I saw a report that the county zoo is asking for people to drop

Avalon Manor - I saw a report that the county zoo is asking for people to drop off their used Christmas trees for enrichment for the larger animals such as bison and lions. Great idea. But I’m wondering what the townships in the county do with all the trees that are left out at the street for collection? If they just go to some landfill or something why don’t they just take them to the zoo anyway?