Direct ex-situ mineral carbonation offers a pathway for permanent CO2 sequestration through reactions with silicate minerals. While conventional mining and processing of feedstocks are energy-intensive and costly, the utilization of pre-ground mine tailings rich in CO2-reactive silicates may provide a more economical alternative. This study evaluates the technical feasibility, technoeconomic assessment (TEA), and life cycle assessment (LCA) of direct aqueous mineral carbonation using domestic nickel mine tailings. Experimental results demonstrated that 16-35 kg CO2 per ton of mine tailings could be sequestered at 125-185 degrees C without additional comminution. Further particle size reduction, or the use of the slime fraction, increased CO2 uptake to 46-91 kg CO2 per ton. Mineralogical characterization confirmed the carbonation of olivine and a fraction of pyroxene to form siderite and magnesite, while plagioclase and quartz remained largely inert. The TEA/LCA analysis revealed a sequestering cost of > $585 per ton CO2, with a net global warming potential (GWP) of at least 1.3 CO2-equivalent. Scenario modeling indicated that achieving cost and environmental targets ($100 per ton CO2 and GWP <1) would require ultrafine tailings with >= 80 % olivine content and the use of low-carbon heat source. This study represents the first integrated evaluation of both the technical feasibility and technoeconomic scenarios of CO2 sequestration using direct ex-situ carbonation route for nickel mine tailings.

Asphalt pavement is a critical component of modern infrastructure, and concerns about its environmental impact have arisen over the years. This paper presents a case study of rubberized asphalt pavement in Dickinson County, Michigan, employing a life cycle assessment (LCA) methodology. The objective of this study is to demonstrate the environmental benefits of rubber incorporation in road construction by scrutinizing the material, transportation, manufacturing and construction stages. By conducting data collection and analysis tailored to Dickinson County's specific conditions, this research offers valuable insights into the environmental performance of rubberized asphalt pavement within a localized context. By comparing the environmental impact between a conventional asphalt section and a rubber pellet-modified pavement section, the findings emphasize the environmental advantages of utilizing recycled rubber in asphalt mixtures. The life cycle results demonstrate that rubber modified asphalt section produces lower greenhouse gas emissions and consumes less energy compared to conventional asphalt sections. These results underscore the significance of considering recycled materials, especially rubber products, in LCA studies.

National and state science standards emphasize student understanding of and engagement in engineering. However, many teachers do not have robust understandings of engineering and their students may not have opportunities to engage in engineering. The COVID-19 Pandemic has likely further decreased opportunities for elementary students to engage in engineering as their teachers grappled with reduced contact time, integration of new technologies and pedagogical approaches, and remote/virtual learning. The purpose of this qualitative case study was to describe how an elementary teacher attended to engineering instruction during virtual learning despite the barriers presented by the pandemic. Aleshia was purposefully selected from a larger sample of 22 grade K-6 teachers because she included engineering in her virtual instruction. Data sources, including interviews, surveys, observations, and lesson artifacts were analyzed using an inductive approach in which the teacher's data corpus was holistically analyzed and interpreted to make meaning and answer the research question (Merriam, 1998). Aleshia's case demonstrates how an elementary teacher leveraged the affordances of digital technology to engage students in engineering design tasks despite the barriers presented by the pandemic. Aleshia's high baseline confidence and beliefs about technology integration may explain why she was able to implement technology-enhanced engineering instruction during virtual instruction. The results have implications for the design and development of PD to support engineering integration into elementary science teaching and the importance of developing elementary teachers' confidence integrating technology into instruction. Ultimately, Aleshia's case demonstrates the resilience, resourcefulness, and creativity of an elementary teacher integrating engineering instruction during the COVID-19 Pandemic when supported through PD initiatives that include a coaching component.

