Health risks of using human excrement as fertilizer

Posted: November 12, 2012 in Uncategorized

Concerns such as heavy metals, pharmaceuticals and personal care products (PPCPs) and pathogens potentially contaminating our food has risen some legitimate questions about the safety of using human urine as fertilizer. The next two blogs will be focused on  summarizing the current scientific-literature on associated risked with using humane urine as a fertilizer. Today’s blogs focuses on heavy metals and pharmaceuticals and personal care products and next Monday’s will be on pathogens. The use biosolids (the sludge or remaining solids from waster water treatment plants) will be addressed in a later blog.

Heavy metals and pharmaceuticals and personal care products (PPCPs)

The use of human excrement as fertilizer is a debated subject as people are skeptical of the presences of heavy metals and organic pollutants (Tidaker, Mattsson et al. 2005). For this reason human excrement are not allowed on organic farms in Europe (Tidaker, Mattsson et al. 2005) and in Canada (Martin 2009). Heavy metals enter the body predominantly through food consumption, with some uptake through the skin and lungs, and concentrations vary greatly (Jonsson, Stintzing et al. 2004; Ronteltap, Maurer et al. 2007). Some studies claim human urine does not have hazardous chemical compounds and heavy metals (Ganrot, Dave et al. 2006). Others state that heavy metals in human urine are lower than most chemical fertilizers (Kirchmann and Pettersson 1995; Jönsson, Stenström et al. 1997; Jonsson, Stintzing et al. 2004; Ronteltap, Maurer et al. 2007). There are concerns about the accumulation of heavy metals in the soil over time (Ronteltap, Maurer et al. 2007). Sludge from waste water treatment plants will contain various other compounds from industries and runoff from storm pipes. Urine separation at the source eliminates such contamination. By manipulating the pH, metals that are present could be precipitated out of solution before application to the fields. Table 8 lists some heavy metals concentrations present in human bodies – human urine has the lowest concentrations compared to human faeces and cattle manure (Jonsson, Stintzing et al. 2004).

Table 3 – Concentration of heavy metals (copper, zinc, chromium, nickel, lead and cadmium) in urine, faeces and farmyard manure from organic cattle farms in Sweden in mg/kg wet mass (Jonsson, Stintzing et al. 2004)

Copper

Zinc Chromium Nickel Lead

Cadmium

Urine (mg/kg)

67

30 7 5 1 0
Faeces (mg/kg)

6667

65000 122 450 122

62

Manure (mg/kg)

5220 26640 684 630 184

23

Throughout evolution mammals have been excreting in terrestrial environments and as all mammals produce hormones, vegetation and microbes are adapted to degrading the naturally produced human hormones (Jonsson, Stintzing et al. 2004). Unused pharmaceuticals’ active ingredients are excreted in the urine, average 64% from a screening assay of 212 pharmaceuticals,  and in the feces, average 35% (Jonsson, Stintzing et al. 2004; Lienert, Bürki et al. 2007). The numbers vary greatly, for example radioactive  ingredients do not degrade and 94% is excreted in the urine, while other pharmaceuticals may excrete 6% of their active ingredients through the urine (Lienert, Bürki et al. 2007). Pharmaceuticals have different biodegradation rates in soils: ibuprofen degrades to non-detectible levels in soils and plants after three months, while 53% of the original Carbamazepine present in urine was detected in soil samples three months after application (Winker, Clemens et al. 2010). Interestingly,  consumption of pharmaceuticals is concentrated in developed countries: 15% of the world’s population in rich countries consumes 90% of total medicines (WHO 2012). As developing countries consume on average per capita fewer pharmaceutical products a year (WHO 2012), human urine could be used without concern of pharmaceutical products, but should be monitored as consumption habits may change.

Overall, you can see there is still limited knowledge on how heavy metals and PPCPs present in the urine could be up-taken by plants, diffused into the hydrological system (into the groundwater and/or into the surface water as run off) and into the soils (Lienert, Bürki et al. 2007; Ronteltap, Maurer et al. 2007; Winker, Clemens et al. 2010). The mobility would be influenced by the compounds molecular weight (Winker, Clemens et al. 2010), pH and presences of organic molecules (Ronteltap, Maurer et al. 2007). There is limited published data on the potential risks of consuming plants with PPCPs. Currently there are no set thresholds as to what values of pharmaceutical should be let into the environment through fertilizer application (Ronteltap, Maurer et al. 2007).

More research is required to gain a better understanding of the risks. We have to also look at what is going into our waters as presently most waste water treatments plants are not able to effectively remove PPCPs from the effluent. So the question is: are PPCPs degraded faster on land (exposed to UV) than in our waters? Much more to come on this subject. Thanks for reading and asking hard questions!

References:

Ganrot, Z., G. Dave, et al. (2006). “Recovery of N and P from human urine by freezing, struvite precipitation and adsorption to zeolite and active carbon.” Bioresource Technology 98: 3112-3121.

Jönsson, H., T.-A. Stenström, et al. (1997). “Source separated urine-nutrient and heavy metal content, water saving and faecal contamination.” Water science and technology 35(9): 145-152.

Jonsson, H., A. R. Stintzing, et al. (2004). Guidelines on the Use of Urine and Faeces in Crop Production. EcoSanRes Publication Series. Stockholm, Stockholm Environment Institute. Report 2004-2.

Kirchmann, H. and S. Pettersson (1995). “Human urine – Chemical composition and fertilizer use efficiency.” Fertilizer Research 40: 149-154.

Lienert, J., T. Bürki, et al. (2007). “Reducing micropollutants with source control: substance flow analysis of 212 pharmaceuticals in faeces and urine.” Water science and technology 56(5): 87-96.

Martin, H. (2009). “Introduction to Organic Farming.” Fact Sheet. Retrieved September 19 2012, from http://www.omafra.gov.on.ca/english/crops/facts/09-077.htm.

Ronteltap, M., M. Maurer, et al. (2007). “The behaviour of pharmaceuticals and heavy metals during struvite precipitation in urine.” Water Research 41(9): 1859-1868.

Tidaker, P., B. Mattsson, et al. (2005). “Environmental impact of wheat production using human urine and mineral fertilisers – a scenario study.” Journal of Cleaner Production 15(2007): 52-62.

WHO (2012). Chapter 4. World pharmaceutical sales and consumption. The World Medicines Situation, World Health Organization.

Winker, M., J. Clemens, et al. (2010). “Ryegrass uptake of carbamazepine and ibuprofen applied by urine fertilization.” Science of The Total Environment 408(8): 1902-1908.

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Comments
  1. drunkymunky says:

    That is why i don;t use animal or human extrements as fertilizer :/ I found Polish company producing good quality fertilizers http://blog.pulawy.com/en/ and I buy from them.. and i believe that if you have just a little farm, you can use some organic stuff from food waste 😉

    • Thanks for you comments but remember inorganic fertilizers do have drawbacks: they’re finite sources, production requires high energy consumption and they have impurities- this Wikipedia article does a good job at describing the pros and cons of both synthetic and inorganic fertilizer, check it out: en.wikipedia.org/wiki/Fertilizer. Inorganic fertilizers are not necessarily safer.

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