odor emissions – Page 2 – Livestock and Poultry Environmental Learning Community

March 5, 2019May 7, 2019

Bioaugmentation of Treatment System for Skatole Degradation: Bioremediation Potential for Odors Reduction at Livestock Operations

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

This Technology is Applicable To:

Species: Swine, Poultry
Use Area: Treatment System
Technology Category: Amendment (biological)
Air Mitigated Pollutants: Odors, Skatole

System Summary

It has been demonstrated that bioaugmentation of bioreactor with enrichment cultures and with a pure culture of Rhodococcus sp. isolated from swine lagoon is a viable alternative in reducing skatole, a main malodorous compound in swine effluent. We found that bioreactor amended with pure culture can degrade skatole as well as the enriched mixed culture after certain lag period. Pure culture bioreactor required longer lag time than the mixed culture. We also utilized these microorganisms in a liquid scrubber and found them to be quite effective in degrading skatole (data not shown). Thus, bioaugmentation of treatment systems with indigenous populations may increase the efficiency of treatment systems and provide a simple, cost-effective bioremediation potential in reducing malodors emission at livestock facilities.

Applicability and Mitigating Mechanism

Bioaugmentation is suitable for most treatment systems that can provide sufficient environmental conditions for growth
Target specific (pollutant)
Total mineralization of pollutant possible
Sustainable technology

Limitations

Requires optimum conditions for growth
Neutral pH and ample amount of oxygen
Need Sufficient amount of essential nutrients
May not work in a competitive exclusion environment and broader application range

Cost

The cost of bioaugmentation of a treatment system is dependent upon the type of the treatment systems. These microorganisms can be easily isolated and cultivated from contaminated sites. The extent of the cost would fall mostly on the purchase of nutrients for growth. In most cases, the required nutrients for growth could be obtained from the target pollutants themselves (e.g., emissions from swine or poultry wastes).

Authors

Nanh Lovanh, John Loughrin, Karamat Sistani; USDA-ARS, AWMRU, Bowling Green, KY 42104
Point of Contact:
Nanh Lobanh, nlovanh@ars.usda.gov

The information provided here was developed for the conference Mitigating Air Emissions From Animal Feeding Operations Conference held in May 2008. To obtain updates, readers are encouraged to contact the author.

March 5, 2019August 14, 2019

Odorgon: Overhead Spray System to Neutralize Odors

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

This Technology is Applicable To:

Species: Poultry, Dairy, Beef, Swine
Use Area: Animal Housing
Technology Category: Chemical Amendment
Air Mitigated Pollutants: Ammonia, Hydrogen Sulfide, Odors

System Summary

Odorgon is a water based formulation that is applied in confined animal feeding operations through a high pressure mist system. Odorgon is sprayed on an automated timer basis from the ceilings through high pressure nylon lines and nozzles to neutralize malodors.

Applicability and Mitigating Mechanism

Unique class of cationic surfactants
Atomized solution sprayed at 600 psi
Buffer resulting in non volatile organic salts
Greatly reduces ammonia & hydrogen sulfide
Creates better environment for animals to thrive in resulting in lower mortality, less culls and less days to finish.
Better conditions for workers/employees
Mitigates neighbor/social issues

Limitations

Water based, subject to freezing
Summer use may be curtailed in

open buildings during windy conditions

Cost

Equipment cost for a 42 by 200 foot finishing building with all components installed is approximately $4900. Annual usage for this facility would average $2100 of Odorgon concentrate or .73 per animal unit but could vary with region/climate. Nursery cost for swine is .19 per animal unit. Odorgon is mixed with water at a rate of 50 parts water to 1 part concentrate resulting in a cost of $1.50 per gallon diluted. Cost also varies based on building dimensions and desired results.

Authors

Steve Opheim, VP Klean Air Inc.
Point of Contact:
Ron Hamilton, rrhamilto@aol.com

March 5, 2019October 21, 2019

Gas Impermeable Film and Sheet for Control of Methane and Odors in Agricultural Applications

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

The proceedings, “Mitigating Air Emissions from Animal Feeding Operations”, with expanded versions of these summaries can be purchased through the Midwest Plan Service.

