How to Ensure Your Projects Meet the Mark—and How TPS Lab Can Help

When a landscape project calls for compost, most people assume any dark, crumbly material will do. But as landscape architects, municipal planners, and spec writers know—not all compost is created equal, and using the wrong material can jeopardize plant health, soil structure, and long-term success.

That’s why more professionals are specifying compost that meets rigorous quality standards, like those outlined by the U.S. Composting Council’s STA Program. And it’s why compost producers turn to labs like TPS Lab, one of the few in the country certified to test and verify STA-compliant compost.

Whether you're writing the spec or reviewing submittals, here's what you need to know.

Why Compost Quality Should Be Non-Negotiable

In high-value landscaping projects, compost isn’t just filler—it’s a biological soil amendment that affects water retention, nutrient delivery, root health, and erosion control. Poor-quality compost can:

• Burn plants due to high salts or ammonia
• Introduce weed seeds or pathogens
• Create drainage or compaction issues
• Cause nutrient tie-up or imbalance
• Lead to expensive replanting or remediation

Compost that looks finished may not be fully cured or stable. The only way to know for sure? Laboratory analysis.

What "Compliant Compost" Actually Means

When landscape specifications call for “STA Certified Compost” or “compost compliant with USCC guidelines,” they’re referring to a strict set of testing and documentation standards. Compost should meet benchmarks for:

• Maturity/Stability (low respiration rates, no phytotoxicity)
• Nutrient Content (NPK, organic matter, C:N ratio)
• pH and Soluble Salts (critical for plant safety)
• Heavy Metals (must fall below EPA limits)
• Moisture Content and Bulk Density
• Pathogen and Weed Seed Reduction (via PFRP validation)

These parameters ensure the compost won’t harm plantings or disrupt soil biology—and that it’s suitable for use in regulated applications.

TPS Lab: A Trusted STA-Approved Testing Laboratory

TPS Lab is one of a select group of laboratories in the U.S. certified by the U.S. Composting Council under the STA (Seal of Testing Assurance) program. That means:

• We follow strict USCC protocols for compost analysis
• We deliver traceable, standardized reports that meet commercial and municipal spec requirements
• We work with compost manufacturers across the U.S. to help them develop and maintain products that consistently meet STA or custom project specs

Whether you're sourcing compost for a new landscape development or writing specs for public works projects, TPS Lab gives you confidence in the material you’re using—or approving.

Spec Writers: Make Your Requirements Stick

If you're writing compost specs, we recommend language that includes:

• STA Program compliance
• Recent lab test results from a USCC-certified laboratory
• Defined thresholds for soluble salts, organic matter, pH, maturity, and particle size
• A requirement for third-party verification (not just supplier statements)

Need help building spec language that holds up in the field and in court? We’re happy to provide guidance.

TPS Lab Helps Compost Suppliers Meet High Standards

We also work closely with compost manufacturers, soil blenders, and distributors to:

• Identify what’s causing failed specs
• Adjust feedstocks or processing practices
• Improve material consistency and value
• Prepare documentation for landscape architects, DOT projects, and municipal contracts

By testing with TPS Lab, suppliers gain a competitive edge—and meet the demands of today’s increasingly quality-conscious specifiers.

 Don't Leave Compost Quality to Chance

In professional landscaping, the wrong compost can mean failed plantings, drainage issues, or liability headaches.

Whether you're designing a streetscape, writing public bid specs, or building out a LEED-certified green roof, TPS Lab is your partner in ensuring compost compliance and performance.

👉 Need help with compost specs or testing? Contact us to speak with a certified expert.

Compost supplier? Explore our testing services and join the ranks of STA-compliant producers across the U.S.