Roads, skid trails, abandoned mining lands, or water-restricted forest lands may require restoration of soil physical or chemical properties. Biochar created from waste wood (slash piles) can be used to restore soil quality and hydrologic functions. Bioenergy production from forest biomass offers a means to reduce wildfire hazard fuel levels, decrease insect and disease outbreaks, and reduce the incidence of invasive species while producing a useful source of renewable energy. However, on-site bioenergy production and the subsequent application of biochar to forest sites raise concerns about increasing water repellency, changing nutrient retention and release, or altering belowground processes.
For more information on this topic, see the Science Spotlights Development of a forest biochar spreader and Using biochar to improve soil quality on decommissioned roads.
This project puts the current effort for biomass-to-bioenergy work into perspective by describing the outcomes of the Coram Experimental Forest bioenergy project from the mid-1970s, discussing the current state of slash pile use, and illustrating how fast pyrolysis can be used instead of slash pile burning to improve soil productivity. Although the use of biochar shows promise in many areas, there are many forest soil impacts that still need to be described. For example, laboratory studies have described changes in soil enzymes responsible for decomposition, infiltration rate, and water holding capacity. Field studies have shown no detrimental effects on tree growth, but all of the impacts of how much, where, when, and what kind of biochar to apply still need to be determined. Biochar applications should be considered on a site-specific basis, because not all biochars and soils are similar.
Numerous field and lab studies are ongoing in the inland Northwest that will help determine the most appropriate biochar sources and soil types for applying biochar. In addition to soil restoration, biochar can also be used to sequester carbon to mitigate climate change.