Biomass fuel is considered a promising substitute for traditional fossil fuels. Amid a great variety of methods for converting the energy in biomass fuel into usable energy, direct combustion is still the dominant technology employed by industry. Because biomass fuel possess a much wider range of physical and chemical properties than fossil fuel, its combustion behavior is similarly diverse (and typically differs from fossil fuel), with a similar range seen in emissions characteristics. To address the variability the fuel stream imposes on the system, this work endeavors to use numerical modeling to investigate biomass combustion in a stoker boiler to provide physically insightful details while requiring minimal time and effort relative to the traditional experimental approach. In the first part of this work, a comprehensive model was developed to investigate the co-firing of different kinds of biomass including oat hulls, wood chips and natural gas with coal in a stoker boiler located in the Power Plant of the University of Iowa. Later, this model is employed in the optimization of the air supply system and plans for efficiently injecting light weight biomass, such as oat hulls, into the stoker boiler. The other key problem is in NOx prediction and reduction for the stoker boiler. This was by combining a standard CFD model describing the turbulent dynamics and combustion with several sub-models specifically developed for this study to model the fuel bed, fuel particle movement, and fuel gasification. To verify and baseline these sub-models, a series of experiments are performed, including a temperature measurement campaign for coal combustion in the boiler, a chemical lab analysis of oat hull chemical characteristics, an experiment measuring oat hull particles' physical properties, and a high-heating-rate gasification test of oat hulls. In particular, the stoker boiler temperature measurements are unique in the number of points measured and the range of firing conditions. The simulation showed that for the co-firing of oat hulls with coal, the flame temperature decreased with increasing oat hull fraction. The oat hull particles follow the flow and burn in suspension due to their light weight. The simulation showed that increasing injection velocity could slightly reduce the peak temperature and thereby reduce NOx levels. It was also observed that there is a critical velocity above which the trend of decreasing CO2 is reversed. The co-firing of other types of biomass such as wood chips and natural gas in the stoker boiler were also studied. The result of co-firing wood chips shows that adding wood chips decreases the flame. The flame zone is also shortened when compared to pure coal, primarily resulting from a higher oxygen environment above the coal bed due to the high oxygen content of the wood chips. Co-firing natural gas with coal resulted in the high temperature zone shifting from the back wall closer to the front wall, significantly reducing the overall flame length. The level of predicted NOx agreed very well with the experimental data. The simulations showed that injecting Urea with the secondary air system on the front wall can greatly reduce the NOx level inside the boiler for minimal cost and effort.

This work deals with the impact of operating parameters on fine combustion particles formation in the flue gas of biomass combustion device. The research part of the work describes the properties of fine particles, its basic division, impact on human health and the environment. The basic knowledge of the influence of biomass combustion process on fine particles production up to 1 µm in size is summarized. The main part describes the experimental setup for evaluating the size distribution of fine particles. The following section describes the experimental setup with measured results for various combustion parameters in laboratory combustion, automatic boilers, as well as in the manual wood-burning combustion device. The main parameters which were tested were combustion temperature, oxygen amount, type of fuel and geometry of the burned biomass. The impact of individual parameters on the formation of the fine particles is evaluated. The final part of the thesis summarizes the ways in which it is possible to significantly influence the emissions of fine particles by the appropriate choice of combustion operating parameters.