Globally, more than 1000 organizations and 175 nations are facing the plastic waste problem and have realized the need to transition from "linear-to-circular" economy of plastics. While the current mechanical recycling technologies for plastics are struggling to increase the U.S. plastic recycling rates beyond 9%, chemical recycling technologies become important complementary technologies to the predominant mechanical recycling that are needed to realize the circular economy in plastics supply chains. Dissolution is one such chemical recycling technology that can recycle waste plastic back into high-quality virgin grade plastic. However, the environmental and economic impacts of chemical recycling of waste polyethylene terephthalate (PET) via dissolution technology using a green solvent are unknown. Our study evaluated environmental metrics such as greenhouse gas (GHG) emissions and cumulative energy demand, and economic metrics such as net present value (NPV), minimum selling price, payback period, return on investment, and discounted internal rate of return for three dissolution processes with polymer recovery via anti-solvent, evaporation, and cooling precipitation techniques. The dissolution process with evaporation technique was the most economically favorable, whereas that with cooling technique was the most environmentally favorable. The anti-solvent approach had low economic performance and the highest environmental impacts. The NPV for all of these technologies ranged from $2.67 MM to $10.93 MM for a capacity of 8,400 MT/year and was found to be the highest for dissolution with evaporation approach and the least for anti-solvent approach. The cradle-to-gate GHG emissions and energy demand for PET dissolution processes ranged from 1.33-3.77 kg CO 2 -eq/kg of chemically recycled (CR) PET and 18.9-56.1 MJ/kg of CR-PET, respectively. These economic and environmental metrics will be helpful in evaluating the sustainability of circular PET supply chains in the U.S.

Polyethylene (PE) films are one of the highest production volume plastic products, but they have very low recycling rates. A novel liquid fed pyrolysis process (LFP) is an advanced recycling technology that can be applied to waste PE films. In this work, two environmental and six economic metrics were evaluated for the LFP process under different scenarios with a baseline production capacity of 8,400 Metric Tons (MT) of pyrolysis products/year. The studied scenarios considered process improvement such as heat integration, changing the final product yields, and location of the LFP process facility (i.e., co-located at a petrochemical facility or located remotely). Results show that producing refined pyrolysis wax in remote areas is the most environmentally favorable and profitable scenario. The LFP process co-located at a petrochemical facility and selling only liquid and gaseous pyrolysis products to the facility would require a capacity of >18,000 MT/year to be economically feasible. Heat integration led to greenhouse gas emission savings of at least 14%, 19%, and 32% for the pyrolysis oil, gas, and wax products, respectively. The LFP process in remote and less populated locations producing a high yield of refined wax may be a feasible solution for increasing recycling rates of PE films.

As one of the most potent greenhouse gases, methane is a critical target for the near-term mitigation of global warming. Efficient, scalable, easy-to-implement, and robust mitigation technologies are urgently needed to assist in reaching methane abolishment. The goal of this research was to test the applicability of active, extremophilic methanotrophic cells as a baseline concept for engineered systems aiming at methane capturing. The system, named living emission abolish filters (LEAFs), represents an array of immobilized biomaterials capable of capturing methane directly from vent streams. The biomaterials were made using cells of Methylotuvimicrobium alcaliphilum 20Z ^R , a robust halophilic methanotrophic bacterium with the ability to consume methane gas at low concentrations. Several critical parameters were tested, including (i) the composition of the matrix and optimal immobilization to increase catalyst load, (ii) the stability of methanotrophic cells, and (iii) the toxicity of trace gases (i.e. CO). We found that hydrogels coated with 2.3 mg cell dry weight/cm ^3 methanotrophic cells represent the best-performing biomaterials. The methane reduction potential of LEAFs fluctuated from 20% to 95% and depended on the methane concentration in the gas stream and the stream flow rates. The potential for commercial-scale deployment and emissions reductions was also evaluated. Total greenhouse gas emissions (combined using the global warming potential GWP _100 ) from an example using a ventilation air methane source over a one-year period was shown to be reduced in two LEAF scenarios by 51% and 75%. Over longer time horizons, more significant reductions are possible as consistent methane consumption can be sustained. The study highlights the overall potential of the liquid-free bio-based composite methane mitigation system. Further improvements essential for system assembly and implementations should include (a) optimization of the cell immobilization protocols to improve cell load and the shelf-life of the system and (b) implementation of matrix moldings for cell immobilization to achieve optimal gas flow and increase the cell-gas interface.

