Browsing by Subject "circular economy"
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Item Open Access Farm to Fork to Farm: Biochar, Compost, Working Landscapes, and a Circular Economy in Warren Co., NC(2023-04-28) Fast, Clara; Bowers, Madeline; Carter, Eliza; Taragittigul, KarinaWorking Landscapes, a non-profit organization located in Warren County, NC, aims to create new value from their natural and cultural assets and share them in more equitable ways. This project explores the market opportunity, community interest, and externalities of installing and operating a biochar unit in and around Warren County. Biochar, a carbon-rich, solid by-product that results from the pyrolysis of discarded woody material sourced from the community, combined with compost generated by Working Landscapes’ food scraps, can increase soil health and contribute to the creation of a circular supply chain. Beyond the economic benefit of waste reduction is the environmental benefit of keeping natural materials from producing greenhouse gasses in landfills. We conducted a market and cash-flow analysis, a geospatial analysis of the soil types, and analyzed results from an electronic survey for community input. To demonstrate a tangible example of a circular supply chain in Warren County and make use of otherwise wasted materials, we recommend that our client invest in biochar production along with scaling up their compost generation. Working Landscapes will gain a new customer touchpoint, reduce its waste, and increase circularity within its supply chain.Item Open Access Forecasting the value of recyclable waste streams for a circular economy transition in Orlando, Florida(2018-04) Kanaoka, KoichiThe circular economy is a paradigm that views waste as a valuable resource, creating value for local economies through waste recycling and reuse. Despite the benefits of waste recovery, the national recycling rate has remained stagnant around 34% for the past decade in the U.S. This Master’s Project for Duke University’s Nicholas School of the Environment aimed to quantify the economic potential of improving recycling rates in the Orlando Metropolitan Statistical Area (MSA) through: (1) forecasting the value of recyclable municipal solid waste generated in Orlando MSA, and; (2) conducting a benefit-cost analysis (BCA) of building a material recovery facility (MRF) in Orlando. Forecasts and BCA were conducted by incorporating uncertainties from commodity price volatility. Results from the study suggested that values of single-stream recycling waste in Orlando MSA may reach $100 million in 2027, from $72 million in 2015. Cardboard and aluminum cans accounted for 70-90% of the waste stream’s value, while only accounting for 32% of the weight. The BCA revealed that building a MRF in Orlando MSA is expected to be profitable for the municipality. The cost for building the MRF was expected to be recovered as early as in the fourth year. Sensitivity analysis showed that an initial processing cost of $85 per ton, a $10 increase from the base model’s $75 per ton, made building a MRF expected to be unprofitable. The results from this study may not apply to other municipalities, since Orlando MSA already had a functioning collection infrastructure for recyclables. The study also raised questions regarding the optimal design of recycling programs.Item Open Access Reducing Waste in the Built Environment(2022-04-22) Seyler, Meghan; Zou, AndyIn 2018, the United States generated over 600 million tons of construction and demolition waste, fueled by increasing housing demand and a lack of viable recycling markets. This problem is acute in the Triangle, where 4,700 new units of residential construction were built between Summer 2020 and Summer 2021 in Durham County alone. With support from a local design-build firm, Haven, and nonprofit, Circular Triangle, this project uses a waste assessments report and custom waste calculator to investigate the social and environmental impacts of landfilling waste, to suggest opportunities for waste diversion in the built environment, and to communicate these results to policy makers to drive government support for circularity in the Triangle. Findings from our study suggest that while untapped opportunities exist for waste diversion, a paradigm shift in legislation, attention, and financial incentives is needed to make circular systems a reality in the built environment. Using an analysis of two accessory dwelling units under construction in Durham as a lens to articulate Haven’s current waste management efforts, this study found that Haven’s waste generation at the two sites is already 7% better than what is expected from the industry benchmark. To communicate broader impact and demonstrate tangible benefits of improved waste management to Haven, it is important to translate these waste numbers into global warming potential. Our carbon emissions analysis speaks to reduced environmental impact across the board if viable alternatives to landfilling waste can be scaled up and implemented. The recommendations outlined in this report, while specifically focused on these two units are broad enough to also be applied to the wider residential construction market. Recommended next steps: -Communicate the need for alternative marketplaces for waste -Encourage waste measurement & engage suppliers -Get policy support to build out the marketplace infrastructure for diversion -Coordinate waste haulingItem Open Access Strategies to Enable a Circular Economy in the Electronics Industry: Electrochemical Recovery of Metals(2017) O'Connor, Megan PatriciaAdvanced electronics and the clean energy industries increasingly rely on rare earth and specialty metals (e.g., yttrium, osmium, and indium; RESE). This may cause a bottleneck effect where demand for these metals cannot keep up with supply from primary extraction alone. Furthermore, few management strategies exist across the life cycle, leading to low recycling rates of less than 1% and little to no reuse of materials. These factors have led the U.S. Department of Energy to label these metals as “critical”, with respect to their importance to clean energy.
