Biofuel supply chain, market, and policy analysis

Renewable fuel is receiving an increasing attention as a substitute for fossil based energy. The US Department of Energy (DOE) has employed increasing effort on promoting the advanced biofuel productions. Although the advanced biofuel remains at its early stage, it is expected to play an important role in climate policy in the future in the transportation sector. This dissertation studies the emerging biofuel supply chain and markets by analyzing the production cost, and the outcomes of the biofuel market, including blended fuel market price and quantity, biofuel contract price and quantity, profitability of each stakeholder (farmers, biofuel producers, biofuel blenders) in the market. I also address government policy impacts on the emerging biofuel market. The dissertation is composed with three parts, each in a paper format. The first part studies the supply chain of emerging biofuel industry. Two optimization-based models are built to determine the number of facilities to deploy, facility locations, facility capacities, and operational planning within facilities. Cost analyses have been conducted under a variety of biofuel demand scenarios. It is my intention that this model will shed light on biofuel supply chain design considering operational planning under uncertain demand situations. The second part of the dissertation work focuses on analyzing the interaction between the key stakeholders along the supply chain. A bottom-up equilibrium model is built for the emerging biofuel market to study the competition in the advanced biofuel market, explicitly formulating the interactions between farmers, biofuel producers, blenders, and consumers. The model simulates the profit maximization of multiple market entities by incorporating their competitive decisions in farmers’ land allocation, biomass transportation, biofuel production, and biofuel blending. As such, the equilibrium model is capable of and appropriate for policy analysis, especially for those policies that have complex ramifications and result in sophisticate interactions among multiple stakeholders. The third part of the dissertation investigates the impacts of flexible fuel vehicles (FFVs) market penetration levels on the market outcomes, including cellulosic biofuel production and price, blended fuel market price, and profitability of each stakeholder in the biofuel supply chain for imperfectly competitive biofuel markets. In this paper, I investigate the penetration levels of FFVs by incorporating the substitution among different fuels in blended fuel demand functions through “cross price elasticity” in a bottom-up equilibrium model framework. The complementarity based problem is solved by a Taylor expansion-based iterative procedure. At each step of the iteration, the highly nonlinear complementarity problems with constant elasticity of demand functions are linearized into linear complimentarity problems and solved until it converges. This model can be applied to investigate the interaction between the stakeholders in the biofuel market, and to assist decision making for both cellulosic biofuel investors and government

Colonization pattern of crop plants by endophytic fungi

Endophytes are fungi or bacteria occurring inside plant tissues without causing any apparent symptoms in the host plants. Fungal endophytes are quite common in nature; some of them are able to work as bio-control agents to defend insects, nematodes and plant pathogens. As endophytic fungi can continuously be presented and expressed throughout the crop cycle. Such an endophytic expression of the entomopathogens within the plant system is expected to be more advantageous than external application of bio-agents. Fungi Beauveria bassiana (strain ATP01, ATP02, Bb03032, EABb04/01-tip and Naturalis) and Trichoderma harzianum (strain T39 and Tu) have been already proved and well-studied as endophytes in host plants to work against either herbivores or plant pathogens.  This study aimed at introducing B. bassiana and T. harzianum to host plant cabbage and faba bean as endophytes. The distribution of the endophytic fungi was investigated by selective medium re-isolation and q-PCR with the comparison ofdifferent inoculation methods.. Bioassays were conducted to test the influence of the fungal endophytic colonization on herbivores.  Main findings: Both B. bassiana and T. harzianum were able to establish in the host plants as endophytes. By different inoculation methods, various colonization patterns were found where B. bassiana had the best fungal establishment in leaf inoculated treatments while T. harzianum had the better performance in below ground inoculated trials (root inoculation and seed inoculation).  With root and seed inoculation, both B. bassiana and T. harzianum had a higher colonization level in faba bean compared with cabbage. The existence of endophytic fungi influenced the development and behavior of the diamondback moth (DBM) Plutella xylostella. DBM larvae feeding on detached B. bassiana (strain ATP02) inoculated leaf had a slower development and a lower body weight. In the dual-choice oviposition choice experiments the DBM significantly preferred control plants to B. bassiana inoculated plants. At a high colonization level, endophytic T. harzianum was able to affect both the feeding choice and oviposition choice in the dual-choice bioassays, although T. harzianum could not kill DBM larvae directly and the endophytic T. harzianum also did not affect the DBM larvae development significantly.  The endophytic establishment of T. harzianum strongly influenced the volatile emission. The green volatile compounds content decreased while the percentage composition of terpenes increased in T. harzianum inoculated treatments.

