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  1. Abstract

    This paper presents an exergy-based sustainability analysis of manufacturing roof tiles from plastic waste in Uganda. Exergy analyses measure the sustainability of industrial processes. This work focuses specifically on the developing country context and on utilizing waste material. A summary of the current plastic waste situation in Uganda, the environmental and health issues associated with plastic waste, current means of recycling plastic waste into new products, and an analysis of the Ugandan roofing market are presented. The motivation for this study is to examine the resources utilized to improve overall exergy efficiency, reduce production costs, and reduce negative environmental impacts. The company, Resintile, is the only manufacturer of roof tiles from plastic waste in Uganda. Their tiles comprised mainly of sand and plastic waste are manufactured in an industrialized process involving drying, extrusion, and pressing. The exergy consumed at each stage including transportation is presented. The extruder consumes the majority of the exergy, but wrapping insulation around the barrel could save over 3 MJ, and a heat engine could provide over 7.5 MJ of usable exergy. The total exergy consumed to produce one batch of seventy-five tiles is over 122 MJ, the potentially recoverable exergy is over 5 MJmore »(4.3% of consumed exergy), and the realistic recoverable exergy is nearly 10.7 MJ (8.7% of consumed exergy). The realistic can be greater than the potential by adding a heat engine to the sand drying process to generate usable exergy rather than merely recover consumed exergy. Resintile’s plastic roof tiles save a net 86.3 kg of CO2 from entering the atmosphere per batch of tiles and adoption of the suggested improvements to the manufacturing process would save an additional 3.8 kg of CO2 per batch.

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  2. Abstract Safely managed waste reuse may be a sustainable way to protect human health and livelihoods in agrarian-based countries without adequate sewerage. The safe recovery and reuse of fecal sludge-derived fertilizer (FSF) has become an important policy discussion in low-income economies as a way to manage urban sanitation to benefit peri-urban agriculture. But what drives the user acceptance of composted fecal sludge? We develop a preference-ranking model to understand the attributes of FSF that contribute to its acceptance in Karnataka, India. We use this traditionally economic modeling method to uncover cultural practices and power disparities underlying the waste economy. We model farmowners and farmworkers separately, as the choice to use FSF as an employer versus as an employee is fundamentally different. We find that farmers who are willing to use FSF prefer to conceal its origins from their workers and from their own caste group. This is particularly the case for caste-adhering, vegetarian farmowners. We find that workers are open to using FSF if its attributes resemble cow manure, which they are comfortable handling. The waste economy in rural India remains shaped by caste hierarchies and practices, but these remain unacknowledged in policies promoting sustainable ‘business’ models for safe reuse.more »Current efforts under consideration toward formalizing the reuse sector should explicitly acknowledge caste practices in the waste economy, or they may perpetuate the size and scope of the caste-based informal sector.« less
  3. Pettigrew, Melinda M. (Ed.)
    ABSTRACT Viral genome sequencing has guided our understanding of the spread and extent of genetic diversity of SARS-CoV-2 during the COVID-19 pandemic. SARS-CoV-2 viral genomes are usually sequenced from nasopharyngeal swabs of individual patients to track viral spread. Recently, RT-qPCR of municipal wastewater has been used to quantify the abundance of SARS-CoV-2 in several regions globally. However, metatranscriptomic sequencing of wastewater can be used to profile the viral genetic diversity across infected communities. Here, we sequenced RNA directly from sewage collected by municipal utility districts in the San Francisco Bay Area to generate complete and nearly complete SARS-CoV-2 genomes. The major consensus SARS-CoV-2 genotypes detected in the sewage were identical to clinical genomes from the region. Using a pipeline for single nucleotide variant calling in a metagenomic context, we characterized minor SARS-CoV-2 alleles in the wastewater and detected viral genotypes which were also found within clinical genomes throughout California. Observed wastewater variants were more similar to local California patient-derived genotypes than they were to those from other regions within the United States or globally. Additional variants detected in wastewater have only been identified in genomes from patients sampled outside California, indicating that wastewater sequencing can provide evidence for recent introductionsmore »of viral lineages before they are detected by local clinical sequencing. These results demonstrate that epidemiological surveillance through wastewater sequencing can aid in tracking exact viral strains in an epidemic context.« less
  4. Thet Wai, Khin (Ed.)
    Water affordability is central to water access but remains a challenge to measure. California enshrined the human right to safe and affordable water in 2012 but the question remains: how should water affordability be measured across the state? This paper contributes to this question in three steps. First, we identify key dimensions of water affordability measures (including scale, volume of water needed to meet ‘basic’ needs, and affordability criteria) and a cross-cutting theme (social equity). Second, using these dimensions, we develop three affordability ratios measured at the water system scale for households with median, poverty level, and deep poverty (i.e., half the poverty level) incomes and estimate the corresponding percentage of households at these income levels. Using multiple measures conveys a fuller picture of affordability given the known limitations of specific affordability measures. Third, we analyze our results disaggregated by a key characteristic of water system vulnerability–water system size. We find that water is relatively affordable for median income households. However, we identify high unaffordability for households in poverty in a large fraction of water systems. We identify several scenarios with different policy implications for the human right to water, such as very small systems with high water bills andmore »low-income households within large water systems. We also characterize how data gaps complicate theoretical ideals and present barriers in human right to water monitoring efforts. This paper presents a systematic approach to measuring affordability and represents the first statewide assessment of water affordability within California’s community water systems.« less
  5. Executive Summary ● As the Biden-Harris administration recommits the US to the Paris Agreement, a robust national net zero emissions strategy, integrated with local and corporate decarbonization targets, will ensure the nation achieves its climate goals. A new nationwide survey of current net zero climate commitments reveals the following: ● The US has a broad foundation of local net zero ambition on which to build a robust national decarbonization pathway. At least 53% of Americans live in a jurisdiction with a subnational net zero target. Furthermore, US companies accounting for at least $5.2 trillion in yearly sales have committed to net zero. ● Discrepancies in the quality of these targets highlight the need for strong federal leadership to raise the bar for existing subnational and corporate targets and spur further ambition to meet the goals laid out in the Paris Agreement.1 ● Existing state, local and private sector targets require improved alignment in governance mechanisms, consideration of equity and use of offsets. ● To achieve net zero emissions in the US by 2050 in an equitable, just, and leastcost manner, the White House Climate Task Force and Congress should enact policies to strategically strengthen and grow subnational and corporate ambition.more »In conjunction, subnational and corporate actors must continue to set and improve upon existing targets. ● Our empirical findings indicate a strong basis of support for federal policymakers to implement a robust national net zero strategy. Four key policies will enable government leaders to connect ambition to action: ○ Pledge: Include a robust net zero pledge in the US’ Nationally Determined Contribution (NDC) submission that exceeds the United Nations Framework Convention on Climate Change (UNFCCC) Race to Zero minimum criteria and adopts key leadership practices. These practices include creating a pledge that is codified in law, covers all greenhouse gases across operations and supply chains and includes an interim target of 50% emissions reductions by 2030. ○ Plan: Publish a national net zero roadmap that includes considerations of equity and justice and places constraints on the role of offsets. ○ Proceed: Align economic recovery spending with the aims of the net zero target, develop sector-specific net zero benchmarks and template strategies and mandate net zero alignment as a condition for federal bailouts. ○ Publish: Publish an annual national progress report that includes the progress of subnational commitments.« less