OKay, this came up recently after I had gotten my quarterly haircut and we were talking about using hair to clean up oil spills.
I know hair is made up of dead cells. And given that some of us take a long time to crop it, it seems to me that hair takes a long time to degrade, since typically we don’t have a head full of rotting hair. So my question is, how long does it take hair to break down? The amount of hair tossed out every day by salons and shops must be significant and contribute to the landfills.
Hair doesn’t rot on your head because the conditions aren’t right - it’s too dry and it’s protected by the oils exuded by your scalp.
In a landfill, it’s not going to break down very fast, because nothing else does either - the typically anaerobic conditions are not conducive to decay, however, I can’t imagine that cut hair represents even one tenth of a percent of the volume of landfilled refuse - probably not even one hundredth of one percent.
If it’s just buried in soil, hair may rot away in a few years - hair, feathers and ground hoof and horn are sometimes used as fertiliser to be applied when planting trees because they decay over the course of years, releasing nutrients in a slow, sustained fashion.
Finally, although it’s technically true that hair is made from dead cells, this may generate misleading impressions about its structure - hair starts off as cells within the follicle, but by the time it exits the skin, it’s completely dead and its structure has changed so that the cells are almost unrecognisable - their contents having been replaced by fibrous material.