What is the difference between delta-9 THC, THCa and Total THC?

By June 5, 2020 No Comments

When talking hemp, you often hear how the crop must be under 0.3% THC for it to be considered compliant with federal regulations. However, “THC” can actually refer to two different compounds, the first being “THCa” the precursor molecule – and the second is the molecule that attaches to the cannabinoid receptor in the body, “delta-9 THC” which is responsible for the psychoactive, intoxicating, and euphoric effects of traditional cannabis.

In order to convert THCa to delta-9 THC, the flower must be decarboxylated. Decarboxylation is caused by time and/or heat.  When you add heat to the inactive compound of THCa it converts to delta-9-THC at a maximum theoretical rate of 87.7%. This is why cannabis isn’t eaten raw to get high, but a flame is used to apply heat to activate the d-9 THC it with heat.

Unfortunately, federal rules are a bit confusing and so many states have struggled to develop a coherent policy framework to govern hemp production.  In 2014 the federal Farm Bill passed created the opportunity for states to have Hemp Pilot Programs.  The success of those pilot programs (Colorado, Oregon, Washington, Kentucky) created a body of agronomic knowledge that would lead to the Farm Bill of 2018 legalizing hemp nationally and removing CBD from the US Controlled Substance List.  While the Federal law states that delta 9-THC is the standard for compliance, some states have opted to use total THC. The problem with that standard is that Total THC is always higher than delta-9 THC so the farmers in Total THC states are afforded less margin for error in the THC levels for compliance testing. States and localities have different standards for compliant THC levels so it is critical for farmers to check with their states and counties to confirm the legal standard for growing within the constraints of the law.

Labs now must now include theoretical total delta 9-THC that may form as a result of the conversion of THCa to the delta-9-THC actually found in the sample. To calculate potential delta-9-THC, the labs apply the maximum conversion rate of 87.9% to the amount of THCa and then add this to the actual delta-9-THC found in the plant.

For Example:

THCa             0.30%
THCa Conversion factor 0.30% x .877
Potential Delta-9-THC 0.26

Potential Delta-9-THC 0.26%
Delta-9 THC   0.03%
Total d9 THC         0.29%

For the 2020 season, some states will continue operating under their 2014 Pilot Programs which specify delta 9-THC but others will operate under the Interim Final Rule created after the 2018 farm bill.  In some of these states, there is no harvest window and delta-9 THC compliance is the only issue for compliance.   Make sure you understand your state and local regulations on testing before planting so that you can organize your testing program to stay within the law and have a successful harvest.

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