You've purchased a composting toilet and are on the path of eco-friendly toileting. You're saving water, and avoiding chemical waste treatment - go you! On average, a single person using a composting toilet will produce about 10 litres of compost per annum. So, when the time comes to empty your composting chamber, what do you do with its contents?
Always dispose of your compost in the appropriate manner. Humanure should always be buried at a minimum of 150mm sub-strata. This prevents surface run-offs, immediate exposure to occupants of the land, and the spread of pathogens by animals and insects. If using an on-floor system with a small chamber that requires frequent emptying, you will need to let your compost mature in a designated composting bin before in-land burial. Burial can be done in a few ways, as detailed below.
Offal Hole or Dedicated Garden Bed
WCTNZ® recommended practice for disposal of composted material into land is by zoning off a dedicated land application area in which to bury the humanure. This can be done by allocating a non-food-crop garden bed, or creating an offal hole.
WCTNZ® recommends creating a dedicated offal hole with a steel or concrete lid. This gives you a dedicated burial area that is easily accessible, saving you regular digging. Simply open the lid, dispose of your compost, close the lid, and you're done! We recommend using steel or concrete for the lid, ensuring it is heavy enough to stay in place, and doesn't allow for the possibility of someone falling through it.
If you're opting for a garden bed and no lid, once the compost is placed in the allocated area, you will need to cover it with 150mm of soil, bark, or mulch.
Planting or Fertilizing Trees
If you want to make use of your humanure, you can use it as fertilizer for your trees (including fruit and nut trees)!
When planting a tree, dig down extra and add compost to the base of the hole before putting the tree in. This allows for greater root ingression into the ground through nutrient rich compost.
If you want to fertilize around an existing tree, you will need to chip into the surrounding surface, making sure to avoid damaging the roots. Place compost into the exposed area, and top with cover material to prevent exposure. You can use soil, mulch, or lawn clippings.
Secondary Treatment in Designated Compost Bins
If your composting chamber requires frequent emptying, you will need to set up a Secondary Treatment System in which the compost can mature before being buried. To do this, you will need two 220L, round, open-base compost bins. Use one of the bins to collect compost for a year. Then, leave it to sit and mature for another year, while you collect compost in the second bin. Leaving the compost to mature over a year gives it ample time to break down, readying it for removal into your designated land application area. This is additionally important in NZ where we have limited seasonal warmth.
What NOT to Do with Humanure
Although composting toilets are designed to kill harmful pathogens in human waste, it is always best to err on the side of caution when handling humanure. You should always dispose of your composted material by burial in an area where there is no risk of exposure to humans, animals, insects, or other pathogen spreading organisms.
While it is fine to use humanure as fertilizer for trees (including fruit and nut trees), you cannot use humanure on food crops.
Do NOT use humanure on:
- Edible plants
- Edible flowers
- Plants used for seeds (e.g. sunflowers, pumpkins, sesame, chia, etc.)
Need help choosing a system? Call WCTNZ® on 0800 022 027 for free advice on system specification and setup. Advanced design consultancy services are also available.
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