Instructables
The Green Pee Cat Litter System uses a non-porous filler, pea gravel in a perforated tray sitting in a second tray that contains an absorbent layer of newspaper with baking soda.
The cat urine flows through the non-porous pea gravel into the second tray where it is absorbed by the news and the odors are neutralized by the baking soda.

All you have to do is scoop out the solids from the pea gravel once a day and change out the newspaper and baking soda once a week.
Once a month or so you change out the gravel. The gravel is hosed off or dumped outside where the rain cleans it and it can be reused.

My cats had to be trained to go on the gravel.
I put regular cat litter on one side of the box and pea gravel on the other side.
There was some mixing of the two as the cat used the box.
Then I gradually used less litter and more gravel.
Now my cats use the new system with only pea gravel and my life is a little easier

Green Pee Cat Litter System is green because it:
1- Stops all the cat litter going into the landfills.
2- Saves the cost of buying cat litter.
3- Recycles newspaper.
4- Saves time changing out cat box.
5- Helps control odor.
 
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Step 1: Drill holes in one tray

Picture of Drill holes in one tray
Holes are drilled in one tray

Step 2: Newspaper and baking soda are put in the bottom tray

Picture of Newspaper and baking soda are put in the bottom tray
Newspaper and baking soda are put in the bottom tray

Step 3: The trays are combined

Picture of The trays are combined
The trays are combined

Step 4: The cats are trained

Picture of The cats are trained
The cats are trained by using pea gravel on one side and cat litter on the other

Step 5: The gravel and litter mix as the cat use the box.

Picture of The gravel and litter mix as the cat use the box.
The gravel and litter mix as the cat use the box.

Step 6: Eventually you can use only gravel.

Picture of Eventually you can use only gravel.
Eventually you can use only gravel.

Step 7: Separate the trays to clean the bottom section

Picture of Separate the trays to clean the bottom section
Separate the trays to clean the bottom section

Step 8: Dump the newspaper and install new paper and baking soda

Picture of Dump the newspaper and install new paper and baking soda
Dump the newspaper and install new paper and baking soda

Step 9: The gravel is dumped once a month or so in an area that it can be washed and reused

Picture of The gravel is dumped once a month or so in an area that it can be washed and reused
The gravel is dumped once a month or so in an area that it can be washed and reused
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iti1 year ago
You can purchase a box system that is designed to use saflower seeds, i think. its three parts: slotted tray with seeds on top, bottom slopped tray to catch urine and a very small plastic box that hold the urine and slides into the bottom tray.

I hooked a hose to the funnel of the the bottom tray and attached the other end to the down drain to sewer. Very easy to do.

I also put one in a bedroom, but have it draining outside to a gallon jug with holes to the flower bed. I add water to dillute the urine.

You can buy plastic pellets to use instead of the seeds.. its cleaner than the seeds, and less expensive, and faily easy to clean. I was them with vinegar.

