Does Manure Solid-Liquid Separation Reduce Greenhouse Gas Emissions on Swine Farms?

green stylized pig logoThere is some research suggesting that separating swine manure into solids and liquids can slightly reduce greenhouse gas (GHG) emissions emitted from the manure itself. It is not likely to be significant enough for separation to be a viable strategy by itself.

The primary reason to use solid-liquid manure separation is to prepare manure for further treatment in a system that can:

  1. generate energy (such as anaerobic digestion, thermal technologies, etc.)
  2. produce products for re-use on a farm (such as bedding for dairy cows),
  3. generate compost or fertilizer.

Any of these options can reduce the GHG emissions or carbon footprint of a farm by replacing fossil-fuel intensive inputs.

For more information

Authors: Rick Fields, University of Arkansas and Jill Heemstra, University of Nebraska


This information is part of the program “Integrated Resource Management Tool to Mitigate the Carbon Footprint of Swine Produced In the U.S.,” and is supported by Agriculture and Food Research Initiative Competitive Grant no. 2011-68002-30208 from the USDA National Institute of Food and Agriculture. Project website.

Exploring Interactions Betwen Agricultural Decisions and Greenhouse Gas Emissions Using Swine Production

green stylized pig logoThe materials on this page are an interactive lab designed to introduce students (high school level) to pig farming and the connections between management decisions  and the greenhouse gas emissions. It also includes information on the economic implications of those decisions. Background information and activities are provided in a graphical (visual) format. Part one can be a stand-alone activity or prepare students for part two.

You can download each of the files individually using the links below or download the entire lab (134 pages – PDF format). The information contains references to Arkansas agriculture and swine production in some areas, but the information is still applicable in other states.

What do you know about swine and greenhouse gases?

This one page (PDF format) fact sheet (including a fun short quiz) can be utilized as part of this lab or as a stand-alone handout to stimulate discussion. Download factsheet

Part One Activity  – The Basics

This section includes five files that introduce the basic concepts of greenhouse gases, swine production systems, and glossary of swine production terms. This activity utilizes both text and graphical presentation of concepts and emphasizes information comprehension. Download Part One

  • Resource information – lesson plan and background information. This includes three aspects of swine management systems including feed management, housing management, and manure management.
  • Farm management system graphics – a visual aid to depict how each individual practice/component contributes to the building of a given pig farm system.
  • Farm flashcards – brief description and graphical rendering of various swine farm components
  • Lab report form – several structured questions designed to
  • Farm management option guide (FMOG)*

*The FMOG also doubles as a scenario key for the completion of Part 2.

Part Two Activity – Challenging

This section provides more in-depth information on swine production systems and greenhouse gases. It provides insight into management obstacles faced by pig farmers in balancing carbon footprints, available resources, producer goals, and legal compliance. This critical-thinking activity is meant to be completed in small groups. Download Part Two

  • Resource information – lesson plan and background information.
  • Farm management option guide FMOG
  • Three scenarios – each covers manure, feed, and housing
  • Flashcards – including health and feed, housing, manure


Authors: Rick Fields and Karl Vandevender, University of Arkansas. For questions about these materials, contact Rick at

This information is part of the program “Integrated Resource Management Tool to Mitigate the Carbon Footprint of Swine Produced In the U.S.,” and is supported by Agriculture and Food Research Initiative Competitive Grant no. 2011-68002-30208 from the USDA National Institute of Food and Agriculture. Project website.

Extension and Education on Swine Greenhouse Gas Emissions

Dr. Karl VanDevender – University of Arkansas:Cooperative Extension Service and Dr. Brian Richert – Purdue University

Sub-Project Overview

The research and modeling work encompassed by this project offers great potential for assisting researchers, policy makers, and especially farm managers to make informed management and facilities decisions regarding GHG emissions while maintaining production and profitability. However for this potential to be realized the swine production community needs to be aware of both its abilities and availability. To this end existing relationships with the National Pork Board U.S. Pork Center of Excellence, and eXtension are being enhanced.

