Raising the Bar: Solvent Direct and ASTM D37 Advance Quality Standards for Extraction Butane

After nearly a decade of pushing for transparency and safety in high purity butane gases used for extraction, we are proud to announce a historic milestone: the first-ever ASTM standard for high-purity butane used in extraction has successfully passed the balloting phase under ASTM Subcommittee D37.04.

This achievement is the culmination of a multi-year initiative led by Solvent Direct in collaboration with a coalition of industry leaders and technical experts. Key contributors include Solvent Direct partners Rami Rodriguez, President of Cortera Gas; Robert McElhattan and Dileep Bendi of Diversified CPC; and our in-house technical experts Kyle Hernandez, Ph.D. Analytical Chemist Randall Shearer, and led by Subcommittee Vicechair – ASTM International D37.04 on Cannabis Processing and Handling, Darwin Millard. It reflects our unwavering commitment to protecting consumers, operators, and manufacturers across the industry.

A Landmark in Accountability

In 2022, Solvent Direct presented its proposed standards to ASTM with one goal in mind: to establish clear, enforceable specifications for liquefied petroleum gases (LPGs)—specifically n-butane, isobutane, and propane—used in extraction and refinement. 

Some of these new specifications and standards include:

• Minimum gas concentration of NLT 99.5% w/w

• Strict limits on contaminants, including:

  • Benzene: < 0.1 PPM (100 PPB)

  • Total BTEX (Benzene, Toluene, Ethylbenzene, Xylenes): < 1 PPM

  • Alcohols: < 5 PPM

  • Sulfur Compounds: < 1 PPM

  • Water: < 5 PPM

  • Non-volatile residues: < 15 PPM

These limits were set based on scientific risk assessments and feedback from Tier 1–4 gas distributors, extract manufacturers, testing labs, and regulators.

Addressing Benzene: The Concentration Effect

One of the most critical inclusions in this standard is the 100 PPB limit on benzene, revised upward from 50 PPB after stakeholder input highlighted limitations in current analytical detection thresholds.

Data suggests that benzene can concentrate 10–20x from gas to final extract. A source gas with 0.1 PPM benzene could yield extracts containing up to 2 PPM—a level far beyond acceptable thresholds in consumable products.

To explore this phenomenon further, we are currently collaborating with several testing laboratories—Tri-Air Testing, Consolidated Sciences (ConSci), and others—on a design-of-experiment to quantify benzene concentration across:

• Current gas supply on the market

• Extracts made using gas that meets the new ASTM standard

• Extracts made from benzene-spiked gases

These tests aim to validate the need for strict limits and are being coordinated under an official ASTM Inter-laboratory Study (ILS), which requires participation from seven certified gas testers.

Navigating the Balloting Process

The proposed standard, WK92862: Standard Specification for Liquefied Petroleum Gases and Gas Mixtures Intended for Use in Herbal Extraction, passed subcommittee balloting with an overwhelming 95.64% affirmative vote:

• Affirmative: 44

• Negative: 2

• Abstain: 84

All negatives were successfully adjudicated, including concerns that the benzene limit was overly restrictive. The final version reflects scientific rigor and regulatory practicality.

The Work Ahead: Data Integrity and Industry Adoption

Future initiatives under ASTM D37 include:

• Traceability specifications for LPG batches (refinery name, DOT cylinder ID, ISO-accredited lab testing at each touch point)

• Specifications for clean-in-place (CIP) protocols

• Standards for sanitary low-temp/high-pressure flow meters

• Definitions for LPG system design best practices

We are also exploring a new standard focused on the Certificate of Analysis (COA) and chain of custody requirements to address ongoing quality control concerns, particularly with Tier 2 and Tier 3 suppliers using outdated or incomplete COAs.

Final Thoughts

This is a defining moment in the evolution of the extraction industry. The quality of a butane extract is unmatched when the solvent is pure. For years, we’ve seen the downstream effects of contaminated, mislabeled, or improperly stored gases. This standard changes that.

As Solvent Direct, CEO Lexis Shontz put it: “We knew the industry needed quantifiable metrics—clear thresholds that labs and suppliers could hit. This isn’t just about compliance; it’s about consumer protection and manufacturing integrity.”

We extend our thanks to the members of ASTM D37.04 and our partners across the industry. Your dedication, data, and drive helped shape a safer future.

Progress like this is what holds gas producers accountable and preserves the integrity of the extraction industry. It’s not just about raising the standard—it’s about becoming the standard.