Kristine M. Wichuk

A review of the effectiveness of current time–temperature regulations on pathogen inactivation during composting

Pathogenic organisms can be present in all types of compost feedstocks. Since the infective dose for many of these organisms is very low, it is generally accepted that pathogens should be reduced t...

Compost stability and maturity evaluation — a literature reviewA paper submitted to the Journal of Environmental Engineering and Science.

Finished compost should be both stable (resistant to decomposition) and mature (ready for a particular end-use) so that it can safely be packaged and transported, and not cause adverse effects during its end use. A variety of methods for evaluating stability and maturity are available; this paper contains a review of the effectiveness of a number of the most commonly used tests, to determine the most reliable approach(es). In the literature reviewed, it was generally agreed that a single, stand-alone test for both compost stability and maturity does not yet exist; therefore, it is best to use a combination of tests. However, there is disagreement in the literature as to what the best combination for evaluation should be, and guidelines and regulations around the world employ a variety of approaches.

Challenges in implementing a functional ISO 14001 environmental management system

Purpose – The purpose of this paper is to present the key findings of a colloquium on ISO 14001. The colloquium focused on three key areas: critical loops and synergies among management system elements, the full spectrum of management system auditing, and integrating management systems.Design/methodology/approach – A total of 40 Canadian experts on environmental management systems from a wide variety of sectors participated in the colloquium.Findings – The colloquium provided insights into implementation issues around the three key areas noted above. The colloquium focused on discussing issues associated with corrective and preventive action, objectives and targets, internal and external auditing, and integrating change into management systems. The issues are presented in detail in the paper.Originality/value – The participants in the colloquium believed that the findings will be of interest to both practitioners and academics in environmental management systems. The findings will also be of interest to p...

Plant Pathogen Eradication During Composting: A Literature Review

The process of composting, when managed in such a way that adequate temperature conditions are achieved, can lead to significant reductions in the levels of many plant and human pathogens. When adequate pathogen reduction is achieved, it is possible to create a beneficial and safe product from waste materials that would otherwise be disposed of in a landfill or incinerator. Time and temperature conditions necessary for the eradication of various types of plant pathogens during composting were evaluated via a literature review. Varying time-temperature conditions have been suggested in the literature and by compost standards organizations in Europe to treat plant pathogens in compost. Literature data suggested conditions for the eradication of phytopathogens were compared with the time-temperatures specified by the Canadian Council of Ministers of the Environment (CCME) and US Environmental Protection Agency (USEPA) for human pathogens. Most bacterial plant pathogens and nematodes, and many fungi and fungus-like organisms (including the Oomycetes and Plasmodiophoromycetes) are likely to be eradicated if compost operations adhere to the human pathogen time-temperature guidelines set out by the CCME and USEPA. Other fungi and fungus-like phytopathogens, and a number of viruses are more heat resistant. Results in the literature have been inconsistent for some hardier species, with some studies showing eradication during composting and others finding that these same species were still viable in finished products. In general, most researchers agree that commercial-scale composting, if monitored and controlled properly, will likely eliminate most phytopathogens, with the exception of a few hardy viruses and fungi/fungus-like organisms such as tobacco mosaic virus, Fusarium oxysporum, and Plasmodiophora brassicae. The higher temperatures and longer exposure times suggested in European guidelines and standards are likely to be effective against a broader range of phytopathogens than the CCME and USEPA requirements. Phytopathogen inactivation in composting trials at different experimental scales was considered. Bench-scale time-temperature studies using pathogen suspensions or cultures on media often did not reliably predict what would happen in full-scale composting systems. If particular pathogens are of concern in a region, either pilot or full-scale studies should be done to evaluate their fate within the composting process used locally, or a more consistently predictive bench scale procedure should be developed.

Development of Time-Temperature Probes for Tracking Pathogen Inactivation During Composting

Pathogen inactivation is expected to occur in compost if temperatures over 55°C (131°F) are maintained for at least 3 days, or 15 days in windrows. However, a literature review revealed pathogen survival in a significant number of processes appearing to meet the prescribed time-temperature criteria. It was hypothesized that pathogen survival may be due to the existence of undetected temperature variations within the compost mass. In order to investigate this possibility, it is necessary to monitor the conditions that a random particle of compost would experience as it passes through the composting process. As no adequate methods currently exist to monitor the temperatures of random particles, it was deemed necessary to develop a method to monitor temperature conditions that random particles of compost material encounter during the high-temperature phase of composting. A self-contained, battery powered temperature probe was designed for this purpose, with properties of size and density similar to those of compost particles, in order to allow it to move freely as it undergoes the composting process (in a manner similar to that of a random particle of material). Preliminary tests were done to ensure adequate device operation prior to manufacturing. Though the results were promising, improvements and further testing were recommended to ensure that the probe could withstand the harsh conditions encountered during composting, and to ensure that it would move randomly during compost agitation.

An enhanced compost temperature sampling framework: case study of a covered aerated static pile.

Spatial and temporal temperature variations exist in a compost pile. This study demonstrates that systematic temperature sampling of a compost pile, as is widely done, tends to underestimate these variations, which in turn may lead to false conclusions about the sanitary condition of the final product. To address these variations, a proper scheme of temperature sampling needs to be used. A comparison of the results from 21 temperature data loggers randomly introduced into a compost pile with those from 20 systematically introduced data loggers showed that the mean, maximum and minimum temperatures in both methods were very similar in their magnitudes. Overall, greater temperature variation was captured using the random method. In addition, 95% of the probes introduced systematically had attained thermophilic sanitation conditions (≥ 55°C for three consecutive days), as compared to 76% from the group that were randomly introduced. Furthermore, it was found that, from a statistical standpoint, readings from at least 47 randomly introduced temperature loggers are necessary to capture the observed temperature variation. Lastly, the turning of the compost pile was found to increase the chance that any random particle would be exposed to the temperature ≥ 55°C for three consecutive days. One turning was done during the study, and it increased the probability from 76% to nearly 85%. Using the Markov chain model it was calculated that if five turnings had been implemented on the evaluated technology, the likelihood that every particle would experience the required time-temperature condition would be 98%.

