9 Search Results

Sustainable fuels for industries that cannot be easily electrified, like aviation and marine, will be crucial to achieving a carbon neutral economy. This work pioneers two green processing pathways to produce a biomass feedstock that is far less viscous at higher solids loadings. This decrease in viscosity could significantly improve the profitability of producing fuels through slurry-based conversion processes like hydrothermal liquefaction or dilute acid pretreatment and bological conversion. Natural biological degradation of corn stover has been shown to lower slurry viscosity by a factor of three and torrefaction has been shown to produce slurries that are 150x less viscousmore » than the original pine residues. Additionally, new insight has been gained into the physical and chemical parameters that impact slurry viscosity. Common parameters in slurry processing, like the average particle size, shear rate, and solids loadings clearly control viscosity and these results are confirmed for biomass. Additionally, new physical parameters like aspect ratio and sphericity as well as chemical parameters like extractives content, non-structural sugars, and zeta potential have also been shown to impact, and be good predictors of, slurry viscosity and processability.« less

MSW is usually contaminated with a variety of undesirable materials (food, chemicals, glass, metal) that can impact downstream applications such as conversion to biofuels. This presentation will showcase two decontamination methods using either a detergent wash or an organic solvent extraction to demonstrate up to 30% increase in biofuel precursor yields for plastic and paper MSW. The economics of the two decontamination methods will also be presented.

Short rotation woody crops have many advantages as perennial bioenergy feedstocks, including high biomass yields, high carbohydrate and low ash contents, and marginal land utilization. Through short rotation coppicing management, these biomass resources can be harvested year round. The challenge of year round harvesting is feedstock quality variability due to leaf content during periods of non-senescence. The low quality leaf fraction results in higher ash and moisture contents and lower carbohydrate content. Mechanical techniques, such as air classification, provide an economically feasible process to separate heterogeneous biomass samples based on particle density, size, and shape. In this work high moisturemore » (>45%) hybrid poplar and shrub willow short rotation crops were air classified using a series of fan speeds for anatomical fractionation of the material. Air classification using an air velocity of ~4.7 m/s removed a majority of the leaf material while retaining 88% and 87% of the hybrid poplar and shrub willow, respectively. At this velocity, the ash content was reduced from 2.34% to 1.67% for hybrid poplar and 2.60% to 2.14% for shrub willow. Concurrently, the carbohydrate content increased from 56.32% to 60.62% and from 54.03% to 55.99% for these same materials. As drying is a cost intensive step for processing high moisture biomass materials, the cost benefits (~$3/Mg dry biomass) for removing low quality, high moisture materials prior to drying were also demonstrated.« less

Feedstock variability is a significant barrier to the scale-up and commercialization of lignocellulosic biofuel technologies. Variability in feedstock characteristics and behavior creates numerous challenges to the biorefining industry by affecting continuous operation and biofuels yields. Recently, feedstock variability is understood and explained largely on the basis of chemical composition. Physical and mechanical properties and behavior of lignocellulosic feedstock in various unit operations, studied through advanced analytical methods, can further explain variability. Such studies will enable us in developing processes and designing equipment to improve operation and conversion performance. In this perspective, we review several advanced analytical methods that measure density,more » moisture content, thermal properties, flowability, grindability, rheology properties, and micromorphological characteristics. We also discuss the correlations and interactions among these properties that reflect the complexity of lignocellulosic biomass as a feedstock and the associated quality metrics and logistics of supplying consistent quality feedstock to a biorefinery. We further examine methods that have not traditionally been used to characterize lignocellulosic feedstocks but have the potential to bridge the gap in our explanation of feedstock variability.« less

Abstract not provided.

Pyrolytic conversion of lignocellulosic biomass utilizes high temperatures to thermally fragment biopolymers to volatile organic compounds. The complexity of the degradation process includes thousands of reactions through multiple phases occurring in less than a second. In this work, the requirements are established for measuring the reaction kinetics of high temperature (>400 °C) biomass pyrolysis in the absence of heat and mass transfer limitations. Additionally, experimental techniques must heat and cool biomass samples sufficiently fast to elucidate the evolution of reaction products with time while also eliminating a substantial reaction during the heating and cooling phases, preferably by measuring the temperaturemore » of the reacting biomass sample directly. Furthermore, these requirements are described with the PHASR (pulse-heated analysis of solid reactions) technique and demonstrated by measuring the time-resolved evolution of six major chemical products from loblolly pine pyrolysis over a temperature range of 400 to 500 °C. Differential kinetics of loblolly pine pyrolysis are measured to determine the apparent activation energy for the formation of six major product compounds including levoglucosan, furfural, and 2-methoxyphenol.« less

This work reports the rheological characterization of hammer and knife-milled lodgepole pine materials as a function of grind size and moisture content. Characterizations included particle size and shape distributions, bulk density, compressibility at 10 kPa uniaxial pressure, elastic recovery from 10 kPa uniaxial pressure, shear strength, effective angle of internal friction, arching in a custom hopper, and feeding performance in volumetric and gravimetric auger feeders. Particle analysis indicates that the width and length distributions of the 3 mm hammer-milled and the 6 mm knife-milled materials are quite similar, and that all the materials have relatively short aspect ratios (< 4).more » Compressibility and elastic recovery both increased with increasing moisture content with both values increasing more than 10% and the effect being most severe for the 3 mm grind. Adding 3 kPa of pressure increased the critical arching width for all hopper arching tests, except for the 25 mm grind material with 20% MC, for which the critical arching width actually decreased with increased pressure. Interestingly, for materials with smaller particle sizes, the volumetric feed rate tends to decrease as moisture increases even though the density of the material increases with moisture content and the auger speeds are the same. Time variability of volumetric feed rate increased dramatically with increasing particle size but the impact of moisture content was not as clear. For nearly all tests, gravimetric auger feeding resulted in better feeding control and substantially decreased time variability in the material feed rate. These tests show that material feed rate and volumetric auger feed rate variability are dependent upon material shear strength, bulk density, and particle size. Shear tests indicate that material strength generally decreased with increasing particle size, although the impact of moisture was not entirely consistent.« less

In this study, terrestrial lignocellulosic biomass has the potential to be a carbon neutral and domestic source of fuels and chemicals. However, the innate variability of biomass resources, such as herbaceous and woody materials, and the inconsistency within a single resource due to disparate growth and harvesting conditions, presents challenges for downstream processes which often require materials that are physically and chemically consistent. Intrinsic biomass characteristics, including moisture content, carbohydrate and ash compositions, bulk density, and particle size/shape distributions are highly variable and can impact the economics of transforming biomass into value-added products. For instance, ash content increases by anmore » order of magnitude between woody and herbaceous feedstocks (from ~0.5 to 5 %, respectively) while lignin content drops by a factor of two (from ~30 to 15 %, respectively). This increase in ash and reduction in lignin leads to biofuel conversion consequences, such as reduced pyrolysis oil yields for herbaceous products as compared to woody material. In this review, the sources of variability for key biomass characteristics are presented for multiple types of biomass. Additionally, this review investigates the major impacts of the variability in biomass composition on four conversion processes: fermentation, hydrothermal liquefaction, pyrolysis, and direct combustion. Finally, future research processes aimed at reducing the detrimental impacts of biomass variability on conversion to fuels and chemicals are proposed.« less