The focus audience of this training is technical service providers (professionals, consultants, engineers, nutritionists, extension swine specialist and educators) who are involved in assisting swine producer’s making both strategic and tactical management decisions. The goal is to develop and implement education and outreach programs focused on the interaction between climate and swine science.

Dr. Richert serves as the nutrition domain editor for the US Pork Center of Excellence and US Pork Information Gateway which also serves as the swine domain for National eXtension. Through this relationship with domain editor for the Environmental section, Erin Cortus, we have initiated the rewriting of the factsheet “Pork production and greenhouse gas emissions” and have started authoring a factsheet on “Pork production, what might your carbon footprint be?”

Karl VanDevender, the project liaison with eXtension has a long history with the Livestock and Poultry Environmental Learning Center (LPELC) which has become the eXtension community of practice working in the area of livestock and poultry manure management. In response to the project needs he has transitioned from a topic area leadership role to a member of the LPELC leadership team, alongside other eXtension professionals. This provides the capacity to ensure that the project and LPELC take full advantage of the synergy of multiple funded projects without undesirable duplication of effort and resources.

The benefits of integration of extension efforts with research and education is that more rapid translation of research results into actionable knowledge will be achieved. Frequent team meetings are established to ensure that there is continual interaction and information exchange.

The working relationship between our project’s Extension component and the LPELC has helped facilitate the recent production of the webcast “Life Cycle Assesment Modeling for the Pork Industry“, which overviews the LCA goals and provides details in the sub-project areas dealing with concepts and research of feed management. Our project  will also be hosting a special session featuring project leads during the LPELC hosted Waste to Worth: Spreading Science and Solutions conference in Denver Colorado, April 2013. The special session will feature a showcasing of the project’s individual and collective works; topics discussed will include: LCA concepts, research and modeling challenges, model results, and economics.

Dr. VanDevender recently published an article in PIG Progress Magazine entitled “A Swine Carbon Footprint Model as a decision aid tool”, in which the efforts of this project were presented. The article stressed the imoportance of continued  management of greenhouse gasses in the livestock industry through improvements in efficiencies.


Sub-Project Objectives

  • Developing the necessary system and protocols for sharing and vetting information and educational materials
  • Strengthening the relationship between this project and eXtension
  • Development and delivery of information both internally and externally.

Contact Information

Dr. Karl VanDevender
Phone: (501) 671-2244

Dr. Brian Richert
Phone: (765)494-4837

Related Projects

Manure Management and Algal Nutrient Removal Impacts on Swine Greenhouse Gas Emissions

Algal Nutrient Removal

Dr. Marty Matlock and Dr. Thomas Costello – University of Arkansas

Sub-Project Overview

Algal biomass offers many advantages over traditional energy crops; algal biomass generates higher yields and requires smaller land area than other energy crops. In addition to biomass production for potential biofuel feedstock generation, algal growth systems can also act as tertiary treatment systems for wastewater. Algal growth can dramatically reduce nitrogen and phosphorus from wastewater. Unlike conventional open pond and photo-bioreactor systems, periphytic systems (e.g., algal turf scrubbers) generally involve the polyculture of micro-algae, which does not require specialized conditions. While algal turf scrubber systems are traditionally used for water treatment, they are also capable of generating high biomass yields.

The Algal Nutrient Removal Team has focused on installation of the test bed for the research. This has included construction of a precision graded base for the 20-ft wide by 200-ft long flow way. Our working hypothesis is that operation of an algal flow-way to treat swine manure will remove nutrients, produce a harvestable biomass residue, and add dissolved oxygen which will decrease potential for nitrous oxide emissions (and possibly methane emissions) during manure storage. Wastewater from the swine finisher unit at the University of Arkansas will provide nutrient input to the Algae Flow-way. The flow way will be tested with manure output from pigs fed conventional diets as well as the custom rations intended to reduce manure nitrogen. Impacts on nutrient removal and algal biomass productivity, as a function of diet formulation, will be measured. Nutrient removal will be documented and data collected will be used in the DNDC model to represent the waste treatment performance of the algal systems

Algal growth systems not only provide a method for nutrient removal from animal waste, but also provide biomass production as feedstock for biofuels which can improve the carbon footprint of swine production and other animal production systems in the U.S. This project will provide field scalable data on life cycle impacts of the technology. Design and construct algal turf scrubber concluded in late summer of 2012, and the system is currently undergoing callibrations in preperation for full-scale trials.

