Aeration for Elimination of Manure Odor and Manure Runoff: What One Professional Engineer Has Learned in the Past 12 Years

Aerobic treatment has potential to be more practical for any size operation, reduce odors, reduce risk of runoff by facilitating application to growing crops, and reduce energy use when distributing manure nutrients.

Farm-based aeration, created through an upward/outward surface flow, was first introduced in the 1970’s and brought partial success.  With significant performance issues, challenges with struvite within manure recycling pipes/pumps, and the growing trend to store manure within pits under barns, further research with manure aeration was largely abandoned.  Very little research has been done on aerobic treatment within manure storage systems since traditional aeration using air blowers has been considered too expensive. Previous research sought to mimic traditional domestic wastewater treatment systems which also purposely perform denitrification.  Not always a goal for farm operations in years past, retaining Nitrogen within wastes used as fertilizer is now usually a goal.  Thus, past aerobic treatment systems were not designed to fully benefit today’s modern farms.

In 2006, hog producers were introduced to an updated version of equipment providing Widespreading Induced Surface Exchange (WISE) aeration, specifically for reducing hog manure odor while irrigating lagoon effluent.  The results became a “wonder” for the site’s CAFO permit engineer. Documentation showed that significant aeration was occurring at a rate much higher than could occur with the energy input used by traditional bubble blowers.  This indicated that aeration of manure ponds and lagoons may not be too expensive after all.  More questions led to a USDA NRCS-supported study, which revealed much more information and brought out more questions. The final report of that study is available at http://pondlift.com/more-info/, along with other information on the technologies described.

 The NRCS-funded study revealed the basis for previous performance failures, while it also showed the basis for getting positive aeration performance at liquid manure storage sites:  Ultimately, this information showed that large reductions of manure odor can be obtained while offering a new paradigm for eliminating most potential manure runoff through WISE aeration as the first step.

The paradigm change summary:

  1. Aeration provides aerobic bacteria based manure decomposition while in storage.
  2. Aerobic bacteria produce only carbon dioxide, which is considered carbon neutral when converting manure’s nutrients to fertilizer, reduced greenhouse gas (Aerobic gives off no other greenhouse gasses such as methane or oxides, and few odors)
  3. “No odor” allows direct distribution of decomposed manure nutrients onto crops during growing season. (Distribution is done during growing season, using automated irrigation equipment).
  4. Low-cost automated manure distribution reduces farm operation costs, but also allows the nutrients to be distributed to equal acres during a wider application time frame (not limited to when crop land is barren in spring or before fall freezeup.)
  5. A wider application time frame allows multiple applications at smaller doses onto growing crops. Depending on nutrient application goals and equipment, irrigation rates can be as little as 1/8th inch of water, multiple times through the year, instead of one large dose.
  6. Irrigation equipment is likely not operating when potential runoff conditions are pending, especially when the entire spring/summer/fall periods are available for distribution.
  7. When nutrients are applied onto growing crops at low dosage rates during periods when irrigation is desired, very little potential for runoff is present. Only a small portion of 1/8” of water onto a crop canopy rarely reaches the ground. The nutrient rich water quickly binds with the dry surface soil when it does get past the crop canopy during summer application.
  8. Current manure distribution distribution requires that most farmers fight to get raw manure distributed onto cropland before spring planting (which is often a wet time of year), OR after crops are harvested and bales removed. Although farmers and regulators wish that all manure handling is performed before freezeup, it is not the case: It happens more than anyone admits.  Manure application to frozen ground is an understated and unquantified manure runoff cause.  Such runoff can be eliminated by the new paradigm of application onto growing crops.

Further, the “side use” of treated effluent has significant benefit compared to raw manure.  Aerobic Bacteria-Laden Effluent (ABLE water) is extremely proficient in its use within flume systems and for automatic flushing of alleys. The aerobic bacteria within the treated water is “hungry” to go to work, to pick up fresh food as it passes over the floor/alley, on its way back to the storage pond.

The layman’s explanation is similar to urban water delivery pipes and wastewater pipes buried within city streets:

  1. Historically, dairy operators quickly learned that fresh well water will create a “slime” on surfaces, causing extremely slippery floors and alleys which injure cows. To eliminate much of the slipperiness, they stopped using fresh water and instead used raw manure from the pond.  In many cases, they would add water to the pond, when manure got too thick and again caused slippery areas.
  2. Unseen by most people are the 2 pipe systems under streets carrying our water and sewer. Factually, one pipe has slime, and the other pipe is amazingly clean: While acknowledging the newspaper notices that fire hydrants are going to be “flushed” several times/year, most don’t realize the purpose for doing so is to flush the slime from our drinking water pipes! The slime is not toxic to humans due to chlorination, but its buildup reduces pipe capacity, and its color is unpleasant to see in drinking water.  In the case of unaerated fresh water used at farms, it tends to grow the slime that dairymen simply can’t afford on their alleys/floors.
  3. Meanwhile, most people won’t look into a sewer manhole to note how “clean as a dinner plate” it looks! Sewerage pipes are designed for high capacity peak flow but normally runn at very low levels. This allows tremendous aeration activity within the system as water tumbles at manholes and as flows change direction.  Thus, the aeration, food, and bacteria within properly operating sewer systems have very little odor, with the bacteria laden effluent continuously cleaning the sewer pipe. Sewer Pipes indeed look “brand new” even after operating for decades!   Those who effectively aerate their manure pond water so they have high aerobic populations within the effluent, and use that effluent for flushing alleys and flumes are quite happy with the resultant cleaning of the alleys, floors, and flumes.

