Biochar Mitigates Manure-Related Odors and Emissions on Pig Farms
Iowa State University researchers have shown that carbon-rich biochar could be used to mitigate many odors and potentially toxic volatile organic compounds emitted from swine manure.
“The results of this study and related research shows the potential to use biochar treatments to improve air quality inside barns, thus improving worker and animal safety, especially during manure agitation,” says Jacek Koziel, professor of agricultural and biosystems engineering at Iowa State University.
Biochar is obtained from a high-temperature process called pyrolysis of certain types of biomass and biowaste, according to an Iowa State University release. Researchers tested two types of biochar in this study: 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 then placed in lab-scale containers simulating deep pit swine manure storage. The researchers then measured emissions of ammonia, hydrogen sulfide, greenhouse gases and several odorous volatile organic compounds.
The red oak biochar significantly reduced ammonia levels, though researchers note the impact leveled off over time. It also decreased levels of several volatile compounds, including skatole and p-cresol. Both of these compounds 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 release said.
The biochar treatments also reduced levels of the other gases, but not significantly in all the trials. The study notes the effect decreased in most treatments over time.
“The benefits of reapplying the biochar need to be considered since the greatest reduction for ammonia and some more odorous compounds were observed within the first few weeks,” Koziel says.
Biochar’s impacts on gaseous emissions are complex, he adds.
“While biochar can reduce some emissions, our study supports previous research showing that it can increase emissions of some gases, especially some greenhouse gases. In future work, various types of biochar need to be explored based on the desired mitigation effect on targeted gases – or the desired generation effect, such as maximizing methane for energy use,” Koziel says.
He believes the lessons learned from this project can also be used to develop treatments to mitigate gaseous emissions from other types of waste.
“We have shown that biochar mitigates gaseous emissions a lot better than many marketed pit manure additives. We are confident that biochar could perform well when allowed to be tested on farms,” Koziel adds.
In a recent related project, his team observed agronomic benefits to the soil with the applied manure-biochar mixture and lowered the risk of nutrient runoff.
“Biochar has also been shown to be effective in dramatically reducing the bursts of hydrogen sulfide during manure agitation prior to pump out. We have observed this on a lab-scale and are confident that biochar could perform just as well on a farm-scale. If given an opportunity to be tested on-farm, the mitigation of hydrogen sulfide with biochar could potentially save the lives of farmers and livestock,” he says.
The research results were published in Atmosphere, as part of a special issue on livestock odor and air quality. Koziel’s co-authors on the article, “Mitigation of Gaseous Emissions from Swine Manure with the Surficial Application of Biochars" are: Zhanibek Meiirkhanuly, a recent alumni of the Iowa State Environmental Science Graduate Program; in the Department of Agricultural and Biosystems Engineering, Baitong Chen, graduate student, Myeongseong Lee, research associate, and Jisoo Wi, visiting scholar; and with the Bioeconomy Institute at Iowa State, Distinguished Professor Robert C. Brown, Chumki Banik, postdoctoral fellow, and Santanu Bakshi, research scientist; and Andrzej Białowiec, a Fulbright Scholar from Wroclaw University of Environmental and Life Sciences.
Funders for the research included the U.S. Department of Energy and the U.S. Department of Agriculture National Institute for Food and Agriculture.
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