BIOCYCLE NOVEMBER 2011 41

HAMPTON Feedlot, a cus-tom beef cattle feeding op-eration in Triplett, Mis-souri, is turning its wastestream into a revenuestream. The feedlot, start-ed in 1972, is completing

construction this month of a $4 millionanaerobic digestion system that willprocess manure from 2,400 of the feed-lot’s 4,000 beef cattle. Digesting themanure will improve the operation’swaste management practices, reduceenergy costs and generate revenuesfrom the sale of renewable energy andfertilizer products.

“We are the first digester for dairy orbeef cattle in the state of Missouri andone of the first in the nation on a feed-lot,” says Terry Smith, a consultantwith Missouri Enterprise and actingconstruction manager on the Hamptonproject. Typically feedlots hold theircattle in an open dry lot system whereit is difficult to collect manure withoutpicking up dirt, rocks and other mate-rials that can be detrimental to di-gesters. At Hampton Feedlot, cattle areheld in 30 open lots and four confine-ment barns with slatted floors builtover manure collection pits.

Currently “clean” manure from thepits is pumped to and stored in a 13-acre lagoon. Waste from the dry lots iscollected and piled on land above the la-

goon. Any drainage from the piled ma-nure goes into the lagoon. Lagoon ef-fluent is applied to nearby crops withcenter pivots and other irrigationequipment. Manure from the dry lots island applied.

Hampton started investigating thefeasibility of anaerobic digestion aboutfour years ago. “We were exploring op-tions to get more value out of our ma-nure as well as reduce the amount wehad to use up each year,” says JimmyDaniels, the feedlot’s secretary and trea-surer. Typically the feedlot producesabout 60,000 gallons of waste a day. In-stalling a digester offered a way to re-duce the volume going into the lagoon.

Hampton enlisted Missouri Enter-prise (ME), a nonprofit consulting or-ganization, to help with a feasibilitystudy, business plan and permitting.“One of the first steps was linkingHampton Feedlot up with the MissouriDepartment of Natural Resources(DNR),” explains Jimmy Story, busi-ness program manager at ME. “Wewanted them to understand that this isgoing to have a positive impact but alsomake sure that they looked at the per-mits needed prior to getting started.”

ME’s feasibility study initially fo-cused on the market potential of the di-gester products and the technology op-tions. To better understand thetechnology and its operation, ME staff

FIRST IN MISSOURI

BEEF CATTLEFEEDLOTROLLS OUTANAEROBICDIGESTER

The inducedblanket reactorsystem will processalmost half of the60,000 gallons/dayof manuregenerated.

Diane Greer

Hampton Feedlot in Triplett, Missouri, holds around 4,000 beef cattle in 30open feed pens and four confinement barns with slatted floors built overmanure pits.

42 BIOCYCLE NOVEMBER 2011

and the Hampton team toured six di-gester facilities in Wisconsin and Min-nesota and conducted numerous tele-phone interviews with digesteroperators. A final step analyzed projecteconomics. The study concluded thatan anaerobic digester would add valueto the business, provide an adequatereturn on capital invested and improvethe environmental stewardship of thefeedlot. Hampton’s Board of Directorsdecided to install a digester to processmanure collected from the pits beneaththe four confinement barns — abouthalf of the manure produced daily bythe operation. Remaining manure willcontinue to be land applied.

Biogas produced by the digester willfuel an engine producing electricity.The power will replace most, if not all,of the electricity purchased from out-side sources. Any excess power will besold. Additional revenues will beearned by drying and bagging thesolids for sale as soil amendments.

Digesting half of the facility’s wastestream will significantly reduce the nu-trient loading in the feedlot’s lagoon.Selling the solids will move nutrientsout of the local watershed. “It gets it outof the environment, keeps it out of thewater and it becomes a useful product,”Daniels explains.

The project should also benefit thelagoon, where sediment is starting toform on the sidewalls. “If not as muchmanure is put into the lagoon, the the-ory is that it will start revitalizing andcleaning itself up,” he adds.

