As concerns about climate change and energy independence grow, biogas production is a promising technology that captures energy from the breakdown of organic wastes. North Carolina, and Duplin County specifically, is well positioned to attract this industry, as it has an abundance of agricultural residue, manure, and food processing waste that can serve as fuel for biogas production. That biogas can then be burned to generate electricity, or processed into natural gas or compressed natural gas (CNG) vehicle fuel.
Biogas production has become a staple of European renewable energy technology, but is still fairly new in North America. Small-scale systems have begun to proliferate over the past decade, particularly on dairy farms. Increasingly, there is a trend to construct large biogas plants that centralize multiple waste streams to improve efficiency and profitability.
This report was undertaken in response to a recent proposal for such a centralized biogas plant in Duplin County, with the goal of providing detailed information on a plant’s operations, its potential impacts, appropriate mitigation techniques, and alternatives. Data for this report was gathered by examining fifteen centralized biogas plants across the country through phone interviews, web-based research and academic literature.
A common community concern surrounding biogas plants is their potential odor. This report finds that while there will be some odor from the plant – 3 to 4 days a year at a well-run facility – overall, the plant will contribute to a reduction of odors in the area. Producing biogas involves the breakdown of raw waste materials and through this process the waste loses much of its odor. At the end of the production process an effluent is left behind that has reduced odor and pathogens and has high value as a fertilizer. As this effluent is used as an alternative to raw manure for field application, and raw manure thus no longer needs to be stored for extended periods, odors will be decreased on participating farms.
Biogas plants are integrated systems that require a tight balance between the waste products available locally and the local need for liquid fertilizer. In Duplin County’s case, the plant must be designed to accept hog waste and provide value to farmers so that they will participate as waste providers. There must also be a productive use of the effluent as fertilizer or this product will become nothing more than a waste product in itself, albeit more inert than the original raw waste.
Biogas production is about improved waste management as much as renewable energy production. It captures value from a waste stream while also cleaning up that waste stream, upgrading it to a more usable form. From an economic development standpoint, it creates new job opportunities in an industry with potential for growth and improves local environmental quality for residents and businesses. Encouraging the growth of this industry can be done through work with stakeholders to increase community awareness and by creating a workgroup to simplify the regulatory process.
At the request of the Duplin County Economic Development Director James Wolfe, this report outlines the opportunities and challenges of a centralized swine waste biogas facility. The report is organized to roughly follow the flow operations of a biogas plant, beginning with the collection of waste materials, proceeding through the biogas plant to the resulting revenue-generating products and effluent. At each stage the process and technology is described and potential issues and solutions are explored through case study examples.
This report focuses on a centralized configuration of biogas production, involving the transportation of waste materials from multiple sources to a single industrial site. Other system configurations are mentioned throughout the report and are catalogued in the final section. Fifteen case studies of centralized biogas plants across the country were considered in developing this report. Data on these plants were gathered through phone interviews, web-based research and academic literature.
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