You often hear claims that your poo is very valuable, that urine is gold, or as the old saying goes, "where there's muck, there's brass". The recent flurry of innovations to treat wastewater and sludge points this way, as excreta can make fertiliser, electricity, protein, charcoal... what is known the sanitation circular economy.
But is it true? A recent study from Cranfield and Mzuzu universities has reviewed the financial value of faecal sludge, i.e. the contents of a toilet pit (often less known than wastewater). Interestingly, there is little actual evidence of this value, as most of the studies analysed had projected rather than actual prices; sometimes assumptions didn't hold and were largely inflated. Most of the reuse is currently done through fertiliser which has a low value. Some emerging technologies like use as cement additivie and Black Soldier Fly larvae could have more value but it's hard to assess their true potential right now: sludge byproducts can be long and expensive to certify.
Realistically, the study finds that you shouldn't expect a value of more than $5 per person per year – unfortunately not quite the circular economy revolution. But see it this way: ff you defecate once per day, it comes to 1 British penny per day. So if peeing is spending a penny, pooping could be earning one.
More information: A Review of the Financial Value of Faecal Sludge Reuse in Low-Income Countries