Iowa State researchers show biochar use to mitigate odors

In Iowa, a new study from Iowa State University shows that carbon-rich biochar could be used to mitigate many odors and potentially toxic volatile organic compounds emitted from swine manure.

The research team tested two types of biochar with different characteristics: biochar from red oak and a highly alkaline, porous biochar made from corn stover. Three 30-day trials were conducted with a thin layer of the biochars applied on the surface of swine manure collected from three Iowa farms. The manure was placed in lab-scale containers designed to simulate deep pit swine manure storage. The researchers then measured emissions of ammonia, hydrogen sulfide, greenhouse gases and several odorous volatile organic compounds.

The biochar worked – at varying levels. The red oak biochar, especially. It significantly reduced ammonia levels (from 19–39%), though the impact leveled off over time. It also significantly decreased levels of several volatile compounds, including skatole (74–95%) and p-cresol (from 66–78%). Both are signature components of swine manure’s odor, and p-cresol can be hazardous if high levels are inhaled or absorbed through the skin.

The biochar treatments also reduced levels of the other gases, but not significantly in all the trials, and, in most cases, the effect decreased over time.