In a new paper published in Water Research, Senecal et al. assessed what hygienic health risks may occur when human urine is dehydrated. The experiment was set up to simulate that the last person using the toilet (before the dehydration medium is changed) is contaminating the medium with misplaced faeces, with no time for dehydration of the urine, i.e. a worst-case scenario. It was found that urine dehydration in itself achieved a concentration < 1 A. suum per 4 g of dehydrated medium which fulfils the WHO guidelines for unrestricted use.
Decentralised sanitation technologies based on source separation of toilet waste have attracted a lot of research attention – the social sustainability of these technologies, not so much. To attempt to fill this gap, members of the Kretsloppsteknik group collaborated with researchers at VIT University, to explore what food consumers in India think of urine recycling. The results were recently published in the journal Water Research, where a survey of 1252 consumers at the VIT University campus revealed: 68% stated human urine should not be disposed but recycled, 55% considered it as fertiliser, but only 44% would consume food grown using it.
In a recent study published in Water Research, members of the Kretsloppsteknik group investigated the possibility of alkalising human urine by anion-exchange and dehydrating urine into a dry fertiliser powder.Fresh urine was passed through an ion-exchanger, stabilised by alkalisation (pH >10), added to an alkaline media (wood ash/alkalised biochar) and dehydrated
Simha, P., Senecal, J., Nordin, A., Lalander, C., Vinnerås, B., 2018. Alkaline dehydration of anion–exchanged human urine: Volume reduction, nutrient recovery and process optimisation, Water Research. In Press. doi: 10.1016/j.watres.2018.06.001.
The saying ‘we are what we eat’ is only part of the story. What we eat is what we excrete, and this means plant nutrients. Human excreta contain the same nitrogen, phosphorus and potassium (N-P-K) as the fertilisers used to produce the food consumed (Winker et al., 2009). However, human excreta are considered unwanted waste throughout the world, creating humanitarian and environmental problems (Baum et al., 2013). In order to replace the nutrients removed from the fields during harvesting, more fertilisers are manufactured in industrial processes that are contributing to environmental changes at global level (Rockström et al., 2009). Recycling human excreta back to agricultural fields would reduce the current dependence on fossil fuel-derived fertilisers (Ramírez & Worrell, 2006). It would also improve crop yields in e.g. sub-Saharan Africa, where fertiliser application is low (FAO, 2015), and protect marine ecosystems in the Baltic Sea by limiting the flow of excess nutrients to surface waters (Rockström et al., 2009).
Within our research group we are working with several methods for returning nutrients from food and wastewater to agriculture. Source separation of waste flows can make for simpler treatment and higher quality of the recovered products. However, the use of source separation systems is far from wide spread. Trying to understand why this is the case and what can be done to increase source separation is also part of our research focus. And we are not alone in looking for opportunities to transition our waste systems into something more sustainable. A recent popular science article in the magasin Extrakt, sponsored by the Swedish Research Council Formas, featured an interview with Jennifer McConville on what is needed to implement these systems at a large scale.