It is known as Pyrolysis.

In confirmatory tests, a procedure specific to the class or family of drug for which the sample screened positive is employed to "wash" or separate the drug itself from the matrix, i.e. blood or urine, in which it resides. The procedure of separating the drug from the sample is called an extraction. The Toxicology Section has different procedures for each class of drug. The general scheme of an extraction is to adjust the pH of the sample, expose the sample to an organic solvent to wash out the drug, collect and concentrate the organic solvent, and derivatize the drug in the sample. Some extractions have a but a few steps in the scheme, while others have many steps. The extraction process is one of the most time-consuming aspects of drug testing.

Organic fertilzer are safe, there is no fear of over use. no need to mix measure or no chemical odor snd they do not burn the roots.

The odor that plumbing material may give is generally termed as "waxy plastic citrus," "fruity plastic" and "burning plastic."  Amongst  the various kinds of plactic pipes available, its known that, cPVC has a low odor potential and it doesn't seem to release many organic chemicals. HPDE actually had the highest odor production, although it doesn't release very many organic materials. The PEX-b pipe had a moderate amount of odors and also a moderate amount of organic chemicals that were released into the air. PEX-a had fewer odors and organics release than the PEX-b pipe.  

It would be wise to ask neighbour as to what kind of pipes they use and whether it is giving them any problem or not.