Anaerobic digestion (AD) involves a set of microbiological reactions and physio-chemical processes to generate biogas, a mixture of predominantly CH4 and CO2. It is commercialized globally; however, AD has limited commercial applications in the U.S. compared to other regions of the world. The main objective of this article is to review different studies on socio-economic and environmental aspects and policies of biogas/biomethane production and to focus on resource availability. The key outcome from this review shows that the anaerobic digestion of food waste and animal manure has great potential to achieve economic and environmental benefits compared to other waste management techniques such as landfilling or conventional manure management. The 12 life cycle assessment (LCA) studies reviewed showed lower impacts for biogas systems and indicated a need for standardization of methodology so that alternative production concepts can be objectively compared. Similarly, economic analyses showed higher profitability for a biogas combined heat and power facility compared to a biomethane facility. By considering a review of the sustainability of biogas, we presented a new multi-criteria sustainable assessment framework that includes three domains: i. resource availability and logistics, ii. process modeling, and iii. impact assessment with primary application to the optimum location and installation of sustainable biogas/biomethane plants in the U.S.

This poster presentation will present baseline data describing teachers' understandings, confidence, and instructional practices regarding digital technology integration within engineering instruction. Data were collected for the "Digital Technology Integration and Engineering Contexts to Support Elementary Students Systems Thinking" project (NSF award # 1850296) prior to professional development. Participants included 27 elementary and middle school science teachers (grades K-8). Data sources included a validated survey that assessed participants' engineering and technology understandings, confidence, beliefs, and practices on a 5-point Likert Scale (1 = not confident/appropriate; 3 = somewhat confident/appropriate; 5 = extremely confident/appropriate). The survey asked participants to rate their confidence using and perceptions of appropriateness to integrate seven digital technologies (static digital images, computer simulations, interactive visualizations, spreadsheets, videos/animations, computer assisted design software, programming technologies). Participants also responded to a prompt in which they described an engineering lesson they integrated the previous year. A subset of participants (n = 12) were interviewed to elaborate on their survey responses and to better understand their classroom integration of engineering and technology. Results indicated that of the technologies to support engineering included on the survey, the teachers reported greatest confidence integrating static digital images (M = 4.0, SD = 1.0) and presentation software (e.g., PowerPoint; M = 4.0, SD = 1.1). In contrast, participants were least confident incorporating CAD software (M = 1.7, SD = 0.8) and probeware (M = 2.2, SD = 1.1). Participants' endorsed integration of most of the targeted technologies to support engineering lessons (M > 4.0 for all but CAD and programming technologies). However, when asked what technologies they had integrated into their instruction, teachers reported including static images and animations into engineering instruction most often (approximately 75% of engineering lessons) and spreadsheets, probes, and CAD least often. Lesson descriptions confirmed this result. Of participants, 21 of 27 described using technology in their engineering lesson. In 17 of these lessons, the technology described was static images or animations. In these lessons, participants described using digital technology to either introduce a design challenge to students or document/communicate final designs; no participant indicated using technology to support the design/development of a solution. These findings demonstrate that while participants generally endorsed technology to support engineering instruction, they had a limited understanding of how digital technology could be used for this purpose, and limited experience incorporating technology to support engineering instruction. Results indicate a need for professional development to help grade K-8 teachers to better understand how technology can be used to support engineering and to facilitate technology use more authentically within an engineering design process.

