CBDa is a cannabinoid within the cannabis plant, when heated it de carboxylate and becomes CBD. CBD is now becoming well known for its analgesic, anti spasmodic, anti bacterial and anti inflammatory properties. It's amazing!
If you want to create CBD at home from your cannabis you will need to help the process and decarboxylate with the use of an oven or other heat implement. There are various sites that talk about decarboxykation. I prefer this one as it is very specific and shows the graph that most people point to: http://cannabischris.com/2012/10/decarboxylation-of-cannabis/
The author describes the two step process for decarbing plant matter with a high CBD content. If you follow these instructions you will decarb your CBD. I hope this helps!
Before you begin to decarboxylate your flower for CBD, I would suggest using a strain that has a high CBD content to ensure you get the most from your flower. Strains that contain a higher CBD content than most include Charlotte’s Web, Harlequin, or even ACDC. There are a ton more. That’s just a few to get you started. I would suggest doing a little bit of investigating on your local dispensary/delivery service’s menu before purchasing your CBD strain. Most places will provide the percentage of THC and CBD in each strain.
When decarboxylating CBD, it should be done at a higher temperature than you’d use for THC since CBD has a higher boiling point. Separating the cannabinoids at home is a little bit more difficult to do without having the industrial machine’s precision. To decarboxylate your CBD, it’s best to do so at 245 degrees F for about 60-90 minutes. You will want to stir it every 10 minutes or so. You’ll know when your CBD has been decarboxylated, because your cannabis will be dry, which will make it crumble easily, and it will be darker than what you started out with.