Long Nguyen

Bio: Long Nguyen is an academic researcher from Drexel University. The author has contributed to research in topics: High-density polyethylene & Life-cycle assessment. The author has an hindex of 4, co-authored 7 publications receiving 86 citations.

Effects of composition and transportation logistics on environmental, energy and cost metrics for the production of alternative cementitious binders

Abstract: The production of cement, the primary ingredient in concrete, is responsible for 5–10% of anthropogenic GHG emissions. Numerous studies have investigated ordinary portland cement (OPC) alternatives with the goal of reducing GHG emissions. This life cycle assessment (LCA) adds transportation as a focus of the assessment, in addition to the process steps from cradle to the gate of finished cementitious product. GHG emissions and cost are assessed for five cement types with comparable performance (1) OPC; (2) blended OPC with slag (SC); (3) blended OPC with fly ash (FAC); (4) metakaolin-based geopolymer (MKG); and (5) high volume limestone alkali-activated slag cements (HLAASCs). Transportation logistics are known to be critical for the cement industry, and this holds true for alternative cements. The influence of feedstock source location and transport mode within the supply chain significantly affect both environmental impacts (up to 80% of GHG emissions) and production cost (up to 65%), and should thus be a major consideration. All OPC alternatives reduce GHG emissions, even at the least beneficial points of their ranges. HLAASC reduces GHG emissions and energy consumption in all cases studied, by up to 95% and 83%. SC and FAC have comparable reductions in GHG emissions and energy, and their ranges overlap. MKG reduces GHG emissions but not energy input for the cases studied, however the energy demand may be closer to the other binders studied where the mineral is available and from low grade sources.

Uncertainties in Life Cycle Greenhouse Gas Emissions from Advanced Biomass Feedstock Logistics Supply Chains in Kansas

Abstract: 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.

Uncertainty in the life cycle greenhouse gas emissions and costs of HDPE pipe alternatives

Abstract: High density polyethylene (HDPE) is a thermoplastic used in many engineering applications but one that imposes environmental burdens when produced and environmental costs at end-of-life (EOL). Replacing pristine HDPE with post-consumer recycled (PCR) HDPE or bio-based polymer (bio-HDPE) in long-lived goods could mitigate those impacts. We investigate cradle-to-gate and cradle-to-grave greenhouse gas (GHG) emissions and costs of four alternative resins, pristine HDPE, pristine/PCR HDPE, bio-HDPE and nanoclay-pristine/PCR HDPE composite, and their use in 100-year drainage pipe, respectively. We construct stochastic LCA models that combine service life prediction from experiments with parametric and scenario uncertainty modeling using Monte Carlo simulation and non-parametric bootstrapping. Results differ significantly on a resin versus pipe product basis owing to the functional unit requirement for meeting pipe service life, if governed by crystallinity and fracture energy, properties that call for greater quantities of material in recycled and nanoclay composite HDPE compared to pristine HDPE. The nanocomposite pipe has varying GHG emissions compared to all alternatives due to high mass requirement if assuming crystallinity and fracture energy govern failure, but this predicted mass may be reduced given that the nanoclay can prolong fracture time, which would reduce GHG emissions and pipe production cost. Despite a large GHG reduction relative to pristine HDPE, the bio-HDPE resin has the highest material production cost; however, considering life cycle costs, the incremental difference among all alternatives is small over a range of discount rates, rendering the bio-HDPE pipe a promising solution for addressing climate change in long-lived thermoplastic assets.

Life Cycle Economic and Environmental Implications of Pristine High Density Polyethylene and Alternative Materials in Drainage Pipe Applications

Abstract: A life cycle assessment (LCA) and cost analysis were conducted to compare the environmental and economic performance of nanocomposite polymers that use pristine and recycled high density polyethylene (HDPE) polymer with pristine, and pristine/recycled HDPE polymeric materials in drainage pipe. We evaluate three performance metrics; (a) non-renewable energy consumption (NRE); (b) greenhouse gas (GHG) emissions; and (c) production costs of the three pipe material alternatives. Original life cycle inventory data for the production of nanoclay from the mineral Montmorillonite were collected for this case study in the United States. Life cycle inventory models were developed for the cradle-to-gate production of drainage pipe used in highway construction that consider the sensitivity of model parameter inputs on the life cycle impact and cost results for the three material options. The GHG emissions for the nanoclay composite pipe are 54 % lower than those for pristine HDPE pipe, and 16 % lower than those for pristine/recycle HDPE pipe. With a slight difference in GHG emissions between the pristine/recycled and nanoclay composite, the production of nanoclay does not introduce a significant environmental burden to the pipe material. On average, the pristine HDPE pipe is 13 and 17 % higher in cost than the pristine/recycled HDPE and nanoclay composite pipes, respectively. Results of the LCA and cost analysis support using recycled HDPE as a substitute for pristine HDPE due to its low energy requirements and production costs. The uncertainty in GHG emissions of manufacturing pristine HDPE causes the largest variation of GHG emissions in nanoclay composite pipe (+3/−2 %). The production cost of the nanocomposite pipe is most influenced by the energy cost of PCR-HDPE (+25/−11 %). Our study suggests that a nanocomposite design that replaces part of the pristine HDPE with recycled HDPE and nanoclay reduces certain environmental risks and material cost of corrugated pipe.

