likely as lessons are learned. Preliminary air emission data shows that most of the nitrogen in the poultry litter is converted to a non-reactive form. The other primary nutrients, phosphorus and potassium, are preserved in the ash or biochar co-products. Plant availability of nutrients in the ash or biochar varies between the different thermal conversion processes and ranges from 80 to 100 percent. The significant volume reduction and nutrient concentration show that thermal conversion processes can be effective in reducing water quality issues by lowering transportation and land application costs of excess manure phosphorus.

Future Plans    

Monitoring will continue for the existing demonstration projects. Based on the lessons learned, additional demonstration sites will be pursued. As more manure-to-energy systems come on-line the clearinghouse will be updated. Based on data collected, NRCS conservation practice standards will be generated or updated as necessary.

Author       

Jeffrey P. Porter, PE, Manure Management Team Leader, USDA-Natural Resources Conservation Service jeffrey.porter@gnb.usda.gov

Additional information                

Thermal manure-to-energy clearinghouse website: http://lpelc.org/thermal-manure-to-energy-systems-for-farms/

Environmental Finance Center review of financing options for on-farm manure-to-energy including cost share funding contact information in the Chesapeake Bay region: http://efc.umd.edu/assets/m2e_ft_9-11-12_edited.pdf

Sustainable Chesapeake: http://www.susches.org

Farm Pilot Project Coordination: http://www.fppcinc.org

National Fish and Wildlife Foundation, Chesapeake Bay Stewardship Fund: http://www.nfwf.org/chesapeake/Pages/home.aspx

Acknowledgements

National Fish and Wildlife Foundation, Chesapeake Bay Funders Network, Farm Pilot Project Coordination, Inc., Sustainable Chesapeake, Flintrock Farm, Mark Weaver Farm, Mark Rohrer Farm, Riverview Farm, Wayne Combustion, Enginuity Energy, Coaltec Energy, Agricultural Waste Solutions, University of Maryland Center for Environmental Science, Environmental Finance Center, Virginia Cooperative Extension, Lancaster County Conservation District, Virginia Tech Eastern Shore Agricultural Research and Extension Center, Eastern Shore Resource Conservation and Development Council, with funding from the USDA Conservation Innovation Grant Program and the U.S. EPA Innovative Nutrient and Sediment Reduction Program.

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. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.

Thermal Manure-to-Energy Systems for Farms

Using manure to generate energy is growing in popularity. Explore the topics below to learn more.

  1. Introduction to Thermal Technologies for Generating Energy from Manure (Combustion, Pyrolysis, Gasification)
  2. Benefits & Challenges of Manure-Based Energy
  3. Farm Manure-to-Energy Case Studies
  4. Start-Up Questions and Considerations (What should I know or ask before pursuing manure-to-energy technologies for my farm?)
  5. Additional Resources on Manure-to-Energy Technologies
Manure-to-Energy in the Chesapeake Region 2016 REPORT

Farm Manure Energy Initiative logoPortions of this information were funded by the National Fish and Wildlife Foundation (NFWF), the USDA, U.S. EPA, and Chesapeake Bay Funders Network. The views and conclusions contained in materials related to the Farm Manure-to-Energy Initiative are those of the authors and should not be interpreted as representing the opinions or policies of NFWF, the USDA, U.S. EPA, or Chesapeake Bay Funders Network. Mention of trade names or commercial products does not constitute endorsement by project funders.

Introduction to Thermal Technologies for Generating Energy from Manure

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There are two general methods for producing energy from manure: the use of heat and the use of bacteria. This page is focused on the use of heat – specifically, on relatively small thermal systems that can be used on a farm to produce energy from excess poultry litter or manure.

The use of bacteria to produce energy from manure is called anaerobic digestion. For more information about anaerobic digestion, explore Anaerobic Digestion and Biogas. Related: Treatment Technologies for Manure

temperature and oxygen levels for thermal technologies

Types of Thermal Energy Production for Farm-Scale Systems

In scientific terms, the use of heat to produce energy from manure is a thermochemical process. Thermal systems are well-suited for manure that is relatively dry, such as poultry litter, because there is less need to dry out the manure prior to processing.

Thermal processes that can convert animal manure into fuel include pyrolysis, gasification, and combustion. These processes differ with respect to temperature and oxygen concentrations, but each converts solid material into combustible, gaseous components, which then creates a hot flue gas. The flue gas is directed through a heat exchanger where heat is captured and moved through a distribution system for use in the poultry houses.

Thermal processes also produce a range of potentially valuable co-products including liquid bio-oils, diesel fuel, and combustible gases. They also produce nutrient-dense products like ash and bio-charcoal (commonly referred to as “biochar”). The concentration of nutrients varies depending on the process, operating parameters, and system design.

Fate of Manure Nutrients in Thermal Energy Systems

In thermal systems, almost all of the phosphorus and potash are conserved in the ash or biochar. While biochar retains some nitrogen associated with organic carbon, much of the nitrogen from these systems is lost in atmospheric emissions. Most is released to the atmosphere in the form of non-reactive nitrogen gas, or N2. Reactive forms of nitrogen may also be released, including oxides of nitrogen (NOx) and ammonia (NH3).

The concentration of phosphorus in the ash or biochar provides a way to transport excess nutrients to phosphorus-deficient regions where the ash or biochar can be used as a fertilizer to replace inorganic, mined phosphorus. Reactive nitrogen, on the other hand, is largely lost from agricultural production. Biochar retains some nitrogen, while systems that produce ash (like gasification and combustion) generally convert almost all of the nitrogen to atmospheric emissions. Given that land application of poultry litter and manure can result in atmospheric emissions of far greater amounts of reactive nitrogen (from 50 to 90 percent of ammonia-nitrogen for surface-applied manure), well-designed thermal manure-to-energy systems can reduce overall atmospheric emissions of reactive nitrogen.

