Purchasing Compost

Today on my Facebook page, I posted some photos of the bulk compost delivery I received yesterday from Home Fires Nursery in Spokane. That has prompted several concerned comments from readers about the safety of the compost so I decided to write a blog post to address those concerns.

If you live in another area of the country, this information should prove helpful to you and it includes resources you might find of interest, too.

The bulk compost originated from a commercial firm called Barr-Tech Compost/Organics Recycling. They make two kinds of compost: one with biosolids and the other without biosolids. The latter is referred to as B-T Green, and that is the only kind of compost Home Fires buys from them to sell to their customers.

I learned that B-T Green does not contain manures. This was important to me because I know that persistent herbicides can occasionally be found in horse manure and I certainly wanted to avoid being the recipient of any compost containing it!

This morning, I spoke with Scott Deatherage from Barr-Tech so I could ask a few more questions about their B-T Green compost. Here’s what I learned from him:

Barr-Tech is certified by the U.S. Composting Council and their products are tested on a regular basis through the council’s Seal of Testing Assurance (STA) program.

Scott mentioned how he has increased the regularity with which their products are tested after hearing that some folks in this region had purchased products from other sources last year that contained persistent herbicides. So he felt it was important to keep an eye on their materials to make sure the herbicides weren’t in them.

He explained to me that the main sources for persistent herbicides — and clopyralid, in particular — are horse manure and Timothy hay. I’ve heard how horses will graze in a pasture, consume grasses that were sprayed with clopyralid, which go through their digestive system without being broken down.

He also explained that in the state of Washington, clopyralid was banned from homeowner use several years ago but is allowed commercially in horse pastures and some other commercial applications. In the state of Idaho, homeowners ARE allowed to use clopyralid, but Barr-Tech doesn’t receive any green materials from Idaho.

Scott told me that they don’t use manures in their compost or Timothy hay. Other potential sources for contaminated green materials include grasses from golf courses but he says they don’t receive grasses from them because golf courses typically have their own facilities to deal with their grass clippings.

Barr-Tech does regular bioassay testing to make sure their compost is completely safe to use. They do this by planting pea and red clover seeds into potting mix containing the compost to make sure they germinate and grow normally. Both are legumes, which are very sensitive to any contaminants.

Just for my own information, I’m going to do a little testing by planting pea seeds in regular potting soil and potting soil with the B-T Green compost mixed in. But after talking with both the owner of Home Fires Nursery and Scott Deatherage of Barr-Tech, I’m feeling more comfortable with using their compost in my garden.

I hope this addresses any concerns you may have. If you’re interested in testing any compost you may have purchased, here’s the method.

Also, Joe Lamp’l, host of PBS’s popular “Growing a Greener World” program, filmed an episode on soil and compost, which includes information on how commercial compost is created. That is definitely worth watching!