Q. What is the correct way to dispose of the Hoshanos, Schach and Lulavim after Sukos?
A. See questions 552 and 3814 regarding the disposal of Shemos in invitations, newspapers and magazines if they are permitted to be placed in the recyclables disposal bins.
In our days most of the yard waste is not buried in landfills in Ontario but rather what is collected is turned into compost. The City's yard waste program allows it to divert approximately 90,000 tonnes of yard waste from landfill each year.
Turning yard waste into compost is obviously not the Halacha most proper and honorable way to dispose of items that were used for a mitzva. When possible one should save it for the fire at the burning of the Chometz before Pesach or similar.
Nevertheless, Horav Shlomo Miller's Shlit'a opinion is that in need one may use it since after all one just placed it into proper paper bags by the curb and it was others that turned it into compost.
Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu Shlit'a.