In 1669, a financially desperate Hamburg merchant and part-time alchemist named Hennig Brand became obsessed with human urine. Early modern alchemists generally believed in transmutation, whereby base metals such as lead could be transformed into precious metals, typically gold. Their main goal was to find the philosopher’s stone, which was not, as the name might suggest, a literal rock, but a substance that could transmute metals.
Brand was convinced that the secret of the philosopher’s stone lay hidden in the golden colour of urine. He collected it in large vats, thousands of litres of the stuff, which he left to putrefy and then boiled down to a thick, dark residue. He, alas, found no gold. What he found instead, glowing faintly in the dark of his workshop, was a waxy white substance that could burst into flame when exposed to air. Brand had isolated phosphorus, a name derived from the Greek phosphoros, meaning light-bringer: the first element discovered since antiquity whose discoverer we can name.
Brand had spent considerable time and money attempting to wrangle a fortune out of human waste. Although he did not find gold, he eventually sold the recipe for 200 thalers. This was a respectable windfall, perhaps equivalent to a couple of years’ earnings for a skilled worker, but a poor price for the monopoly on one of the most spectacular chemical secrets in Europe. The recipe was refined and improved, not least by removing Brand’s insistence on allowing urine to become so putrid that it bred worms. It turned out that fresh urine was quite sufficient. In 1680, Robert Boyle developed his own method for producing phosphorus and used it to ignite sulphur-tipped splints, a forerunner of the modern match.
By 1769, it had become obvious that other, more hygienic sources were available. Bones are rich in calcium phosphate, and bone ash became the primary raw material for phosphorus production. Today, phosphorus is mostly obtained from mined phosphate rock. But there is a neat irony in its origin story. Phosphorus was first distilled from waste by a man who mistakenly thought it would yield gold, and 3½ centuries later, we often treat it as waste again, rather than as a valuable commodity.
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This matters because phosphorus is finite and has no substitute. It is part of the irreplaceable scaffolding of every living cell. It is in DNA, RNA, ATP, cell membranes, bones and teeth. In 2024, an analysis of EU import data put extra-EU imports of phosphorus fertiliser and phosphate at close to €4 billion, with nearly €1 billion coming from Russia. And yet we have abundant quantities of it here. So much, in fact, that excess phosphorus is one of the main causes of Lough Neagh’s algal bloom crisis.
Modelling of Lough Neagh attributes somewhere between 56 and 61 per cent of the phosphorus entering the lough to agriculture, with much of the rest coming from wastewater treatment and septic tanks. And because the wider Lough Neagh–Lower Bann catchment covers more than 5,000sq km and reaches across the Border into Monaghan, this is not a problem any single jurisdiction can fence off.
Agriculture is responsible for almost two-fifths of Ireland’s greenhouse gas emissions, much of it methane from the digestive systems of cattle. Anaerobic digestion is one part of tackling that. Capture methane from slurry and food waste in a sealed tank, burn it or scrub it into biomethane for the gas grid, and a climate liability can become a source of renewable energy. Ireland has committed to up to 5.7 terawatt-hours of indigenous biomethane by 2030 and has published a National Biomethane Strategy to get there.
There is, of course, a catch. Phosphorus cannot simply be burned or digested away. What comes out of the tank, the digestate, still contains the phosphorus that went in, but now in a concentrated material that has to go somewhere. If digestate is spread back on to land in catchments already overloaded with phosphorus, it risks becoming a more industrialised version of the same process that is choking Lough Neagh.
But there is an alternative model. If anaerobic digesters are conceived as hubs that gather manure from many farms, produce biomethane, and then process the digestate into a refined, transportable fertiliser, they become a means of taking phosphorus out of catchments that have too much of it while supplying the gas grid from an indigenous source.
In that sense, this is not simply an agricultural issue. It is an issue of policy, infrastructure and co-ordination. A sustainable economy for this island has to be circular, and ensuring that resources can move effectively between both jurisdictions is as important for energy security and decarbonisation as it is for saving Lough Neagh.
- Stuart Mathieson is research manager with InterTradeIreland
