Lithic Analysis of an Early Archaic Assemblage on the Great Plains: The Spring Creek Site (25FT31)

Early Archaic sites on the Great Plains are few in number and often little studied and poorly reported, as they are almost always found via salvage or compliance archaeology. Of those Early Archaic sites that have been studied, rarely has the recovered debitage been analyzed in detail nor have tools been fully evaluated for use-wear. This thesis describes the lithic assemblage from the Spring Creek (25FT31) site located in southwestern Nebraska. As one of two important early sites in the state, detailed lithic analysis will complement the thorough analysis of faunal remains conducted in the 2000s. This thesis presents the methods used to complete debitage and tool analyses including use-wear analysis. By using lithic analysis along with fauna analysis, archaeologists can gain better understanding of the relationship of the resources procured by Early Archaic hunter-gatherers on the Great Plains landscape. Advisor: Phil R. Gei

Pyrolysis kinetics of hydrochars produced from brewer’s spent grains

The current market situation shows that large quantities of the brewer's spent grains (BSG)-the leftovers from the beer productions-are not fully utilized as cattle feed. The untapped BSG is a promising feedstock for cheap and environmentally friendly production of carbonaceous materials in thermochemical processes like hydrothermal carbonization (HTC) or pyrolysis. The use of a singular process results in the production of inappropriate material (HTC) or insufficient economic feasibility (pyrolysis), which hinders their application on a larger scale. The coupling of both processes can create synergies and allow the mentioned obstacles to be overcome. To investigate the possibility of coupling both processes, we analyzed the thermal degradation of raw BSG and BSG-derived hydrochars and assessed the solid material yield from the singular as well as the coupled processes. This publication reports the non-isothermal kinetic parameters of pyrolytic degradation of BSG and derived hydrochars produced in three different conditions (temperature-retention time). It also contains a summary of their pyrolytic char yield at four different temperatures. The obtained KAS (Kissinger-Akahira-Sunose) average activation energy was 285, 147, 170, and 188 kJ mol(-1) for BSG, HTC-180-4, HTC-220-2, and HTC-220-4, respectively. The pyrochar yield for all hydrochar cases was significantly higher than for BSG, and it increased with the severity of the HTC's conditions. The results reveal synergies resulting from coupling both processes, both in the yield and the reduction of the thermal load of the conversion process. According to these promising results, the coupling of both conversion processes can be beneficial. Nevertheless, drying and overall energy efficiency, as well as larger scale assessment, still need to be conducted to fully confirm the concept

Is Steam Explosion a Promising Pretreatment for Acid Hydrolysis of Lignocellulosic Biomass?

For the production of sugars and biobased platform chemicals from lignocellulosic biomass, the hydrolysis of cellulose and hemicelluloses to water-soluble sugars is a crucial step. As the complex structure of lignocellulosic biomass hinders an efficient hydrolysis via acid hydrolysis, a suitable pretreatment strategy is of special importance. The pretreatment steam explosion was intended to increase the accessibility of the cellulose fibers so that the subsequent acid hydrolysis of the cellulose to glucose would take place in a shorter time. Steam explosion pretreatment was performed with beech wood chips at varying severities with different reaction times (25–34 min) and maximum temperatures (186–223 °C). However, the subsequent acid hydrolysis step of steam-exploded residue was performed at constant settings at 180 °C with diluted sulfuric acid. The concentration profiles of the main water-soluble hydrolysis products were recorded. We showed in this study that the defibration of the macrofibrils in the lignocellulose structure during steam explosion does not lead to an increased rate of cellulose hydrolysis. So, steam explosion is not a suitable pretreatment for acid hydrolysis of hardwood lignocellulosic biomass

Supercritical Water Gasification of Biomass in a Ceramic Reactor:Long-Time Batch Experiments

Supercritical water gasification (SCWG) is an emerging technology for the valorization of (wet) biomass into a valuable fuel gas composed of hydrogen and/or methane. The harsh temperature and pressure conditions involved in SCWG (T > 375 °C, p > 22 MPa) are definitely a challenge for the manufacturing of the reactors. Metal surfaces are indeed subject to corrosion under hydrothermal conditions, and expensive special alloys are needed to overcome such drawbacks. A ceramic reactor could be a potential solution to this issue. Finding a suitable material is, however, complex because the catalytic effect of the material can influence the gas yield and composition. In this work, a research reactor featuring an internal alumina inlay was utilized to conduct long-time (16 h) batch tests with real biomasses and model compounds. The same experiments were also conducted in batch reactors made of stainless steel and Inconel 625. The results show that the three devices have similar performance patterns in terms of gas production, although in the ceramic reactor higher yields of C2+ hydrocarbons were obtained. The SEM observation of the reacted alumina surface revealed a good resistance of such material to supercritical conditions, even though some intergranular corrosion was observed

Processing Miscanthus to high-value chemicals: A techno-economic analysis based on process simulation

