Nth-plant scenario for forest resources and short rotation woody crops: Biorefineries and depots in the contiguous US

Abstract

• Nationwide depots & biorefineries to meet target costs, quality & quantity from woody resources. • Forest residues: trees, tops & limbs. Short rotation crops: poplar, willow, pine, & eucalyptus. • Maximum accessible forest residues at $79.07/dt & $85.51/dt was 103 and 106 M dt at any ash target. • Short rotation woody crops increased total to 153 & 195 M dt at 1% & 1.75% ash & $85.51/dt cost targets. • Woody resources could address 55% of EPA’s goals, 195 M dt/year at $85.51/dt cost & 1.75% ash target. Estimating the US potential of woody material is of vital importance to ensure cost-effective supply logistics and develop a sustainable bioenergy and bioproducts industry. We analyzed a mature conversion technology for woody resources for the contiguous US that takes advantage of economies of scale: the nth-plant. We developed a database to quantify the total accessible woody biomass within a distributed network of preprocessing depots and biorefineries considering both quality specifications for conversion and a target cost to compete with fossil fuels. We considered two categories of woody biomass: 1) forest residues from trees, tops and limbs produced from conventional thinning and timber harvesting operations as well as non-timber tree removal; and 2) short rotation woody crops such as poplar, willow, pine, and eucalyptus. A mixed integer linear programming model was developed to analyze scenarios with woody feedstock blends at variable biomass ash contents and cost targets at the biorefinery. When considering a target cost of $85.51/dry ton (2016$) at the biorefinery, the maximum accessible biomass from forest residues in 2040 remained constant at 106 million dry tons regardless of ash targets. Including short rotation woody crops as part of the blend increased the total accessible biomass to 153 and 195 million dry tons at ash targets of 1% and 1.75%, respectively. We concluded from our analysis that woody resources could address about 55% of EPA’s (Environmental Protection Agency) target of 16 billion gallons of cellulosic biofuel.