This Technology is Applicable To:

Species: Swine, Dairy, Beef, Poultry
Use Area: Manure Storage, Manure Treatment
Technology Category: Covers
Air Mitigated Pollutants: Odors, Methane, Ammonia

System Summary

For many years, food packaging has incorporated barrier layers to contain odors, flavors, oils and moisture along with the food contents while excluding contamination and oxygen. Until recently, agricultural films and geomembranes were monolithic structures employing only a single polymer or blend. Recent advances in extrusion and lamination equipment allow the incorporation of these barrier layers in large scale agricultural structures and operations such as floating covers over animal waste storage, containment geomembranes for biogas generation, silage storage and fumigation films.

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Co-extruding a thin layer of ethylene vinyl alcohol (EVOH) in a linear low density polyethylene (LLDPE) geomembrane dramatically reduces the permeability to a wide range of gases and volatile organic carbon molecules including: methane, ammonia, carbon dioxide, oxygen, aromatic hydrocarbons, aliphatic hydrocarbons, methyl bromide and most odorous compounds. Methane permeabilites for four geomembranes are given below.

**Methane Permeability (cc/(m2*day))**
PVC	LLDPE	HDPE	Barrier LLDPE
0.76 mm (30 mils)	1.0 mm (40 mils)	1.0 mm (40 mils)	0.5 mm (20 mils)
900	690	300	<1

Applicability and Mitigating Mechanism

Barrier to noxious gases and odors
Useful in cover and containment systems

Limitations

EVOH is a crystalline polymer and is not elastic. It is flexible but should not be used as part of an elastomeric structure.

Cost

Engineered floating covers with ballasted weight systems, gas extraction systems and rainwater removal systems costs vary greatly. For waste lagoon of about 1/2 acre in size, the cover system can cost from $150,000 to $200,000. Addition of the barrier layer to the geomembrane adds less than $5,000.

Authors

Gary Kolbasuk, Raven Industries, Engineered Films Division
Point of Contact:
Gary.Kolbasuk@Ravenind.com

March 5, 2019October 21, 2019

Negative Air Pressure Cover for Preventing Odor Emission from Earthen Manure Storage

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

The proceedings, “Mitigating Air Emissions from Animal Feeding Operations”, with expanded versions of these summaries can be purchased through the Midwest Plan Service.

This Technology is Applicable To:

Species: Swine
Use Area: Manure Storage
Technology Category: Covers
Air Mitigated Pollutants: Odors

System Summary

An impermeable synthetic cover system was developed by DGH Engineering in Manitoba, Canada for mitigating odor emission from earthen manure storage basins (EMSB). The system uses lightweight plastic as the cover so that it is affordable to producers. An air pumping system creates negative pressure between the cover and the manure surface to hold down the cover to ensure the cover is robust enough to withstand wind forces. The air pumping system consists of small exhaust fans (four to six fans of 50 – 70 L/s each) and perforated ducts placed about the EMSB perimeter. Odor emission from the NAP covered EMSB (due to the air pumping system) is negligible (1%) in comparison with the open EMSB. Additional benefits of the NAP cover system include the retention of manure nitrogen, thus increasing the fertilizer value of manure; isolating precipitation from the manure, thereby increasing storage volume; and reducing greenhouse gas (methane) emissions.

Applicability and Mitigating Mechanism

Large surface areas of earthen manure storage basins emit large amount of odor to the atmosphere
A NAP cover forms a physical barrier between the manure surface and the atmosphere to prevent odor release into the atmosphere
The negative pressure between the cover and the manure surface holds the cover down to resist wind forces.

Limitations

When using traditional agitation and pump-out equipment, removing and replacing the cover for pump-out may increase the wear on the cover and add labor and time to the pump-out operation.
An air assisted agitation system should be used.

Cost

The capital cost varies from $10.00 to $15.00 per m², installed. The annual cost per pig marketed for typical 5,000 and 10,000 head swine finisher operations is estimated to be $1.40 and $1.13.

Authors

Q. Zhang¹, D. Small ²
¹University of Manitoba, ² DGH Engineering
Point of Contact:
Doug Small, dgh@dghengineering.com

March 5, 2019October 21, 2019

A Review of Permeable Cover Options for Manure Storage

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

The proceedings, “Mitigating Air Emissions from Animal Feeding Operations”, with expanded versions of these summaries can be purchased through the Midwest Plan Service.

