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The effect of nanoclay on the plane-strain fracture behavior of pristine High density polyethylene (HDPE) and recycled HDPE blends was studied using the essential work of fracture (EWF) concept. The failure mode of EWF tested specimens was found to be associated with the specific non-EWF ([β.sub.B][w.sub.p,B]). Adding 6-wt% of nanoclay to pristine HDPE and 2-wt% to recycle-blends greatly decreased the [β.sub.B][w.sub.p,B] values and led to a transition from ductile to brittle failure mode. A fractographic study revealed that the difference in failure modes was caused by the changes in micro and macro morphologies, which could be related with the specific EWF ([w.sub.e,B]). In the ductile failure, [w.sub.e,B] is governed by the fibril size; adding nanoclay and recycled HDPE to pristine HDPE decreased the fibril size and subsequently lowered the we B value. In the brittle failure, the we S value was enhanced by creating a rough fracture surface. Adding nanoclay to pristine HDPE, a steadily decrease in [w.sub.e,B] was measured until 4-wt% after which the change was insignificant. Conversely, nanoclay content more than 2-wt% in recycle-blends greatly decreased the [w.sub.e,B] value. A transition map was constructed to illustrate the potential failure mode and the associated fracture morphology based on the tested material compositions. POLYM. ENG. SCI., 56:222-232, 2016. [C] 2015 Society of Plastics Engineers, INTRODUCTION High density polyethylene (HDPE) is one of the most widely used engineering plastics. With good mechanical properties, corrosion resistance, low cost, and ease of processing, the use of HDPE [...]

Manufacturing lightweight aggregate (LWA) (ie, porous ceramics) by means of a sintering technique requires a delicate balance among three conditions: (a) forming a sufficient amount of molten liquid phase during sintering, (b) reaching an appropriate viscosity for solid‐liquid suspension, and (c) emitting a sufficient amount of gas that can be entrapped by the liquid phase to form pores. This study evaluates these three conditions in the production of LWAs made from two types of waste coal bottom ash (low‐calcium and high‐calcium), and relates them to the formation of LWA pore structure. A thermochemical analytical approach, including thermodynamic modeling and the Browning viscosity model, was used to quantify the extent of the liquid phase and calculate its viscosity. In conjunction with thermochemical analysis, an experimental approach including quantitative x‐ray diffractometry, thermogravimetric analysis, and x‐ray computed tomography was also used to identify the candidate chemical compounds that contribute to gas emission during sintering and to evaluate the LWA pore structure. The results indicated that a mass fraction of at least 50% for the liquid phase is required for a successful entrapment of emitted gaseous phases during sintering. Larger pores were observed in the microstructure of LWA samples made using high‐calcium bottom ash in comparison to those made with low‐calcium bottom ash. This observation was mainly attributed to the high‐calcium samples forming liquid phases with lower viscosities and emitting higher amounts of gaseous phase during sintering than did the low‐calcium samples. It was found that the gaseous phase was generated by hematite reduction and anhydrite decomposition, which led to the release of O2 and SO2. [ABSTRACT FROM AUTHOR]

Technologies for upgrading fast pyrolysis bio‐oil to drop‐in fuels and coproducts are under development and show promise for decarbonizing energy supply for transportation and chemicals markets. The successful commercialization of these fuels and the technologies deployed to produce them depend on production costs, scalability, and yield. To meet environmental regulations, pyrolysis‐based biofuels need to adhere to life cycle greenhouse gas intensity standards relative to their petroleum‐based counterparts. We review literature on fast pyrolysis bio‐oil upgrading and explore key metrics that influence their commercial viability through life cycle assessment (LCA) and techno‐economic analysis (TEA) methods together with technology readiness level (TRL) evaluation. We investigate the trade‐offs among economic, environmental, and technological metrics derived from these methods for individual technologies as a means of understanding their nearness to commercialization. Although the technologies reviewed have not attained commercial investment, some have been pilot tested. Predicting the projected performance at scale‐up through models can, with industrial experience, guide decision‐making to competitively meet energy policy goals. LCA and TEA methods that ensure consistent and reproducible models at a given TRL are needed to compare alternative technologies. This study highlights the importance of integrated analysis of multiple economic, environmental, and technological metrics for understanding performance prospects and barriers among early stage technologies. [ABSTRACT FROM AUTHOR]

