By: Dr Kate Saffin
I am on long term medication (or a course of anti-biotics), will the drugs live on in the compost?
This is a good question as, composting aside, we are currently flushing enormous amounts of pharmaceuticals into our waste water systems. There is quite a lot of research on the subject, particularly relating to veterinary drugs as they will end up in the soil either as excreted or as manure applied to crops.
Much of the research deals with contamination by pharmaceutical waste i.e. by products from production. I am planning a more detailed review but a brief search of the main sources suggests that pharmaceuticals vary in the extent to which they degrade in soil but when composted they degrade to acceptable levels (between 10mg per kg and 100mg per kg depending on the drug) within 20 weeks. This occurred regardless of whether the composting was mesophilic (cool) or thermophilic (hot).
There is evidence that current sewage management systems aren’t necessarily dealing with pharmaceutical waste completely either and that quite a lot are still there at the point at which the waste is apparently ‘treated’ and is being discharged into a water course.
So, the medication you excrete in your poo will probably degrade better in your composting toilet system than flushing it. However, if you are emptying your wee onto land then it is possible it the medication in it won’t degrade thoroughly. In this case the ideal would be for you to be composting both wee and poo (as Joe Jenkins, author of Humanure does); however, this needs more space and more sawdust/cover material and might not be practical if you are a boater or otherwise living off grid on the move. You might like to aim to empty your wee container at an elsan point as far as possible (even though it isn’t perfect).
Key research identified by Joseph Jenkins and online discussion
This article is American but provides a fairly clear summary of medication in waste water that I suspect applies to the UK as well.
A UK based review but draws on worldwide research (2005)
A UK government review, now quite old (2000), but very thorough and technical. However, the executive summary is manageable!