It didn’t take us long to learn that contaminants in the feedstock would cause major problems. During the first grind of yard debris we lightly picked out trash ahead of time and let the grinder go. Each plastic bag quickly turned into 15 pieces of small plastic. With windrows 1 & 2 it had become routine to walk along the windrow and pick out plastic and other contaminants. Not happy with all of the job security involved in cleaning out trash, we became much more aggressive regarding contaminants on the second grind. Working together with the WINGS program (WINGS offers work, housing, education, and support for formerly homeless men) we had a team of guys pulling out contaminants during the grinding process. The difference was astounding. The post-grind pile was remarkably cleaner and will create higher quality compost.
Hands down the best thing is to have clean, source-separated material coming into the site. For yard debris droppers at the transfer stations we beg you to please keep plastic, painted wood, treated wood, coke cans, beer bottles, engine blocks (no really), concrete and any other non-organic material out of the yard debris. We know that you can save $12/yard by sneaking trash into the yard debris, but it will save us a ton of work and make superior compost, if you don’t.