Above the Dirt: A Look into North Carolina’s Clean Energy Future through Waste-carbon Harvesting

Why Study Organic Wastes as Energy Sources?

Compare the Potential: The United States has tremendous organic resources available, such as food waste, crop residues, animal manures, and human waste. Americans need only look out the window of their home or office to see the reasons why – we live in a very ‘green’ country. In most states, we have a temperate climate with ample resources that promotes our ability to inhabit and cultivate; which means we create organic wastes. However, Americans have been slow to realize the huge potential that may be derived from these organic resources in the form of bioenergy. Why have we spent so much time evaluating the energy resources buried deep in our soils, rather than recognizing the opportunity right in front of us, above the dirt?

What did we do?  

This presentation provides an overview for establishing infrastructure systems that capture, purify, and transport the biogas that may be derived from these organic resources to create an infinite energy reserve to draw from, creating jobs and bolstering our economy. Potential uses for energy products that may be derived from organic wastes are discussed, as well as the barriers, challenges, and economics of waste to energy systems. The presenter’s home state of North Carolina is examined in more detail, describing and comparing the potential for harnessing the energy value from wastes that lie above the dirt.

The Potential:

To understand the infinite possibilities and advantages of the use of bioenergy nationwide, let’s first explore the possibilities in just one state, North Carolina. According to Census Bureau migration patterns in 2013 across the U.S. showed that North Carolina remains in the top 3 fastest-growing states in the nation. While predominantly an agricultural state, N.C. has an abundance of potential to be derived from organic resources in the form of bioenergy. N.C. places second in the U.S. for the production of pigs and turkeys and it ranks fourth in the production of broiler chickens. This generates an abundance of organic wastes, particularly in animal manures, which as people are beginning to understand, gives our state of North Carolina the potential to be a leader in supplying renewable energy.

Map of permitted hogs

According to sources such as the Environmental Protection Agency (EPA), the U.S. Department of Agriculture (USDA) and the Renewable Energy Laboratory (NREL), the organic waste resources in North Carolina – stemming from municipal waste (solid waste and sewage) and agriculture (animal manures) – are among the richest in the nation. Imagine the Potential: North Carolina can harvest energy value from crop residues, food waste and crops to produce infinitely renewable energy that can also improve air and water quality impacts. Anaerobic digestion is one common approach to harvesting the energy content of these organic wastes and other feedstocks.

Biomass resource of the United States, methane emissions from manure management map

What have we learned?  

The development of bioenergy systems is one of the ways in which we can be good stewards of our earthly resources. By reusing the carbon readily at hand above the ground – which is often already creating a negative environmental impact in the form of waste – these bioenergy systems can provide for our fuel and energy needs while simultaneously achieving improvements in environmental quality. There are many ways in which we can accomplish the reuse of carbon through the harvesting of energy value associated with organic wastes. There are over 16,000 permitted municipal WWTP’s in the U.S., and about 10% utilize anaerobic digestion. Coupled with the thousands and thousands of farms, landfills, and biotechnology manufacturing facilities, our ability to develop renewable biogas fuels for transportation and electrification is astounding.

NC "all bioenergy" facilities map (with NG pipelines)

Future Plans  

As a country we need to step away from how we have always done things (buying foreign sources of oil, and using fossil fuels, and relying solely on power plants) and be receptive to innovative approaches that improve climate action initiatives and foster stewardship of our earthly resources so that we can do better environmentally and plan so there be enough water, energy and food for the future. These recommendations start on a state to state level, and progress through our country, and across the world. We need to take better care of our environment, and uses our resources to reduce pollution and greenhouse gases, and harvest the energy from our wastewater and agricultural sources that lie above the dirt.


Gus Simmons, P.E., Director of Bioenergy, Cavanaugh & Associates, P.A. gus.simmons@cavanaughsolutions.com

Additional information                 




Duke Energy Carbon Offsets Initiative

NREL – www.nrel.gov/gis

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.





Next Generation Technology Swine Waste-to-Energy Project

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* Presentation slides are available at the bottom of the page.

