WithersRavenel, Design and Oversight of Waste Treatment / Energy Production Facility Installation
WithersRavenel, farmer William “Billy” Storms, and a team of consultants together performed a wastewater treatment “miracle,” building North Carolina’s largest state-of-the-art renewable energy facility that converts swine waste into electricity.
North Carolina has roughly 9 million hogs on farms scattered throughout the eastern part of the State. Traditionally, these farms have relied on lagoons and land application for the treatment and disposal of animal waste. But in 1997, concerns about the potential environmental impacts of hog farming led the State to place a temporary suspension on swine farming using lagoons. Existing farms were grandfathered, but new farms were required to meet “environmentally superior technology” (EST) standards established by the State.
Since the enactment of the suspension, there have been no new hog farms introduced in North Carolina, which has hurt the State’s ability to compete with other swine-producing regions. Spurred by a desire to foster environmental advancements in farming and bolster the economy, the State enacted a new bill that encourages innovative treatment technologies by mandating utilities to purchase Renewable Energy Credits (REC) generated from swine waste.
I thought about this possibility for a long time. I did not know how to do what I wanted, but I found some folks who helped us get there. WithersRavenel gave me exactly what I asked for and I am tickled with it.
— William ``Billy`` Storms, Owner, Storms Farm
Farm owner William “Billy” Storms is one of the many farmers whose farm used a lagoon to manage swine waste. As a lifelong farmer, Mr. Storms understands that open-air treatment lagoons have a poor reputation among some lawmakers and citizens: they are accused of creating sickening odors, releasing ozone-destructive levels of methane into the atmosphere, and contaminating groundwater and streams. He had long considered a more environmentally positive way of handling swine waste, but did not know how to reach this goal. With the passage of the new bill, Mr. Storms seized the opportunity to transform his 600-acre operation from a waste producer to an energy generator.
Backed by a $500,000 North Carolina Green Business Fund grant, Mr. Storms approached WithersRavenel for design, permitting, fund allocation, and construction oversight of the project. With the help of developer AgPower Partner and Barnhill Construction Contractors, Storms Farm is now the largest swine biogas renewable energy facility in North Carolina, capable of generating 600 kW of electricity—enough to power about 300 homes.
Storms Farm, like other swine farms in North Carolina, was originally designed to flush the livestock houses with water that was captured in a lagoon, treated, and applied to crops in a closed system. This process works because of the way it dilutes the waste. But in order for the waste to be useful for energy generation, it needs to be concentrated instead. In some cases it is possible to convert open lagoons to ambient covered lagoons to achieve this result, but in the case of Storms Farm, the operation was too large and too spread out for this approach to work. Piping waste from 23 barns, some of which were separated by as much as a mile, to a new covered lagoon was likely to lead to build-up in the pipes and eventual maintenance issues or system failure.
Instead, WithersRavenel recommended a heated mesophilic digester system with cogeneration, which itself presented two major hurdles. First, it required a complete replacement of the farm’s decades-old manure management system with modern scraper technology. But as a progressive and adaptable owner, Mr. Storms embraced this change, citing the value of reducing ammonia gas in the barns for both animal and human worker health. Second, the system has an extensive track record on dairy farms, but no record of use on a comparably sized swine farm in the U.S. The system is popular on swine farms in Europe, but is used for swine manure mixed with other substrates; no reliable data containing only swine waste exists. Undaunted, WithersRavenel oversaw the collection and testing of multiple manure samples from local farms to estimate the biogas yield and validate investment in the project.
The final design involves pumping manure into a 1.1-million-gallon in-ground concrete anaerobic digester, where naturally occurring mesophilic bacteria destroy volatile solids and kill pathogens. The resulting high-quality inorganic waste product, which is virtually pathogen- and odor-free, is a sustainable replacement for soil conditioner, fertilizer, peat moss, and bedding materials. Methane previously released into the atmosphere is captured and converted into energy to be sent to the Four County Electric Membership Corporation grid.
Driven by grant and tax credit deadlines that controlled funding, WithersRavenel met all project milestones and finished as less than 25% over the original cost estimate—a remarkable feat considering the scale of the project and the lack of available data on swine farm biogas operations using a mesophilic digester system.
Mr. Storms, who has taken on the challenge of running what is essentially a small wastewater treatment and power plant with gusto, gave a speech at the ribbon cutting in June 2014 expressing his satisfaction.
The American Association of Engineering Companies’ North Carolina chapter recognized WithersRavenel with a 2015 Engineering Excellence Award in Energy for the project.