Report Prepared by:
University of Manitoba
March 1998

INTRODUCTION

With the large number of manure storage lagoons that are in place in Manitoba or being planned, there is naturally an interest by producers and government regulatory agencies in the use of chemical and biological materials that are purported to reduce or eliminate the odours associated with these swine manure storage lagoons. It is extremely difficult to rate the effectiveness of odour-reducing products because there are no reliable machines that can measure odours as effectively as the human nose. Of the numerous odour-control products available it is likely that some, under the appropriate environmental and management conditions, may be effective for reducing odour intensity and/or improving odour quality. However, some may prove to be ineffective. Information regarding the efficacy of commercial products for odour control is needed by livestock producers.

The purpose of these studies was to develop a protocol to measure swine manure odour from lagoons and to concurrently test some commercial odour abatement products using this protocol. Further, analytical chemical studies were done to measure the level of known odour-causing constituents in the manure and the effect of certain odour control products on swine manure to lower the level of these constituents.

Study 1 - Field Study

A preliminary field experiment was initiated in the late summer of 1997 to determine whether a system could be devised to measure odorous gases emitted from a swine manure storage lagoon. Various sites were visited and a facility at Domain Pork with four identical lagoons attached by pipe to four barns with similar numbers of animals was selected. This facility allowed the testing of three products plus a control nontreated lagoon. Two of the lagoons were already under treatment with commercial products. The third lagoon was treated with a product named CB-PA.

An odour panel was simultaneously formed and trained to determine differences inodour levels. Ten butanol standard solutions (0 to 5000 ppm) were prepared and used by the panel in evaluating odour levels.

Sample Collection

Samples of odorous air from the lagoons were collected by pumping 32 litres (2 litres/minute for 16 minutes) through a plastic cassette originally designed to collect airborne dust. This cassette contained approximately 30-mm diameter circle of cotton cloth. The cloth was designed to absorb the odours. Cotton swatches similar to this have been used by other researchers for this purpose under different conditions (Litcht and Miner, 1978). The cassette was sealed after the 16-minute collection period and transported to the University of Manitoba for odour intensity evaluation. The odour panel compared and/or ranked each cassette according to odour levels.

Results and Discussion

Odours measured downwind of lagoons

Odour samples were collected approximately 3-4 metres downwind of the various lagoons. Three commercial products, CB-PA, ESP Enzyme (ESP) and a Link 2000 product (L-2000) plus a control lagoon were tested. The testing started three weeks after the CB-PA lagoon (the last lagoon to be treated) was treated. One treated lagoon was tested against the control lagoon each week. The odour panel chose the lagoon with the stronger odour in comparison testing. The CB-PA treated lagoon was determined by the panel to be lower in odour compared to the untreated lagoon. The same lagoon (CB-PA) on a subsequent week tested lower than the L-2000 treated lagoon. The ESP treated lagoon tested stronger than the control lagoon. Therefore, of the three products tested, the CB-PA seemed to perform the best in odour abatement.

Odour of air pumped through liquid samples removed from the lagoons.

The same three treated lagoons were tested using a slightly different protocol. The top liquid was sampled from three locations around the lagoon, mixed and 200 ml were placed in a glass Erlenmeyer flask. Eight litres of air (2 litres/minute for 4 minutes) was pumped through the manure. The exhausted air was passed through a plastic cassette containing a swatch of cotton cloth. The cassettes were compared by a panel as to which lagoon was stronger in odour. The ESP lagoon was lower in odour compared to the control. The CB-PA lagoon was also lower than the control lagoon and lower than the L-2000 lagoon.

Intensity of lagoon odours compared to a butanol numerical scale.

The odorous downwind lagoon air (Table 1.) was ranked by the odour-testing panel to standard butanol samples ranging in concentration from 0 to 5000 ppm similar to the procedures of Williams and Schiffman (1996). Due to the protocol set up only a few samples were tested on the numerical butanol scale. These samples were collected on different days under various environmental conditions. The measurements, however, seemed to be consistent from day to day and between replicate sampling. The numerical values for the CB-PA lagoon and the L-2000 lagoon compared lower than the FSP treated lagoon which supports the previous comparison testing. The value of the CB-PA lagoon was 2.44 butanol units which were approximately 50% of the average control lagoon values of 5.46. Again these studies seem to indicate the effectiveness of the CB-PA material.