Use recycled or recyclable bedding.
This can be bought in the store or made at home. If you use a paper shredder at home, don't throw the paper in the trash. Put it in your hamster's cage as bedding instead. They'll enjoy playing in it and it will reduce waste, as well as save you money on store-bought bedding. If you do go store-bought, most hamster bedding will be green to a certain extent, but if it can be recycled or has been made from recycled materials, it's even better.
Edible hideaways offer shelter and reduce waste.
Hamsters love to sleep and hide in various shelters. Dual purpose shelters made for eating or chewing are greener than those made from plastic. Once the plastic ones wear out or are no longer used, into the landfill they go. But if you purchase chewable or edible hideaways, your hamster will most likely devour much or all of the material before it goes to the waste bin. Because it's edible, what's left is most likely biodegradable, unlike plastic.
Use chew toys that double as treats.
Your hamster needs something to chew on in order to keep his teeth healthy. Chew toys like alfalfa sticks and small twigs are great for this because they double as a treat. That way, there is little to none left to throw away when they finish with it. You may have to experiment with a few different edible chew toys to see what your hamster likes best.
Keep a small catch dish under your hamster's water bottle.
Even properly installed water bottles will drip from time to time, especially during or right after use. Keeping a small dish underneath prevents the bedding from getting wet. This reduces the frequency of cage cleanings, thereby reducing the amount of bedding being used. Also be sure the bottle is properly secured and working correctly. A leaky water bottle not only wastes water, but causes too much dampness in your hamster's cage. This can lead to mold if not changed often enough and a high waste of bedding if changed accordingly.
Make homemade treats.
Not only will your hamster enjoy fresh treats, but you'll reduce plastic and transportation waste that comes from store-bought treats. Just be sure to get approval from your hamster's vet to make sure the homemade treats are safe. Here's a recipe on homemade vegetable bread snacks for hamsters.
*I originally published a version of this via Yahoo Contributor Network