I asked the folks at Withers & Ravenel to give share more about their project, how it was conceived, and how it was designed.
Why Swine Farms? What was the genesis of this Project?
North Carolina is “pork proud”, with approximately 9 million hogs on farms scattered throughout the eastern part of the State. These farms rely on open pit lagoons and land application for the treatment and disposal of animal waste. However, open-air treatment lagoons have a poor reputation among some lawmakers, residents and environmentalists. They are accused of creating sickening odors, allowing methane to escape into the atmosphere, and contaminating groundwater and streams.
Because of environmental concerns, the State temporarily suspended permitting the construction and operation on any new swine farms utilizing lagoon treatment systems in 1997, and required new farms to meet “environmentally superior technology” (EST) standards. Since the enactment of the suspension, there have been no new hog farms introduced in North Carolina.
Tax Credits, Legislation, and Funding
In 2007, the State passed Senate Bill 3, which pushes the use and development of renewable energy standards, the State took a big step toward encouraging innovative treatment technologies for swine waste by mandating utilities to purchase Renewable Energy Credits (REC) generated from swine waste. The Bill also provides a 35% State tax credit in addition to the Federal 30% tax credit.
Spurred by the availability of the NC Green Business Fund grants from the 2009 American Resource Recovery Act, Withers & Ravenel conceived the 600kW renewable energy project and assembled the project team, which included developer AgPower Partners LLC, Withers & Ravenel engineers, and Barnhill General Contractors.
The project was able to receive over $2 million dollars in grants and tax credits, including a $500,000 grant from the NC Department of Energy and $1.5 million grant from the US Treasury. The Owner, Billy Storms, was able to finance the balance of the project cost through a loan with the Cape Fear Farm Credit Association.
Engineering a Plan for the System
In North Carolina, swine farms flush the houses with water in a closed system with a lagoon providing storage and treatment of waste which is then applied to crops. With this process, the waste is diluted to around 1-2% solids. However, in order to reduce the water content for more efficient temperature control of the anaerobic digestion, the waste needs to be between 5-10% solids.
With the implementation of scraper technology, swine waste volume was significantly reduced by eliminating the added liquid from the flushing system. This made the Storms Farm much less reliant on the volume required in the existing lagoons, reduced the required size of the anaerobic digester, providing benefits to both the waste handling concerns and to energy production. The scraper system also reduced the amount of ammonia gas in the barns, which is beneficial to animal and human worker health.
Most digester systems for swine manure in North Carolina have relied on ambient covered lagoons. However, at Storms Farm, with the scale of a 600 acre farm and swine houses separated by as much as a mile, it was not cost-effective to build and cover a new lagoon to treat the waste using anaerobic digestion. The distance between the 23 barn complex made it problematic to pump waste because of build-up in the pipe known to cause maintenance and failure problems.
After review of viable technologies, Withers & Ravenel recommended DVO Anaerobic Digesters to supply the digester technology for Storms Farm. DVO has an extensive tract record using their patented mixed plug-flow digester technology on dairy farms, but there was no comparable swine waste facilities using mesophilic digestion in the US. Europe has a substantial number of facilities that use swine manure mixed with other substrates, but there was no reliable source of data for the gas yield using solely swine waste substrate.
As a result, Withers & Ravenel took multiple manure samples from local farms and had them tested to help estimate the biogas yield. Even with this data, there was very little information to collaborate the projected biogas yield. After all alternatives were evaluated, the most cost-effective, efficient option was to construct a heated mesophilic digester system with cogeneration and to convert the barns to scraper manure removal systems.
Geotechnical borings were done and revealed the need to raise the digester above grade due to a high ground water table. This required sloping the backfill around the tank as insulation to maintain the needed 95 degree temperature in the mesophilic process. The report also revealed the need to pre-load the site to avoid potential settling of the digester and cogeneration building. This additional grading and site work was necessary from the original conceptual site plan.
The Digester Operation
The scraper system scraps the waste to a gravity collection system and storage tanks behind each barn. Two vacuum trucks and drivers empty each of the 23 tanks daily to collect the manure collected from each of the barns, drive to the digester facility and empty the manure into the influent pump station.
Manure is pumped into the 1.1 million gallon in-ground concrete digester where the temperatures are maintained above 95 degrees (mesophilic) and the natural occurring anaerobic bacteria destroy the volatile solids, produce the bio-gas containing 65% methane, kill pathogens, and produce a high quality inorganic waste product virtually pathogen and odor free for storage and, eventually, land application as fertilizer. At Storms Farms, about 60,000 gallons of swine waste is processed each day. The biogas is “scrubbed” of corrosive components and combusted in an 845 HP gas driven engine/generator integrated system provided by Martin Machinery, from Latham, Missouri.
The digester produces wastewater that is free of pathogens and odors and removes 90% of the phosphorus and 75% of ammonia nitrogen. The electricity – enough to power over 300 homes – is sold to North Carolina Electric Membership Corp.’s grid network.