Environmental Impacts

Thermal manure-to-energy systems can help address nutrient imbalances in high-density animal production areas, but it is important to use clean technologies with low emissions in order to avoid transferring a surface and groundwater problem to the atmosphere.

Technologies evaluated by the Farm Manure-to-Energy Initiative resulted in atmospheric reactive nitrogen emissions that were generally better than or, at the very least, similar to land application of poultry litter that is immediately incorporated, a strategy recommended to reduce ammonia emissions.

However, the Farm Manure-to-Energy Initiative project identified particulate matter as a pollutant of concern for some thermal manure-to-energy technologies. At high temperatures typical of gasification and combustion, potash (which is abundant in poultry litter) volatilizes and can produce fine particulate matter in the form of potassium chloride or potassium sulfates. While some technologies have achieved low particulate matter emissions, others need additional work before they will be eligible for installation in states that set strict limits for particulate matter emissions.

Depending on the location and the size of the installation, emissions of particulate matter and NOx are often a consideration for air permitting. Data on other criteria and hazardous air pollutants associated with the proposed technology may also be required. To learn more about air permitting associated with thermal energy production, see Start-Up Questions and Considerations.

 equipmentequipment

Thermal manure-to-energy systems, like the examples shown here, use heat to produce energy from manure.

Components of a Farm-Scale System

Thermal systems are adaptable to different scales, but the technologies vary widely in their design, effectiveness, and cost. Most are still in the early phases of commercial development, and many are still in the research and development phase.

Thermal, farm-scale systems typically include some combination of the following components. Each configuration differs depending on the vendor’s technology and the specific goals and needs of the farm where the system is installed:

  • Covered manure storage area
  • Feed hopper and conveyor belt
  • Thermal manure-to-energy unit (combustion, gasification, or pyrolysis)
  • Heat exchanger or boiler
  • Heat distribution unit (ductwork or piping)
  • Emissions control unit
  • Ash or bio-char collection unit

The Farm Manure-to-Energy Initiative conducted several case studies between 2012-2015 to document the performance of farm-scale systems in the Chesapeake region.

More Resources on Thermal Technologies


Farm Manure Energy Initiative logoDevelopment of this information were funded by the National Fish and Wildlife Foundation (NFWF), the USDA, U.S. EPA, and Chesapeake Bay Funders Network. The views and conclusions contained in materials related to the Farm Manure-to-Energy Initiative are those of the authors and should not be interpreted as representing the opinions or policies of NFWF, the USDA, U.S. EPA, or Chesapeake Bay Funders Network. Mention of trade names or commercial products does not constitute endorsement by project funders.

Combustion of Poultry Litter: A Comparison of Using Litter for On-Farm Space Heating Versus Generation of Electricity

Waste to Worth: Spreading science and solutions logoWaste to Worth home | More proceedings….

Abstract

This presentation will compare using litter as a replacement for LP gas for on-farm space heating with using litter to generate electricity. The comparison includes heating system efficiency, amount of LP off-set possible, value of plant nutrients in the litter, quantity and value of plant nutrients in the litter ash, impact of brokerage, and costs of producing the energy. It was concluded that using litter on-farm as a source of space heat and using the litter ash as fertilizer could provide a potential value of $48 per ton of litter. However, on-farm combustion of litter to produce electricity resulted in a loss of about – $3/ton of litter. Therefore, if a heating and ash management system can be implemented in a cost-effective manner use of litter to off-set 90% or more of the heating energy requirements would be the better of these two alternatives.

Why Is Energy Use Important in Poultry Production?

Modern poultry production requires substantial amounts of energy for space heating (propane/LP gas), ventilation, feed handling, and lighting. It was determined that annual LP gas consumption in broiler houses can range from 150 to 300 gallons of LP per 1000 square feet of floor space with an average of about 240 gal LP/1000 ft2 observed in South Carolina. Similarly, broiler production in South Carolina requires about 2326 kWh/1000 ft2 of house area. As a result, a 6-house broiler farm in SC uses about 30,240 gallons of LP and 293.076 kWh of electricity annually. The cost for energy for a 6-house farm is on the order of $57,456 per year for LP ($1.90/gal LP) and $35,169 per year for electricity ($0.12/kWh). Energy costs have more than doubled over the last decade and as a result producers are very interested in ways to reduce on-farm energy costs by using the energy contained in the litter. The objective of this study was to compare using litter as a replacement for LP gas for on-farm space heating with using litter to generate electricity.

What Did We Do?

Our analysis included heating system efficiency, amount of LP off-set possible, value of plant nutrients in the litter, quantity and value of plant nutrients in the litter ash, impact of brokerage, and costs of producing the energy.

What Have We Learned?

It was concluded that using litter on-farm as a source of space heat and using the litter ash as fertilizer could provide a potential value of $46 to $55 per ton of litter. However, on-farm combustion of litter to produce electricity resulted in a loss of about $3/ton of litter. Therefore, if a heating and ash management system can be implemented in a cost-effective manner use of litter to off-set 90% or more of the heating energy requirements would be the better of these two alternatives.

Future Plans

This information is being used in extension programs that target poultry producers.

Authors

Dr. John P. Chastain, Professor and Extension Agricultural Engineer,  School of Agricultural, Forestry, and Environmental Sciences, Clemson University, jchstn@clemson.edu

Additional Information

Chastain, J.P., A. Coloma-del Valle, and K.P. Moore. 2012. Using Broiler Litter as an Energy Source: Energy Content and Ash Composition. Applied Engineering in Agriculture Vol 28(4):513-522.

Acknowledgements

Support was provided by the Confined Animal Manure Managers Program, Clemson Extension, Clemson University, Clemson, SC.

 

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.