It's time for a new loo. We can thank the Victorians for our water sewerage system, but the 'flush and forget' approach to sanitation is unsustainable.
Around the world 2.5 billion people have no access to a toilet, and 1,400 children die every single day as a result of unhygienic sanitation. These figures are as outrageous as they are shocking. But nobody wants to talk about it, because - well - it's just not very nice, is it?
Part of the problem lies in our own 'flush and forget' water sewerage systems, brought to London by pioneering Victorian engineers such as Joseph Bazalgette in response to the rising tide of human waste and cholera in the capital. Since then, water flush toilets and large-scale sewerage systems have spread rapidly through countries that have the money and infrastructure to support them.
But it doesn't have to be this way.
At the time when Bazalgette put forward his grand plan for London's sewers, others - like Henry Moule - were proposing designs for 'dry' toilets.
Moule's earth closet found some favour in some place, notably parts of India under the British Raj. But today the Victorian 'white porcelain gods', with their insatiable appetite for water, are revered around the world as the pinnacle of hygiene. This makes it hard for alternative designs to gain traction, even when a water-based system is the least practical sanitation solution.
Rachel Erickson runs tours of London's unusual and historical toilets. She explains, "I was talking to a woman who works with slum communities in India, and she said that even though water-borne sanitation is not the best solution there, it's what people want because it's what they see the president using. If President Obama would use a dry toilet, then they'd probably start to be interested."
Despite the PR problem, engineers and designers are working hard on bringing alternative toilets to some of the 2.5 billion people who lack them. At the UCLoo festival in December 2013, visitors were bowled over by some of the innovative designs.
For example, the Tiger Toilet - less fearsome than its name suggests - relies on voracious tiger worms to digest human waste, creating a rich compost that can be easily collected. In contrast, the LooWatt seals people's poo in biodegradable bags that go into an anaerobic digester, generating valuable biogas and fertiliser. This system is being tested in Madagascar, generating electricity for heating water and charging mobile phones - it's ironic that many people in the settlement where LooWatt is being trialled have a mobile phone, yet few have access to a decent loo.
Forget 'flush and forget'
While the problems of bringing sanitation to the developing world are mainly related to lack of infrastructure, here in the UK we have issues of our own. Every day, the average Londoner uses around 50 litres of drinking water to get rid of their waste.
Environmental engineer Dr Sarah Bell, from UCL, finds this scandalous. "We take water from our environment, treat it to a very high standard, then flush it down the toilet. If someone arrived from another planet and saw that this is what we did to one of our most precious resources, they'd think we were insane."
Could dry toilets catch on in the UK, or are we too addicted to our flush-and-forget habit? To be successful, any alternative system would have to fit with the existing infrastructure we already have. It's possible to imagine something like a hygienically-sealed cartridge that gets put out for collection alongside the rest of our unwanted waste. But, as we've seen with the problem of dry toilets elsewhere in the world, it has to be seen as a desirable solution.
Time to talk about toilets
Having access to a hygienic and safe toilet should be a basic human right. In some parts of the world, such as the slums of Kenya, just going to the loo is a hazardous business. Women and girls are at risk of sexual assault and small children can fall in to open pit latrines, as well as the health problems associated with such close contact with human faeces.
Nobody wants to have to use a stinking pit latrine or a 'flying toilet' - a plastic bag of poo chucked into the street. If you think that's disgusting, remember that the people having to live in these situations think the same. But because of the global community's reluctance to talk openly about sanitation, and the reluctance to embrace new designs, more than two billion people are stuck with it.
The impact of bringing toilets into the 21st century could be huge and the need is desperate. Not just in terms of the health, economic and cultural benefits, but simply because of basic human dignity.