Biomass is a natural resource that is both abundant and sustainable. Its efficient utilization has long been the focus of research and development efforts with the aim to substitute it for fossil-based feedstock. In addition to the production of biofuels (e.g., ethanol) from biomass, which has been to some degree successful, its conversion to high value-added chemicals is equally important. Among various biomass conversion pathways, catalytic conversion is usually preferred, as it provides a cost-effective and eco-benign route to the desired products with high selectivities. The research of this thesis is focused on the conversion of biomass to various chemicals of commercial interest by selective catalytic oxidation. Molecular oxygen is chosen as the oxidant considering its low cost and environment friendly features in comparison with commonly used hydrogen peroxide. However, the activation of molecular oxygen usually requires high reaction temperatures, leading to over oxidation and thus lower selectivities. Therefore, it is highly desirable to develop effective catalysts for such conversion systems. We use kegging-type heteropoly acids (HPAs) as a platform for catalysts design because of their high catalytic activities and ease of medication. Using HPA catalysts allows the conversion taking place at relatively low temperature, which is beneficial to saving production cost as well as to improving the reaction selectivity. The strong acidity of HPA promotes the hydrolysis of biomass of giant molecules (e.g. cellulose), which is the first as well as the most difficult step in the conversion process. Under certain circumstances, a HPA combines the merits of homogeneous and heterogeneous catalysts, acting as an efficient homogeneous catalyst during the reaction while being easily separated as a heterogeneous catalyst after the reaction. We have successfully applied HPAs in several biomass conversion systems. Specially, we prepared a HPA-based bi-functional catalyst (Au/Cs2HPW12O40) that enabled the selective conversion of cellobiose to gluconic acid with a very high yield of 96.4% (Chapter II); we realized a direct oxidative conversion of cellulose to glycolic acid (yield of 49.3 %) in a water medium for the first time, by using a phosphomolybdic acid catalyst (chapter III); we found that a vanadium-substituted phosphomolybdic acid catalyst (H4PVMo11O40) is capable of converting various biomass-derived substrates to formic acid and acetic acid with high selectivity, and under optimized reaction conditions, high yield of formic acid (67.8%) can be obtained from cellulose (chapter IV); we discovered that the vanadium-substituted phosphomolybdic acids can also selectively oxidize glycerol, a low-cost by-product of biodiesel, to formic acid, and interestingly this conversion can be performed in highly concentration aqueous solution (glycerol: water = 50: 50), giving rise to exceptionally high conversion efficiency (chapter V). These results reveal that HPAs are useful and suitable catalysts for selective oxidation of biomass, and that the reaction pathway is largely determined by the type of addenda atom in the HPA catalyst. The optimization of the reaction conditions and processes in these systems are also discussed in this thesis.

Arundodonax (Giant reed Plant) contains cellulose, hemicellulose and lignin and considered as a biomass resources for biofuels. Cellulose is a polymer of several d-glucose linked units coupled with beta-1, 4 glycosidic bonds. The lignin must be broken down to obtain cellulose.Brown and white rot fungusbreak down lignin through a fenton mechanism using hydroxyl radicals. Current work explores degradation of cellulose byisolating microbial communities followed by inoculating 1% carboxymethyl cellulose (CMC) or arundodonax in nutrient media. The microbes demonstrate long-term viability using CMS or arundodonax the sole carbon source.Pretreatment with microbes result in enhanced enzymatic hydrolysis at 50 °C using commercial cellulase over time. The simple dinitrosalicylic acid assay method quantifies glucose, the main product of enzymatic hydrolysis.

Sweetpotato (Ipomoea batatas (L.) Lam.) is one of the major tropical root crops of the world and it is widely distributed throughout the tropical and temperate regions of Africa, Asia and the Americas. During harvest and post-harvest handling, the skin can be separated from the underlying tissue of the storage root. Storage root damage contributed to income losses for producers. To minimize these loses, producers set the skin of the sweetpotato by removal of the vines prior to harvest. New mechanical (undercutting) and cultural (biochar) methods were developed and tested. Mechanical undercutting would sever the feeder roots of the plant causing drought stress and initiate the skin set reaction. Application of biochar was used to change soil physical properties to reduce skinning in storage roots. The new practices may give producers options to increase the storage life of the crop.

Energy issues in the United States are currently receiving a very high priority. There is a strong desire to replace fossil fuels with alternative sources of energy since fuel prices are rising dramatically, and for the harming effect on the environment. Biomass is one of the most promising alternative sources of energy. In this study, hydrothermal liquefaction with alcohol co-solvents was applied on giant miscanthus (Miscanthus giganteus) feedstock. All liquefaction experiments were conducted in 5500 series Parr® reactor. The most important parameters that affect the liquefaction process were studied. The yield of the liquefaction process was determined gravimetrically and the produced bio-oils were characterized. Bio-oil obtained at the optimum conditions was upgraded using different solid acid catalysts and the chemical composition for the upgraded bio-oil was determined. In a new study, the solid acids were added directly during the liquefaction process to produce upgraded bio-oil in one liquefaction/upgrading step.

Rivercane, Arundinaria gigantea, is the native woody evergreen grass that has exhibited rapid population decline since European colonization of North America. Agriculture and urban expansion have reduced this important ecosystem type to remnant populations. This poses challenges to current restoration efforts by minimizing genetic diversity and limiting healthy host sites for propagation. Objectives of this research were to test four methods of establishment that would promote the greatest survivability and growth of propagules. Non-irrigated field studies indicated greatest rivercane growth response when planted in increased shade (60 - 85% light reduction). Monthly plantings indicated that February offered the greatest probability of survival. Application of slow release 19-6-12 fertilizer (33.3 g) enhanced growth, but fertilizer applications are not recommended without adequate soil moisture. Halosulfuron (72.6 g a.i./ha) applications for weed control showed no damage to rivercane plants compared to control.

