Blog from the Environmental Engineering Research Group at SLU
We are making history! Our dried urine was applied with a seeder while planting barley. This could be the first time that urine fertilizer was applied in such a way. The fact that we are able to produce a urine based fertilizer that is usable with conventional farming equipment is very exciting. We have three treatments: no fertilizer, conventional fertilizer and urine fertilizer. The urine fertilizer has 7.2 % nitrogen and we applied 100 kg N per ha.
At VA SYD’s head office, our innovative toilet system is now being installed to dry the urine to solid fertilizer, directly under the toilet. By sorting out the urine, most of the nutrients can be recycled from the sewage. We, researchers, at the Swedish University of Agricultural Sciences (SLU) have been developing the new technology, which will be tested in Malmö and Lund, within the REWAISE project.
We recently published a new paper on the use of Magnesium Oxide as an alkaline substrate for dehydrating urine in the journal Frontiers in Environmental Science.
https://www.frontiersin.org/articles/10.3389/fenvs.2020.619901/full
Abstract: Fresh human urine, after it is alkalized to prevent the enzymatic hydrolysis of urea, can be dehydrated to reduce its volume and to produce a solid fertilizer. In this study, we investigated the suitability of MgO to alkalize and dehydrate urine. We selected MgO due to its low solubility (<2 gL−1) and relatively high saturation pH (9.9 ± 0.2) in urine. Using a laboratory-scale setup, we dehydrated urine added to pure MgO and MgO mixed with co-substrates (biochar, wheat bran, or calcium hydroxide) at a temperature of 50°C. We found that, dehydrating urine added to a mixture of MgO (25% w/w), biochar, and wheat bran resulted in a mass reduction of >90% and N recovery of 80%, and yielded products with high concentrations of macronutrients (7.8% N, 0.7% P and 3.9% K). By modeling the chemical speciation in urine, we also showed that ammonia stripping rather than urea hydrolysis limited the N recovery, since the urine used in our study was partially hydrolyzed. To maximize the recovery of N during alkaline urine dehydration using MgO, we recommend treating fresh/un-hydrolysed urine a temperature <40°C, tailoring the drying substrate to capture NH+4 as struvite, and using co-substrates to limit the molecular diffusion of ammonia. Treating fresh urine by alkaline dehydration requires only 3.6 kg MgO cap−1y−1 and a cost of US$ 1.1 cap−1y−1. Therefore, the use of sparingly soluble alkaline compounds like MgO in urine-diverting sanitation systems holds much promise.
Contact: Prithvi Simha
The findings from our multinational study that surveyed the attitudes of about 3800 people from 16 different countries, are now published in Science of the Total Environment and available here: https://doi.org/10.1016/j.scitotenv.2020.144438.
Highlights:
– Cross-cultural & country-level factors explanatory of respondent attitudes identified
– Respondents had positive intention overall but were unwilling to pay price premiums
– Social norms and cognitive awareness of urine’s benefits & risks featured strongly
– Building consumer trust via context-specific messaging can improve acceptance
Our main findings are best summarised by this picture below, which shows the strengths of association for factors explaining attitude of food consumers towards human urine as fertiliser. Factors are grouped by demographics, social norms, benefit/risk perception, substances that respondents believed are normally excreted in urine, and environmental outlooks. Dots are proportional and indicate the strength of association (Cramér’s V values); dashes indicate categories that could not be analysed due to insufficient data.
Picture inserted shortly.
Contact: Prithvi Simha
The Urine Drying team at SLU (together with Sanitation360, Spiran and Gotlands Bryggeri) have been awarded 2.9 MSEK from JTI to test using our dehydrated urine as a fertilizer for barley destined for beer production. The objective of the project is to produce a tailored dry fertilizer from urine and a new, more sustainably produced, beer that tastes exactly the same as conventional produced beer.
Jenna Senecal was interviewed by Modern Farmer about the potential to safely recover nutrients from human urine to help protect the environment. Scroll down to read the article.
We are very pleased to share with you the 1st edition of the Guide to Sanitation Resource Recovery Products & Technologies. The Guide is a popular science publication that gives an overview of the possible resources that can be recovered and provides guidance on treatment processes to achieve safe products for reuse. The specific objectives of this document are:
The Guide to Sanitation Resource Recovery Products and Technologies is primarily a reference book. It is intended to be used by engineers, planners, end-users, researchers, technology developers, sanitation entrepreneurs, non-governmental organisation (NGO) staff and students who are interested in creating circular systems for resource use. It aims to support and enable decision making for increased resource recovery by providing information on key decision criteria for a range of recovered products and treatment technologies, thus highlighting the diversity of options available for resource recovery.
Links to download the guide:
https://pub.epsilon.slu.se/21284/
https://www.susana.org/en/knowledge-hub/resources-and-publications/library/details/4008
Last week, following our joint article on urine recycling in The Conversation Africa, Prof. Christopher Buckley from the University of KwZulu-Natal was interviewed by SAfm, South Africa’s national public radio station. In his interview with Stephen Groote, Prof. Buckley talked about our group’s pioneering urine treatment technology, alkaline dehydration, and how the technology holds promise for implementation across Africa. In the coming year, along with Prof Buckley’s research group and local stakeholders, we are hoping to implement our urine drying technology in Durban, South Africa. Listen to the interview below –
Björn was invited as Sweden’s representative in the Vietnames Agritech conference during the 28th of November. The title of his talk was technical solutions in relation to “Challenges in Post-Covid Environment for Agriculture Sector”. His focus of the presentation and the panel discussion was that the circular economy can reduce the pollution of the environment as we remove the nutrients from the linear flow of today. At the same time do we increase the resilience in the agriculture as we can replace up to half of the imported mineral fertilisers with local waste and wastewater generated fertilisers. The new Covid era gives new opportunities for global collaboration and knowledge sharing over the internet.
Jenna Senecal was interviewed by Popular Science, a widely distributed magazine in North America, about the potential to safely recover nutrients from human urine to help protect the environment. Scroll down to read the article –