Effects of recycled HDPE and nanoclay on stress cracking of HDPE by correlating J c with slow crack growth

Abstract: 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., 2017. Published [2017]. This article is a U.S. Government work and is in the public domain in the USA.

Opportunities and challenges in sustainable supply chain: An operations research perspective

Abstract: Sustainable Supply Chain have become a cornerstone to any company that seeks to achieve sustainable goals. A company's image is no longer related to the old paradigm of being sustainable in its own activities, but instead is associated with a strong collaboration between all supply chain stakeholders, towards a sustainable activity. It is then critical to create new methods and tools to account for the three pillars of sustainability: economic, environmental and social, in a multi-stakeholder chain. In this context, operational research (OR) methods play a key role in supporting sustainable supply chain activities. This paper aims to review the trends and directions of OR methods applications towards the achievement of sustainable supply chain. A set of 220 papers has been reviewed to identify the OR methods being employed, the levels of decision considered and how sustainability practices were treated through OR. We found that optimization models applied to strategic level decisions are the most preponderant studies. Moreover, it was verified that sustainability has been mainly tackled by assessing economic and environmental aspects, leaving behind the social aspects. Additionally, OR-based studies do not yet present a clear definition of sustainability, a fact that is proven by the number of environmental and social methodologies explored. Based on the major trends identified in the literature, a research framework is derived, pointing towards a future research agenda in the area.

Environmental sustainability of biofuels: a review

Abstract: Biofuels are being promoted as a low-carbon alternative to fossil fuels as they could help to reduce greenhouse gas (GHG) emissions and the related climate change impact from transport. However, there are also concerns that their wider deployment could lead to unintended environmental consequences. Numerous life cycle assessment (LCA) studies have considered the climate change and other environmental impacts of biofuels. However, their findings are often conflicting, with a wide variation in the estimates. Thus, the aim of this paper is to review and analyse the latest available evidence to provide a greater clarity and understanding of the environmental impacts of different liquid biofuels. It is evident from the review that the outcomes of LCA studies are highly situational and dependent on many factors, including the type of feedstock, production routes, data variations and methodological choices. Despite this, the existing evidence suggests that, if no land-use change (LUC) is involved, first-generation biofuels can-on average-have lower GHG emissions than fossil fuels, but the reductions for most feedstocks are insufficient to meet the GHG savings required by the EU Renewable Energy Directive (RED). However, second-generation biofuels have, in general, a greater potential to reduce the emissions, provided there is no LUC. Third-generation biofuels do not represent a feasible option at present state of development as their GHG emissions are higher than those from fossil fuels. As also discussed in the paper, several studies show that reductions in GHG emissions from biofuels are achieved at the expense of other impacts, such as acidification, eutrophication, water footprint and biodiversity loss. The paper also investigates the key methodological aspects and sources of uncertainty in the LCA of biofuels and provides recommendations to address these issues.

Sustainable biorefineries, an analysis of practices for incorporating sustainability in biorefinery design

Abstract: The incorporation of sustainability in the design of biorefineries is central for the development of the biobased economy. In this paper sustainability methods and metrics in current biorefinery design practices are analyzed to identify challenges and opportunities for future improvements in the field. Generally, there is a need for an integral analysis that includes societal impacts and goes beyond the automatic use of metrics for predefined issues. Although efforts have been made to develop more integral sustainability analyses for biorefinery design, they are often challenged by disciplinary boundaries that yield a narrow scope of analysis (e.g. conversion process, supply chain), and are blind to contextual settings or stakeholder perspectives. Multi and trans-disciplinary, inclusive and context aware approaches are identified as opportunities to overcome them in future developments.

Environmental performance comparison of bioplastics and petrochemical plastics: A review of life cycle assessment (LCA) methodological decisions

Abstract: There is currently a shift from petrochemical to bio-based plastics (bioplastics). The application of comprehensive and appropriately designed LCA studies are imperative to provide clear evidence on the comparative sustainability of bioplastics. This review explores the growing collective of LCA studies that compare the environmental footprints of specific bioplastics against those of petrochemical plastics. 44 relevant studies published between 2011 and 2020 were reviewed to explore important methodological choices regarding impact category selection, inventory completeness (e.g. inclusion of additives), boundary definition (e.g. inclusion of land-use change impacts), representation of biogenic carbon, choice of end-of-life scenarios, type of LCA, and the application of uncertainty analysis. Good practice examples facilitated identification of common gaps and weaknesses in LCA studies applied to benchmark bioplastics against petrochemical plastics. Many studies did not provide a holistic picture of the environmental impacts of bioplastic products, thereby potentially supporting misleading conclusions. For comprehensive evaluation of bioplastic sustainability, we recommend that LCA practitioners: embrace more detailed and transparent reporting of LCI data within plastic LCA studies; adopt a comprehensive impact assessment methodology pertaining to all priority environmental challenges; incorporate multiple plastic use cycles within functional unit definition and system boundaries where plastics can be recycled; include additives in life cycle inventories unless there is clear evidence that they contribute long-term carbon sinks; account for (indirect) land-use change arising from feedstock cultivation; prospectively consider realistic scenarios of deployment and end-of-life, preferably within a consequential LCA framework.

Life-cycle and environmental impact assessments on processing of plant fibres and its bio-composites: A critical review:

Abstract: From the beginning of humanity, our generation has been on the edge of finding suitable solutions to increase the product’s life-cycle and reduce the environmental impact of the product. Life-cycle...