Metallurgical coke is an important component of the iron and steel industry. It is obtained from high quality coking coals like bituminous coal. However, due to the limited resources and high levels of Green house Gases, alternatives to the product are of high demand. Availability of raw materials is an important factor. The product should have high heating value, strength and lower emissions. Research is being done on form coke technology; to produce high quality substitutes with inexpensive materials like lignite. A biomass-based form coke production process is developed. Two types of raw materials are selected at beginning of process. However, an ideal choice of raw material is evaluated by comparing the quality of the specimens produced from each substance. Various stages of the process are developed and their operating conditions are evaluated. The specimens developed are sent to a test facility to test reactivity and strength after the reaction.

Syngas is an interesting energy source for metallurgical processes, as an energy carrier syngas is an efficient way of utilizing the energy in biomass. Utilizing syngas in fuming processes as a carbon source instead of coal was an approach to minimize carbon dioxide emissions produced in the fuming process. In the fuming process, secondary materials are processed to improve the extraction of copper, lead, and zinc.  The objective of this project was to find a suitable biomass and gasification agent that result in syngas with a high percentage of carbon monoxide and a low percentage of carbon dioxide. Because of the high need of carbon in the fuming process, syngas could be a suitable reduction agent. The most efficient thermo-chemical process for syngas production from biomass is gasification.  The investigated biomass where sawdust, wood, and a co-gasification with a percentage of peat. The gasification agents investigated where carbon dioxide, oxygen, air, and hydrogen. This was investigated by using FactSage8.1 to simulate the gasification and co-gasification of chosen biomasses and gasification agents. Stoichiometric calculations of the fuels and gasification agents were done to get the correct reduction and combustion reactions.  The results from the simulations showed that carbon dioxide was the best gasification agent and gasifying sawdust alone results in the highest simulated levels of carbon monoxide in the gasification temperature between 1000 to 1200 ᵒC.  Other studies showed that biomass gasification with carbon dioxide or a mixture of at least 60 percent of carbon dioxide as a gasification agent was a promising way for energy production and lowering carbon dioxide emissions. It also shows a correlation between increasing carbon dioxide as a gasification agent and higher level of carbon monoxide in the produced syngas. Other studies implied that the maximum level of carbon dioxide that results in the maximum fraction of carbon monoxide and methane was 60 percent.  Each gasification agent investigated have advantages and disadvantages, they lead to different gas composition, by-products, and heating value, which gasification agent to use depends on the result wanted. Carbon dioxide was the gasification agent that shows the best result in a simulated environment, but the same result cannot be guaranteed in real-life experiments, and discrepancies are to be expected. Further study in form of a real-life experiment are needed to compare with the simulated results, as the effects of ash forming elements and test of gasifier are needed.

Surface mining for coal in the Appalachian region has removed over 0.6 million Ha of mixed mesophytic forest. Successful reforestation would be beneficial, but questions remain concerning application of reclamation and reforestation methods on operational scales. Four experiments were performed testing these methods on newly reclaimed and previously reclaimed, but unused, former mines. On newly reclaimed sites, loose grading during reclamation reduced erosion and increased plant community diversity compared to smooth grading. Seeding only annual ryegrass (Lolium multiflorum) for erosion control, along with tree planting, increased plant community diversity and improved survival and growth of hybrid American chestnut (Castanea dentata x Castanea mollissima), compared to conventional seeding. Surface water infiltration was positively correlated with herbaceous ground cover. On older mines, subsoil ripping to alleviate compaction improved tree survival and growth, in some cases, after five growing seasons. Of the three species groups planted, including Eastern white pine (Pinus strobus), mixed native hardwoods had the best survival and hybrid poplar (Populus deltoides x Populus trichocarpa) produced the most biomass. Hybrid American chestnuts survived and grew better when planted as bare-root seedlings than when planted as ungerminated nuts in tree tubes, demonstrating the potential for planting bare-root chestnut seedlings along with other species when reforesting reclaimed surface mines. This can aid in restoring American chestnut, functionally extinct since the blight (Cryphonectria parasitica), to its former range. These cultural practices can be employed to accelerate reforestation of mined lands, but many questions remain about their capability to fully restore ecosystem structure and processes. / Master of Science