Biogas and RNG at Duke University


Due to the significant available supply in North Carolina, Duke University has been exploring the potential of how biogas and renewable natural gas (RNG) from biogas can help meet campus climate neutrality goals and the University’s energy needs. Specifically, the University has sought to achieve carbon offsets through the capture and destruction of biogas along with the opportunity to procure RNG for the campus steam plants. Both of these options are driven by a desire for Duke University to leverage its climate and renewable energy goals to help address other long-standing environmental, social justice and economic issues across North Carolina.

History of Biogas at Duke University

In 2010, Duke University’s Carbon Offset Initiative led a partnership with Duke Energy and Google to demonstrate a full-scale swine waste-to-energy system in Yadkin County. The system captures methane gas or “biogas” that results from the breakdown of hog waste. This gas is burned in an onsite microturbine to generate electricity.

Methane gas has a global warming potential some 34 times more detrimental than carbon dioxide. Capturing this gas reduces the harmful impact on the environment, and it also creates a renewable fuel that can be burned to generate energy – offering a double dividend.

The Yadkin County system provided data that Duke University used to model a way to scale energy production from animal waste (and eventually other waste-generated methane) from a single-system approach to a multi-farm approach that would reduce biogas costs while increasing its energy production potential.

Thanks in part to the University’s efforts to test a full-scale waste-to-energy system and create a roadmap for development of the state’s swine waste-derived biogas, the pork industry is expected to embark soon on a major biogas development effort while compliance with the swine waste-to-energy requirement of the NC Renewable Energy and Energy Efficiency Portfolio Standard (NC REPS) appears finally to be within reach.

Loyd Ray Farms image
Loyd Ray Farms is a swine waste-to-energy project managed by the Duke Carbon Offsets Initiative. The waste is flushed into an anaerobic digester where bacteria turn it into biogas. This biogas is used to generate renewable electricity onsite.


Exploring an Untapped Renewable Resource

Duke's initial plans for biogas only included offsetting those emissions it could not reduce. Using biogas on-site at Duke University was not possible at the time. But due to technological advancements brought about in part by the Loyd Ray Farms project and policy changes, Duke University began to consider biogas/RNG as a direct fuel source.

Using biogas from livestock and other waste operations has multiple direct climate benefits.  First, its capture and destruction can generate carbon offsets by avoiding methane emissions by preventing those emissions from being released. These carbon offsets can be applied against baseline emissions the University cannot avoid. Second, the biogas can be used to generate electricity or a renewable alternative to natural gas thus curtailing fossil fuel-based emissions. 

Biogas technology diagram
Biogas technology diagram courtesy of N.C. DEQ's EPC Biennial Report (2018)

While substantial effort has been applied to achieving carbon reductions from agricultural waste emission controls, in more recent years Duke has placed increasing emphasis on finding ways to replace the conventional natural gas it uses with RNG produced from state biogas resources. Use of RNG at Duke is consequential because nearly half of the University’s operations rely on natural gas. If the University could avoid some or all of its use of conventional natural gas, it could dramatically reduce its baseline emissions. Moreover, in cases in which RNG is sourced from livestock operations, the University not only displaces conventional natural gas with a renewable but it also helps farmers avoid methane emissions their farms would otherwise have emitted, making livestock operations a particularly attractive climate focus. 

In late 2016, Duke University began a formal assessment to determine if a sufficient supply of biogas could be secured in North Carolina to reduce the need for fossil fuels on campus and support the University’s commitment to climate neutrality by 2024.    

Next Steps on Biogas and RNG

Duke University’s evolution from carbon offset procurer to direct RNG user stems in large part to changes in economics, technology, and policies around the capture and use of biogas in N.C. In addition, increasingly lucrative incentives for renewable compressed natural gas and liquified natural gas replacements for fossil-derived transportation fuels are accelerating RNG project development. The University’s investment in Loyd Ray Farms, and subsequent analysis of the energy production capability of biogas based on the experience gained from the project, have helped not only to create an RNG market in NC but also opened the door for the University to run parts of its campus on RNG. As the University gains access to RNG supplies, it will continue to do its part to make RNG available to all North Carolinians.   

In addition to shifting focus from carbon offsets to RNG, Duke University is also anticipating a pivot toward other biogas sources beyond swine waste. It is intentionally seeking to expand the sources from which it obtains RNG so that it can use its demand signal to catalyze alternative supplies that receive less consideration as a source of RNG. Sources being considered include food processing plants, co-digestion of poultry litter, landfill-derived biogas, biogas from wastewater treatment plants, crop residues, and dairy operations.  In all cases and opportunities, the University will continue its commitment to considering the broader impact of every biogas and RNG purchase.