The effects of recycled high density polyethylene (HDPE) and nanoclay on the stress crack resistance (SCR) of pristine HDPE were evaluated using the Notched Constant Ligament Stress (NCLS) test. The test data were analyzed by both linear elastic fracture mechanics (LEFM) and elastic plastic fracture mechanics (EPFM). The LEFM approach uses the stress intensity factor K to define the two failure mechanisms: creep and slow crack growth (SCG). In contrast, using the J‐integral in EPFM, which emphasizes the nonlinear elastic‐plastic strain field at the crack‐tip, revealed a short‐term failure stage prior to the creep failure. In this article, a power law correlation between the fracture toughness Jc and SCG was found under a plane‐strain condition. Increasing recycled HDPE content lowered the SCG resistance of pristine HDPE by decreasing Jc. Adding nanoclay up to 6 wt% also decreased Jc while simultaneously, lowering the stress relaxation of nanocomposites, leading to longer SCG failure times at low J values. POLYM. ENG. SCI., 58:1471–1478, 2018. © Published [2017]. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Uruguay is pursuing renewable energy production pathways using feedstocks from its agricultural sector to supply transportation fuels, among them ethanol produced from commercial technologies that use sweet and grain sorghum. However, the environmental performance of the fuel is not known. We investigate the life cycle environmental and cost performance of these two major agricultural crops used to produce ethanol that have begun commercial production and are poised to grow to meet national energy targets for replacing gasoline. Using both attributional and consequential life cycle assessment ( LCA) frameworks for system boundaries to quantify the carbon intensity, and engineering cost analysis to estimate the unit production cost of ethanol from grain and sweet sorghum, we determined abatement costs. We found 1) an accounting error in estimating N2O emissions for a specific crop in multiple crop rotations when using Intergovernmental Panel on Climate Change( IPCC) Tier 1 methods within an attributional LCA framework, due to N legacy effects; 2) choice of baseline and crop identity in multiple crop rotations evaluated within the consequential LCA framework both affect the global warming intensity ( GWI) of ethanol; and 3) although abatement costs for ethanol from grain sorghum are positive and from sweet sorghum they are negative, both grain and sweet sorghum pathways have a high potential for reducing transport fuel GWI by more than 50% relative to gasoline, and are within the ranges targeted by the US renewable transportation fuel policies. [ABSTRACT FROM AUTHOR]

To meet Energy Independence and Security Act (EISA) cellulosic biofuel mandates, the United States will require an annual domestic supply of about 242 million Mg of biomass by 2022. To improve the feedstock logistics of lignocellulosic biofuels in order to access available biomass resources from areas with varying yields, commodity systems have been proposed and designed to deliver quality-controlled biomass feedstocks at preprocessing "depots". Preprocessing depots densify and stabilize the biomass prior to long-distance transport and delivery to centralized biorefineries. The logistics of biomass commodity supply chains could introduce spatially variable environmental impacts into the biofuel life cycle due to needing to harvest, move, and preprocess biomass from multiple distances that have variable spatial density. This study examines the uncertainty in greenhouse gas (GHG) emissions of corn stover logistics within a bio-ethanol supply chain in the state of Kansas, where sustainable biomass supply varies spatially. Two scenarios were evaluated each having a different number of depots of varying capacity and location within Kansas relative to a central commodity-receiving biorefinery to test GHG emissions uncertainty. The first scenario sited four preprocessing depots evenly across the state of Kansas but within the vicinity of counties having high biomass supply density. The second scenario located five depots based on the shortest depot-to-biorefinery rail distance and biomass availability. The logistics supply chain consists of corn stover harvest, collection and storage, feedstock transport from field to biomass preprocessing depot, preprocessing depot operations, and commodity transport from the biomass preprocessing depot to the biorefinery. Monte Carlo simulation was used to estimate the spatial uncertainty in the feedstock logistics gate-to-gate sequence. Within the logistics supply chain GHG emissions are most sensitive to the transport of the densified biomass, which introduces the highest variability (0.2–13 g CO2e/MJ) to life cycle GHG emissions. Moreover, depending upon the biomass availability and its spatial density and surrounding transportation infrastructure (road and rail), logistics can increase the variability in life cycle environmental impacts for lignocellulosic biofuels. Within Kansas, life cycle GHG emissions could range from 24 g CO2e/MJ to 41 g CO2e/MJ depending upon the location, size and number of preprocessing depots constructed. However, this range can be minimized through optimizing the siting of preprocessing depots where ample rail infrastructure exists to supply biomass commodity to a regional biorefinery supply system. [ABSTRACT FROM AUTHOR]