What Do I Do With Waste from a Composting or Dry Toilet?

Composting and dry toilets are an increasingly popular choice across the UK for those looking to reduce water use, live off-grid, or make their homes and holiday sites more environmentally friendly. These waterless systems are easy to use, require minimal maintenance, and are designed with sustainability in mind.

However, one of the most common questions new users ask is: What do I actually do with the waste?

In this blog, we’ll walk you through how to handle, process, and reuse waste from both composting toilets and dry toilets, using guidance from Biolan’s tried-and-tested models: the Simplett, Simplett Plus, and "eco" Composting Toilet

First, Let’s Understand the Types of Toilets

Dry Toilets like the Biolan Simplett and Simplett Plus do not contain any internal composting mechanism. Instead, they simply collect solids and liquids (separately), and the solid waste is transferred to an external composter such as the Biolan Quick Composter 220eco to fully complete the composting process.

Whilst many dry toilets listed online claim to be “composting toilets” - they actually aren’t. They are simply waste separators and collectors. Proper composting needs time, heat and bulk to convert a waste product into usable compost - and dry toilets do not provide these conditions. They are simply the first step in the process - but read on for more details.

Composting Toilets such as the Biolan eco Composting Toilet are thermally insulated units that physically produce compost inside the toilet itself, turning waste into humus (a soil-like substance) over time. These are designed to be emptied less frequently and work well in year-round use. The thermal insulation is the key - double walls with insulation between them, create the heat you need for the composting process to be successful.

What Happens to Solid Waste?

1.     In Dry Toilets (Simplett & Simplett Plus)

Solid waste is collected in a removable plastic container with a carrying handle - usually 28-30 litres in capacity. You can use a biodegradable liner bag in the container to make emptying cleaner and simpler, or pad out the container with newspaper at the bottom. When full, the bag and container contents are transferred to an external composter for further processing. This will take some time.

It’s important not to compost the contents directly into the ground or in your garden without proper treatment. Human waste needs time to break down safely to eliminate pathogens.

Once the waste is in a compost bin:

• Add a bulking material to maintain the right balance for aerobic decomposition, and to reduce odours.
• Turn the contents regularly and keep the pile moist (but not too wet) to encourage breakdown.

Leave the compost for at least one year before using it. When fully matured, it should be dark, crumbly, and odour-free, very similar to soil.

It’s advisable to only use composted human waste around trees, shrubs, or ornamental plants, rather than directly on fruit or vegetable beds, unless local guidance permits.

2.     In the Composting Toilet eco

This toilet model is designed to carry out the composting process inside the unit. Thanks to its insulated structure, the composting process can continue all year-round - even during damp and cold UK and Irish winters.

• Use a spade to scoop out the matured compost from the hatch at the base of the unit.
• Use the compost as top soil (from 6-8 weeks) or compost for a further 6 months to produce mature compost material.
  You may need to transfer to an additional container if the quantities of waste you are treating exceed the composter's capacity.

It’s recommended to only remove the compressed, composted contents up to the top of the service hatch, to ensure the composting process (above) remains active.

What About Liquid Waste?

Both dry and composting toilets separate liquid waste (mainly urine) from solids but in different ways. Managing this part of the waste “stream” is just as important.

How to Handle Urine / Seep Liquid

• In the Simplett and Simplett Plus, urine is collected in a separate canister (usually outside of the toilet cabin / hut). Canisters are typically 10 litres in volume and should be emptied every few days depending on use. Remember, if we all drink about 2 litres of liquid per day then  this is roughly the amount of liquid that will come out as urine.
     
  
• In the Composting Toilet urine passing through the composter will generally evaporate, but any excess “seep” liquid will collect at the bottom of the composter underneath a specially designed seepage plate, and will then transfer to a separate canister, which  also needs to be monitored and emptied periodically.