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Increasingly, circularity indicators for material, energy, and water systems guide circular economy design. While indicators for products made from recycled carbon-based materials are somewhat common, peer indicators for waste nitrogen-derived products are limited. It is important, however, to develop such indicators to guide emerging technologies that transform waste nitrogen into products. In this study, we summarize the nitrogen circularity indicator literature, emphasizing the agricultural and wastewater sectors. Next, we use the Material Circularity Indicator (MCI) developed by the Ellen MacArthur Foundation, to quantify the circularity of products made from waste nitrogen in swine manure. We considered four test cases using different technologies to recover nitrogen from the manure. Our analysis indicates that technologies that seem to increase circularity on the surface may not yield a substantial increase in MCI results. Finally, we discuss the strengths and weaknesses of using the MCI for product-level analysis and further developments. 

Electric vehicle batteries contain many internationally sourced critical minerals. Seeking a stable mineral supply, the US Inflation Reduction Act sets a market-value-based target for battery critical mineral content. In 2027, for an electric vehicle to be tax-credit eligible, 80% of the market value of critical minerals in its battery must be sourced domestically or from US free-trade partners. We determined that the target may be achievable for fully electric vehicles with nickel cobalt aluminium cathode batteries, but achieving the target with lithium iron phosphate and nickel cobalt manganese batteries would be challenging. We also note that a mass-based target could avoid some of the challenges posed by a market-value target, such as volatile market prices. We further conclude that the approach the Act has taken ignores the environmental effects of mining, non-critical minerals supply, support for recycling and definitions that avoid gamesmanship.

 

The nitrogen cycle needed for scaled agriculture relies on energy- and carbon-intensive processes and generates nitrate-containing wastewater. Here we focus on an alternative approach—the electrified co-electrolysis of nitrate and CO2 to synthesize urea. When this is applied to industrial wastewater or agricultural runoff, the approach has the potential to enable low-carbon-intensity urea production while simultaneously providing wastewater denitrification. We report a strategy that increases selectivity to urea using a hybrid catalyst: two classes of site independently stabilize the key intermediates needed in urea formation, *CO2NO2 and *COOHNH2, via a relay catalysis mechanism. A Faradaic efficiency of 75% at wastewater-level nitrate concentrations (1,000 ppm NO3− [N]) is achieved on Zn/Cu catalysts. The resultant catalysts show a urea production rate of 16 µmol h−1 cm−2. Life-cycle assessment indicates greenhouse gas emissions of 0.28 kg CO2e per kg urea for the electrochemical route, compared to 1.8 kg CO2e kg−1 for the present-day route. 

Abstract Methane emission reductions are crucial for addressing climate change. It offers short-term benefits as it holds high short-term reductions in radiative forcing. Efforts towards the reduction of methane emissions are already underway. In this study, we compared and analyzed the mitigation benefits of cutting large amounts of methane emissions from the oil and gas sector on short-time scales with reducing an equivalent amount of carbon dioxide using carbon capture and storage (CCS). Characteristics of CCS are that it would require substantial infrastructure development and that it incorporates deployment delays. Results illustrate that prioritizing quickly deployable methane emission reduction alternatives that necessitate minimal construction is an efficient approach to achieve near-term climate change relief. Graphical abstract 

Abstract Even in advanced economies, underperforming infrastructure is a persistent rural development challenge, with the case of non-compliant small drinking water systems (SDWSs) especially concerning because of the importance of safe drinking water to human health. While technical and financial deficits are known contributors to SDWS underperformance in rural settings, the role of local cultural and social context in water governance are less clear. The need for interoperable concepts that help explain how local contextual factors influence rural water governance and operation motivates this study. Drawing on insights from community resilience and critical infrastructure scholarship, this study draws attention to a previously overlooked dimension of local infrastructure governance: social memory. Archival research and 25 semi-structured interviews with experts and local stakeholders inform the paper’s reconstruction of the 100 years history of an SDWS in rural Montana, USA and analysis of the contemporary social memory it has generated. The study finds that social memory acts as a medium through which the lived experience of infrastructure influences priorities and values about its governance, especially in the context of small towns. Three major themes in the dynamics of social memory of infrastructure are described, including longevity, aesthetic and material qualities, and articulation with economic trajectories. In addition to establishing social memory as an effective conceptualization of the generative influence of infrastructure in water governance at the local scale, the paper has implications for policy; specifically, the observation that in addition to financial and technical capacity, historical experience is a powerful driver of infrastructure governance and outcomes such as underperformance.