How Biochar Captures Odors in Air Filtration

Biochar gives filter manufacturers a renewable carbon material for capturing selected odor compounds. Molecules collect on surfaces within its pores, while its surface chemistry helps determine which compounds it holds. Commercial pine biochar has already been tested in a pilot filter treating air from a swine facility.¹

That application puts the carbon directly in the airflow. As air moves through the filter bed, odor compounds come into contact with the biochar and can remain on its surfaces.

Pine biochar in an operating odor filter

USDA researchers ran a filter filled with commercial pine biochar in a swine barn for 21 days. Air leaving the filter contained much lower levels of the measured odor compounds, including compounds that contribute strongly to manure odor. Separate tests with the same pilot system also captured hydrogen sulfide.¹

The research examined individual compounds as well as their contribution to odor. A gas present at a relatively low concentration can have a strong smell, so concentration alone does not tell the whole story. The researchers used odor thresholds to assess that contribution and found a substantial decrease across the filter.¹

This was a bed of commercially produced pine biochar operating in an air-treatment unit. It gives manufacturers a practical example of how wood-derived carbon can move from a bulk material into filtration equipment.

Developing the surface for the gas

Pore space gives molecules places to collect. The chemistry of those surfaces adds another way to influence capture, especially when the target gas reacts with particular chemical groups on the carbon.

Ammonia research makes that distinction clear. Steam activation greatly increased the tested biochars’ surface area without significantly improving ammonia capture. Phosphoric-acid activation, which changed their surface chemistry, produced a much larger improvement.²

Other laboratory work tested biochars made from several plant materials, including wood, against toluene, acetone, and cyclohexane. The materials captured these gases, with performance influenced by both surface area and the organic material remaining after pyrolysis.³

For manufacturers, that creates several routes for development: selecting the starting biomass, adjusting how it is converted into biochar, and further processing the carbon for the intended gas.

A renewable input for filtration development

Wood biochar connects air-treatment media with a renewable source of carbon. Its role can begin with a bulk material for further processing or a fine powder for incorporation into an engineered medium.

Wakefield supplies wood-based biochar inputs and can help with material specifications, samples, packaging, and bulk supply. Explore Water & Air Filtration to compare options for your process.

For facilities working with the organic material itself, biochar in composting offers a related approach: managing some odor compounds while retaining more nitrogen in the compost.