Purpose The purpose of this life cycle assessment (LCA) study was to determine the life cycle impacts for production and distribution of a humanitarian supply item under various supply chain paradigms in order to illustrate the potential environmental benefits of organizing production and supply operations for these items in novel ways. To do this a case study is used on a family-size water storage and dispensing bucket, such as the 14L-capacity polyethylene (PE) bucket commonly produced by Oxfam International. Methods The LCA is cradle-to-gate including production and transportation of PE plastic feedstock, fabrication of the water bucket, and transportation of the bucket to a common distribution site representative of a humanitarian aid location. Three different humanitarian aid locations are used to illustrate the range of potential impacts for each processing and supply system: Nepal, South Sudan, and Peru. Six processing and supply scenarios were investigated: 1) centralized Oxfam traditional system, 2) centralized commercial Chinese supply and distribution, 3) quasi-centralized Field Ready supply and distribution, 4) distributed supply and distribution system with 3-D printing, 5) distributed supply and distribution system with 3-D printing and local waste feedstock, and 6) distributed supply and distribution system with extrusion molding and local waste feedstock. Results and discussion The results found the major contribution to total GHG emissions are electricity usage for manufacturing and shipping feedstock and final product. Among Systems 1–3, System-1 and System 2 are environmentally poor as the electricity emissions in Pakistan and China are high. System 3 was an improvement as the products are manufactured locally. Decentralized supply and distribution system with 3-D printing (System 4) is less compatible with regions of high grid emissions. In System 5, the same equipment has been used, but with local waste feedstock, which shows an improvement of 67.7% for Nepal and 65.5% for Peru because of the reduced shipping emissions, even if the manufacturing emission is the highest among all of the systems. System 6 is feasible for all three locations. Conclusions It is concluded that manufacturing should be prioritized on grids where the electricity emission is lower using local waste feedstock as it is the most efficient approach; however, a further study should be done on operating the FPF/FGF 3-D printer or extrusion molding systems powered with distributed photovoltaic systems in order to complement this process and produce the most environmentally responsible production.

Many actions are underway at global, national, and local levels to increase plastics circularity. However, studies evaluating the environmental and socio-economic impacts of such a transition are lacking at regional levels in the United States. In this work, the existing polyethylene terephthalate and polyolefin plastics supply chains in Michigan were compared to a potential future (‘NextCycle’) scenario that looks at increasing Michigan’s overall recycling rate to 45%. Material flow analysis data was combined with environmental and socio-economic metrics to evaluate the sustainability of these supply chains for the modeled scenarios. Overall, the NextCycle scenario for these supply chains achieved a net 14% and 34% savings of greenhouse gas (GHG) emissions and energy impacts, when compared with their respective baseline values. Additionally, the NextCycle scenario showed a net gain in employment and wages, however, it showed a net loss of revenue generation outside of Michigan due to the avoided use of virgin resins in Michigan.

Evaluating six economic and two environmental performance metrics for recycling of waste PET via solvent-based dissolution–precipitation processes.

The household is an important locus of decision-making regarding food, energy, and water (FEW) consumption. Changes in household FEW consumption behaviors can lead to significant reductions in environmental impacts, but it can be difficult for consumers to compare the relative impacts of their consumption quantitatively, or to recognize the indirect impacts of their household consumption patterns. We describe two novel tools designed to address this problem: A hybrid life cycle assessment (LCA) framework to translate household consumption of food, energy, and water into key environmental impacts including greenhouse gas emissions, energy use, and water use; and a novel software application called HomeTracker that implements the framework by collecting household FEW data and providing environmental impact feedback to households. We explore the question: How can a life cycle assessment-based software application facilitate collection and translation of household consumption data to meaningful environmental impact metrics? A case study in Lake County, Illinois is presented to illustrate use of the HomeTracker application. Output data describing environmental impacts attributable to household FEW consumption in the study area are shown in order to illustrate key features and trends observed in the case study population. The framework and its associated output data can be used to support experimental research at the household scale, allowing for examination of what users purchase and consume over an extended period of time as well as increased understanding of household behavior trends and environmental impacts, and as future work.

