By Jennifer Thorpe
St. Marys Cement announced at their fourth quarterly Community Liaison Committee meeting last Thursday that they have identified limestone as the source of odour in their raw material feed.
During their search to identify the odour-causing component of their production process they made a significant investment in new technology which required training and outside consultation with Zorix Environmental, but it has delivered results. Their lab diligently tested numerous samples from the raw feed, from limestone to petcoke to kiln feed mixtures, by heating samples in a tube oven (similar to the cement process) and analyzing captured emitted gases using a sensory olfactometer and an electronic analyzer.
When the limestone samples consistently tested higher in odour units, the lab then tested samples taken from limestone cores drilled from the active quarry; they found that different depths did indeed have different odour concentrations but very randomly. Since limestone comprises 75-80% of the required raw material mixture it cannot be eliminated or substituted. Instead, SMC plans to focus on odour abatement through improved dispersion.
Air quality monitoring by the Ministry of Environment, Conservation and Parks continues to indicate that the issue is one of odour and not an exceedance of the province’s Ambient Air Quality Criteria (AAQC). Krysta-Leigh Johnston, Environment Officer for the MECP, reviewed the Second Interim Report results at the Community Liaison Committee meeting, pointing out there were no exceedences of the AAQC for chemicals of concern in St. Marys, which includes SO2 levels following the changes in allowable limits in March 2018. Reports are available on the Town of St Marys website.
Moving forward, SMC committed to determining and refining the best option for a stack extension by 2020. Using CALPUFF, a complex long-range transport air dispersion computer program which considers local weather, topography and land use as well as measured odour emissions from the stack, two options to mitigate community odours have been identified: optimum stack height extension, or combination of a stack height extension and stack flow rate increase.
The public has been invited to submit questions to SMC, the Perth District Health Unit, or the MECP in advance of each quarterly meeting. At their final meeting, SMC offered an open question period to the public and invited a dozen experts, analysts and consultants to attend so that any questions could be answered by the relevant professionals. Former town councillor Don Van Galen agreed to serve as the facilitator. Unfortunately, less than ten members of the public showed up, with noticeable absences from members of the CBC-featured St. Marys For Clean Air Facebook group.
Questions regarding the stack extension were answered by Bridget Mills, Senior Environmental Engineer (Air Quality) from BCX Environmental Consulting as well as SMC. Mills described the amount of data collected to inform the model and explained that every hour of data collected from the past five years is applied using worse case emissions and at each point it must meet the standards. She stated that dispersion will improve with elevation because wind speed increases with height. SMC is looking at alternative options to increase flow, such as the additions of fans or use of coning.
St. Marys Cement welcomes questions from the public. Contact Kara Terpstra, Environmental Coordinator for SMC.