Advanced Woody Biomass Logistics for Co-Firing in Existing Coal Power Plant: Case Study of the Great Lakes States

Abstract

One of the core decisions on securing the supply of biomass to co-firing power plants is the design of a proper logistics system. Though technologies have been developed to improve the characteristics of feedstock, their effects in the logistics systems have received less attention. This paper compares the conventional woody biomass logistics system with the advanced woody biomass logistics system that includes the torrefaction process to upgrade the feedstock. More specifically, this study uses a mixed integer linear program to integrate conventional and advanced biomass logistics and applies them to a case study of 26 coal power plants in the Great Lakes states to determine the most feasible logistics system for each plant. The results revealed that the amount of cost savings from the advanced woody biomass logistics depends on the capacity and location of the power plant. To categorize the cost savings of individual plants, it was found that plants can be divided into seven groups based on three parameters: 1) annual coal tonnage shipped (total capacity), 2) availability of biomass in the vicinity, and 3) average distance from biomass collecting sites. Overall savings from advanced logistics were small, but plants within each of the groups demonstrated similar cost reductions. The sensitivity analysis showed that trucking costs and feedstock purchasing costs were most sensitive to variation. From torrefaction effects, energy content after torrefaction had more significance than mass reduction.

Optimal Level of Woody Biomass Co-Firing with Coal Power Plant Considering Advanced Feedstock Logistics System

“…Table A2. Capital and operation costs of conventional and advanced logistics for woody biomass co-firing (Ko and Lautala [36]).…”

“…In the earlier study, the co-firing ratio was kept fixed and changes in advanced logistics system costs were calculated, based on the ±10% cost change of the parameters identified above. Based on those analyses, biomass transportation cost was one of the most sensitive factors for cost variation at the fixed co-firing ratio [36]. However, as indicated in Figure 9, torrefaction cost is more critical for selecting the optimal level of biomass co-firing.…”

“…Majority of data collection and pre-processing is based on Ko and Lautala [36] which also includes a detailed description of pre-processing steps. The procurement areas for woody biomass feedstock cover softwood sawmills (for mill residues) and collection points (for forest residues) located in the centroid of each county within the 16 states that cover all potential feedstock origins (Figure 4).…”

“…All spatial analysis, such as distances between origin-destination (O/D) pairs, are determined in the Network Analyst of ArcGIS 10.5 based on actual road and rail network provided by the US Department of Transportation [37]. Values for the following parameters are taken from Ko and Lautala [36], and provided at Tables A1 and A2 in Appendix A.…”

“…However, as indicated in Figure 9, torrefaction cost is more critical for selecting the optimal level of biomass co-firing. One interesting aspect of the sensitivity analysis outcomes is to compare them with sensitivity analysis conducted in an earlier study [36]. In the earlier study, the co-firing ratio was kept fixed and changes in advanced logistics system costs were calculated, based on the ±10% cost change of the parameters identified above.…”