SOIL in the Lab: Making Sure our Compost is Safe

It’s a warm, sunny day here in the SOIL Cap-Haitien office. We’re bustling with activities: building a new office, expanding our toilet service network, and of course – making compost. Since we opened our permanent compost site last year, we’ve filled 18 bins with a mix of human waste and cover material at a balanced ratio to facilitate thermophilic composting. After about 8 months, each 12m3 bin is transformed into rich compost that can be used in garden and farm operations.

But before we even turn a compost pile for the first time, there are several factors we look at to ensure we are meeting standards. The first is that once a bin is full we consider it “closed” to new material, and we start monitoring temperatures in specific areas of the pile. After ensuring we are meeting World Health Organization standards for sanitizing compost at 122 degrees Fahrenheit (50 degrees Celsius), we take samples and bring them into our lab to verify that we are effectively ensuring pathogen die-off.

Erinold Frederic, SOIL Sanitation Supervisor, carefully collects SOIL compost samples for pathogen testing.

Thanks to the re.source sanitation team for introducing us to this equipment, we now regularly use IDEXX testing, a respected technology using E. coli most-probable-number (MPN) counts as a pathogen indicator. Several months ago we realized that we had tested every single bin with negative results; no sign of E.coli. And then we wondered: “Are we really following all procedures so that our E. colicounts are far under the minimum line to be concerned about? How can we be sure?”

As an experiment, we tested a bin from the week it was closed until it achieved protocol temperatures. Sure enough, we found high counts of E. coli in the fresh bin, but by the end of the month when the bin had maintained high temperatures for a week, E. coli counts were down to zero! It’s gratifying to know that not only are we producing sanitized compost, but also that when you put the right elements together, nature can do amazing things.

Using a handy tracking sheet, we know which bins we need to test and when.  Although a user-friendly technology, we have a few lab techs in the office who have taken on the testing system full force, adapting it according to previous CDC (Center for Disease Control and Prevention) protocols to meet our needs. We will be even better suited to do lab testing once we fully move into our new office, which will have a room specifically designated for compost testing. Onwards and upwards!