In February of 2024 I had a plan to make the first urine diverting dry flush toilet. I'd thought about it for some time but had resisted the idea... Now, despite the uncertainty around how it might be received, I think this could be a game changer for off grid living.
In this blog I'll be picking apart the cause of my resistance and why I think this opens up a world of opportunity for toilet systems.
Automatic sealing toilets have been around for a few years now. Basically a toilet securely seals your waste in a plastic bag so it can't harm others or the environment. The bags or waste can then be readily disposed of in the trash or incinerated.
It's not hard to see why someone who likes the idea of compost toilets for their circular nature wouldn't like bagging toilets:
But when you introduce 2 key ideas to the concept of a bagging toilet, you realise everything changes and new opportunities arise. These 2 key ideas are
Replacing a plastic bag with a compostable bag seems straight forward enough, right? Well, not exactly. Plastic pollution is a big problem, but compostable plastics are still plastics. They take a long time to break down outside a compost pile (and even months in a compost pile!). Putting compostable plastic in landfill wasn't going to cut it either.
Simply swapping fossil plastic for plant-based plastic comes with compromises. Even fossil-based plastic bags allow air to pass through them slowly - think of a balloon slowly deflating over weeks. Compostable plastics aren't as good as petroleum based plastics (yet) in their ability to contain gas molecules
While bio-based plastics come from plants, we use petro-based fertilisers to help grow those plants. We then use more fossil fuels to transport them and process them into bio-plastics. HOWEVER, I believe petroleum-based plastic is unsustainable in the long term. We simply have to stop making plastic waste that can't be recycled or broken down. There are very smart people working on these problems and I believe creating demand for bio-plastics will enable solutions from that industry.
Even if a bagging toilet's bag were replaced with a compostable bag, that's not the whole story. Until now, bagging toilets have used SAPs - Super Absorbent Polymers (plastic) to magically turn liquids into gels. (Gels is the The G in WAG bag). These amazing materials help mitigate the risk of a split bag, but they are NOT typically compostable. In fact, they're just another form of plastic.
How does urine diversion change anything for bagging toilets? Not thinking this through was the reason I waited so long to develop the S1. Treating liquids and solids separately makes sense. Once I opened up to this idea, the benefits kept coming and suddenly my focus shifted to how to do it.
How many times a day do you poop? how about pee? While pooping is a fairly regular occurrence of 1-2 time per day, peeing is a much more frequent and varied affair. Wasting plastic to entomb urine for posterity didn't really feel like a good use of plastic (or money).
I deliberately referred to urine as humane waste above - but it's only waste if you waste it. Human Urine contains 80% of the Nitrogen and 50-80% of the Phosphorous in sewage, but makes up just 1% of the volume. By separating urine at source, you don't need to turn it to a gel, but can in fact use it as a fertilizer. Urine even self-sterilizes if you just store it for a few months.
Once the urine (and associated pee powder) are removed from bagging toilets - the next question is what to do with the poop? By removing the liquid and nutrient content in the urine, problematic treatment techniques become, well, less problematic...
Because only poop, paper and compostable plastic should be in the toilet the bags and everything in them can now be safely composted. (anything else should go in a separate bin - just like it should with a flush toilet). That would make the S1 the first compostable toilet - it doesn't compost or even start to compost - but it is compostable!
The contents of your poop in a compostable bag are perfect to make methane to generate power through anaerobic digestion. In Europe, investments have been made into implementing anaerobic digestion at wastewater facilities as a supplementary income stream so the infrastructure is already in place. In Madagascar and South Africa, Loo-Watt's system uses anaerobic digestion to generate heat and power from poop to provide hot water and charge phones for happy customers.
People have a natural hesitation towards putting composted poop on vegetables. I love composting toilets as much as the next person selling composting toilets, but you have to control the composting process closely. If sufficient temperatures aren't achieved, an extended period of time needs to elapse for the compost to be safe, and that costs money.
I wasn't initially a fan of burning poop due to the loss of nutrients, but those are mostly in the urine. That leaves bacteria and fibre as the joint-second components of poop at 5%-9% each (water is first at 75%), There's not a lot going to waste when you incinerate a poop.
Indeed, burning poop is also a sure-fire way to kill any pathogens it contains and save lives. This is the whole point of sanitation systems after all. Keeping the liquids separate makes it a LOT easier and economical to burn poop for heat recovery or power generation.
With our company origins in the nomadic RV and campervan communities, we're particularly interested to hear your thoughts about burning your poop when off-grid. Burning poop and paper may be more convenient than disposing of the contents of a compost toilet into a public trash bin.
No - all the carbon you eat comes from plants that pull it from the atmosphere in the first place. Whether you eat the plant itself, or the animal that ate the plant on your behalf, putting the carbon in your poop back into the atmosphere does not mean you're contributing additional carbon to the atmosphere.
When I realised we now had a dryish waste stream, It opened up to other options and other crises that sanitation could alleviate. Pyrolysis is heating stuff in the absence of oxygen. It releases lots of flammable gasses (that can heat the next stuff) leaving behind just the carbon pulled from the atmosphere.
This opens up the possibility of making poop a carbon negative industry as well as a sanitation solution! Co-composting the remaining carbon (biochar) has been shown to turbo-charge the composting process.
I can't help but get excited when I think of the social benefit of jobs sequestering carbon, providing sanitation and improving soil fertility in one fell swoop.
Before I can get excited about the possible opportunities a new toilet like this opens up, I need to answer one important question.
That's where our community and customers come in. Through the crowdfunding of Cuddy and the feedback request for Cuddy Lite, we've continuously listened and improved our solutions. The S1 is another opportunity for our community to give us feedback and develop a toilet that fits with their needs and values.
Once we know this is a toilet people want, we can design the best systems possible.
If you want to help shape the future of the S1 and get the biggest discounts on our future crowdfunding page then sign up to follow the S1 sealing toilet crowdfunding campaign here.
Richard is the Co-Founder and CEO of CompoCloset, and the mastermind behind the Cuddy Composting toilet.
After a career algorithmic trading, he had plans to follow his long held passion for AI but the pandemic brought about an unexpected twist.
After installing a composting toilet in his campervan he caught the sanitation bug (not the dysentry kind) and saw an opportunity to change the world for the better and help bring safe sanitation to the 2.6 Billion without it.
He's now on a mission to make the best off-grid toilet possible both for you and the planet!
Follow along for the latest news!
