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.
Today, a guest post on the green design issues that are becoming realities from Penny Olmos, who is associated with Holloway Houston, Inc. a leading industrial lifting equipment manufacturing company. Welcome, Penny!
The scorching heat singed us and the winter wave chilled us — more than ever before. What are we heading to? Earthquakes, volcanoes, tsunamis, tornadoes and extreme temperatures? Mother Nature is warning us in myriad ways. And the good news is that we are heeding her calls after long. Saving our natural resources and going green has found many takers. We have seen many eco-friendly homes and buildings designed and created in the last decade. Green homes are here to stay. We look at the popular green home design and construction trends in 2014 that are about to transform the landscape of green realty.
Rise of Net Zero Energy Homes
It seemed impossible until a couple of years ago but 2014 will witness a rise in net zero energy homes. These are homes with zero net energy consumption. The total amount of energy used by these buildings annually equals the amount of renewable energy created on the property. This is the greenest and the most energy efficient house you can possess. And you do not need to cut down on any of your comforts. There are heating, cooling, entertainment and utility appliances functioning in the house like they would in any other home.
The only difference is that it happens much more efficiently. Air source heat pumps are becoming the choice of heating and cooling in such green houses. Solar photovoltaic systems that are installed on the roof function to cover all energy use in the house including charging of electric cars. Zero energy homes are being sold in states with an abundance of sunlight and solar energy like Arizona, Texas and California.
Use of Micro-Windmills
Solar energy-powered homes have taken the realty market by storm, but the trend to watch out for this year will be micro-windmills. These are so small that ten of them can be accommodated on a grain of rice. But do not underestimate these tiny wonders. These micro-mills harness the air for electricity. They are very cost-effective. These nano windmills will soon power entire homes. Their developers claim these tiny wonders can be mounted on the walls of the home to harvest air motion and derive cheap and quick energy.
Smart Collection of Energy Usage Data
All those interested in having a green home need to first determine their energy consumption and where is it being used. The smart thermostat is going to be a key feature in a lot of energy-efficient green homes where owners want minimum wastage of energy.
These devices can transmit accurate live data about energy usage via your smartphone and help you monitor it as well. Thus the homeowner is equipped to configure all appliances in a way that uses minimum energy. Another reason smart thermostats will find their way into many eco-friendly homes in 2014 is the drastic drop in the price of their hardware.
Energy-Efficient Lighting and Heating
Natural light is going to be one of the key realizations of green living in 2014. Architects, Interior designers and homeowners are putting a lot of thought into deciding the number of windows to make and their best placement, so as to allow maximum light into the house. The right windows can be an equally good source of the much-needed winter heat. Install windows with a solar heat gain coefficient of 0.55 to allow maximum heat to pass through your windows.
Another easy step towards a green home is switching from single pane windows to double or triple glazed windows. They will reduce the heat entering the building and consequently the energy consumed by the AC.
For homes where natural light availability is difficult, tubular skylights are an effective and energy-efficient source. Tubular skylights transmit sunlight into the house through roof openings. Tubular lighting also works for providing natural light to the basement and to the first floor of a two-story building. Most tubular daylight devices are equipped with optional dimmers that allow you to control the degree of light in the room. You can dim these energy-efficient lights as and when you like.
Production of energy exhaustive incandescent lights is set to drop in 2014. Developers, interior designers, and home owners are all turning to LED lighting. Investing in LED lights is not just about going green but also about saving the green in your pocket. Home design experts say that built-in LED ceiling lighting can illuminate the whole room. You can say goodbye to those energy consuming bulky ceiling lights and lamps.
Changes in water heating standards, made in the year 2014, will make them even more efficient. Jeff Wilson, HGTV host and author of The Greened House Effect, says that replacement of “incandescent light bulbs and reform in water heating measures alone will save billions of dollars and enormous amount of pollution.”
Radiant Barrier Roof Panels
If there are ways to reduce heating costs, those that cut cooling costs cannot be far behind. Radiant barrier roof panels are extremely energy-efficient. This type of solar board roof sheathing can reduce your air-conditioning requirements by half a ton. There are many radiant barrier roof panel installation systems in the market that eliminate the need for felt paper, making the building process even more environment-friendly.
These roof panels are an attractive option for both the builders and the homeowners. Builders save money on the HVAC equipment and homeowners save on energy costs.
There will be more green homes in USA than ever before as more people take an interest in healthy living and proper utilization and conservation of all available resources. Thinking of going green? Include energy efficient and water saving devices in your homes. Make use of solar and wind energy, bring down your bills, and prevent environmental pollution and degradation.
Thanks Penny for your thoughts. Another option, particularly for commercial ventures, is a green roof system such as those provided by XeroFlor America (headquartered in Durham) which uses pre-vegetated mats. (disclosure: XeroFlor America is a friend of the Firm.)
Your turn. What green design do you like? Have you considered? Share in the comment section or drop me an email.
The North Carolina Department of Transportation (NCDOT) has shut down Bonner Bridge on the Outer Banks this week due to emergency safety concerns. The life safety issues were discovered after routine sonar scanning identified excessive scouring (i.e., sand erosion) on the support structures of the bridge.
The bridge, erected in 1963, is the only road over Oregon Inlet, so the NCDOT is providing extended ferry service during the bridge repairs, which could take as long as 90 days.
The Bonner Bridge has been slated for replacement for several years following damage from Hurricane Irene, but legal challenges from environmental groups as to the location of the replacement have prevented DOT from breaking ground on a $215.8 million repair contract.
As of midday on Friday, December 6th, NCDOT engineers report the following:
· The dredge is on location and the anchors are set.
· The crew has been developing ideas on alternate discharge pattern/configurations etc.
· The Army Corps of Engineers 404 & DENR Water Quality Permits are issued.
· Permit modification for enlarged discharge area to allow flexibility in using the tides & attack angles to assist in filling scour holes has just been issued.
To read the positions and concerns of the environmental groups related to the bridge replacement, go to the Southern Environmental Law Center’s webpage.
Your turn: Now that the bridge is back in the news, what is your opinion as to where the replacement bridge should be located? Do the environmental groups’ contentions have merit? Share your thoughts in the comments below.
Photo (c) Smkybear.