This Technology is Applicable To:

Species: Beef, Dairy, Swine
Use Area: Manure Treatment
Technology Category: Covers
Air Mitigated Pollutants: Ammonia, Odors, Hydrogen Sulfide

System Summary

Covers have been demonstrated to provide effective odor and air emissions control for manure storage structures. Impermeable covers made from flexible synthetic materials provide excellent odor and emissions control, but typically have a high capital cost requirement. Permeable covers provide an alternative to impermeable synthetic covers. Permeable covers will typically not provide as great a level of odor control as impermeable covers, but the initial capital cost is lower. Permeable covers do not require gas or rain water collection systems since gases are allowed to migrate through the cover and rainwater will infiltrate through the cover into the storage. Permeable covers have been successfully constructed from a variety of materials including straw, light weight expanded clay aggregate (LECA), ground rubber and geotextile materials. Materials such as straw, have a short lifespan (from two to six months depending on manure solids content and rainfall levels), while materials such as LECA have been shown to remain viable for more than ten years. Various permeable cover materials have been shown to reduce odor from 40% – 90%, and to reduce ammonia from 40% to 80% depending on permeable cover material and depth.

Applicability and Mitigating Mechanism

Permeable covers provide a layer on the manure surface that shields the manure surface from contact with the air
Most permeable cover materials provide an aerobic zone in the cover material that will help control odor
No gas or water collection systems are required since both gases and rain water will pass through the permeable cover material
Some permeable cover materials such as straw provide a short-term solution, while other like LECA can last more than ten years

Limitations

Some permeable cover materials (such as straw) have very short effective lives (2 – 6 months)
Long-term permeable cover materials (such as LECA) can have costs near those of synthetic impermeable covers
If a permeable cover material sinks into the stored manure, it must be dealt with during land application
Rainwater volume must be accounted for in the manure storage since direct precipitation will infiltrate into the manure storage

A permeable straw cover on an earthen manure storage structure.

Cost

Permeable covers can provide reductions in odor, ammonia and hydrogen sulfide emissions from manure storage facilities. A wide variety of organic and manmade materials have been utilized to construct permeable covers with variable results and costs ranging from $0.10 to $1.75 per square foot installed. Straw is the least cost permeable cover material with an approximate cost of $0.10 per square foot installed. Longer lasting materials such as LECA have installed costs that can exceed $1.00 per square foot installed. Permeable cover materials are typically floated on the stored manure surface and can provide an aerobic zone that manure gases must pass through when released. Permeable covers can be used with earthen, concrete and steel manure storage systems and with slurry manures generated by swine, dairy and beef animals.

Lightweight expanded clay aggregate (LECA) cover on a concrete swine manure storage tank.

Authors

Robert Burns and Lara Moody, Iowa State University
Point of Contact:
Robert Burns, rburns@iastate.edu

March 5, 2019August 13, 2019

Characterizing Ammonia Emissions from Swine Farms in Eastern North Carolina – Part II. Potential Environmentally Superior Technologies for Waste Treatment

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

This Technology is Applicable To:

Species: Swine
Use Area: Manure Storage
Technology Category: Other Treatments
Air Mitigated Pollutants: Ammonia, Odors, Pathogens

System Summary

The need for developing environmentally superior and sustainable solutions for the management of animal waste is vital for the future of animal farms in North Carolina, the U.S. and the world. In addressing that need, the North Carolina Attorney General initiated the development, implementation, and evaluation of environmentally superior swine waste management technologies (ESTs) that would be appropriate to each category of hog farms in North Carolina. This study focuses on the emissions of nitrogen in the form of NH3 from different components/processes involved in hog waste handling and treatment, including waste storage lagoons, hog houses, and spray fields at eight selected EST sites.

A flow-through dynamic chamber system and two sets of open-path FTIR spectrometers measured NH3 fluxes continuously from water holding structures and emissions from housing units at the EST and conventional LST sites. In order to compare the emissions from the water-holding structures at the ESTs with those from the lagoons at the conventional sites under similar conditions, a statistical-observational model for lagoon NH3 flux was used. A mass balance approach was used to quantify the emissions. All emissions were normalized by nitrogen excretion rates.

