Top Image: Courtesy of The Institute for Local Self-Reliance (ILSR)

By Juliana Beecher

The Institute for Local Self-Reliance (ILSR) has developed a new, free, online course on Reducing Contamination at Community Composting Sites. The course consists of two 30-minute videos with “knowledge checks” at the end of each. Once a final exam is passed, participants receive a certificate of completion. Managing contamination can take significant time and labor. While the main audience of the course is community composters, ILSR notes that it’s also “relevant to anyone producing compost above the backyard scale and for programs that involve or support community composting.”

In addition to the video modules, there are two learning activities for composting site operators to deepen knowledge and understanding of best practices to reduce contamination and produce high quality compost for use in growing food and more. The first learning activity is Developing a Contamination Management Plan. This activity stresses including people involved in every stage of collection and composting in the developing of a plan to ensure all perspectives are present and engaged. It’s formatted as a discussion among a group or groups of stakeholders, with discussion prompts and solutions for addressing contamination split into Upstream, On-Site, and Post-Processing stages. A blank table is provided for filling in contamination management actions to be taken, and users are prompted to draw a Contamination Management Material Flow Diagram. Example diagrams are provided (see Figure 1).

Figure 1. Example of a Contamination Management Material Flow Diagram from ILSR’s Developing a Contamination Management Plan learning activity. Click here to expand this image.

The second learning activity is Conducting a Contamination Audit. This is focused on macro (“visible to the naked eye”) contamination — how much and what types exist, and where in the process interventions are needed to reduce it. An audit can be used to develop a baseline contamination level or measure contamination over time following reduction interventions. ILSR suggests tailoring the list of contaminants to be measured to a composting site’s needs and feedstocks (e.g. cardboard may be a contaminant or an accepted feedstock). The audit is broken into the following steps:

Before you begin:

1. Decide who will audit and where (i.e. establish a work area).
2. Decide when you will audit (e.g. seasonality, frequency).
3. Decide what contaminants to measure.
4. Decide what material to audit (e.g. incoming feedstocks, mixed feedstocks, compost overs).

Instructions:

1. Collect audit supplies and the materials that will be audited.
2. Collect and measure the composite sample. (Three method options utilize different size containers: 30-gal bin, 5-gal buckets, or loader bucket.)
3. Estimate the dry weight of the composite sample. (See Figure 2. The guide acknowledges that dry weight is often used in regulations related to contamination, rather than volume.)
4. Separate contaminants from the composite sample.
5. Measure the contaminants.
6. Estimate the contaminant level of the composite sample.

Figure 2. Visual guide for estimating dry weight of a compost sample from ILSR’s Conducting a Contamination Audit learning activity. Click here to expand this image.

ILSR adapted the audit steps from CalRecycle’s Field Method for Estimating the Level of Physical Contamination in Compostable Material. ILSR’s guide includes a blank Compost Contamination Audit Form with a table for contaminants.

These contamination learning activities are the latest in a suite that ILSR has developed. ILSR’s activities are designed to be low-tech and user-friendly. Other learning activities include Identifying Compostable Materials, Hand Squeeze Moisture Test, Microbe Identification Under the Microscope, and more. All activities are available in English and Spanish.