Chemical and microbiological properties of clam processing wastes in relation to national guidelines for wastes as soil additives

With environmental concerns on the rise, clam processing plants in New Brunswick are being asked to dispose of waste shells in an environmental friendly manner. A previous study on clam processing wastes (CPW) showed their potential as an agricultural liming agent. However, CPW must meet provincial (e.g., New Brunswick and Québec) and national (e.g., Canada and United States of America) standards for the utilization of wastes as soil additives, particularly with regard to heavy metal and faecal coliform contamination, before they may be spread on agricultural lands. In this study, the chemical and microbiological properties of CPW were characterized. The presence of faecal coliforms and Escherichia coli in the CPW was below the most probable number (MPN) method detection limit (< 3 MPN g-1 dry weight), indicating an absence of contamination by human or animal feces. Where total coliforms were detected, levels were far below the most restrictive standard for faecal coliforms (1000 MPN g-1, dry weight). Levels of all 11 heavy metals of interest were also below the most restrictive standards applied in New Brunswick and Québec, and below those in the national guidelines (Canada and United States of America). The liming potential of CPW, demonstrated in pot experiments, may therefore be tested in Canada as well as in the United States of America at the field conditions without restrictions, other than the conventional good agricultural practices.