DIGESTER SELECTION AND CONFIGURATIONHampton started construction on the

210,000-gallon digester system, de-signed by Logan, Utah-based Andigen,LLC, in January 2011. The system iscomposed of six, 35,000 gallon modified

induced blanket reac-tors (IBR) operating attemperatures between100° to 105°F (meso-philic range). “It is ahigh rate system with a50 percent volatilesolids destruction rate,”explains Kevin Pack,vice president of Andi-gen.

Hampton selected thesystem because it ismodular and expand-able. The size of the digester can be read-ily increased by adding extra tanks if thefeedlot decides to capture more waste bydoing away with some of their dirt pensand moving to more confinement, Smithexplains. Hydraulic retention time isfive days or less. “That is another reasonwe went with Andigen,” Daniels says.“Their technology is a lot faster process.”

An IBR is patterned after an upflowanaerobic sludge blanket (UASB) reac-tor but modified to handle higher solidsconcentrations. The reactor naturallyforms a thickened area of sludge(“sludge blanket”) in the lower portionof the tank that contains high concen-trations of bacteria throughout thetank. Bacteria in this sludge blanketdigest the manure, forming biogas. Bio-gas produced by bacteria in the sludgeblanket attaches to the solids, causingthe material to float up through thetank. At the top of the tank the materi-al hits a submerged, conical septumthat knocks the gas off the solids. Thebiogas rises through an opening in thecenter of the septum and exits the topof the tank. The solids tend to sink backdown the tank after the gas is knockedoff. Effluent also passes through theopening in the septum and exits thetank via a pipe located above the sep-

tum. The system doesnot employ any me-chanical or hydraulicmixing, which wouldflush the bacteria outwith the effluent. Thenet result is more bac-teria per cubic foot inthe tank.

Hampton expects tofeed 26,200 gallons ofwaste daily to the sys-tem. “On feedlots thecows produce a lot lessmanure because beefcattle are fed differentlythen dairy cattle,” Packexplains. “You have todesign and size the sys-tem appropriately sinceyou have less total vol-

ume of manure per cow. Each feedlotwill vary somewhat but at Hampton wefound that the cows average about 80

lbs/day of manure. This will vary how-ever from 60 to 100-lbs/day dependingon the size of the animal and their feed-ing regimen. On a dairy the milk cowsaverage 147-lbs/day of manure.”

Manure will be scraped 3 to 4 timesa day into the pits beneath the barns.Deep pits with agitators were added atthe end of each barn to receive and mixthe scraped manure. “For two of thebarns we combined the pits,” Smith ex-plains. The combined pit measures 20-ft. by 40-ft. by 8-ft deep. The storagepits at the other two barns each mea-sure 30-ft. by 12-ft. by 8-ft. deep.

Liquid from the lagoon will hydratethe manure to 7 to 8 percent solids, aconsistency that will allow the waste tobe pumped to a reception pit, measur-ing 20-ft. by 30-ft. by 12-ft. deep, at thedigester. Two of the barns are locateddownhill from the digesters. GEAHoule based in Drummondville, Que-bec, Canada, designed the system thatwill pump the manure 1,500 yards and40-ft. uphill to the reception pit. Agita-tors in the reception pit homogenizemanure from the four barns. The mois-ture level of the material will be ad-justed using lagoon effluent.

Manure is sent from the reception pitto an input pit, measuring 10-ft. by 14-ft. by 12-ft. deep, where any substratesfor codigestion will get mixed into thewaste. Hampton is planning on codi-gesting other wastes at a later date.

Only manure frombeef cattle in theconfinement barns(left) will be treatedin the reactors.Deep pits withagitators (shownunder construction,below) were addedat the end of eachbarn to receive andmix the scrapedmanure.

The induced blanket reactor system iscomprised of six digester tanks, eachwith 35,000-gallon capacity.

BIOCYCLE NOVEMBER 2011 43

“Right now the main focus is to digest themanure.”

From the input pit manure is pumpedinto the bottom of the digester. Along theway the material passes through a heatexchanger, which uses heat capturedfrom the generator to warm the materi-al to 105° to 108°F.

