Using Forest Residues from Forest Operations
Federal forestland managers have identified 28 million acres of National Forest lands in the western U.S. that are characterized as having unnatural or excessive amounts of woody vegetation, leaving these areas prone to catastrophic wildfires and susceptible to insect attack and degradation.
In addition, approximately 68 million dry tons of forest residues produced during traditional logging and land-clearing operations go uncollected in the U.S. every year. Forest residues include unmerchantable trees, small-diameter trees, tops, limbs and chunks. These residues are often left in the forest or are collected into piles and burned.
Why are forest residues either left or burned in the forest? Two factors are the high cost (approximately more than $50/bone dry ton) of collecting and transporting these residues to end user markets, and the low market prices (approximately $25-40/bone dry ton) paid for delivered forest residues.
Several studies have developed innovative forest biomass operations that effectively improve access to harvesting sites and economic efficiency. However, the inherent inefficiency of transporting low-density and high moisture content biomass feedstock to market still remains a fundamental economic barrier to its increased utilization.
New technologies that are capable of converting previously wasted or underutilized forest residues into high quality and sustainable bioenergy and useful bio-based products are emerging. By using biomass conversion technologies, we can add value to residues in the field while significantly reducing transportation costs.
Unmerchantable materials produced from fuel reduction thinning and restoration operations could be comminuted (i.e., chipped or ground up) to high quality feedstocks for the production of bioenergy and bio-based products. Integration of biomass conversion technologies with in-forest biomass comminution operations can provide an alternative to the expensive and inefficient long distance transport of high moisture, low energy density forest residues. While this concept has been discussed to a large degree within the literature, it has not been achieved because biomass conversion technologies have not been successfully deployed and the low cost production of high quality feedstocks from forest residues remains a significant challenge. Biomass conversion technologies can effectively convert comminuted forest residues into energy fuels with desired characteristics (high energy density, low or no moisture content, and high market value) within the forest, resulting in a significant increase in transportation efficiency and economic feasibility.
In addition, our project will examine improvements in logistics and the development of new tools for the collection and transportation of forest residues.
Effectively utilizing forest residues can offset the costs of forest restoration and fire hazard treatments while facilitating follow-up forest management activities. Further, the use of these bio-based forest products can improve air quality, reduce greenhouse gas emissions, sequester carbon, amend soil, and create employment in rural forestry-dependent communities, while reducing the nation’s reliance on imported fossil fuels.