How Do You Test Humanure?

For the full version of this article, written by TE Board Member and Civil Engineering Professor Kari Scholtes, P.E., Ph.D., check out our free Substack post or subscribe to our Patreon.

Our first compost sample, bagged up and about to be sent off for testing!

We just took samples from our first compost pile to "come of age" and sent them off for testing! While we wait (im)patiently for the results, we wanted to share with you what's on all our minds lately: what's in a compost test?

At Toilet Equity, we don’t just turn human waste into compost—we make sure it’s safe, effective, and regulation-ready. That means rigorous testing to ensure our compost can be used without a second thought (except maybe, "Wow, this is amazing!").

What’s in a Test? 

Compost testing falls into two main categories: regulatory and non-regulatory.

Want to dive deep into the nitty-gritty of the tests?

• Regulatory tests focus on pathogen reduction and safe levels of metals and other potential contaminants. In other words, we’re making sure the compost won’t cause harm when applied to land.

• Non-regulatory tests help determine nutrient levels, salinity, and how well the compost supports plant growth—useful info for end users looking to amend soil.

Class A vs. Class B Compost 

Class A compost is the gold standard, safe for use on public lands, gardens, and even root crops. It undergoes strict testing to meet low pathogen thresholds. Class B compost is still valuable but limited to less direct uses like timberland and forage crops.

Our compost piles heat up to 130-140°F (54-60°C) for about a week—plenty of time to knock out harmful microbes. We follow up with lab tests to confirm safety, and even re-compost outer straw layers that might not have reached high enough temperatures. Because when it comes to safety, we don’t cut corners (or compost them prematurely).

New Regulations & Emerging Concerns 

In 2025, new rules around PFAS (aka “forever chemicals”) will take effect, capping allowable levels for land application. Traditional biosolids have been scrutinized for PFAS contamination, so we’re excited to see how our dry composting process compares. Our approach avoids many of the risks associated with wastewater-based biosolids, but we’ll be watching the data closely.

What else can you test compost for?

Why Testing Matters 

Properly tested compost isn’t just safer—it’s a powerful tool for soil health and sustainability. Our work ensures that human waste is transformed into something beneficial, rather than becoming another environmental burden. That’s what giving a S.H.I.T. (Sustainable, Healthy, Innovative Toilets) is all about.

Want to get the extra dirty details on compost testing? Check out the full blog post for free on Substack or subscribe to our Patreon for early access each month!

Read the full blog

This article originally appeared in our April 2025 email newsletter.