Odour Production, Evaluation and Control

Project: MLMMI 02-HERS-03


To put odour production, odour evaluation and odour control in typical hog operations into perspective in the current Manitoba circumstance.


Qiang Zhang
University of Manitoba


Status: Completed
Started: 2002-01-01
Completed: 2002-10-09

Funding Partners: who have contributed to MLMMI in support of this project:
MRAC - $18,170
Manitoba Pork Council and industry groups - $36,330

Amount Funded: $54,500.00
Performer Funded: $0.00
Total Cost: $54,500.00


First Progress Report received Apr. 3/02
Second Progress report received Jul 15/02
Final report due September 1, 2002; received Oct 9/02.


An extensive literature review has been conducted to collect and analyze information on technologies and practices in odour measurement and mitigation. The review and analysis are focused on the following nine areas: (1) odour measurement and odour evaluation technologies; (2) odour production and odour release quantification; (3) feed additives and dietary manipulation for odour reduction; (4) manure additives; (5) in-barn manure handling systems; (6) manure storage design and management; (7) biofiltration; (8) dust control; and (9) emerging technologies for odour measurement and control. The suitabilities of odour management technologies to Manitoba are evaluated in terms of cost and climatic conditions.

Over 168 odour compounds have been identified in livestock odours. These individual odour compounds may be measured with analytical instrument such as GC or GC/MS, but there is no established correlation between the individual odour compounds and the human perception of odour. The most reliable way of measuring odour is using the human olfactory sense (nose). Dynamic-dilution olfactometers with trained human assessors are considered to be the industry standard for measuring odour concentration. However, there are considerable inconsistencies in the design and operation of olfactometers. A national standard should be developed, or existing standards, such as the European Union Standard, should be adopted, to provide guidelines for conducting olfactometry measurements of livestock odours. The human sniffing technique shows the potential of evaluating odour directly in the field. This technology is relatively inexpensive and may be adopted by various levels of regulatory agencies for evaluating odour complaints.

Research on the quantification of odour emissions from swine operations has been mainly focused on production buildings, with limited information available on manure storage, land application and mortality disposal. Odour emission rates vary widely among different facilities and within the same types of facilities. Reported odour emission rates range from 0.1 to 62 OU/s per m2 of floor area for various swine production facilities. Limited data have shown that emission rates from earthen manure storage (EMS) are mostly below 10 OU/s per m2 of manure surface area. An EMS normally exposes a much larger surface area than other storage types, and is therefore commonly associated with more odour complaints. Odour emission from land application could be minimized by proper injection. Adoption of manure injection by producers has appeared to shift odour complaints from land application to animal production facilities and manure storage units. Field measurements should be conducted to collect odour emission data from earthen manure storage under Manitoba climate conditions. Scientific methods should also be developed to assess the downwind impact of odour sources from swine operations and to establish setback requirements for Manitoba conditions.

Dietary manipulations have been shown to potentially reduce odour generation in swine operations. Although much of research to date has been done elsewhere, primarily in the Netherlands and the Midwestern region of the US, the results of the majority of the research can be translated to the Canadian situation either directly or with further refinement. However, differences in primary cereal crops used in feed and the associated differences in chemical composition warrant further research in Manitoba.

Many chemical and biological products are being marketed as manure additive for odour control. Research reported in the literature is mostly focused on the evaluation of manure additives, with little on the mechanism of action or the development of products. Researchers have reported conflicting results on the effectiveness of using manure additives. This is partially due to the lack of universally accepted protocols for evaluating manure additives. Although some existing manure additive products have been shown to be effective in odour reduction under laboratory conditions, they may not perform well in actual production facilities. Many other factors, such as the building, ventilation, manure handling, feeding, and the overall management practice, may conceal the effect of manure additives in actual production facilities.

The in-barn manure handling system plays an important role in odour management. An effective manure handling system should promote quick separation of manure from animals to minimize odour generation. Properly designed slatted floor systems provide an effective way of separating manure from animals with minimum efforts. If manure is stored under the floors in the barn, well-designed ventilation systems are necessary to provide under-floor pit ventilation for minimizing odour problems. Solid manure systems usually result in less odour emission, but are more expensive and difficult to operate. Research should be conducted to evaluate solid manure handling systems for Manitoba conditions, in terms of their effectiveness in odour reduction, economic feasibility, and agronomic impacts of using solid manure as fertilizer.

Open-top manure storages such as earthen manure storage (EMS) are a main source of odour from swine operations. Covering the manure storage is an effective way of minimizing odour emission. Biocovers, such as straw, provide a cost-effective and farmer-friendly solution to odour problems associated with EMS, however they have not been adopted on a widespread basis by the swine industry. The straw cover is easy to apply, but will sink over time, and thus reapplication is required. Additional agitation and straw chopping are required for pump-out if straw covers are used. Straw covers also increase the volume of manure that must be transported. Synthetic plastic covers that provide complete year-round odour control in a cost-effective manner are commercially available. Research is needed to quantify the odour reduction by using various covers under Manitoba conditions.

Treating manure before or during storage may reduce odour emission from manure storage. Some technologies that have been studied are solid-liquid separation, anaerobic digestion, and composting (for solid manure). Most odorous compounds are contained in small manure particles. Therefore, removal of fine particles is necessary for effective odour reduction when using solid-liquid separation. Anaerobic digestion is performed in closed digesters and it reduces odour emission by converting odorous intermediate products of anaerobic decomposition into odourless end products of carbon dioxide and methane. Mesophilic and thermophilic anaerobic digestion seem hard to be accepted in Manitoba because of associated high heating cost during long and cold winter. Anaerobic digestion at lower temperatures of psychrotrophic or psychrophilic range holds some potential for Manitoba conditions.

Biofiltration is a potential technology for reducing odours from livestock facilities. Open-bed biofilters are the most common style for treating exhaust air from livestock facilities. The open-bed filters usually use compost and wood chips as filter medium and odour removal efficiencies of between 75% and 90% may be achieved. Biofilters associated with livestock operations generally do not need supplementary heat; the heat from the exhaust air and exothermic microbial activity in the filter bed is usually sufficient to keep the filter bed in the right temperature range even under Manitoba climate conditions. Despite the success of open-bed biofilters, there is a need to continue research efforts to improve both the economics and aesthetics of biofiltration systems for livestock operations.

Dust may act as an important odour carrier. Odour compounds attached to small dust particles stays in the air longer, thus having a greater downwind impact. Furthermore, many of the respirable dust particles are odorous because of their fecal origin. Spraying oil or oil-water mixture inside the building seems to be effective in reducing dust and odour emissions. Other options, such as mechanical and electrical dust removal, are expensive.

One of the greatest obstacles to the advancement of odour management is the difficulty of measuring odour itself. Olfactometers are only capable of measuring the odour concentration. The electronic nose (e-nose) technology has the potential of measuring both quality and quantity of odour. Research is needed to correlate human perceptions of odours to e-nose measurements and to develop portable e-noses for field measurements of odour.


Full Report

Manitoba Pork represents 613 Manitoba hog farms