Thermochemical biorefineries for the production of chemicals and materials can play an important role in the bioeconomy. However, their economic viability is often questioned under the premise of the economy of scale. This paper presents a regional, modular biorefinery concept for the production of the platform chemicals hydroxymethylfurfural (HMF), furfural and phenols from the lignocellulosic perennial miscanthus, which can be cultivated on marginal and degraded areas. The paper focuses on the question of the minimum selling price of HMF and the optimal plant size for this purpose, using the region of Baden-Württemberg, Germany, as an example. Based on small pilot plant results, a scalable process simulation was created via AspenPlus. This allows different scenarios and process combinations of this multi-output biorefinery concept to be compared with each other. Using this, a minimum sales price for the main product HMF is calculated using methods of dynamic investment cost calculation according to the net present value method. Based on this, the plant capacity was scaled. The scenarios and sensitivity analyses show that, with an accuracy of ±15%, regional biorefineries could already offer platform chemicals at prices of 2.21–2.90 EUR/kg HMF at the current stage of development. This corresponds to three to four times the price of today\u27s comparative fossil base chemicals and is thus a competitive option from the authors’ point of view. The local biomass and the heat prices were identified as the main influencing factors. As a result, the selection of the location will have a decisive influence on the economic viability of such concepts in the case of further development and optimization of the process in first demonstration plants

Hydrothermal carbonization of fructose—effect of salts and reactor stirring on the growth and formation of carbon spheres

Hydrothermal carbonization (HTC) has become a promising technology for the production of hydrochar and carbon spheres. Several studies indicate a strong dependency of the reaction conditions on the sphere diameter. The usage of additives, such as salts, is one possibility to increase the size of the spheres. However, the growth mechanism which leads to larger particles is not fully understood. In this work, kinetic studies of HTC with fructose were performed with different salts as additives. The growth of the particles (the increase in size) has been compared to the formation rates (increase in yield) of hydrochar by using the reaction rate constants from the kinetic model. The results indicate that the acceleration of the growth rate is independent of the formation rate. It is therefore assumed that coagulation, as a growth mechanism, took place. With longer reaction times, the particles reached a stable particle size, independently from the added salts; therefore, it was assumed that the particles underwent some sort of solidification. The state of matter can therefore be described as an intermediate state between liquid and solid, similar to mesophase pitch. Experiments with a stirrer resulted in squashed particles, which supports the model, that the particles exhibit emulsion-like behavior

Properties of Hydrochar as Function of Feedstock, Reaction Conditions and Post-Treatment

Hydrothermal carbonization (HTC) is a promising technology to convert wet biomass into carbon-rich materials. Until now, the chemical processes occurring and their influence on the product properties are not well understood. Therefore, a target-oriented production of materials with defined properties is difficult, if not impossible. Here, model compounds such as cellulose and lignin, as well as different definite biomasses such as straw and beech wood are converted by hydrothermal carbonization. Following this, thermogravimetic (TGA) and FTIR measurements are used to get information about chemical structure and thermal properties of the related hydrochars. Some of the isolated materials are thermally post-treated (490 °C and 700 °C) and analyzed. The results show that at “mild” HTC conversion, the cellulose part in a lignocellulose matrix is not completely carbonized and there is still cellulose present. Thermal post-treatment makes the properties of product materials more similar and shows complete carbonization with increase aromatic cross-linking, proven by TGA and FTIR results

Adsorption and recovery of phosphate from aqueous solution by the construction and demolition wastes sludge and its potential use as phosphate-based fertiliser

This study aimed to investigate phosphate removal from aqueous effluents by an inorganic sludge from the inert part of construction and demolition wastes (CSW) as adsorbent. It is also discussed the application of the loaded P adsorbent as potential fertiliser. The CSW was also thermally treated at 800¿°C for 2¿h (CSW-T), and its influence in the P removal was also investigated. The characterisation techniques highlighted low porosity on CSW and CSW-T adsorbents and that they are mainly formed by oxides which could enhance the P uptake and recovery. In pH experiments, P adsorption increased as initial pH increased, at pH higher than 7.8 the P removal sharply increased due to the formation of calcium phosphate precipitate. The mechanism of the P adsorption onto CSW indicated that the process was mainly controlled by chemical bonding or chemisorption. The results showed that CSW-T was more effective for P removal in comparison to CSW based on the Liu isotherm, the maximum sorption capacity attained was 24.04 (CSW) and 57.64¿mg¿g-1 (CSW-T). Based on the Avrami’s kinetic models, the time for attaining 95% of saturation was 212.6 (CSW), and 136.6¿min (CSW-T). CSW and CSW-T showed the highest phosphate-removal performance among many adsorbents found in the literature; therefore, this kind of waste can be used widely as an inexpensive phosphate-recovery adsorbent. Besides, the P loaded adsorbents could be used as potential fertilisers which could be an interesting and efficient way of reuse for this waste.Peer ReviewedPostprint (published version