Biogas produced by the digesters willfuel a 300-kW Martin Machinery gener-ator that is expected to produce enoughelectricity to satisfy on-site electricalneeds. Any excess power will be sold toKansas City Power and Light throughHampton’s sister corporation, HamptonAlternative Energy Products (HAEP),under an interconnection agreement.Integration of the on-site power systemrequired a total redesign and reconfigu-ration of the feedlot’s electrical system.Backup power will be provided by the lo-cal utility.

Effluent exiting the digesters will flowto a pit and then to a Houle two-rollersolids separator. Separated liquids willgo into a sparge pit and get recycled backto the digester. “We are looking at otheroptions for what to do with any surplusliquids,” Smith says.

HAEP received a Value Added Grantfrom the Missouri Agriculture and SmallBusiness Development Authority to as-sess the feasibility of drying and baggingthe solids produced by the digester. Mis-souri Enterprise assisted HAEP with theproject and enlisted the services of St.Louis-based Marketing Ideas along withuniversities and private labs. The up-graded solids were found to be a beneficialfertilizer with a viable market. The finalstep, a technology assessment to deter-mine the best means to upgrade the prod-uct, will be completed shortly.

The process to upgrade the solids willuse waste heat from the generator to re-duce the moisture level of the solids from67 to 70 percent to 10 percent or less andkill any remaining pathogens. Hamptonexpects the generator to produce 22 mil-lion BTUs of waste heat during the win-ter and 45 million BTUs in the summer.“We think we have enough heat,” Danielssays. “We are just trying to figure outhow to use it efficiently.”

PERMITTING AND FINANCINGPermitting the digester, the first sys-

tem in Missouri to utilize cattle ma-nure, took over two years. Hampton’snutrient management plan was up forrenewal at the same time, which fur-ther complicated the process. “It wasvery challenging as no one really un-derstood what we were trying to accom-plish,” Daniels says. “But we found allthe regulatory agencies and power com-

panies willing to work at getting usthrough the process. Many of the gov-ernment agencies worked together tomove things forward.”

Since the feedlot was already regulatedby Missouri DNR as a CAFO (ConfinedAnimal Feeding Operation), the projectonly needed a water construction permitfrom DNR’s Water Protection Program(WPP). The WPP worked with EPA Re-gion 7 on various issues including the per-mitting, explains Ming Xu, Energy Spe-cialist, Division of Energy, Missouri DNR.Due to the small size of the engine gener-ator no air permit was required. The pro-ject was also subject to a NEPA (NationalEnvironmental Policy Act) review. “DNRstaff spent quite a bit of time workingwith both Hampton and U.S. Departmentof Energy’s NEPA review team to obtaina clearance,” Xu says.

The project received a $450,000 grantfrom the Energize Missouri RenewableEnergy Biogas program, run by theDNR Division of Energy and funded bythe 2009 American Recovery and Rein-vestment Act. USDA Rural Develop-ment provided an 80 percent loan guar-antee through the Renewable Energyfor America Program (REAP). Hamptonapplied for a Section 1603 TreasuryGrant. Issuance of the grant is pendingcompletion of the project. “Grant fund-ing is very important,” Daniels says.“Without the subsidies the ROI (returnon investment) for the project would notwork as well.”

Hampton will generate renewable en-ergy and carbon credits. “The credits arenot of great value or quantity since we areonly producing 300-kWh,” he adds.

ROLE MODELXu wants Hampton to serve as a role

model for other CAFOs. “We hope the in-stallation of a digester will prove toHampton and other feedlots that there isa better way to manage manure frombeef production, specifically transition-ing from an open lot system to movingthe cattle under roof where the manurecan be collected.”

There are currently 7 beef CAFOs inMissouri. “Over the past few years anumber of CAFOs expressed interests indeveloping digester projects,” Xu says.“However, being the first one is alwaysrisky both technically and financially. Alarge number of cattle farms in Missourihave the similar capacity of 4,000 to5,000 cows. Hampton’s success will like-ly establish a good example and moreprojects may follow.” �

Diane Greer is a Contributing Editor toBioCycle.

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Reprinted With Permission From:November, 2011