Through this design, Withers & Ravenel was able to develop Storms Farm into the largest swine biogas renewable facility in North Carolina, generating 600kW of power with an operating capacity of 95%.
The volume reduction due to the implementation of the scraper system and digestion process has allowed the treated effluent to be returned to one of the existing lagoons, reducing the dependence on the original six lagoons on the site.
Future projects to remove the inorganic solids remaining in the effluent by dewatering and to treat for additional phosphorous and ammonia nitrogen removal are in the planning stages in order to meet the additional requirements of an EST standard farm.
What was the Owner’s involvement?
Billy Storms, owner of Storms Farms was instrumental in getting the Project off the ground, through financing the project, through the willingness to change the method of manure management and by accepting the technological challenge of running what is, essentially, a small wastewater treatment and power plant. He was a true partner in the project and was directly responsible for the selection and installation of the manure scraper system in all of the barns, implementing the operations of the truck collection system, the digester and generator systems as part of the farm operations.
What can we learn from this project?
This project demonstrates a method to economically build new swine farms without total dependence on the historical open air lagoon treatment system, and flushing system collection methods, a conversion that is necessary to meet the State EST standards. The system also develops renewable energy meeting the goals in Senate Bill 3 requiring swine waste to be utilized in a percent of the production of renewable energy.
However, because of the cost, risk, and complexity of the project, its applicability may be limited to a handful of existing farms in North Carolina. Larger farms, preferably more than 50,000 animals, are required in order to have the scale to produce the amount of energy to have an economical rate of return on investment.
Thanks, Withers & Ravenel, for the detailed project description. Your turn: Thoughts? Comments? Questions for the team? Shoot me an email or post in the comments below.
Photos (c) Withers & Ravenel; Pig outline courtesy Pixabay.
As I noted earlier this week, the ACEC of North Carolina’s Engineering Excellence Awards gala was held last month. 13 amazing projects were awarded recognition, including projects involving environmental and coastal issues, higher education facilities, and government projects.
Each project was important, unique, or challenging in some manner. In my next post, I will highlight one of the most unusual– the Swine Farm Biogas project by Withers & Ravenel. In the meantime, here are all of the winners, which I’ve loosely sorted into categories:
Coastal & Environmental projects
Sea Bright to Manasquan Profile Survey, NJ (McKim & Creed)
American Tobacco Trail Pedestrian Bridge, Durham, NC (Parsons Brinckerhoff)
Town of Hillsborough Riverwalk, Hillsborough, NC (Summit Design and Engineering Services)
Swine Farms Biogas Renewable Energy Project, Bladenboro, NC (Withers & Ravenel)
Campus & Higher Education projects
South Halls Renovation, Penn State, University Park, PA (Clark Nexsen)
Science & Technology Building, Fayetteville State University, Fayetteville, NC (McKim & Creed)
Marsico Hall, University of North Carolina, Chapel Hill, NC (Mulkey Engineers & Consultants)
Military, Municipal, & Highway projects
Carolina Field of Honor War Memorial, Kernersville, NC (Woolpert)
Broad Avenue Bus Terminal, High Point, NC (Mulkey Engineers & Consultants)
The diversity of the award-winning projects was very clear, as even a cursory review of the projects demonstrates. I recommend you follow the links to the specific projects to see some great photos and hear more about the projects in detail.
In the meantime, tell me what project you would have given the “best in show” award to if you were the judge. Or, was a project left out of the awards that you thought superior to some of these? Share your thoughts about both these projects, and any others that you think should have made the cut, in the comments section.
Want to know how bats may effect your engineering plans? Want to hear about cool new bridges? Read on.
Over the past month, I’ve had the pleasure of attending two events hosted by the North Carolina Chapter of the ACEC (American Council of Engineering Companies). The first of these was the Joint Transportation Conference, held in conjunction with the NC DOT. The second was the annual ACEC Engineering Excellence Awards. At both events, I learned interesting information that engineers should know. Today, I will discuss the Transportation Conference, including some new regulations and unusual design methods. I will save the highlights from the Excellence Awards for later this week.
1. It’s a cave, it’s a bat, it’s bats, man! Did you know that your future bridge project may be effected by the Northern Long-Eared Bat? It’s true. Right now, the federal government is considering listing the bat on the Endangered Species List, due to the 98-99% mortality rate the bats are experiencing due to “white nose syndrome”. Over 1,700 projects in North Carolina could be impacted, including work on bridges, culverts, abandoned buildings, and guardrails–essentially, any activity involving tree clearing, structure demolition/removal, or structure maintenance. On November 26th, 2014, the US Fish and Wildlife Service extended the comment period to discuss the implications of listing the bat on the endangered species list. If the bat is listed, there is no grandfathering of projects. All projects will immediately be required to engage in protective activities. Stay tuned, but be aware that your transportation projects could be effected starting sometime next year.
