Washington’s waste makes gardens grow

Even people who are enthusiastic recyclers of plastics and cans and paper can be squeamish when it comes to talking about how we deal with human waste. It doesn’t seem like a polite topic for conversation.

But the discussions – and more importantly, the technology – has been changing. Now it’s time to talk about ‘toilet resources’ rather than human waste. When I was teaching human security and peacebuilding, I used to show learners an entertaining TED Talk given by the Malaysian entrepreneur who took on the task of putting toilets on the world map. He used humour because otherwise, people found the topic distasteful.

Zurich. Photo by Patrick Federi on Unsplash

The value of looking at our waste as a resource is that it is an opportunity. The Toilet Board Coalition, created in 2015 to drive private sector engagement in creating universal access to sustainable sanitation products and services, says the Sanitation Economy is the “biggest opportunity in a century to transform sanitation systems into a smart, sustainable and revenue generating economy”, which could be worth billions. It estimates the sanitation economy opportunity to be worth $62 billion in India alone by 2021.

Part of that opportunity involves reprofiling human waste as “toilet resources” which can be converted into other valuable resources. For example, the 33 billion litres of waste generated by 15.6 million global tea workers and their families could be “converted into one of the following: 7.6 billion MJ of biofuel, 12 billion MJ of Biogas (heat), 1.4 billion kWh (electricity), 2 million tonnes of co-compost at a 3:1 ratio, regenerating 16,000 tonnes of Phosphorus, 17,000 tonnes of Potassium, 23,000 tonnes of Nitrogen.” 

Science journalist Lina Zeldovich has just written a book called The Other Dark Matter: The Science and Business of Turning Waste into Wealth and Health, which is about to be published. Here’s an excerpt from Amazon’s description:

“Because of the diseases it spreads, we have learned to distance ourselves from our waste, but the long line of engineering marvels we’ve created to do so—from Roman sewage systems and medieval latrines to the immense, computerized treatment plants we use today—has also done considerable damage to the earth’s ecology. Now scientists tell us: we’ve been wasting our waste. When recycled correctly, this resource, cheap and widely available, can be converted into a sustainable energy source, act as an organic fertilizer, provide effective medicinal therapy for antibiotic-resistant bacterial infection, and much more.”

Zeldovich “profiles the pioneers of poop upcycling, from startups in African villages to innovators in American cities that convert sewage into fertilizer, biogas, crude oil, and even life-saving medicine” and ”shows how hygienic waste repurposing can help battle climate change, reduce acid rain, and eliminate toxic algal blooms.”

And, as it turns out, one of the places this kind of reprofiling is happening is in the capital city of the USA – Washington, D.C. Nautilus has a fascinating excerpt from the book that shares this story of how human waste is being turned into fertilizer for gardens.

DC Water’s Blue Plains Advanced Wastewater Treatment Plant: A Resource Recovery Facility processes the human waste of about 2.2 million people who live, work, or visit the capital and the area that surrounds it but it doesn’t describe itself as a waste treatment plant. Instead, it describes itself as “a resource recovery facility”. 

Christopher Peot, the plant’s director of resource recovery, is trying to change the mentality of the sanitation business. “There’s no such thing as waste, only wasted resources,” he told Zeldovich. “So we don’t process waste here. We recover resources.”

And those resources increasingly are going to help improve soil fertility and generate power for homes.

“One of the most ecologically savvy sewage treatment facilities in the country, DC Watr uses the so-called thermal hydrolysis or THP process, which renders sludge harmless and converts it into a safe form of fertilizer,” Zeldovich writes.

To do this, it uses a system originally designed in Norway. The Cambi system consists of a pre-heating tank, called a pulper, and a series of upright cylinder tanks, in which sewage is heated to 300 degrees Fathrenheit and pressurized to six atmospheres for half an hour to kill pathogens.

The sludge is loaded into the so-called biodigesters, which work like our stomachs, breaking down complex molecules into smaller bits, dramatically reducing how much ‘dark matter’ must be treated further. “Without the digesters, the plant would generate 1,100 tons of biosolids daily, which even in their pathogen-free form still need to be trucked somewhere, with the use of fossil fuels. The microbes reduce this amount to nearly one third.”

The microbes produce methane, which burns to spin the plant’s electrical turbines, generating 10 megawatts of power –  enough to power about 8,000 homes. The rest becomes Bloom, which is marketed in 25-pound bags by Blue Drop after it ages and dries the ‘black gold’, as Zeldovich calls it.

“I grow everything with it, squashes, tomatoes, eggplants,” Bill Brower, a resource recovery engineer, tells her. “Everything grows great and tastes great. And I’m not the only one who thinks so. We’ve heard from a lot of people that they’ve got the best response they’ve ever seen from the plants. Particularly with leafy greens because that nitrogen boost does well with leafy plants. And the plants seem to have fewer diseases and fewer pests around—probably because Bloom helps build healthy soils.”

Bloom also has proven popular with landscape architects and construction companies that buy good soil for horticultural use, says Zeldovich. “As they clear sites for new developments, they often strip off the topsoil, which later needs to be replaced. Bloom helps restore the damage done—and it doesn’t smell like manure, so tenants don’t complain.”


This Is Some Good Shit. Nautilus, Nov. 10, 2021

Bloom website.

Read more:

Oregon Is Turning Sewage into an Endless Supply of Green Energy. Reasons to be Cheerful, Mar. 17, 2022