Why didn't you use fucking google before posting such a question :P
http://www.atmospure.com/information/activated%20carbon%20and%20adsorption.htm (http://www.atmospure.com/information/activated%20carbon%20and%20adsorption.htm)
http://www.tifac.org.in/news/accarbon.htm (http://www.tifac.org.in/news/accarbon.htm)
http://www.fao.org/docrep/X5555E/x5555e07.htm (http://www.fao.org/docrep/X5555E/x5555e07.htm)
http://home.att.net/~africantech/GhIE/ActCarbon.htm (http://home.att.net/~africantech/GhIE/ActCarbon.htm)
There's no way the equipment needed to produce activated charcoal is going to cost you less than the price of buying it already made, unless you're going to use many kilotons monthly ;D On the other hand, if your charcoal manufacturer friend wants to invest in the equipment, then it's time to start doing some research instead of posting such questions expecting others to do it for you ;)
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000529519-utfse.gif)