“We combined slurry from a farm in the lab with calcium cyanamide, a chemical that has been used as a fertilizer in agriculture for more than 100 years,” Holtkamp says. “This brought methane production to an almost complete halt.”
Overall, emissions fell by 99 percent. This effect started barely an hour after the addition and persisted until the end of the experiment half a year later. The long effectiveness is important, because slurry is not simply discarded. Rather, it is stored until the beginning of the following growing season and then spread on the fields as a valuable fertilizer. Months of storage are therefore quite common…
But the substance has other advantages as well: It enriches the slurry with nitrogen and thus improves its fertilizing effect. It also prevents the formation of so-called floating layers – these are deposits of organic matter that form a solid crust on the slurry and hinder gas exchange. This crust usually needs to be regularly broken up and stirred in.