“Project: Pet Septic Tank” came about after we became first-time dog owners and very quickly started to feel terrible about the number of small plastic sacks of dog waste we were sending to landfill. There had to be a better and more environmentally friendly way of coping with our puppy’s ‘output’!
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At the time we also had two cats (now sadly no longer with us, and sorely missed), and although they were much (much) better at dealing with their waste all by themselves, we did have an indoor litter tray that we were also emptying into landfill on a regular basis.
After stumbling across a related post on composting waste on the internet, the idea of creating a septic tank for our pets' waste was born:
Step 1: Buy a plastic or metal dustbin, with a lid. We used a 70 litre plastic bin (which copes well with the output from our now 25-30kg dog).
Step 2: Dig a hole in the ground deep and wide enough so that you can bury the bin, leaving just a couple of inches exposed above ground.
Step 3: Cut the bottom off the bin.
Step 4: Drill ~10mm holes all around the sides of the bin, going from the bottom of the bin to the point at which the bin will be exposed above ground (you only want holes in the part of the bin that will be in the ground).
Step 5: Place the bin in the hole in the ground.
Step 6: Fill the bottom of the bin with 3-4 inches of gravel - this will aid drainage.
Step 7: Start filling with animal waste. (Note: if you are going to fill with waste from a cat litter tray, you must be using biodegradable litter, such as wood pulp.) We use small plastic scoops (the sort you can buy for emptying cat litter trays) to collect the dog waste from the garden and deposit in the bin.
Step 8: After three or four days of collecting animal waste, add some septic tank starter enzymes, as per the instructions (ours came in plastic sachets, in which case it’s a good idea to add some water to help break the sachets down).
Step 9: Top up the enzymes once every 4-6 weeks and add a little water if the contents of the bin look a little dry.
We found that the tank never gets more than half full as the enzymes do their job and break the waste down. These days we only ever use dog waste bags when out with our dog in public places, so the tank has saved us money as well as having saved many hundreds of plastic bags from going to landfill.