Dust, Odor Test Results Mixed

A team of Canadian scientists explored the use of canola oil and a low-protein diet in reducing dust and odor emissions of grow-finish rooms.

They found that sprinkling oil reduced total dust emissions by 76%, but sprinkling canola oil and feeding a low-protein diet did not have a clear effect on odor levels. And reducing the dust levels inside the rooms did not decrease building odor emissions.

Oil sprinkling has been shown in previous studies to reduce dust and gas emissions from pig barns, possibly affecting the level of odors exhausted from the barn.

This study used four rooms at the Prairie Swine Centre, Elstow, Saskatchewan, to measure the impact of four different treatment combinations on dust and odor emissions over three grow-finish cycles: a normal protein diet with no canola oil, a normal protein diet with canola oil, a low-protein diet with fermentable carbohydrates and canola oil, and a low-protein diet with fermentable carbohydrates but no canola oil. Dust and odor levels were monitored in the four rooms during the trials.

Oil application greatly reduced total dust emissions while not impeding pig performance. The experimental diets had no significant effect on dust levels.

Because of the high variability in results for odors, researchers concluded that neither oil sprinkling nor the experimental, low-protein diet affected odor emissions.

Researchers: Michel Payeur, Ernie Barber, Claude Lague, University of Saskatchewan; Stéphane Lemay, Ruurd Zijlstra, Liliane Chenard and Shala Christianson, Prairie Swine Centre. Contact Lemay at (306) 667-7444 or lemay@sask.usask.ca.

Hydrogen Sulfide May Reach Harmful Levels

Researchers at the Prairie Swine Centre in Saskatoon, Saskatchewan, studied six pig farms to assess levels of hydrogen sulfide (H₂S) that farm workers are exposed to while pulling manure pit plugs and power-washing barns.

Results revealed that pulling plugs on manure pits generated high concentrations of H₂S (Table 1), reaching 1,000 parts per million (ppm) in some cases. Power washing posed much less of a threat to workers.

All of the farms had plug-pulling events that exceeded safety standards established by the Occupational and Safety Regulations of Saskatchewan. The agency recommends that a person not be exposed to more than an average concentration of 10 ppm H₂S for a period of eight hours, and an average of 15 ppm for a period of 15 minutes, classified as short-term exposure limits (STEL).

Saskatchewan labor officials defined 100 ppm as immediately dangerous to life or health (IDLH).

In the study, measurements of H₂S were recorded while workers performed regular manure management duties in gestation, farrowing, nursery and grow-finish rooms. H₂S levels were measured near plugs when pulled to empty pits and also within a short radius of the plug location. H₂S concentrations were also recorded at chest level of workers power-washing rooms.

Results indicated that in four of the six monitored pig barns, pulling manure pit plugs produced dangerously high levels of H₂S.

The levels of H₂S released following a plug pull did not follow a predictable pattern. Sometimes the maximum level was reached in less than four minutes after the plug was pulled. At other times, the concentration increased and went through a series of intermediate peaks before reaching the maximum level.

While the highest concentrations were usually recorded at the plug or sewer hole, there were times when it was recorded elsewhere in the room. There was no predictable distribution pattern for a H₂S peak location.

Power washing produced lower H₂S levels than plug pulling, although STEL was sometimes reached shortly after washing started and was exceeded for a long period of time.

Researchers suggested that gas monitors be provided to all workers in the vicinity of a plug pull or power-washing event. Training and standard operating procedures are needed for workers to deal with routine operation and emergency situations generating high H₂S concentrations.

Researchers: Liliane Chenard, Stephane Lemay and Claude Lague, Prairie Swine Centre. Contact Lemay at (306) 667-7444 or lemay@sask.usask.ca.

Weigh Merits of Lagoon Covers

Make the best business decision for your operation when selecting a lagoon cover, says the Alberta Agriculture, Food and Rural Development (AAFRD) AgTech Centre.

“Essentially, both straw and synthetic lagoon covers are effective odor management options,” says Brian Sexton, AAFRD project manager. “However, there are pros and cons of straw and synthetic covers that producers must consider to make an informed decision.”

Decisions on a cover include cost, odor reduction, ease of installation and ease of emptying the lagoon.

A straw cover is a better economic choice, based on research results and experience. But a synthetic cover offers a “leave-it-and-forget-it,” low-maintenance option.

“Economically, a straw cover might be a better choice because it's generally constructed with on-farm supplies and equipment such as straw and a bale processor,” says Sexton. “A synthetic cover is expensive, and the price keeps going up when you consider the cost of a fan and buying a replacement cover every few years. Once it's on, though, there's little labor until it's time to empty the lagoon. That's the trade-off.”

Straw covers cost about 2¢/sq. ft. and synthetic covers 65¢ to 95¢/sq. ft. Straw covers must be reapplied at least once per year, while a synthetic cover lasts several years.

Synthetic covers are made of different materials and are essentially a tarpaulin, pulled over a lagoon and secured at the edges with a heavy layer of soil. It is critical to have an exhaust fan to remove manure gases that form under the cover, and to create negative air pressure that holds the cover tight to the manure surface to withstand high winds.

Applying a straw cover is typically done with a bale processor that can shoot straw up to 73 ft. across the lagoon. Specialized bale processors with a blower can throw straw up to 183 ft. The straw is either applied directly on the lagoon's surface or on top of a straw flotation device, such as polystyrene floats. The key is uniform application.

“Barley is the only straw effective enough for an unsupported cover,” says Sexton. “It floats the best and lasts the longest.”

By starting with a straw cover chopped to lengths of 8-10 in., reapplication should only be required annually.

Both straw and synthetic covers control lagoon odors, but in different ways. “A straw cover reduces odor by acting as a type of biofilter, trapping some of the odor and gas particles. Odor is reduced significantly and consistently with straw, by about 75%, but it doesn't eliminate odor entirely,” says Sexton.

By completely sealing in gases, a synthetic cover reduces odor by about 95%. “It's safe to say that almost zero odor is emitted from a synthetic cover, but each time gas makes its way to the exhaust fan and escapes, a raw, concentrated odor the equivalent of an uncovered lagoon travels downwind.”

Emptying a lagoon is a final consideration. With straw, proper agitation is required before pump out. “Chopper or trash pumps produce a fine end product that easily flows through pipes. Straw not only plugs pumps, it can plug the manure application nozzles and equipment,” he points out.

With a synthetic cover, agitation is still required before emptying, but plugging is not an issue. But wind ripping the cover can be.

For more information, contact Sexton at (403) 381-5885 or Rich Atkins, Agtech Centre, (403) 329-1212.