Biofuel supply chain and bottom-up market equilibrium model for production and policy analysis

Renewable fuel is attracting increasing attention as a substitute for fossil based energy. The US Department of Energy (DOE) has identified pyrolysis based platforms as promising biofuel production pathways. Although the biofuel market remains in its early stage, it is expected to play an important role in climate policy in the future in the transportation sector. In this thesis, we will first propose a biofuel supply chain model to study the supply chain design and operational planning for advanced biofuel production, then a biofuel market model is developed to study the interactions between farmers, biofuel producers, blenders, and consumers along the biofuel supply chain in the market competitive setting. For the biofuel supply chain model, the focused production pathway is corn stover fast pyrolysis with upgrading to hydrocarbon gasoline equivalent fuel. The model is formulated with a Mixed Integer Linear Programming (MILP) to investigate facility locations, facility capacities at the strategic level, and feedstock flow and biofuel production decisions at the operational level. In the model, we accommodate different biomass supply and biofuel demand scenarios with supply shortage penalty and storage cost for excess biofuel production. Numerical results illustrate the supply chain design and operational planning decision making for advanced biofuel production. Unit costs for advanced biofuel under changing of scenarios are also analyzed. The case study demonstrates the economic feasibility of biofuel production at a commercial scale in Iowa. The second part of the thesis work focuses on analyzing the interaction between the key stakeholders along the supply chain. A bottom-up equilibrium model is built for biofuel market to study the competition in the advanced biofuel market, explicitly formulating the interactions between farmers, biofuel producers, blenders, and consumers. The model simulates the profit maximization of multiple market entities by incorporates their competitive decisions in farmers\u27 land allocation, biomass transportation, biofuel production, and biofuel blending. As such, the equilibrium model is capable of and appropriate for policy analysis, especially for those that have complex ramifications and result in different reactions from multiple stakeholders. For example, the model can be used to analyze the impact of biofuel policies on market outcomes, pass-through of taxes or subsidies, and consumers\u27 surplus or producers\u27 profit implications. The equilibrium model can also serve as an analytical tool to derive market prices of biomass, advanced biofuel, and the value of the Renewable Identification Numbers. Moreover, the model can be used to analyze the impact of the market structure or firms\u27 ownership setting that may arise due to oligopoly competition in the advanced biofuel market

Graphs with many independent vertex cuts

The cycles are the only $2$-connected graphs in which any two nonadjacent vertices form a vertex cut. We generalize this fact by proving that for every integer $k\ge 3$ there exists a unique graph $G$ satisfying the following conditions: (1) $G$ is $k$-connected; (2) the independence number of $G$ is greater than $k;$ (3) any independent set of cardinality $k$ is a vertex cut of $G.$ The edge version of this result does not hold. We also consider the problem when replacing independent sets by the periphery

Ultimate boundary estimations and topological horseshoe analysis of a new 4D hyper-chaotic system

In this paper, we first estimate the boundedness of a new proposed 4-dimensional (4D) hyper-chaotic system with complex dynamical behaviors. For this system, the ultimate bound set Ω1 and globally exponentially attractive set Ω2 are derived based on the optimization method, Lyapunov stability theory and comparison principle. Numerical simulations are presented to show the effectiveness of the method and the boundary regions. Then, to prove the existence of hyper-chaos, the hyper-chaotic dynamics of the 4D nonlinear system is investigated by means of topological horseshoe theory and numerical computation. Based on the algorithm for finding horseshoes in three-dimensional hyper-chaotic maps, we finally find a horseshoe with two-directional expansions in the 4D hyper-chaotic system, which can rigorously prove the existence of the hyper-chaos in theory