CO2 utilization via reverse water gas shift (rWGS) reaction has been proposed as a path to the sustainable utilization. This work presents a detailed process modelling study where steam methane reforming (SMR) generated hydrogen was combined with rWGS to produce syngas (CO + H-2) with various hydrogen-to-carbon oxide ratios. To further decrease CO2 emissions that may offset the benefits of CO2 converted in rWGS, electrification of endothermal reactors, both SMR and rWGS was considered where CO2 emitting fuel burning in the furnace was replaced by the emerging ohmic (resistive) heating. Material and energy inventory obtained from process design calculations was used to perform Life Cycle Analysis (LCA) to calculate environmental impacts of CO2 consumption and reactor electrification. The results showed that greenhouse gas emissions, in CO2 kg equivalent, were the lowest when both SMR and rWGS were heated using wind-generated electricity, decreasing from 25 to 10 kg CO2 equivalent for H-2:CO = 2:1 while the conventional electricity mix used for furnace electrical heating across the board of scenarios generated highest environmental impacts, much higher than those that used natural gas as fuel. Process economics calculations suggested that, when both SMR and rWGS were electrically heated, the process only showed product syngas cost parity with the conventional fuel heated design when electricity cost was ~$0.008/kWh. This suggests that CO2 utilization scenarios involving process electrification need to be carefully considered from the total design perspective so they do not produce more greenhouse gases than in conventional non-electrified scenarios.

For a salt or other conservative contaminant contamination event in a water distribution system, opening fire hydrants to flush the system is currently an accepted decontamination method. However, all the contaminated flushed water is discharged to the local surroundings of the fire hydrants and imposes an environmental impact. Another system decontamination alternative can be using a containment pond to catch the contaminated water. To reduce environmental impacts of flushing salt from a water distribution system a comparative life cycle assessment study has been performed for both conventional flushing and for flushing contaminated water into a containment pond. This was performed using SimaPro software for both of these decontamination options and the impacts have been assessed using the IMPACT 2002+ methodology. The results show that environmental impacts can be reduced by 25% for rural areas, 69% for urban roads, 61% for urban lawns, and 64% for mixed land use. In addition, a sensitivity analysis reveals the two most sensitive variables resulting in the finding that a 10% change in the time needed for system decontamination led to a 10% change in environmental impact and a 10% change in the area of land exposed to contaminated water discharge led to an 8% change in environmental impact.

Plastics are useful and beneficial materials that contribute to an improved quality of life, yet they generate significant solid wastes and emissions and consume significant energy resources. Systems analysis is incomplete on current linear production systems of plastics supply chains and their associated processes. Our study combines material flow and life cycle assessment data sets of polyethylene terephthalate (PET) and the main polyolefin polymers in the United States, comprising over 70% of plastics flows. This study estimates the total greenhouse gas (GHG) emissions and energy consumption of these supply chains, including transportation and end-of-life processes, lacking in prior studies. We calculate annual GHG emissions and energy consumption of these plastic supply chains to be 101 MMT CO2-eq and 3248 PJ in 2019, respectively. The GHG emissions of these supply chains represented 1.5% of the total U.S. emissions and 5% of the total U.S. industry-related GHG emissions. The total energy consumption of these supply chains represented 3.1% of the total U.S. energy consumption in 2019. Transportation of PET and polyolefin plastic materials contributes 5% and 2% to the total supply chain GHG emissions and energy consumption, respectively. This baseline study provides a benchmark and enables a comparison to future circular production systems for plastics in the United States.

Solar photovoltaic (PV) growth can be stalled due to social acceptance. Agrivoltaics can improve social acceptance by enabling dual use of land. The most popular type of agrivoltaics in North America is grazing sheep under conventional PV farms. The environmental benefits of this integrated agrivoltaic system are unknown, so this ISO-compliant life cycle assessment study investigates the environmental performance of sheep-based agrivoltaic systems. This study investigated agrivoltaics to produce a combined output of electricity and agricultural goods, in comparison to conventional methods (various electric grid generation mixes in the U.S. and plane pastures) for producing that same quantify of service in both categories. Agrivoltaics is twice as land use efficient as providing sheep and PV services separately. In addition, the global warming potential of agrivoltaics was found to be 3.9% better than conventional PV and sheep grazing separately, and represents two orders of magnitude improvement (280%-894%) over conventional grids in the U.S. and sheep production. Only considering emission reductions from shifting sheep to PV farms for grazing, the U.S. could conserve 5.73E8 kg CO2 eq per year from sheep raising, which is equivalent to removing 117,000 average automobiles from the road. To house the current national 5.2 million domestic sheep in agrivoltaic systems, the U.S. has the potential to expand utility scale PV by a factor of four. The results of this study provide further evidence that agrivoltaic systems are superior to conventional ground-mounted PV systems because they have dual purposes and reduce the environmental impacts associated with producing food and electricity. It is clear that encouraging sheep grazing on all appropriate conventional PV systems is warranted.

