Each method of extracting CBD from Cannabis has its pros and cons, and there are 3 species of Cannabis that produce CBD. Generally speaking, it is common practice to source the substance from the most CBD-rich species Cannabis ruderalis (commonly known as hemp) because the concentration of CBD is vastly higher in hemp than other species.
This essential hemp oil is collected as a by-product of commercial hemp production for clothing, building materials and 25,000 other common products.
Commercial hemp production has largely used distillation to extract the hemp oil from which more pure CBD is subsequently refined. Some CBD extraction methods are safer and more healthful such as supercritical CO2 extraction which involves expensive equipment but produces a cleaner, higher quality, and more effective CBD oil.
DIY methods or home-based methods often involve chemical solvents such as butane and hexane which leave residues that are not healthful and should be avoided.