The goal of this thesis was to target the problem of material criticality and provide specific scientific advancements needed to mitigate this issue to enable a circular economy within the electronics industry. After identifying these needs across the life cycle, it was apparent that the manufacturing and end-of-life stages were where technological contributions could have the biggest impact. In response to this need, I then focused on building a device capable of recycling RESE for direct reuse in industrial manufacturing.
First, I outlined the technical objectives and advancements needed across the electronics life cycle to enable a closed-loop system. Here, I focused on detailing tasks including: (1) design devices for disassembly, (2) materials for substitution, (3) manufacturing processes that enable the use of recycled materials, (4) fabrication efficiency, (5) technology interventions to enable e-waste recovery, (6) methods to collect and separate e-waste components, (7) technologies to digest and recover RESE, and (8) technologies to separate commercially desirable, high-purity outputs.
Second, I developed a technology to tackle one of these necessary advancements, which was developing a device to recycle RESE from industrial waste streams. The objective was to build a technology capable of selectively recovering and separating RESE on individual filters to enable direct reuse. Here, I successfully built a carbon nanotube (CNT)-enabled filter device that electrochemically recovered and separated RESE from bulk metals, recovering them as metal oxides. I also detailed the mechanism of recovery, which was determined to be an oxygen reduction mechanism, and separation was based on hydroxide stability.
To increase the selectivity of the device, I then tested redox mediators (i.e., organic molecules that facilitate electron transfer and redox equilibrium) in the system to obtain direct metal reduction to reclaim zero-valent metal instead of metal oxides. Here, the goal was to develop a method to separate these metals based on their reduction potentials instead of their hydroxide stabilities. Results indicated that these mediators did not transfer electrons to the metals as anticipated, but instead were binding to the metals themselves, or were transferring the electrons to the oxygen, providing another pathway for enhanced oxide deposition.
Next, a variety of metal recovery techniques were tested to reclaim the metals off the CNT filters to provide metals for reuse in industrial manufacturing. Here, solution-based and solid-based methods were utilized, with acid washing and full filter combustion giving the highest recovery values, near 100%. Metal selectivity between acids indicated potential for further separation capability. Finally, my observations from the other chapters identified many key design modifications needed to enable the successful scale up of this technology. Here, I detail the specific designs modifications needed and provide rationale for each.
The contributions from my work include providing specific scientific advancements needed to enable a circular economy in the electronics industry, as well as providing a technology to recover and separate RESE from mixed metal streams. I also detail other strategies to further advance this technology, as well provide a detailed outline of design modifications needed for scale up. This set of work provides motivation and an outline of research needed to encourage academia and industry to pursue work in this critically important field.
Overall, this technology could offer several advantages including: enhanced recovery of high-value specialty minerals using low-cost CNT filters, reduced need for mining Earth-rare minerals in politically unstable or environmentally undesirable locations, and reduced emissions of toxic elements or nascent industrial minerals that have yet unknown toxicities or environmental impacts.