Sub-Project Objectives

  • Measure algal productivity.
  • Quantify impact of algal nitrogen uptake on swine system GHG emissions.

Contact Information

Dr. Marty Matlock
Phone: (479) 575-2849

Dr. Thomas Costello
Phone: (479) 575-2847

Solids Separation

Dr. Karl VanDevender – University of Arkansas. Cooperative Extension Service

Sub-Project Overview

Many technologies being considered incorporate some type of manure separation to concentrate manure solids, nutrients, and energy content. An LCA study in Denmark showed that energy recovery (incineration, gasification, and anaerobic digestion) had lower GHG emissions than traditional land application of swine manure. Other studies point to the complexities of manure management system design options in relation to GHG emissions. This portion of the project will quantify the effect of various solid separation approaches on the chemical composition of the manure generated by the feed trials at the University of Arkansas facilities during this project ,and generate the necessary manure solids for the thermo-chemical conversion portion of this project. Design and construct a pilot scale mobile solids separation system (see image below) is currently approaching completion and anticipated to be ready to begin trial calibrations soon.

Sub-Project Objectives

  • Capture and separation of manure from the UA animal experiments.
    • This unit contains systems to allow for various combinations of mechanical screen and filter bag separation, with and without chemical treatment; and is designed to operate in a batch mode with a capacity of 1000 gallons per batch.
  • Determine overall characteristics for the feed trial manure samples to provide additional validation data for the animal physiology sub-model.

Contact Information

Dr. Karl VanDevender
Phone: (501) 671-2244

Auger Reactor Gasification

Dr. Sammy Sadaka – University of Arkansas. Cooperative Extension Service

Sub-Project Overview

Due to the high moisture content, it is not economical to transport raw swine manure over long distances. As a result, manure is spread on land close to the source at high application rates. The energy content of dry manure is in the range of 12 to 18 GJ/ton, about half that of coal. In recent years, wet and dry gasification of algal biomass has been investigated by several researchers. Fluidized bed and downdraft gasification of algal biomass showed various challenges due to the nature of algae biomass. An auger gasification system (see image below) developed in the University of Arkansas, Bioenergy Laboratory, may help to simplify the air gasification process for this type of biomass. Algal biomass was gasified using the auger system during preliminary tests. Several improvements to the system took place during the first year to ensure smooth operation. Our long-term goal is to provide technology to convert swine manure and/or algal biomass to biofuel via a continuous gasification process. Energy conversion technology could provide a revenue stream of about $23 billion/year to the livestock industry.

Sub-Project Objectives

  • Modify the existing gasification unit to handle swine manure and/or algal biomass.
  • Test the performance of the gasifier
  • Optimize the operating parameters to maximize producer gas quality.
  • Study the effect of reactor temperature on the process yields (gas, char, and tar), as well as on the process efficiency.
  • Perform mass and energy balances on the gasifier.

Contact Information

Dr. Sammy Sadaka
Phone: (501) 303-0522

Related Projects

Solid-Liquid Manure Separation

Many, if not most, systems designed for manure treatment depend on reliable solid-liquid separation. What is solid-liquid separation for manure and when is it something to consider doing for your farm?

Defining Manure from a Solid-Liquid Separation Perspective

Manure can be thought of as a mixture of water, minerals, and organic components. Some of the minerals will be soluble and dissolve in the water, while the rest will tend to settle to the bottom or float to the top of the manure storage. The density of the organic components will determine whether they settle to the bottom of the storage unit, remain in suspension, or form a floating crust. The amount of water, source of manure, and manure handling system will determine the extent of these trends. More on solid-liquid separation’s role in manure storage….

