'A mission for fewer emissions'  August 9, 2017 American Society of Agronomy

Summary: Manure is a reality in raising farm animals. Manure can be a useful fertilizer, returning valued nitrogen, phosphorus, and potassium to the soil for plant growth. But manure has problems. Odor offensiveness, gas emissions, nutrient runoff, and possible water pollution are just a few. New methods may reduce these negatives while potentially adding some positives: biochar covers.
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In addition to the inconvenience of odor, manure can release gases connected to air pollution and climate change. Methane, nitrous oxide, ammonia, and hydrogen sulfide are examples. Scientist Brian Dougherty and colleagues researched methods to reduce these negatives while potentially adding some positives: biochar covers. Biochar is plant matter, such as straw, woody debris, or corn stalks, that has been heated to high temperatures in a low- to no-oxygen environment. The result is a black, carbon-rich material similar to charcoal.

Dougherty says biochar is like a sponge. "Biochar provides a structure with lots of empty pore space" he says. "The outer surface may appear small but the interior surface area is absolutely massive. A few ounces of biochar can have an internal surface area the size of a football field. There is a lot of potential there for holding on to water and nutrients."

In addition to its hidden storage capacity, the surface of the biochar tends to have a chemical charge. This gives biochar the ability to attract and hold nitrogen, phosphorus, and potassium ions, metals, and other compounds. Biochar can also float (some types more than others). That attribute means it can trap gases at the water's surface.