Sanitation systems as biorefineries: Dry toilets are the secret to the bioeconomy.

Separett asked me to write a piece for them, but didn’t think this first draft was appropriate for what they intended. I like it, so here it is. (The second draft was even better 🙂 )

A quick snap of a poster at the Separett factory. Not the best quality and couldn’t find a similar thing online, but this really captures what dry toilets represent to me.

Sweden releases about 17 000 tonnes of Nitrogen into receiving water bodies  each year (2012 data) and needs to halve its nutrient release into water bodies. Small-scale wastewater systems, and municipal wastewater treatment plants, are the largest point sources of phosphorus release and are a significant factor in causing eutrophication in receiving waters. Long-term sustainability demands that society reuse the nutrients contained in its wastewater. Today’s agriculture is not self-sufficient regarding plant nutrients, which leads to a significant annual demand for rock phosphates for artificial fertilizers. If the plant nutrients contained in society’s wastewater can be reused for agricultural use, these would become part of a cycle which could bring significant environmental and financial benefits. A basic premise of (bio)process engineering is to decouple the solids and the liquids because they behave differently and have different requirements – see for example the first step in a sewage works; it is primary settling tanks (PSTs).  A basic premise of cleaner production is source separation. Taking these two premises to their logical conclusion with regards to sanitation leads us to urine diversion, dry toilets.

The Toilet Board Coalition has been formed to develop these opportunities in an approach they call the Sanitation Economy. I believe dry toilets represent the best way to utilise the nutrients in sanitation in the bioeconomy and approaching sanitation as an industrial ecosystem.

The nutrients from sanitation is a problem, but also an opportunity to contribute to the bioeconomy.  Green Building Councils around the world are incorporating metrics for zero waste and even resource recovery into their buildings, for example the recent Bullitt Centre in Seatle, USA, billed as the “Greenest Commercial Building in the World”. Bruce Oreck, former U.S Ambassador to Finland, asserted at the recent dry toilet conference held in Tampere, Finland that dry toilets need to find a place in urban centres as well. Dry toilets in cities have greater potential than conventional methods to contribute to urban greening and enable urban environments for both biomass production and for environmental improvement and other ecosystem services.

On national levels this approach is built into water and bioeconomy strategies. The Swedish bioeconomy strategy has defined a bio-based economy (bioeconomy) as an economy based on … “increased added value for biomass materials, concomitant with a reduction in energy consumption and recovery of nutrients and energy as additional end products” and the Finnish water strategy has explicitly included a focus on increasing the reach of dry toilets, in an integrated context of “Industrial circular economy solutions and closed solutions, Nature-based solutions in waste and urban runoff treatment and Dry sanitation solutions”. Finland’s Natural Resource Strategy focuses on using natural resources intelligently, which includes a greater focus on decentralisation, which dry toilets necessarily is an example of.

Dry toilets are the environmentally responsible option and represent economic opportunities. But from an interior design perspective, dry toilets can give more freedom of placement and visual aesthetic than flush toilets. It is for this reason that I have a dry toilet in my home. For me, a dry toilet represents freedom in everyday life.

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