Faeces to fertiliser: innovations to solve the world’s toilets crisis
- Pit latrines still best for regions without sewage systems
- Improvements include membranes to collect faeces and dry flushes to save water
- Community buy-in crucial to toilet innovation success
First, some good news. Since the year 2000, the number of people forced to defecate in the open has fallen by more than half to an estimated 673 million. However, 2 billion people still lack basic sanitation services, with more than 700 million relying on rudimentary holes or pits, a World Health Organization (WHO) report showed last month.**
The problem is concentrated on around 60 high-burden countries, mostly in Africa and Asia, where water is scarce and infrastructure — such as sewer systems and water treatment plants — can be difficult to maintain. Open defecation is widely practised in some countries, but it is not a suitable alternative. It contaminates food and water through flies and can be dangerous to girls and women, as it forces them to seek out isolated spots away from their homes.
But changing toilet practices is surprisingly difficult. “It’s something quite intimate,” says Rémi Kaupp, a sanitation engineer for the UK-based charity WaterAid. “People don’t want governments or agencies to impose what kind of toilet they have in their home. What they want is someone to deal with the aftermath.”
“People don’t want governments or agencies to impose what kind of toilet they have in their home. What they want is someone to deal with the aftermath,”
Rémi Kaupp, sanitation engineer, WaterAid
The answer for Kaupp is on-site sanitation. The traditional pit latrine, where waste is collected in a pit under a seat, is the go-to solution for most households without access to a sewage system. But latrines have their own problems. Pits need to be emptied, a job that is dangerous without proper equipment. The waste stinks. If latrines are shared, they may get so dirty people resort to open defecation instead.
In Tanzania, a project led by WaterAid established a professional and safe pit emptying service for locals in Dar-es-Salam’s Kibondemaji district. The service processes faecal sludge to make cooking gas, manure fertiliser and water fit for gardening. The service is paid-for, but market research in the community meant the team managed to set a price that was affordable, says Abel Dugange, WaterAid’s director of technical services in Tanzania.
Dugange describes how his team needed to set up infrastructure from scratch. “To have a complete sanitation business chain, we needed to have, for example, transfer stations for solid waste collections, before they are ferried to major dumping sites.” He says the biggest challenge they faced was funding and buying land for this purpose. “Sanitation businesses seemed not to be well known to most banks, so it took time to educate them.”
Dugange’s team also needed to provide workers with safety tools, such as proper boots, masks and gloves. Dealing with faecal sludge is a health hazard, which makes collection and storage difficult in low-income, low-resource settings. Due to the hassle of digging new pits, many communities share latrines, which reduces the work load for individuals, but can also make latrines less safe and private.
A smelly businessThe answer could be collection of faeces in the home. A team at the University of Delaware in the United States is working on a membrane liner with ventilation holes that can be put into standard 40-litre drums. The laminate liner allows the water to evaporate from the faecal matter while retaining pathogens. As a result, the contents dry out and are safer to remove and handle.
The technology was field-tested in Kanpur, India, but problems remain with the time the sludge needs to dry, and with smells. “The laminate works best in warm and dry climates, since these conditions enhance evaporative drying,” says Paul Imhoff, an environmental engineer at the University of Delaware, who worked on the study. He added that the costs were too high but remained positive that the technology had promise. “There is a need for less expensive laminate membranes and better design to allow more efficient air flow and drying,” he says.
Other innovations cover settings where sewage systems are available, but water is scarce. A water toilet uses around 14 litres a flush, which, for a family with two children, translates into around 250 litres of water a day. At Britain’s Cranfield University, a team has developed a “waterless” flush, where faeces are deposited in a rotating bowl, which is then scraped clean using a swipe activated by a handle.
Diagram showing parts of a dry flush toilet
The system requires neither water nor electricity and can be installed in a traditional white ceramic toilet, making it attractive for individual households. A field test in eThekwini in South Africa showed that the swiper worked reasonably well, but since no water ran down the sides of the bowl, fouling of the porcelain remained a problem. The system also struggled to deal with menstrual blood.
“The design and the white colour of the pedestal were praised, but the functionality of the flush was noted to still need improvement,” says Jan Hennings, a PhD student at Cranfield who worked on the trial. “Ultimately, we believe that the flush could function well enough that it could be implemented with other waterless sanitation technologies.”
From faeces to fertiliserIf faecal sludge is safely collected, it can turn into an important resource. Human faeces contain beneficial biomaterials and, through composting, make excellent soil conditioners. However, even with sanitation systems present, many poorer cities fail to dispose of faeces properly. In Maputo, Mozambique, for example, nearly 90 per cent of faeces are collected through latrines, but more than half is left untreated due to unsafe disposal, leakage and lack of proper treatment facilities.
An example of a waste-flow diagram: Maputo, Mozambique. Credit: Peter Hawkins
A project in the Bangladeshi municipality of Sakhipur co-composts human faeces and other solid biowaste before selling it on to farmers as fertilisers. Abdullah Al-Muyeed, WaterAid’s head of policy and advocacy in Bangladesh, says that nearly half of the faeces created in the area are now turned into compost at a special plant.
“The first barrier was integrating people and the municipality in decision-making to treat both faecal sludge and solid waste together,” he says. Al-Muyeed and his team worked over several years with local leaders and the farmers’ school to bring about a change of mind. Another barrier was the price of the resulting compost, which, even now, is subsidised by the government to make it affordable.
However, the system now brings much-needed income to the region and has raised awareness of faeces as a resource. “The technology is very much applicable to other countries as well,” Al-Muyeed says.
In many countries, toilets are still a matter of money. In Namibia, the WHO report showed, only four per cent of the country’s poorest have access to one, compared to nearly 90 per cent of the richest. So toilet innovation must tackle not only the technical challenges of providing safe sanitation, it must consider local preferences, finances and customs.
Kaupp says the best toilet is always the one that works for the user. It must be a pleasant, private space where faeces are taken away promptly and processed safely. “That’s what we want,” he says, “for people not to worry about it.”
**This article was amended on 31 July, 2019. It originally stated that ‘an estimated 673 million people around the world still do not have access to even the most basic toilet facilities’. SciDev.Net wishes to clarify that this figure refers to the number of people who defecate in the open. Almost 1.4 billion lack access to the most basic toilet.