You’ve undoubtedly heard of the California gold rush of 1849. But any mention of the “coprolite rush” in southern England that took place around the same time would probably draw blank stares. Yet digging for coprolites in the fields of Bedfordshire and Cambridge probably had a greater effect on society than panning for gold in California.
So, what are coprolites? The term, from the Greek “kopros” for “dung,” and “lithos,” for “stone,” was coined in 1829 by the Reverend William Buckland, first professor of geology and mineralogy at the University of Oxford. Buckland had identified some mysterious stones he discovered on a geological excursion as fossilized animal droppings. Before long, it became clear that this was not an isolated find; the land was full of thick seams of the fossilized remains of animals that had succumbed to a major rise in sea level millenniums earlier. Fossilization occurs when the empty spaces within a buried organism fill with water rich in minerals that then combine with the organism’s natural chemicals to form a solid deposit. In the case of coprolites, that deposit is calcium phosphate. And that is one important chemical. Indeed, when it comes to feeding the world, it is essential.
Phosphorus is a vital element for all living organisms. It is a component of biomolecules such as DNA, the classic “blueprint” for life, as well as of ATP, the molecule that transports chemical energy in cells. Bones and tooth enamel are made mostly of hydroxyapatatite, which is a complex form of calcium phosphate. Where does all the phosphorus we need come from? Basically from plants that we either eat directly, or indirectly through meat. And where do plants get their phosphorus? From the soil.
The connection between the composition of soil and a plant’s nutrient needs was first formulated in a systematic fashion by the noted German chemist Justus von Liebig early in the 19th century. Liebig was concerned that farm production could not keep pace with the growth of the population unless crop yields could be increased. Being a master at chemical analysis, Liebig managed to determine the chemical composition of many plants and concluded that for growth they had to absorb a number of elements from the soil, with phosphorus being the crucial limiting factor. It didn’t matter if there were enough of the other nutrients; an insufficient supply of phosphorus would stunt growth.
In his classic 1840 work titled Organic Chemistry and Its Applications to Agriculture and Physiology, Liebig provided a formula for the combination of minerals he believed should be added to soil to replenish its nutrients, emphasizing the importance of “rock phosphate,” a naturally occurring form of calcium phosphate. This was really the beginning of what might be called scientific farming, a concept that appealed to John Bennet Lawes, a Hertfordshire landowner who decided to test Liebig’s theory. And who better to help with the experiment than Henry Gilbert, a chemist who had trained under Liebig in Germany?
Even before he heard of Liebig’s work, Lawes was aware of the possibility of fortifying the soil with calcium phosphate. He knew that some time in the early 1800s farmers had discovered that waste bone shavings dumped by Sheffield knife manufacturers made the soil more fertile. This had actually precipitated a frantic search for crushed bones, with battlefields being scoured and mummified cats from Egyptian pyramids and skeletons from Sicilian catacombs being imported into England.
Lawes knew that bones were essentially a source of calcium phosphate, so this meshed with Liebig’s theory of fertilization. But when he tested “rock phosphate,” he found it to be relatively insoluble, making the absorption of phosphorus by a plant’s roots inefficient. He wondered whether the solubility of calcium phosphate could somehow be increased, and eventually discovered that treating the bones with sulphuric acid did exactly that. “Super phosphate of lime,” as the novel substance was christened, turned out to be amazing, making Lawes’s turnips grow at an unprecedented rate. It was now time to capitalize on the discovery with the launch of the Lawes Artificial Manure Co.
Liebig did not take the challenge to his authority by a “mere farmer” well — and proceeded to sue Lawes, claiming that he had actually come up with the idea of dissolving calcium phosphate in sulphuric acid first. Lawes won the suit, and with that William Buckland’s discovery of coprolites took on new importance. Here was a ready, easily available source of calcium phosphate. By the 1860s, digging for coprolites became a huge industry in Bedfordshire and Cambridgeshire, particularly around the town of Shillington.
Harvesting coprolites was hard work, as was separating the fecal remains from clay in wash mills. And treating the residual powder with sulphuric acid was a nasty job, resulting in many accidents. No wonder that wages for coprolite workers were higher than for agricultural labourers. The men spent money freely, especially in the numerous pubs that opened. Coprolite miners turned out to be a huge boost to the local economy with blacksmiths, carpenters, boot makers and particularly brewers benefiting. But there were also reports of drunkenness, theft, rape and assault.
The boon and the coprolite industry itself skittered to a halt at the end of the century as Europe became flooded with cheap fertilizer made from phosphate deposits that had been discovered in the United States. Today, there is concern that these deposits will soon run out and that the world will face a fertilizer crisis. Since humans excrete a lot of phosphorus, there are major efforts being made to recover phosphorus compounds through sewage treatment. Under the right conditions, magnesium ammonium phosphate, or “struvite,” an effective fertilizer, can be extracted from waste water. Struvite may be this century’s coprolite.
Today, there is virtually no vestige of what at one time was a thriving industry in England, although there still is a Coprolite St. in Ipswich. Actually, one other curious reminder remains. Before 1881, the name of Shillington was actually “Shitlington,” but the spelling was supposedly changed to prevent a shock to Queen Victoria’s ears should her majesty show some interest in the coprolite industry.