The USDA Forest Service is driving the development of new technology for making biochar, a carbon rich soil amendment that can help restore degraded soil. Air curtain burners, also called air curtain incinerators or fire boxes, were designed principally as a pollution control device for open burning. The Rocky Mountain Research Station is partnering with industry and land managers to develop new air curtain burners that turn piles of unmerchantable wood waste into biochar.

Rocky Mountain Research Station soil scientist Debbie Page-Dumroese and others are working with Air Burner Inc. under a Cooperative Research and Development Agreement to innovate ways to create useful biochar from woody biomass. The team was recently awarded a patent for their mobile biochar production system designed for their air curtain burner. The new system is called the CharBoss.

The CharBoss has the capability to separate charcoal from the burning biomass using a mobile through-put method, or conveyor belt, that expels the biochar from the burner and subsequently quenches it. Page-Dumroese says, “Mobile processing of woody residues into biochar means that there will be less open burning resulting in fewer slash piles burned, less smoke and particulates emitted, and ultimately a higher value product.”

The CharBoss has fewer size and moisture content limitations than existing mobile biochar production machines, and it can consume material from most burn piles with minimal to no preparation. The new technology immediately quenches the coals to reduce the risk of fire and increase the rate of application or transport to another site. The team’s current machine burns at a rate of 1 to 2 tons per hour.

Recent Rocky Mountain Research Station research shows how biochar can enhance forest resilience and tree seedling quality. One goal of the CharBoss development is to recover or offset costs of land treatments to reduce non-merchantable vegetation by producing a product that has value for augmenting and restoring degraded soils. On Oct. 5, 2020, the CharBoss team held a field demonstration in Bandon, Oregon, to show off how the equipment can be used to combat the invasive woody shrub gorse; thereby reducing the biomass into a product that can aid in restoration. The CharBoss team recorded the demonstration and it is available online.

The mobile CharBoss system provides a landscape management opportunity and offers a value-added product for vegetation management activity that previously had none. Page-Dumroese says, “Using mobile processing helps rural economies by providing a way to get people into the woods doing forest restoration, applying biochar to forest soils or using it to reclaim local abandoned mine sites.” This new mobile biochar technology provides forest managers with opportunities not only to remove unwanted biomass, but to benefit from the biochar created in the process.