Also, you can just put the setup on plastic stand, drill a hole in the top of the shelf and funel/tube it to a one gallon jar with about an inch of vinegar in it. Works great. This is how i did it for testing. Do not pour this on anything you want to live outside, the vinegar kills it.
ladybozarth2 years ago
OH YES; forgot to mention; that when I scoop the solids I do use newspaper (cut a full sheet by 1/4 & keep large stack in bin close by). Newspaper does keep any smell from escaping. DO NOT FLUSH CAT SOLIDS!!! If you're not sure why; google it!!
ladybozarth2 years ago
I have utilized the bottom tray with small amount of water which I change once to twice a day which is easy since I keep cat box in (2nd) bathroom bathtub; therefore; making it easy to empty in toilet; wash tray and return; no fuss; no smell. Tried newspaper and still have to discard and newspaper tends to hold urine smell which do not want in garbage can even though outside.
Gadgetnow2 years ago
Great Idea, I may have missed the answer to my question but can aquarium gravel be used for this? We have tons of newspapers and this is a great idea on how to use them. Thanks
Nephih2 years ago
How crucial is it that pea gravel specifically is used? Would fish tank gravel work the same?
ladybozarth2 years ago
this is great system; wish I had seen it "before" I bought the Febreeze system; which works wonderful; just don't like the "pee pads" and going to landfill; which is how I came across your instructable. I have tried using newspapers but want to rid the smell (Febreeze pad worked great for that); will try the water as not interested in "washing"; the less "trash" the better.
jolea092 years ago
Hi, we're looking to try this as we've recently become short of money... But... We can't really afford baking soda, is there anything else cheaper to use?
I read lately in www.animalshelter.org to use wood pellets, seems to be at least half the price of regular litter. I too was amazed how the rain spout washed the pea gravel, thanks!
We are excited to try this! I was going to try the Tidy Cat Breeze system, but this is much cheaper and I love the idea of being able to rinse and reuse the gravel. I would probably buy puppy pads and use them in the bottom instead of news papers, but I understand some don't want to add these pads to landfills, but I think it would work better for us.
RiverCats3 years ago
Thank you KittyF. I will check out the cedar/pine question with my cousin who is a vet with the University of Wisconsin in the research division.
Cedar is poisonous, or a carcinogen to rabbits, and I believe cats also. Use great caution. I would avoid altogether!
pwasniewski3 years ago
Great idea--thanks for posting!
satori713 years ago
this is a very ingenious and inspiring instructable. It has made me examine most products that I used to but and realize that almost anything that we use can be created for much less if we just consider the possibilities. Thank you so much. I now have 3 of these going in my home and so far so good. Living in the northeast its a challenge to wash the pea gravel during the cold months though. To resolve this I got additional litter boxes and drilled holes in them so I can have one with clean pea gravel to replace the dirty one while that one sits in my garage soaking. This way I don't have to go outside in the frigid winter to wash pellets or wash them in my bathtub or some other indoor contraption. This also allows the pea gravel to soak in some water rather than running the hose or shower for a while to clean it which uses up much less water.

I am wondering if aquarium filter pellets (activated charcoal) would help with odor.
RiverCats5 years ago
Great idea. No more litter tracking, yes! A friend of mine from England has trained her 7 cats to use cedar hamster bedding, instead of litter, in the box. She dumps it every couple of days. She says it controls the odor and is very cheap (but it does tend to stick to the longhair cats fur occasionally). I think I may try that in the bottom pan with some baking soda. This would take care of the newspaper ink fumes concern, and it should be fully bio-degradable. Any thoughts?
I'm almost certain that cedar is poisonous to cats. check online or at the pet store before you try cedar. PINE Is ok, but Cedar is NOT.
KittyF4 years ago
I don't know, I'd check with somone on that.  Cat litter is so acrid I'd expect it to be able to kill the organisms that aid in composting.  or the worms that some people use for composting.   Same with mulch, doesn't sound like a good idea.   Just my thoughts.
you very happily compost newspaper and cat wee. it is fine.

DO NOT however compost cat poo. It has [pathogens in it. You can dig a trench 6 - 8 inches below ground and put it in there and it will eventually decompose and keep the pathogens out of the top soil layer. DO NOT put the trench near fruit trees or vegetable gardens.