Current management strategies for utilizing increasing amounts of liquid digestate, the main byproduct of anaerobic agricultural and municipal solid waste digestion, pose significant environmental risks if utilized directly for agricultural purposes as a nutrient-containing soil improver. Instead, efficient removal and precipitation of nitrogen present in the digestate have been recently proposed in the form of ammonium bicarbonate, NH4HCO3, and a new process was designed to produce solid NH4HCO3 fertilizer material from the liquid digestate using distillation. Environmental impacts of this new process can be advantageous over the direct disposal of digestate to the soil. To further understand and improve the underlying economic and environmental implications of this technology, several new scenarios are proposed and evaluated in this work, which examines the influence of key process variables, including (a) process improvement to obtain a portion of the heat necessary for the distillation process using solar concentrators and (b) fate of the post-processed liquid digestate stream, including disposal into the wastewater treatment plant, release into the water body, or direct land application. An optimized solid NH4HCO3 synthesis scenario was designed using a distillation column with 95% nitrogen recovery. Solar steam generation was incorporated to reduce fossil fuel-generated steam consumption in the distillation column reboiler. This resulted in the distillation column operating at 1.5 bar and a low reflux ratio. This allowed column bottoms to operate at 118 degrees C for 5 h per day utilizing only solar steam. A detailed economic analysis of the overall process was performed and showed that $20/tonne of feed credit was necessary if the product was valued at $0.10/lb in the most realistic base case scenario. The life cycle assessment (LCA) modeling results obtained suggest that the integration of solar heating can provide important benefits in regard to the overall environmental impacts, but for many environmental impact metrics, including greenhouse gas (GHG) emissions and eutrophication potential, the choices of where to dispose of the post-processed digestate stream and the resulting assumptions about N and C mobilization at that stage can exert a larger influence on the overall environmental impact. Further experimental work is needed to provide certainty to the factors that are used to estimate nitrogen and carbon fate within LCA modeling frameworks.

The world is witnessing an unprecedented generation and accumulation of fiber-plastic wastes resulting in various challenges due to inconsistency, waste-stream heterogeneity, conveying issues, self-heating, and difficulty in pelletization. This study presents a novel pilot-scale system that integrates torrefaction and extrusion to convert mix fiber-plastic waste into fuel pellets. The produced pellets have low cost, high heating value, better uniformity, and low environmental impact. They can be used as solid fuels or as feedstock for pyrolysis and gasification. To evaluate the pellet cost and its environmental impact, we performed Techno-Economic Analysis (TEA) and Life Cycle Assessment (LCA). The TEA integrates research findings from the torrefaction-extrusion project with the techno-economic models and estimates the costs, energy consumption, and mass balances for pelletizing and torrefaction. The analysis indicates that the baseline cost of producing uniform pellets is about $55.28/dry tonne (2020$). LCA results indicate that the torrefied product has cradle-to-gate embodied greenhouse gas emissions that are net negative, although they are higher than a comparable forest-derived woodchip product. Fossil energy demand for the torrefied product is lower than the forest-derived chip, indicating the torrefied product has strong potential for use as an environmentally beneficial feedstock for future processing.

Flushing using fire hydrants is a very common way to get rid of contamination in any water distribution system. Unfortunately, this process directly exposes contaminated water to the environment. This contaminated water can end up in agricultural fields, natural water bodies, and even in treatment plants. One solution can be building a contaminant flushing pond to hold that water; however, the use of the pond also involves some environmental impact beginning from its construction phase. A life cycle assessment study has been performed using SimaPro software for both hydrant flushing and contaminant flushing pond processes, and the impacts have been assessed using the IMPACT 2002+ methodology. The results show that decontamination using flushing ponds can cause less environmental impact than decontamination using fire hydrants.