The Loyd Ray Farms project is the first swine waste project in the State of North Carolina to generate and transfer renewable energy credits (RECs) to a public utility.  Utilizing an anaerobic digester as primary treatment, this waste treatment system is designed to meet the Environmental Performance Standards set forth by NC law for new and expanded swine facilities through the use of nitrification/denitrification and further treatment. The system implemented at this farm utilizes anaerobic digester technology to turn raw animal waste into biogas.  The biogas is used to fuel a microturbine, generating electricity to power the environmental treatment system, and about half of the farm. Related: Manure value & economics

The farm is a finishing swine operation that houses approximately 9,000 pigs near Yadkinville, NC.  The concept for this approach was conceived by the team in 2006, followed by economic and performance modeling, permitting, and construction of the commercial-scale system.  The project was commissioned on May 27, 2011.  Funding for construction was provided by Duke Energy and Duke University, with support from USDA-NRCS and the NC Division of Soil and Water Conservation.  Google provides operational funding support in exchange for a portion of the carbon offsets created.

Loyd Ray Farms is the only innovative Swine waste system in North Carolina that generates Renewable Energy Credits for an electric utility,  which generates enough power for  the treatment system and has enough surplus electricity to power about half of the farm.  Cavanaugh collaborated in this study with Duke University, Duke Energy,  and Google with funding from NC Soil & Water Conservation and USDA/Natural Resources Conservation Service.

Forefront: Tatjana Vujic of Duke University views the meter readings

The project began as a conversation about greenhouse gas emissions, sources for renewable energy, and sustaining the state’s swine industry among Duke Energy, Duke University, Google, and Cavanaugh.  That conversation led to a project that is getting attention around the world, for its successes in combining strategies to address the concerns for generating renewable energy from agricultural sources, sustaining agriculture, and addressing farming’s relationship to climate change.

The system’s goals: generating about 500 megawatt-hours of electricity annually, reducing greenhouse gas emissions equivalent to 5,000 tons of carbon dioxide annually, reducing ammonia and odor emissions from the farm, and improving the quality of treated wastewater on the farm.”

Is Manure to Energy Important?

We will discuss the successes and challenges in partnered efforts by farmers, electric utilities, and other stakeholders in the marrying of renewable energy generation with enhanced environmental treatment and green house gas emissions reduction, including the economics of such effort.

What Did We Do?

Waste generated by the animals is flushed into an anaerobic digester where bacteria consume the waste and respire energy-rich biogas.  The biogas fuels a microturbine that generates electricity, and excess gas is flared.  After digestion, the liquid waste is further treated to achieve the Environmental performance Standards set forth by North Carolina for Innovative Swine Waste Treatment Systems.

The process by which the stakeholders came together in a partnership, the technologies and approaches selected, and the successes/challenges that can be gleaned for advancing future projects.  The Loyd Ray Farms project is the first Swine Waste-to-Energy project in the State of North Carolina to place RECs on the North Carolina Utilities Commission REC Tracking System, and is the first swine farm in North Carolina to transfer RECs to Duke Energy.  Coupling techniques to improve the environmental treatment system employed at the farm, the Loyd Ray Farm project is also the first ‘Innovative Swine Waste Treatment System’ permitted that utilizes an anaerobic digester as a primary form of waste treatment.


William G. “Gus” Simmons, Jr., P.E. Cavanaugh & Associates, P.A., gus.simmons@cavanaughsolutions.com

Gus Simmons, lead designer, M. Steve Cavanaugh, Jr., and Marvin Cavanaugh, Sr. during the commissioning of the system.  Cavanaugh developed the concept for Duke University in an effort to create a cost-effective solution that converts swine waste into renewable energy while achieveing a superior level of waste treatment and a reduction in the carbon footprint created by the conventional waste management system.

Gus Simmons, P.E., is the Director of Engineering at Cavanaugh & Associates, a consulting firm specializing in stewardship through innovation.  An NC State University graduate with a BS in Biological & Agricultural Engineering, Gus  has worked for a major agricultural producer where he was Director of Environmental Affairs and Engineering Services, managing engineering and construction for facilities in the US and Europe.  Gus has designed, permitted, and managed over 5,000 acres of wastewater irrigation in NC, and thousand of acres of wastewater irrigation in the Western US. He has assisted many municipalities and private entitites with the development and implementation of reclaimed water systems and reuse irrigation systems, and has actively participated in alternative wastewater management strategies for the NC Pork Industry.  His recent sucessess include the engineering design of an anaerobic digester for animal waste to energy project in Yadkinville, NC which has gained world-wide recognition for its successes in generating RECs and greenhouse gas credits.

Additional Information

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.