The single most important factor affecting the tendency to separate is the amount of water in the manure. With low moisture (solid) manure, very little apparent separation takes place. As the moisture content increases the tendency for separation also increases. When characterizing manure’s physical characteristics it is often thought of as being a solid, semisolid, slurry, or liquid. From a practical perspective separation is limited to liquid, slurry, and sometimes semisolid manure.

When is it Desirable to Separate Solids and Liquids?

Whether the tendency for manure to separate into liquid and solid fractions is desirable depends on the objectives of the manure handing systems. In concrete pits and holding ponds it is usually undesirable because the manure often needs to be remixed to remove settled solids and obtain uniform material for land application.

In other situations this tendency for separation is desirable. If some of the land application sites are significant distances from the manure source, being able to concentrate manure solids reduces the volume and expense of transportation. In some areas of the nation phosphorus application rates are an environmental concern. Separating the phosphorus with the solids while leaving most of the nitrogen with the liquids may be an option. After separation, the liquids could be land applied near the manure source as a nitrogen fertilizer. The solids could be transported and applied to fields in need of phosphorus fertilizer.

Source: CC 2.5 karl vandevender; Livestock and Poultry Environmental Stewardship Curriculum Lesson 20.

Benefits of Separation and Uses for the Components

Even if transportation distance and phosphorus application rates are not a concern using solids separation prior to storage reduces the solids accumulation in holding ponds and lagoons. This increases the time between sludge removal operations and maximizes the liquid storage capacity of the holding pond or lagoon.

Another potential benefit is the reduction in odors. Under the anaerobic conditions found in holding ponds and lagoons microorganisms produce odorous compounds. Reducing the amount of available manure with solids separation tends to reduce the production of objectionable odors.

In animal confinement systems where water from holding ponds and lagoons are used to flush manure from the barns, solids separation can result in a better quality recycle flush water.

The separated manure solids have a reduced moisture content and increased nutrient concentration both of which increase its value as a fertilizer source. In addition, depending on the resulting moisture content it becomes a potential compost ingredient. Where the resulting compost may be used as bedding or potentially marketed off farm.

Manure separation is also likely to play a critical role in preparing manure for conversion in into energy. Different energy conversion technologies will require the manure to have different physical and chemical properties.

Solid-Liquid Separation Options

There are a lot of different options for solids separation. Some, like settling basins, use gravity and time to allow manure solids to settle out of solution. These systems are a non mechanical low tech approach with the resulting solids typically being a wet slurry. In contrast the mechanical approaches such as inclined or vibrating screens, belt or screw presses, centrifuges, and many others result in separated solids that while still having significant moisture can be handled and stored as a solid material.

Often the separation process can be enhanced through the use of chemicals. Some chemicals work by converting soluble mineral compounds into insoluble compounds. Other chemicals work by causing smaller particles to clump together into larger particles. Depending on the situation these chemicals may be used by themselves or combined.

Recommended Reading About Solid-Liquid Separation

Author: Karl VanDevender, University of Arkansas

Mobile Manure Apps

This webcast features a developer who has worked extensively with university extension as well as many other clients in sports, journalism, and agriculture. Two manure management apps are demonstrated followed by a panel discussion that features more manure-related apps and discusses challenges, opportunities and lessons learned when creating those apps. This presentation was originally broadcast on January 16, 2015. More… Continue reading “Mobile Manure Apps”

Livestock Mortality Composting – Beyond the Basics Part 1

The topics for this webcast include: pile characteristics for effective composting, management and environmental considerations when siting and managing composting facilities; mortality compost nutrients for on-farm use; and teaching the benefits of mortality composting to producers. This presentation was originally broadcast on August 15, 2014. More… Continue reading “Livestock Mortality Composting – Beyond the Basics Part 1”