Modification and Industrial Applicability of a Temperature Probe Capable of Tracking Compost Temperature on a Random Particle Level

ABSTRACT It is generally accepted that exposure of all compost particles to temperatures ≥55°C for at least three consecutive days is a sufficient criterion for a compost to be considered hygienic. Nonetheless, there are no known studies confirming that routine composting operations consistently provide the conditions to meet this criterion. The objectives of this study were: (i) to develop a self-contained temperature probe capable of mimicking random particle behavior in compost and recording the temperature it is exposed to, while withstanding adverse operating conditions; (ii) to validate the probes physical characteristics in a field-scale operation; and (iii) to assess the recovery of probes from a full-scale compost operation. Two field trials found the probes do behave like random particles and that the aluminum case adequately protected the probes circuitry and cryovial. Another two trials were conducted to analyze probe recovery. Temperature probes were randomly introduced into a freshly built aerated static pile. In the first trial, 80 m3 of material was screened in one day and the probe recovery efficiency was 100%. In the second trial, screening of 440 m3 of material was completed in three days and 79% of the probes were recovered. The inability to achieve a recovery rate of at least 90% could be due to the high moisture content (≥50%) of the material being screened, the high fraction of oversized material, and, most importantly, the heavy reliance on visually locating the probes in the screen overs.

The Impact of Various Contaminants on the Trace Metal Content of Compost

The trace metal content of municipal solid waste (MSW) compost affects the quality and potential end uses of the finished product. The impact of typical contaminants found in the organic fraction of MSW on the trace metal content of compost was investigated. Contaminants including alkaline batteries, galvanized nails, zinc-plated screws, copper wires, and electronic cables were exposed to a thermophilic composting process for three weeks. The increase in trace metal content in the compost product was measured at the end of the composting process. The results showed that low-quality alkaline batteries, galvanized nails, zinc-plated nails, and copper wires had a significant impact on the zinc, copper, arsenic, lead, and cobalt contents of compost. Copper wires showed the highest impact on copper content, which was 52% of the Canadian Council of Ministers of the Environment (CCME) Category A limit in the final compost. Galvanized nails contributed to final levels of zinc reaching 30% of the CCME Category A limit. To ensure that CCME Category A criteria can be achieved, it is recommended that contaminants made from bare copper or coated with zinc be removed from the composting feedstock.

An Enhanced Direct Process Temperature Validation Framework in Composting: Case Study of a Full-Scale Covered Aerated Static Pile

ABSTRACT To ensure the safety of compost products, the Canadian Council of Ministers of the Environments compost guidelines specify upper limits for certain pathogenic and indicator microbes, which are presumably achieved by exposing every particle of compost to temperatures ≥55°C for at least three consecutive days. A rugged temperature probe that behaves like a random compost particle was used to investigate whether every compost particle meets the time temperature criterion and to measure sanitation efficacy. An inoculum consisting of Salmonella enterica var. Meleagridis, Escherichia coli K12, and phi-S1 bacteriophage (all at levels of ∼1 × 106 CFU/PFU mL−1) was added into 17 probes. The probes were randomly introduced into a covered, aerated static pile along with 17 probes that only monitored the temperature. After 56 days of composting, with one pile turn the probes were recovered. Organism levels were determined via culture-based methods. Before turning, 80% of the randomly introduced probes satisfied the time-temperature criterion. After turning, this number increased to 87%, demonstrating that turning is somewhat useful for sanitation. The cool zones largely remained mesophilic with the pile turning having minimal impact, which could potentially be an indication that the pile was not turned thoroughly. One of the 17 probes with cryovials reached only 40.2°C, and survival of S. meleagridis (2.5 × 106 CFU ml−1) was observed. The remaining probes with cryovials exceeded 55°C and were pathogen free. It appears that the specified time-temperature conditions are likely adequate. However, more observations are needed before a firm conclusion can be made.

Composting Effect on Three Fungal Pathogens Affecting Elm Trees in Edmonton, Alberta

The City of Edmonton, Alberta, produces compost from a mix of wood chips and biosolids at its aerated static pile composting facility. A portion of the wood comes from the Citys Parks Branch, which supplies clean wood waste to the composter, and sends wood known to be diseased to landfill. However, wood from other wood suppliers is not necessarily screened, allowing the possibility that diseased wood might still be processed. It was of interest to determine the fate of some important Edmonton-area plant disease organisms during composting, in order to determine if infested wood actually needs to be diverted away from the composter. The current study focused on the fate of three fungi: Dothiorella ulmi; Verticillium dahliae; and V. albo-atrum. Wood chips inoculated with the three organisms of interest were placed into a newly constructed aerated static pile at various locations. The chips were retrieved during the first active composting stage and tested for pathogen survival. At locations where temperatures exceeded 40°C, all three pathogens were inactivated. However, survival of fungi was observed in cooler zones of the pile (e.g. near the surface). It is expected that mixing in subsequent stages of composting will move all material into the high-temperature zones.