Six of the eight ESTs that contained an anaerobic lagoon as part of the system did not substantially reduce ammonia emissions and therefore require additional technical modifications to be qualified as unconditional EST relative to ammonia emissions reductions. Two of the eight ESTs did not contain an anaerobic lagoon component. Both of these farms showed substantial reductions in NH3 emissions from their water-holding structures. Under the conditions reported herein these two potential ESTs meet the criteria established for ammonia emissions as described for ESTs.

Applicability and Mitigating Mechanism

Differs for each of the ESTs

Limitations

Differs for each of the ESTs

Cost

Is different for each of the ESTs (range is approximately $90-400 reported as 10 year annualized cost ($ per 1000 lbs. steady state live weight per year).

Authors

V.P. Aneja¹, S.P. Arya¹, I.C. Rumsey¹, C.M. (Mike) Williams²¹Department of Marine, Earth and Atmospheric Sciences North Carolina State Univesity, ² Department of Poultry Science, & Director, Animal and Poultry Waste Management Center, North Carolina State University
Point of Contact:
Viney P. Aneja, viney_aneja@ncsu.edu

March 5, 2019October 21, 2019

A Surface Aeration Unit for Odor Control from Liquid Swine Manure Storage Facilities

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

The proceedings, “Mitigating Air Emissions from Animal Feeding Operations”, with expanded versions of these summaries can be purchased through the Midwest Plan Service.

This Technology is Applicable To:

Species: Swine, Dairy, Poultry
Use Area: Manure Storage
Technology Category: Aeration
Air Mitigated Pollutants: Odors

System Summary

A surface aeration system composed of an aerator module with six venturi air injectors has been demonstrated to effectively reduce odor level (measured by odor detection threshold) emitted from an operating swine manure anaerobic lagoon. Past research reports have shown that partially aerating manure can reduce the power consumption by up to 80% as compared to full aeration, while still achieving satisfactory odor amelioration. Data from this project provide further evidence that it is not only feasible but also affordable for animal producers to consider using this technology to control odor. A reduction in odor detection threshold by about 67% was achieved after the surface aeration system started operation in the test lagoon for about 10 days. It was also observed that the aeration treatment could maintain a dissolved oxygen level of 0.3 mg/L in the top lagoon liquid and the aerated layer worked like a biological cover that had the capability of destroying the odorous compounds passing through it. Although the surface aeration technology presented in this paper is tested in swine manure lagoons, it is expected that the technology can also be applied to manure lagoons of other animal species such as dairy and poultry. As a matter of fact, there are already experiments being carried out on a poultry lagoon in Texas using the same aeration apparatus, the results from which will be compared with those presented here. It is anticipated that the aeration system will be available to animal producers in the near future.

Applicability and Mitigating Mechanism

The surface aeration system can be applied to any open liquid manure storage facilities
Odorous compounds are intermediate products during anaerobic digestion and, without treatment, they will be emitted into air causing odor problems
Aeration is to provide oxygen to the aerobic microorganisms in the liquid so that they can actively decompose these odorous compounds
Surface aeration establishes a biological cover in which aerobes use the provided oxygen to clean up the odorous materials before they reach the air

Limitations

This technology is not suitable for in-barn manure storage structures such as deep pits
Since the surface aeration system is placed outdoors, the ambient temperature should always be above freezing point so the technology cannot be used in northern states of the country in winter.
Ammonia emission from the lagoon liquid under treatment may be increased due to increased pH in the liquid and the mixing effect

Cost

The capital cost of this surface aeration system is relatively inexpensive and all the venturi air injectors are commercially available (under $200/each). For a one-acre lagoon, the equipment cost including materials and installation may be anywhere between $10,000 and $15,000 and the running cost (for a 4.5 horsepower pump running 24 hours a day, 365 days a year) will be 4.5 hp x 0.75 kW/hp x 24 h/day x 365 day/year = 29,565 kWh. Assuming the price per kWh being at $0.07, the total annual cost for the operation will be 29,565 kWh x $0.07 = $2,070. Considering the particular lagoon receiving manure from 4,000 head finishing pigs and 2.5 production cycles a year, the treatment cost per pig marketed is only around 21 cents.