Cheers.
jany4 years ago
There is a big difference from baking soda and the box you show in the picture, That is made especially for cat odor and cost around $3 to $4. Regular baking soda is under a dollar. Arm & Hammer makes them both.
bloodgain jany4 years ago
I've used both. From my experience, the only difference is a bit of fragrance in the much more expensive "cat litter deodorizer". The baking soda is the active ingredient. I buy it in bulk from Sam's Club, and it's a very cheap and effective solution.
melmcc4 years ago
Melody, I use a litter made from what we in RSA call meilies (corn) It also has a pine smell, very little odor and can go into the garden after you have clean the poops out. I have a tray something like this but it is time to replace it. You have been such a help with this. I have a small boarding cattery and find the litter trays you buy are too small for some of the big males. They then get themselves in the tray but the most important part hangs over the side. I can go and get a second tray, drill the holes and we are off. I use a type of pebble which you can wash but the corn litter is better and if the urine can drain away it will last longer. I use a cat friendly antiseptic in the bottom tray but it cat get heavy ( have more than one cat in the house) so I will try the newspaper and soda idea. Thank you very much.
forgesmith6 years ago
Cool. It can be made greener. One, don't hose the gravel off, put it in a bucket, add water to cover, wait. The remaining wastes will go into the water, pour off the water and air dry the gravel, don't even rinse. Two, well, there's a big "yuck" factor with this one. Don't use newspaper. Keep it out of the landfill and recycle. Instead, use soft thick fabric, big enough piece of it, dust it with the baking soda as you fold it up so it's in all the layers. Maybe use an old bath towel. To clean the fabric, well, um, just toss in the washer with your clothes. Hey, you trust the washer to clean your shorts, not much difference there. The socks I peel off after a long day in the work boots, they're definitely biohazardous waste yet they go in my washer (eventually), clean up good enough. The cats won't care. Eventually the fabric will degrade too far and need replacing, but that's at worst one piece going to the landfill vs perhaps a few hundred pounds of wet newspaper. Heh, pea gravel, nice touch. However, when I first saw the title I thought it said "Green PEA." And I was thinking, well, bag of dried peas is cheap enough, will soak up liquid, compost well, probably even smell well, let's see what it looks like... Yet I'm still glad I clicked!
If you have a compost bin (or a garden plot to bury it in), you can compost/bury the newspapers. Most newspapers use soy ink (don't use the glossy inserts...just the newsprint), so there should be no polution; plus, the paper is a high carbon material, the urine is a nitrogen, so the mix should be perfect for quick composting. (though there is still Pwag and bitterbug's warning about Toxoplasmosis...so maybe just bury the papers in a non-edible plant area).
I've heard that toxoplasmosis happens when the stuff with pet wastes in the compost don't reach an internal temperature that would kill the evil bacteria. So composting the cat pee newspaper in a large pile/bin outside for at least six months, and then using that compost in the garden would probably be ok. Mixing these materials with small, or indoor composting projects, though, could pose a health risk.
You can use that compost around trees but not on plants that you will be eating . It rains / you water and the compost splashes on you lovely strawberries then you or your kid eats the strawberries straight from the plant and eat cat compost. Sorry to be such a pian in the rear but oldest sister is vet med, and I get to listen to that stuff. :(
There are plenty of posts around the internet about composting cat litter/waste. In general, it's safe as long as you let it compost for longer than average (I think the general consensus was about six months).

Remember, feral cats (who are the most likely carriers of toxoplasmosis) are just wandering around pooping wherever they want. It doesn't get composted. As long as you follow good-sense precautions, composting cat waste is totally safe.
If I lived in a warmer climate, I'd just get an old colander and keep the used gravel outside through a few rains. Cat urine has a very distinctive aroma, and clothing with pee in it never quite stops smelling. You could rinse the towel before putting it in the washer, but at that point there's sort of an impasse of wasting water to get the pee out of the towel vs. putting newspaper in the landfill in order to use new newspaper.
I use white vinegar in loads of laundry regularly to get rid of cat urine smells. 1/4 cup a load works good. Enzyme treatments like stink free work good but sometimes can fade clothes. With some items, even those methods didn't work, so I wouldn't wash clothes together with the towel. For someone wanting to compost the cat waste, they might want to look into something like this vermaculture that dramatically reduces cat waste ecoli. http://www.amnh.org/nationalcenter/youngnaturalistawards/2005/Eric.html
All right, I'm convinced.  That description of how to use the towel, and why I should not be so icked out that I don't try this, was a fun read.
Pwag forgesmith6 years ago
Have to watch this washing the cloth in your washer if you have a pregnant lady in the house. There might be that cat box baby disease thinger to worry about.
bitterbug Pwag5 years ago
Toxoplasmosis Gondii. That's a good point. I'd also be very leery of washing a cat urine soaked blanket in the washing machine. A cat's sense of smell is MUCH better than ours. Imagine if there's trace amounts of cat urine smell on everything in the closet? Wouldn't have to worry about using a litter box ever again.
wash the toweling in natures miracle or any other enzymatic pet odor neutraliser.
sam125874 years ago
I use a generic version of feline pine (pine pellet bedding for farm animals the larger pellets work well for us & it's tons cheaper) & it works great - warning though :
The pine will make the garden acidic for about a year so you might want to put it in a  compost heap to rot a little first.
My garden last year was "fried" from the pine - only 2 litter boxes worth! the soil was so hot that only one plant did much the rest were just leaves.
Hopefully this year will be better.