2. Is that a pirate on your map or is it worse–soil contamination?
At the conference, we also heard from the GeoEnvironmental Section of NC DOT on their geologic symbols for known or potential contamination. Known contamination consists of soil or ground water samples that have been analyzed; or by evidence of such contamination as cracked transformers, battery casings, unusual odors while excavating, or new anecdotal information about past use. Potential contamination, in contrast, is for areas where there is no data, but historical maps or photos which indicate current or assumed past uses of possible contamination, such as gas stations, dry cleaner facilities, auto body facilities, chemical manufacturers, landfills, and manufacturing plants. Both known and potential contamination sites are important for designers, as they consider:
- large cuts, drainage, utilities, or stream relocations in contaminated areas
- selecting chemical resistant construction materials
- additional costs for materials, remediation
- other unanticipated costs or complications
3. Water, water everywhere! We also heard what’s new with the Highway Stormwater Program, including the updated Post-Construction Stormwater Program and the companion Stormwater BMP Toolbox manual. To learn more about these programs, check out:
- The NCDOT Stormwater website, which contains useful links; and
- The Highway Stormwater youtube chancel of training videos, which is still in development but will include environmental sensitivity maps, nutrient load accounting tools, and stormwater management plans.
4. Cool, cool bridges One of the highlights of the conference was hearing about some truly unique bridge designs, including:
- The Tappan Zee Hudson River Crossing, in New York, featuring twin-tower cable stayed structures and all electronic toll collection
- Vietnam’s Dragon Bridge, a truly working piece of art; and
- The Milton-Madison Bridge Slide, (Indiana/Kentucky) the longest bridge slide in North America. The Milton-Madison Bridge Slide was a feat of engineering design. Using “truss sliding” a new 2,427 foot long truss was moved along steel rails and plates and “slid” into place atop the existing, rehabilitated, bridge piers.
What about you? Did you attend the conference? If so, what insight did you take away? Share in the comments, below.
Do you like modern architecture? Is Frank Lloyd Wright someone you wish you could have met?
If so, then you’ll want to check out the new “Masters Gallery” of the North Carolina Modernist Houses (NCMH) group. With changes and additions announced this week, it’s Gallery is America’s largest open digital archive of Modernist houses, as well as the internationally known Modernist architects who designed them.
Currently, the Gallery showcases over 30 architects with extensive house histories and over 10,000 photos. The Gallery is extensive and searchable and includes, among many other notables, Frank Gehry and, of course, Frank Lloyd Wright.
To view the NCMH Masters Gallery, go to http://www.ncmodernist.org/ and click on “Masters Gallery” under the Archives listing. Be careful, though, because NCMH founder and director George Smart, you can spend many addictive hours looking around. Hey, at least this addiction doesn’t require a trip to the gym afterwords!
Photo courtesy WikiMedia Commons.
What are your top construction building projects in North Carolina? Do you have a “short list”? Author Ralitsa Golemanova of JW Surety Bonds does, and she has the reasoning behind them. Ralista’s Top 5, which all “present a different facet of exceptional modern design and construction” are presented below.
Her list, in no particular order, includes:
1. The North Carolina Museum of Art’s West Building Expansion
The 127,000 square-feet West Building Expansion of the North Carolina Museum of Arts won the 2011 American Institute of Architects (AIA) Honor Award for Architecture. The Building is largely made of aluminum panels. One of its specificities is that it does not have any windows. Instead, visibility is ensured through 360 skylights that allow delicate natural light to enter the inner galleries.
2. The Bank of America Corporate Center in Charlotte
The skyscraper is 871 feet tall and was completed in 1992, is allegedly the tallest building between Atlanta and Philadelphia, and can be seen from 35 miles away.
3. The Bell Tower Development project at UNC-Chapel Hill
The huge $175 million Bell Tower Development includes a 710 car parking deck, a 25 thousand-ton chilled water plant, a new Genome Science Laboratory Building which will provide approximately 210,000 square feet of modern classrooms, laboratories and offices including nine wet labs, four bioinformatics labs, a 250 seat lecture hall, a 450 seat lecture hall, an 80 seat classroom, and four 30 seat seminar rooms.
4. The Biomanufacturing Research Institute & Technology Enterprise (BRITE) at NC Central
The BRITE construction was a $17.8 million endeavor, which is spread out over 59,900 square feet and complements the existing science buildings. The project includes a four-story 65,000 square foot building to provide hands-on learning experiences for biotechnology students.
5. The James B. Hunt, Jr. Library at NC State
Priced at $93.75 million, the 221,122 square feet library is designed with maximized light and views of nature in mind. With its LEED Silver certification, it provides natural heating and cooling, as well as usage of rainwater with the help of green roofs and rain gardens.
What about you? Do you have a list of favorites?? Share in the comment section of the blog.
Photos of Art Museum and Hunt Library both courtesty of Wikipedia via cc.