Running Afoul of Composting

UBC researchers analyze the potential health risks from three composting facilities in British Columbia
UBC researchers analyze the potential health risks from three composting facilities in British Columbia

UBC Reports | Vol. 54 | No. 11 | Nov.
6, 2008

By Catherine Loiacono

As more and more cities jump onto the composting eco-wagon, UBC researchers are assessing whether the process has an impact on human health.

“Even though it is an eco-friendly practice, we know biohazards may be present,” says Karen Bartlett, associate professor at UBC’s School of Environmental Health. “There are disease-causing organisms present throughout the process. As more cities begin mass composting and as urban and rural interfaces merge, we want to know if the process is safe.”

Composting is a natural process, which reduces the volume of waste that goes into landfills. Microorganisms including fungal and bacterial species break down and convert the raw ingredients, which can include, plant and vegetable waste, sewage sludge, wood chips, and other organic materials into a simpler substance that can be used as a soil conditioner. The wastes can contain disease-causing microorganisms such as Listeria, Salmonella, and E.coli. However, composting remains successful because as the 
organic material heats up and decomposes the disease-causing micro-organisms die.

“We have the unique opportunity here in British Columbia because we are able to study different composting technologies, in Vancouver, Kamloops, and Kelowna, simultaneously and under different environmental conditions,” says Jim Atwater, UBC associate professor of civil engineering. “We will be able to make recommendations to the composting industry, which could help prevent both acute effects and chronic lung disease.”

In Kelowna, compost is built into a pile over a series of pipes, which can either blow or suck air through the pile.  In contrast, in Kamloops and Vancouver, the compost is built into open piles or windrows which are turned using equipment such as front end loaders, or a machine which straddles the entire pile and turns the material as it passes overtop. Approximately five to 10 workers are employed at each site.  Job tasks at the composting facilities include blending the composting material, building the piles, turning the piles (windrow only), moving the pile after the heating phase, and screening the final product.

“Workers are exposed to massive blooms of organisms that can potentially cause lung damage in high doses,” says Bartlett “At present, there have been a few studies from countries where composting is a bigger industry than in Canada. These studies show that some workers experienced ill health associated with breathing organic dust.”  Acute health effects included organic dust toxic syndrome and a flu-like illness. Chronic health effects can include permanent lung scarring and the development of hypersensitivity pneumonitis.

The researchers compared composting methods for exposure to fungal spores, thermophilic spore-forming bacteria, and endotoxins and for the presence of disease causing- microorganisms by inserting data loggers into the different composting piles.  The researchers also examined environmental conditions during summer and winter to capture temperature, relative humidity, and precipitation as the climate may accentuate or suppress the release of bioaerosols.

Preliminary results from the study, which was funded by Worksafe BC, demonstrate that climate does play a role. “The dry air in Kamploops and Kelowna has an impact on the dispersion of microorganisms during the process and a buffer zone between the composting facility and other facilities may be required,” says Bartlett. “On the other hand, the amount of rain in Vancouver has an impact on the dispersion of these micro-organisms and a buffer zone may not be required.”

“What we were surprised to find is that the internal temperatures are more variable than we anticipated and in only one instance of testing, the minimum required temperature to kill microorganisms was not met,” says Atwater. “More research needs to be done on whether the compost piles are reaching the minimum temperature required to kill these disease-causing micro-organisms.”

Preliminary results also suggest that, workers sitting in modern air-conditioned equipment cabs will not be exposed to concentrations high enough to be detrimental to lung health. However, workers outside of cabs should wear respirators.

The composting industry is expected to grow rapidly as more Canadian cities make use of this technology to reduce the amount of waste going into landfills. “There is every reason to expect the growth of this industry to continue, as Canadian cities have no alternative but to burn, bury, or convert solid waste,” says Bartlett. “However, even though it is still relatively small in Canada, as more workers are employed, the chances of recognizing disease increases.”


Composting at UBC’s Vancouver campus uses an in-vessel system,
the preferred mechanism for composting, according to Bartlett. "The
composting facility at UBC is a large closed system that
controls odours, moisture and temperature so microorganisms
can still do their job, without having as great of a potential
to effect human health."