Authors

Jun Zhu¹, Chunying Dong¹, Cutis Miller¹, Liang Wang¹, Yecong Li¹, Saqib Mukhtar²¹University of Minnesota, ² Texas A&M University
Point of Contact:
Jun Zhu, zhuxx034@umn.edu

March 5, 2019October 21, 2019

RAPP Technology for Control of Gas and Odor from Swine Manure Pits

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

The proceedings, “Mitigating Air Emissions from Animal Feeding Operations”, with expanded versions of these summaries can be purchased through the Midwest Plan Service.

This Technology is Applicable To:

Species: Swine
Use Area: Manure Storage
Technology Category: Chemical Amendment
Air Mitigated Pollutants: Odors, Ammonia, Carbon Dioxide, Sulfur Dioxide

System Summary

This gas and odor reduction technology, Rapp Technology, consists of an oil cover and a neutralizer that is an alkaline solution. The laboratory study in swine manure reactors to simulate deep manure pit demonstrated statistically significant reductions of ammonia, carbon dioxide, sulfur dioxide, and odor from the treated reactors. Compared with previously tested commercial manure additives, this technology is more effective in mitigating gas and odor emissions from simulated deep manure pits.

Applicability and Mitigating Mechanism

The oil cover is added at initial application. It floats on the surface of the manure slurry to slow the releases of gases and odorous molecules while allowing excrement to pass through.
The neutralizer solution is injected beneath the oil cover periodically. It neutralizes the volatile fatty acids and phenols in the slurry to their ammonium salts. Such salts are more prone to stay in the aqueous slurry because they are more water-soluble and less volatile than the original acids.

Limitations

The oil cover is not suitable for applying on the manure on the barn floors.
The effect of neutralizer on emission reduction could not be differentiated from the effect of oil cover in the lab test.
Future high quality field studies are needed.

Cost

During the lab test, the oil and the neutralizer (both by Custom Formulating & Blending, Bristol, IN) cost $1.13 and $ 0.67 per reactor, respectively. According to Juergens Environmental Control (Carroll, Iowa) for field application of the neutralizer, the fixed cost of the system for 1000 to 8000-pig finishing operations averages $2.50 – $5.00 per pig per 3-year term (shipping and labor not included). The cost of neutralizer operation averages $ 0.01 per pig per day over one year.

Authors

Ji-Qin Ni¹, Sam Hanni¹, Albert J. Heber¹, Warren M. Kosman², Gary Rapp³, ¹Purdue University, ²Valparaiso University, ³Juergens Produce and Feed Company
Point of Contact:
Gary Rapp, garyrapp@westianet.net

March 5, 2019October 21, 2019

Water Requirements for Dust Control on Feedlots

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

The proceedings, “Mitigating Air Emissions from Animal Feeding Operations”, with expanded versions of these summaries can be purchased through the Midwest Plan Service.

This Technology is Applicable To:

Species: Beef, Dairy
Use Area: Animal Housing
Technology Category: Facility Management
Air Mitigated Pollutants: Dust, Odor

System Summary

Feedlot dust contributes to cattle illness along with potential non-attainment of PM10 emission standards in localized areas of North America. Increasing the surface moisture content decreases the potential for entrainment of PM10 particles during evening cattle activity resulting in improved cattle health and attainment with air quality standard. Individual feedlots vary in capacity, pen density and overall area necessitating educational outreach efforts including one-on-one technology transfer. A computer model was developed to enable feedlot owners to evaluate their particular facilities including the potential water requirements and cost of mitigating dust and other air emissions. The water requirement is estimated based on initial soil moisture, desired final moisture content, surface coverage area, soil wetting depth, sprinkler efficiency and application time. These parameters are used to estimate well capacity, main and branch water pipe size, number of wetting zones based on sprinkler head capacity, application time and nozzle requirements. Pumping requirements are based on application rate, pump efficiency and total head losses. Operational costs are based on an initial investment in the system along with pumping cost. This results in a total cost per head per month based on the fixed and variable cost.

