The provision of plumbing products and services that can save water, use less energy and ultimately look out for the environment is encapsulated in the role of the ‘green’ plumber. In light of this, it seems another type of plumber is on the verge of brightening the industry – the ‘yellow’ plumber.

A rapid depletion in available phosphorus reserves (a key ingredient in the recipe for agricultural prosperity) has led researchers across the globe to begin developing urine diverting toilets. As human urine is a readily available source of phosphorus, this new toilet product aims to capture urine and reuse it in agricultural fertilisers – hence the name, ‘yellow’ plumber.

Urine diverting toilets are one step closer to becoming a common feature in buildings of the future, as they are already being trialled in Sweden, Germany, the Netherlands, United States and China. Although the first-generation toilets are still progressing through the feasibility stage, it is essential for plumbers to have a basic knowledge of how they work and what the installation process will involve, especially as Australia is set to follow suit in a home-grown initiative.

Research pioneers at the University of Technology Sydney (UTS) have recently started a research action project to explore the use of innovative urine diverting toilets in an institutional setting. Led by the university’s Institute of Sustainable Futures (ISF), a challenge grant involving 10 collaborators will aim to enable the safe nutrient capture and reuse of urine from the first-generation toilets installed on campus during a trial period.

UTS associate professor of sustainability Cynthia Mitchell, says urine diverting toilets are the most feasible way to extract urine from sewerage.

“One option is to collect the sludge from the sewerage treatment and incinerate that to create a by-product which is rich in phosphorus. You can also do a form of chemical precipitation at a sewerage treatment plant but that could result in a cocktail of heavy metals,” she says.

“If you capture the urine at the beginning of the waste process, you don’t have all of those mixing problems. It’s like adding milk to a cup of tea; you can get it out, but it’s very difficult.”

She says that urine diverting toilets involve subtle tweaks to the standard toilet design, resulting in what you might describe as a ‘funny dunny’.

“There are a whole lot of trade-offs that you have to make during the design process and different companies will make different trade-offs, resulting in different strengths and weaknesses of the finished product,” she says.

“Basically, it is a standard toilet that has two holes instead of one. There are slightly different variations in the designs, but most of the technologies have either one flush for both bowls or separate flushes.

“For example, the Dubbletten design from Sweden tries to ensure a very good separation between urine and faeces as well as reduce the water that is used in toilets generally. Their design has quite a high bridge between the bowls and a very low volume flush for the urine.”

The first-generation design of urine diverting toilets at UTS has come with its fair share of difficulties, particularly as the trial is a retro-fit installation in an existing toilet block.

“Urine is quite concentrated in terms of salt and if it sits for any period of time you get a precipitate forming, which makes it complicated to have a separate S-bend. There are also significant behavioural changes that are not being dealt with yet,” Cynthia says.

“Even so, we’re excited to take on the challenge as there has been no development of urine diverting toilets in Australia so far.