Buy your cat food in bulk.
There are several pet stores now that are selling pet food in bulk, which means without packaging. Take your own container/bag to the store and fill up. I typically look for wholesale pet stores because it's usually these locations that I find pet food in bulk. Also, make sure the quality of the food is still to your standards. I always value nutrition over packaging.
Make your own cat food.
Buy raw ingredients to make your own cat food instead of purchasing the kibble or canned food. Do this by taking your own containers to the butcher to have filled. There are some mixed reviews on whether or not it's better for your cat so I suggest you do your own research. Keep in mind that there are additional vitamins and minerals that cats will still require that you'll need to buy separately, in glass, to add to their food.
Buy your cat food in recyclable packaging.
More and more pet food companies are "going green" with their food packaging like TLC Pet Food. As long as the food quality lines up with what you feed your cat, opt for this option. Terracycle also offers a recycling program on certain pet food packaging, like plastic lined bags, that you can send to them.
Give your non-recyclable pet food bags a second life.
If none of the above suggestions work for you, you can at least give that bag a second life. Use the bag to fill up with thrift store donations, use them to transport mulch and soil back home from the landscaping store, use it to store your compost, turn it into a tote bag, or use it as your garbage can liner.
Having a zero waste litter box can be tricky. Especially, if you live in an apartment or rental. However, there are ways to do it or at the very least, reduce the overall waste the litter box can produce.
Use sawdust, mulch, or dirt as your "litter"
But will the cats use the box? Trust me they will. Some cats will take to a new litter a lot quicker than others so I recommend slowly incorporating the new stuff gradually. You can get sawdust, mulch, and dirt package free from your local landscaping store or even for free on sites such as Craigslist.com. Most traditional pet litters come with "fragrances" to minimize the odors. I just add baking soda in with mine to reduce the smell. Keeping the litter box maintained also helps.
Compost the doo-doo.
Using the natural cat litters allows you to compost the waste. Build a cat doo specific compost bin and keep it away from your garden.. Over time the poop and litter will naturally break down. You can use the compost when it has fully broken down, however, I would just stick to ornamental plants and not your garden produce - just to be safe.
Check to see if your local/city compost programs take animal waste.
If you don't have your own yard to compost you kitties' waste, check to see if your cities' compost program accepts animals waste. Some might.
Train your cat to go outside.
If you live in an area that isn't highly trafficked, you could train your cat to potty outside just like your dogs. I'm currently considering installing a "catio" to see if my kitties will start going outside rather than using the litter box indoors.
Buy bulk litter.
Some pet stores like Petco allow you to purchase your clay litter in bulk. This doesn't make it completely zero waste but does reduce the overall plastic waste that is getting sent to the landfill.
Buy litter in compostable packaging.
Purchase litter in paper bags or cardboard containers. That way, plastic waste is being reduced and the natural packaging can be composted.
Utilize items you already have or make your own.
It's very easy to make cat toys from old ripped up clothing or by simply attaching a string to a stick. I even bring in pine cones from the yard for them to play with. A cardboard box is a house favorite among my feline herd - those usually keep them busy. We also make cat scratching posts from some scrap wood and rope. Cats will play with anything, they're not picky.
Cats can eat and drink out of bowls you already own, there's no need to buy anything special. Also, check around your house for something you can repurpose into a litter box. It's always better to try and make do with what you already have then to buy new.
Buy all natural/quality items.
Did you know that a lot of pet toys are made from or filled with plastic and are toxic? Instead of purchasing cheap toys from the store, regardless if they're packaged or not, always opt for the all natural/compostable toys. This ensures that, when they wear out, they can be composted and not sent to the dump.
One of my favorite all natural pet toy companies is Purrfectplay! Check out their amazing selection of pet safe toys!
Opt for second hand.
Thrift stores are great for finding second hand pet products such as toys, bowls, litter boxes, leashes, collars, you name it! Buying second hand takes new products out of the waste stream and is better for your wallet. Also, check friends and family for any items they'd give you for free.
Buy in Bulk.
Many pet stores have treats in bulk where you can skip the packaging and use your own containers.
Make homemade treats.
Make your kitty treats from scratch. There are many recipes out there that are quick, cheap, simple, and very healthy for your cat. It sure beats the questionable treats that you get at the store.
I hope I have covered everything that you've had questions on regarding "greening" your cat. With a few changes, the amount of waste your cat produces could be reduced quite a bit or even eliminated all together!
What do you do to reduce your kitties' waste?