Contamination Removal and Reduction
In 2009 the author began working with the city of Whitehorse compost facility to tackle the very real problems of blowing plastics and broken glass in the pristine wilderness environment: circumstancesthat had prompted a previously enthusiastic customer base to walk away. As part of a range of actions,the Whitehorse facility gained approved input statusunder the Canada Organic Standard for the screened compost in 2012. The Canada Organic Standard requires due diligence andongoing improvement with every inspection, necessitating an action plan for contaminants. Added to this,the screening overs were approximately 70% wood chips, which translated into about $15,000 worth of wood chips being landfilled annually. A contaminant removal solution was clearly needed.
The author began experimenting with a self-built prototype vacuum system, which showed promise,but was consistently limited in its performance. Aliterature reviewrevealed a dearth of informationdealing with compost contaminants and related separation techniques. However, several seed cleaning and mineral processing techniques were identified, adapted for the composting environment, and underwent lab and field scale testing. Considerable time was spent characterizing the common contaminants, and grouping them according to the physical properties that either help or hinder separation. This presentation describes some of these separation techniques, the contaminant groupings separated by them, and the performance range that can be expected.
A vital component of this work has been developing a replicable and simple methodology for evaluating separation performance in the field. It has been found that accurate collection of performance data for the basic groupings of contaminants has been an essential tool inthe development and refinement of separation techniques.The methodology for measuring contaminationisdiscussed,including some of the advantages and disadvantages of the technique.
In conclusion, although this work has yielded effective and practical technology, it would be a much simpler solution to prevent contamination in the first place, which would mean restricting or banning the use of a wide range of packaging. It is encouraging that there is such a movement afoot. Further work is required in understanding the fate of micro-plasticsand other micro-contaminants in compost and the wider environment. Part of this work is the need to develop field-accessiblemethodologies for measuring micro-contaminant levels at the compost facility. As more research comes forward demonstrating the presence of micro-plastics in food plants, it is inevitable that composters will be faced with a need to somehow control contaminants on a micro level as well as themacro level as is the case today.