Lastly, ABLE water likely has traits of “compost tea”:  Compost Tea is made by steeping in water, a quantity of completed compost, rich with soluble nutrients, bacteria, fungi, protozoa, nematodes and microarthropods.  After removing the steeped compost solids, the remaining effluent is rich with those items recognized by many as necessary for building the soil and most effective for plant growth.   The tea is to be used quite soon after it is created, but aeration can lengthen the storage period.  Within aerobically treated manure ponds, because aeration is being performed continuously, compost tea-like benefits are anticipated to be included to crops having the WISE treated effluent application.

What did we do?

A basic hypothesis for WISE technology was developed in 2014 to explain why aeration levels are significantly higher compared to bubble blower technology.  This hypothesis explains how/why results are being obtained and allows purposeful thought on how to maximize performance.

Meanwhile, engineering solutions were developed for the two main issues of equipment available at the time: 1) Previous equipment was heavy and required boom trucks/cranes to install/remove it for servicing (250 to 900 lb.), and 2) The propeller orientation/shape would inherently draw in stringy material that wraps on the propeller shaft, which then requires removal (see problem 1).  New equipment was designed that weighs less than 120 lb. and is easily installed by hand (Figure 1).

Figure 1. One of two WISE technology models, this for open ponds (44” wide). The other model fits through a doorway to be installed in the manure storage pits of deep-pit hog barns.
Figure 1. One of two WISE technology models, this for open ponds (44” wide). The other model fits through a doorway to be installed in the manure storage pits of deep-pit hog barns.

What have we learned?

After years of testing the new design, the equipment proved to be able to operate without inviting stringy material to wrap on the propeller and to be easy to handle by hand.  The design was declared an engineering success and marketing began.

In addition, nitrogen retention rates for aerobic manure treatment are much higher than published, most likely due to the traditional domestic wastewater treatment process assumptions of the 1970’s and the use of partial aeration, due to high costs of bubble blowers, instead of continuous aeration used within WISE aeration activity.

Prior to the 2018 North American Manure Expo, data was collected at 3 different farms in the Brooking SD area, each farm having a different brand/style of providing aeration. Due to the uncontrolled variables, results varied within each farm and also varied from the other farms.  Although no clear specific results were determined, one specific trend was that installing equipment at a higher operational rate (1 device/50 animal units) than the study used (1 device/70animal units), offered higher nitrogen retention than can be expected from the NRCS funded study, which is higher than currently published aeration rates.   This leads me to believe that there may be some misunderstood biological process for retaining nitrogen within aerobically treated effluent using WISE aeration.  It appears there are some things unequivocally misunderstood about aerobic manure treatment and the nutrients retained, most likely also associated with the items commonly identified/targeted with Compost Tea discussions.   The potential for changing the current manure handling paradigm to one where odor is not an issue, and application of manure nutrients onto growing crops which might also reduce manure runoff   warrants further study.

The presentation will also touch on some basic misunderstandings about ammonia/ammonium, provide “do’s” and “don’ts” of installations and/or studies, and identify additional subjects for study.

What are the next steps?

  • Associated technology is being developed to perform foliar application. If farmers can’t handle manure differently, why would they do additional work, just to distribute it the same way they do now?  The presentation will include basic information for a Self-Propelled Extremely Wide Portable Linear Irrigator (SPEWPLI).  This equipment is projected to be able to irrigate/fertigate a full 160-acre field in 5 passes, and then be quickly moved to the next field.  It is anticipated that manure pumpers would use existing equipment to deliver liquid manure to fields and use the SPEWPLI equipment as an alternative to conventional drag-hose injection.  Foliar feeding has proven beneficial, applying nutrients directly onto growing crops (in canopy) when they best increase yields. By changing the distribution window to summertime, farmers don’t need to apply only in spring or in fall, or leave fields un-planted so manure can be applied in the summer.

While most farmers will not spend money to buy technology which only rids manure of odor while they continue to handle it as they have in the past, since there is very little economic return for only controlling odor, there are other aspects of WISE aeration technology to provide economic return, which then provides odor relief as a “free” benefit.

  • More information is needed on the benefits of distributing manure nutrients directly to growing crops and on the economics of low-cost, automated systems.
  • More information is needed in maximizing aeration for the energy used by way of this technology.
  • More information is needed in how nitrogen can possibly be tied up and reserved by the other bacteria, fungi, protozoa, nematodes and microarthropods within compost tea-like effluent.

A listing of such subject study items, likely to be doctorate dissertation level projects, will be included in the presentation.

Because our brand resolves issues that other equipment has, we will make it available for academic study at field sites and for others to use for additional research in the use of WISE aeration technology.

John Ries, PE, Pond Lift, Elk Point, SD, johnries@pondlift.com

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