This dissertation proposes a framework in support of biomass supply chain network design. This framework relies in the use of trucks for short distance biomass transportation, and relies in the use of rail for long-haul, and high-volume transportation of densified biomass. A hub and spoke network design model is proposed for the case when biomass is shipped by rail. These models are created and solved for the following problems: 1) designing a biomass supply chain to deliver densified biomass to a coal fired power plant for coiring and 2) designing biomass-to-biorefinery supply chain using rail for long-haul, and high-volume shipment of densified biomass under economic, environmental, and social criteria. The first problem is modeled as a Mixed-Integer Linear Programming (MILP). A Benders’ decomposition-based algorithm is developed to solve the MILP model because its large size makes it difficult to solve using CPLEX. The numerical analysis indicates that the total unit transportation cost from the farm to a coal plant is $36/ton. Numerical analysis also indicates that biomass cofiring is cost efficient compare to direct coal firing if the renewable energy production tax credit is applied and biomass is located within 75 miles from a coal plant. The second problem is also modeled as a MILP mode. This MILP identifies the number, capacity and location of biorefineries needed to make use of the biomass available in the region. A case study is created using data from a number of States in the Midwest USA. The numerical analysis show that 24.38%-26.12% of the target cellulosic biofuel set by the Energy Independence and Security Act of 2007 can be met at delivery cost $4.01 to $4.02 per gallon. The numerical analysis also reveals the tradeoffs that exist among the economics, environmental impact, and social objectives of using densified biomass for production of biofuel. Finally, this dissertation presents a detailed analysis of the rail transportation cost for products that have similar physical characteristics to densified biomass and biofuel. A numbers of regression equations are developed in order to evaluate and quantify the impact of important factors on the unit transportation cost.

An increasing emphasis on mitigating global climate change (global warming) over the last few decades has created interest in a broad range of sustainable or alternative energy systems to replace fossil fuel combustion. Biomass, when harvested responsibly, is a renewable fuel with many uses in replacing fossil fuels. Cofiring biomass with coal in traditional large-scale coal power plants represents one of the lowest risk, least costly, near-term methods of CO2 mitigation. Simultaneously, it is one of the most efficient and inexpensive uses of biomass. Alternatively, biomass can be transformed into useful products through gasification to produce clean syngas for highly efficient gas turbines, or feedstock to produce light gases, fuels, chemicals or other products. A large portion of this investigation focused on the effect of cofiring biomass on the near burner region of a commercial coal flame. This research included first-of-their-kind field measurements of flame structure and particle properties in front of a full-scale burner fired with biomass and coal, including measurements of particle size and composition, gas velocity, composition, and temperature in the near-burner region of multiple cofired flames in a 350 MWe full-scale power plant in Studstrup, Denmark. A novel sampling and analysis technique was developed enabling the estimation of the fraction of biomass in the flow as a function of position and the burnout of biomass and coal particles separately. These data show that biomass particles do not follow gas stream lines to the same extent that coal particles do. This is consistent with the larger sizes, slower heating and reaction rates, and higher momentum of biomass particles. This research also includes first-of-their-kind single particle continuous measurements of particle mass, surface and internal temperature, size, shape, during biomass pyrolysis and gasification. The single particle measurements provided among the most highly resolved and repeatable biomass gasification results reported to date for wood, switchgrass and corn stover. All three samples showed greater gasification reactivity to H2O than to CO2. The experiments included results in both reactants individually and combined. One of the most important findings of this work was the experimental confirmation that as the char particles gasify, their ash fractions increase and reaction rates decrease on both an intrinsic and external surface area basis. The analyses in this work show that this decrease in burnout quantitatively corresponds to the change in the predicted fraction of the surface that is ash and does not reflect any change in organic reactivity. Reaction rate parameters suitable for relatively simple power-law models based on external surface area describe all the data reasonably well.

Increasing concern for energy sustainability has created motivation for the combustion of renewable, CO2 neutral fuels. Biomass co-firing with coal provides a means of utilizing the scaled efficiencies of coal with the lower supply availability of biomass. One of the challenges of co-firing is the burnout of biomass particles which are typically larger than coal but must be oxidized in the same residence time. Larger biomass particles also can increase the length of the radiative region and alter heat flux profiles. As a result, oxygen injection is being investigated as a means of improving biomass combustion performance.An Air Liquide designed burner was used to investigate the impact of oxygen enrichment on biomass combustion using two size distributions of ground wood pellets (fine grind 220 µm and medium grind 500 µm mass mean diameter). Flame images were obtained with a calibrated RGB digital camera allowing a calculation of visible radiative heat flux. Ash samples and exhaust NO were collected for a matrix of operating conditions with varying injection strategies. The results showed that oxygen can be both beneficial and detrimental to the flame length depending on the momentum of the oxygen jet. Oxygen injection was found to improve carbon burnout, particularly in the larger wood particles. Low flow rates of oxygen enrichment (2 to 6 kg/hr) also produced a modest increase in NO formation up to 30%. The results showed medium grind ~500 µm mass mean diameter particle combustion could improve LOI from 30% to 15% with an oxygen flow rate of 8 kg/hr. Flame images showed low flow rates of O2 (2 kg/hr) in the center of the burner with the fine particles produced a dual flame, one flame surrounding the center oxygen jet and a second flame between the volatiles and secondary air. The flame surrounding the center oxygen jet produced a very high intensity and temperature (2100 K). This center flame can be used to help stabilize the flame, increase devolatilization rates, and potentially improve the trade-off between NO and burnout.