Applicability and Mitigating Mechanism

Design sprinkler package for open lot dust control
Economic analysis of the dust control system
Spreadsheet based model – easy to use
Provides quick evaluation of when inputs parameters are varied
Estimates daily water requirements per head for dust control

Limitations

Results dependent on input parameters
Assumes water application is uniform
Assumes initial cost of installation of a sprinkler package is known
Adequate water availability for dust control

Cost

The cost of dust control on open feedlots ranges from $0.60 to $2.40 per marketed head. The cost of the infrastructure of the sprinkler system or water application equipment is reduced with increases in feedlot capacity or marketed head per year. The fixed cost represents 60 to 80 percent of the annual cost. The variable costs are dependent on the days per year necessary for attainment of PM10 emissions from open feedlots or earthen dry lots commonly found in the High Plains region of the North America.

Authors

Joseph Harner ¹, Ronaldo Maghirang¹, Edna Razote¹¹Kansas State University
Point of Contact:
Joseph Harner, jharner@ksu.edu

March 5, 2019October 21, 2019

The Use of Vegetative Environmental Buffers For Livestock and Poultry Odor Mitigation

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

The proceedings, “Mitigating Air Emissions from Animal Feeding Operations”, with expanded versions of these summaries can be purchased through the Midwest Plan Service.

This Technology is Applicable To:

Species: Poultry, Dairy, Beef, Swine
Use Area: Animal Housing and Manure Storage
Technology Category: Vegetative Buffers
Air Mitigated Pollutants: Particulate Matter, Odor, Ammonia

System Summary

Vegetative Environmental Buffers (VEBs) – linear arrangements of trees and shrubs planted near and around livestock/poultry production sites – have been shown to incrementally mitigate odors, particulates, and ammonia through a complex of dynamics. Among the most important dynamics are: 1) enhancement of vertical atmospheric mixing through forced mechanical turbulence – leading to enhanced dilution/dispersion of odor; 2) odor filtration through particulate interception and retention – odor largely travels by way of particulates; capturing particulates also captures odors; 3) odor/particulate fallout due to gravitational forces enhanced by reduced wind speeds; 4) adsorption and absorption of ammonia onto and into the plant – this is due to a chemical affinity that ammonia has to the waxy coating on tree leaves; 5) softening socio-psychological responses to odor due to improved site aesthetics and creating “out of sight, out of mind” dynamics; and 6) improved producer/community relations by using highly visible odor management technology.

Applicability and Mitigating Mechanism

As air moves across vegetative surfaces, leaves and other aerial plant surfaces can remove odors, dust, gas, and microbial constituents of airstreams.
VEBs can mitigate odors/ particulates from all livestock/poultry species;
VEBs are size neutral technology and can be used to mitigate odors/particulates from all sources of odor: buildings, manure storage, and land application.
Trees/shrubs are among the most efficient natural filtering structures in a landscape.

Limitations

Mitigation effectiveness is highly site specific and will vary considerably from farm to farm.
VEBs often require considerable land area and may take up to five years to become physically effective.
Care in VEB design must be taken to avoid causing snow deposition, ventilation, and on-farm visibility problems.
At best, odor/particulate mitigation will be “incremental” and therefore should be always used with other odor management strategies.

Cost

Costs for VEB systems are highly variable and are site/design specific – but for midsized producers (and larger) VEBs likely amount to just a few cents per animal produced. There are three main categories of expenses associated with VEBs: 1) Site prep costs, 2) tree establishment costs, and 3) long term maintenance costs. It should be noted that the majority (usually in the range of 40-70%) of the total cost is “upfront” and is tied to the cost of the initial planting stock (e.g. older, larger nursery stock can be considerably more expensive than bare-root seedlings but such an investment may “buy time” in VEB establishment). Long term maintenance costs vary depending upon the overall health of the VEB. It should be recognized that there are expenditures that occur regularly throughout the life of a VEB and maintenance is an annual process, however as a VEB system matures the annual maintenance requirements will likely decrease over time.

Authors

John C. Tyndall¹¹Department of Natural Resource Ecology and Management
Point of Contact:
John C. Tyndall, jtyndall@iastate.edu