This is a wonderful idea - I'll definitely be trying this out. I've been putting newspaper in the bottom of the box for years as a bottom absorbent layer. 

chubbyvegan4 years ago
re: essential oils, they will be in the lower pan and not in contact with or accessible to the cat if the instructions are followed correctly, but good to know.  

re: smell, i found a product called Anti-Icky Poo that works really well, and comes highly recommended.

re: self cleaning litter boxes, i have several complaints.  my husband bought one and our cat's back paw was sliced open, resulting in infection, renal failure and over $1000 in vet bills.  she's ok, but now on modified kidney diet.  also, the cartridges don't lock in properly, so litter ends up underneath the thing and you have to clean up much more than you normally would.  there are several nooks & crannies that catch litter and need to be cleaned out.    you can only use certain litter.  the stuff that comes with it is corn based, but the cartridges aren't reusable and the thing requires electricity, hardly what i call "green."
chubbyvegan5 years ago
I've been using this system (ok, my cat, not me) for several months, and it seems to be working really well! I like the idea of putting water in the bottom tray. Lemon juice is a good odor neutralizer, but I've heard that cats detest citrus. Maybe a few sprigs of fresh lavender or drops of oil in the water? I have rotating batches of gravel so that it can be properly rinsed and aired out over time. I also soak in vinegar if the odor is especially potent, but you have to be sure it doesn't smell like vinegar when reusing it, or the cat may decide that's not the place to go, anymore. If you use a towel instead of newspaper, you can rinse it, then soak in vinegar prior to washing. It works as a fabric softener, too! Thanks for sharing a fantastic idea!
I know this is a year later, but, the best item I've found for getting rid of pet odor is Yard Odor Killer   stool &urine deodorizer made by Garmon Corp.  1-888-628-8783  www.naturvet.com. 
I know this post is old, but I had to post a reply. You should never use essential oils around cats, or at the very least you should be very cautious and prudent as to their usage. Cats cannot metabolize them in the same way humans or even dogs can, and most essential oils (especially in the amounts we humans with our weak noses use) can make cats very sick, especially if they make contact with cat's skin.
Oh, also, I'm a big fan of putting baking powder at the bottom of litter boxes. It neutralizes the urine.
Maybe tea tree oil? I have a Hamilton Beach 04271R TrueAir Plug-Mount Odor Eliminator near my litter box. I use an extension cord, and put it on top of the litter box hood. The stinky air gets pulled through a carbon filter before getting back into the rest of the room.
DWRead6 years ago
Does the poop get covered enough to prevent odor from reaching the rest of the house? The rain gutter is great idea!
LannyPlans (author)  DWRead6 years ago
I have not noticed much difference with the smell from poop. I have not discovered all the possible uses and combinations. One thing that I noticed when training and still using cat litter is that the cats would scratch the litter down to the bottom and pee. The pee would flow into the bottom tray without soaking the litter. So cat litter with the double tray may also be a good system. LannyPlans
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