It’s kind of hard to say and it’s becoming very popular in the compost industry (particularly in California). I first heard Evan and Neil Edgar use it a year or so ago and I credit them for its origin (although they are so modest they say the term has been around for at least four or more years).
CASP is one of those industry terms, like the term in-vessel, that has more than one definition. CASP is a term used by some of the CA Air districts to mean BACT (best available control technology). When they use the term they are talking about a cover similar to our AC Composter™: an impermeable cover that is part of an ASP compost system that captures and controls VOC’s and GHG’s.
CASP has also been used to describe covering a pile of compost (aerated or not) with wood chips or finished compost so that it acts like a small biofilter. This technique is also called an “in situ” and “pseudo” biofilter. Please note: in order for this technique to work properly the pseudo biofilter must remain thoroughly moist.
So the next time you are among a gaggle of composters, toss out a CASP or two and see how other folks define the term.