From the City and County of Honolulu, Dept of Env Services:
Recycle your Christmas trees.
Remove all ornaments and tinsel (and no flocked trees). Place them at the curb (in your green cart) for pickup on your regular every-other-week green waste collection day; drop them off at any of the City’s Refuse and Recycling Convenience Centers seven days a week or at the composting facilities.
For households in the cart pickup system, please note that the tree has to fit inside the cart. Cut the tree into lengths up to three feet and trim branches to ensure that it will fall freely from the cart during collection. If cutting the tree is a bother, you can drop it off whole at the nearest City Convenience Center.
For households on a manual collection route, cut the tree into lengths up to three feet and place at curb on your refuse day. If cutting the tree is a bother, you can drop it off whole at the nearest City Convenience Center.
Please be aware that the State has discontinued the special treecycling sites at parks and other locations around the island. Do not bring your trees to these sites. Use curbside collection or look for the list of City drop-off sites. Condos and commercial buildings can deliver large loads of trees directly to composting facilities – there will be no tip fee charge over the holidays for Christmas trees, courtesy of the City.