Humanure, as an ecological sanitation system, provides for the recycling of human faeces and urine to meet inter alia open nutrient requirements in agriculture. In doing so, secondary resources are recycled by composting or technically processing the human waste into fertilizer, animal feed or fuel.[1]
Composting human faeces is similar to composting ordinary food leftovers or leaf litter. The fermentation system with an appropriate storage time is a simple form of composting toilet that promotes the composting of human faeces and organic carbon materials. Composting at a high temperature eliminates the possible germ load by destroying pathogenic organisms. There are different methods of mechanized or manual composting (see below the stage of development and current dynamics).
Due to the spread of liquid manure from industrial livestock farming on intensively farmed areas, many antibiotic residues get into the groundwater. In addition, hormones, drugs and chemicals in the wastewater of hospitals and the (pharmaceutical) industry also cause a high input of trace substances, which are transported in the form of sludge from sewage treatment plants back into the agriculture and thus into the water cycles. The treated water from sewage treatment plants is also increasingly causing eutrophication of water bodies.
Ecological sanitation through dry/compost toilets or through container systems saves the high drinking water wastage of flush toilets of an average of 35 liters per person per day. Instead, valuable nutrients and carbon are returned into the soil in order to restore soil fertility. Moreover, the cultivation of carbon in the soil causes less harm to the climate. Furthermore, energy consumption for sewage disposal and fertilizer production is reduced. [2]
The `innovative’ aspect of Humanure is the paradigm shift to also use human feces for fertilizing growing foods, and instead of treating them as a human 'waste', they are perceived as valuable products that can be recycled to meet important nutrient balances for soil, water and climate.
The use of human faeces and urine for fertilization goes back a long time in history. Already more than 7000 years ago, the indigenous population of the Amazon enriched the fertility of the rainforest soil with the help of the so-called 'Terra Preta', which is composed of plant remains, dung, coal, clay fragments, bones and human faeces. A first type of compost toilet was invented in the middle of the 19th century by the English clergyman Henry Moule[3], after cholera killed about 10,000 people in London. At the same time similar systems were developed in the USA, in which a bucket was placed under a chair, which, after being used, was given a layer of ashes, earth or similar material to reduce odors. Since the 1990s, there has been a wide range of compost toilets available for purchase in Europe.
In many places, especially since the publication of Joseph C. Jenkins' book 'The Humanure Handbook' in 2013, compost toilets are being built by individuals who carry out the composting and fertilization in the garden themselves, as it is a cost-effective and self-constructible system in addition to the positive environmental influences. Through centrally organized collection, transport and treatment, entire residential complexes in urban areas could also convert to compost toilets with a system of replaceable faeces cartridges. Some companies are experimenting with building decentralized sewage treatment plants with microorganisms and plants on their roofs. As an organized form, there are also many (technical) approaches in countries of the Global South, especially in order to counteract the difficulties in densely populated regions without sewage connections[4].
Due to toxic bacteria such as coliform bacteria, composting toilets can, depending on the system used, pose a higher risk of infection than classical toilets[9]. Proper composting can improve sanitation and reduce coliform bacteria content by more than 99% according to a study[10]. Also when fertilizing with human excrement, proper storage and handling is important to minimize risks. [11]
The situation is different for the input of pollutants into the environment, which is known from the use of sewage sludge in agriculture. This way heavy metals and organic pollutants can enter the environment[12]. "Open questions in sewage sludge assessment concern the contamination of sewage sludge with persistent organic pollutants, the spread of antibiotics causing resistance and the safety of sewage sludge with regard to epidemics"[13]. These questions have also not yet been clarified with regard to the use of Humanure.
In order for compost toilets to be widely used in urban areas, numerous hurdles still have to be overcome. These include social acceptance, legal requirements and knowledge gaps regarding the design and handling of the toilets[14].
[1] Krause, A. et al. (2015): Kohlenstoff- und Nährstoffrecyling mit Bioenergie- und ökologischer Sanitär-Versorgung. Conference Paper: Workshop "Biokohle im Gartenbau - Verwertung von organischen Reststoffen zur Schließung von Energie- und Stoffkreisläufen", Volume: Book of Abstracts, Botanical Garden, Berlin, pp. 47-50
[2] Nana (2012): Permakultur: Klima wandeln mit Menschenmist. Klimaschutz. https://reset.org/blog/permakultur-klima-wandeln-mit-menschenmist (20.02.2020)
[3] Öko-Energie (2018): Komposttoiletten—Sauber und umweltfreundlich! https://www.oeko-energie.de/produkte/komposttoiletten/index.html (20.02.2020)
[4]Technology systems are being developed to counteract the shortage of drinking water and the parallel lack of sanitary facilities, especially in countries of the Global South. Human excrement, which consists of 85% water, is heated to a high temperature, so that the resulting water vapour is filtered and cooled in the next step to produce distilled drinking water. The remaining dry excrement is reused as an energy supplier for heating. In this process, additional electricity is generated, which can be supplied to the local electricity systems. It also offers the possibility to use waste as fuel. (Sedron Technologies (n.d.): Janicki Omni Processor. https://www.sedron.com/janicki-omni-processor/how-it-works/ (20.02.2020)).
[5] Sedron Technologies. (n.d.). https://www.sedron.com/ (20.02.2020)
[6] Hohler, S. (2019): Ein WC-Sitz aus Bambus, eine Spülung mit Holzspänen. Tages Anzeiger.
https://www.tagesanzeiger.ch/zuerich/stadt/ein-wcsitz-aus-bambus-eine-spuelung-mit-holzspaenen/story/17725677 (20.02.2020)
[7] Clivus Multrum—Composting Toilets (2020). http://www.clivusmultrum.eu/ (20.02.2020)
[8] Separett—Waterless toilets (n.d.). Separett website: https://www.separett.com/en-gb/ (20.02.2020)
[9] Nakagawa, N. et al. (2006): Application of microbial risk assessment on a residentially-operated Bio-toilet. Journal of Water and Health, 4(4), pp. 479–486. https://doi.org/10.2166/wh.2006.0031; Stenström, T.A., Seidu, R., Ekane, N., Zurbrügg, C. (2011). Microbial exposure and health assessments in sanitation technologies and systems - EcoSanRes Series, 2011-1. Stockholm Environment Institute (SEI), Stockholm, Sweden. p. 103ff
[10] Hertel, C. (2017): Nutzung von Komposttoiletten auf dem Stuttgarter Kirchentag 2015 als praktisches Beispiel von Nachhaltigkeits-kommunikation in den Bereichen Ressourcenschonung, Stoffstrommanagement, Kreislaufwirtschaft und Klimaschutz des deutschen Kirchentags. p. 30.
[11] Winker, M. et al. (2009): Fertiliser products from new sanitation systems: Their potential values and risks. Bioresource Technology, 100(18), pp. 4090–4096. doi.org/10.1016/j.biortech.2009.03.024
[12] Oliva, J. et al. (2009): Klärschlamm – Materialien zur Abfallwirtschaft. Umweltbundesamt, Klagenfurt, Wien. p. 55.
[13] ibid, p. 56.
[14] Anand, C. K., & Apul, D. S. (2014). Composting toilets as a sustainable alternative to urban sanitation – A review. Waste Management, 34(2), pp. 329–343. https://doi.org/10.1016/j.wasman.2013.10.006; Branstrator, J. (2014). The Barriers To Adopting Composting Toilets Into Use In Urban And Suburban Locations In The United States. Open Access Theses. https://docs.lib.purdue.edu/open_access_theses/304 (20.02.2020)
