I had a Pixma in my old office and I remember when Staples stopped accepting the cartridges for recycling.
Just checked with the Canon site and it says that, since the inkjet cartridges are essentially plastic, so you can just put them with your other plastic recyclables.
Here's the statement:
Unlike Canon’s all-in-one cartridges, these toner containers are made mainly of plastic material making local recycling and local energy recovery possible and thereby reducing environmental impacts associated with the transportation of collected containers across the country.
Yes, It is a great machine!