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Wastewater treatment plants (WWTPs) with anaerobic digestion of biosolids produce an ammonia-rich sidestream out of which nitrogen can be recovered through air stripping. Recovered ammonia can be used to produce ammonium sulfate (AS) for agricultural use, enabling the circular return of nitrogen as fertilizer to the food system. We investigate the cost and life cycle environmental impact of recovering ammonia from the sidestream of WWTPs for conversion to AS and compare it to AS production from the Haber Bosch process. We perform life cycle assessment (LCA) to investigate the environmental impact of AS fertilizer production by air-stripping ammonia from WWTP sidestreams at varying sidestream nitrogen concentrations. Techno-economic analysis (TEA) is performed to assess the break-even selling price of sidestream AS production at a WWTP in the City of Philadelphia. Greenhouse gas emissions for air-stripping technology range between 0.2 and 0.5 kg CO 2 e/kg AS, about six times lower than the hydrocarbon-based Haber-Bosch process, estimated at 2.5 kg CO 2 e/kg AS. Further reduction of greenhouse gas emissions is feasible by replacing fossil-based energy use in air-stripping process (82-98 % of net energy demand) with renewable sources. Also, a significant reduction in mineral depletion and improvement in human and ecosystem health are observed for the air-stripping approach. Furthermore, the break-even selling price for installing sidestream-based AS production at the Philadelphia's WWTP, considering capital and operating costs, is estimated at $0.046/kg AS (100 %), which is 92 % lower than the 2014 estimate of AS's average selling price at farms in the United States. We conclude that even with varying ammonia concentrations and high sidestream volume, air-stripping technology offers an environmentally and economically favorable option for implementing nitrogen recovery and simultaneous production of AS at WWTPs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

District heating (DH) systems can improve energy efficiency, reduce greenhouse gas (GHG) emissions, and be a cost‐effective residential space heating alternative over conventional decentralized heating. This study uses radiative forcing (RF), a time‐sensitive life cycle assessment metric, to evaluate space heating alternatives. We compare forest residue and willow biomass resources and natural gas as fuel sources against decentralized heating using heating oil. The comparison is performed for selected locations in the Northeastern United States over a 30‐year production timeline and 100 observation years. The natural gas and willow scenarios are compared with scenarios where available forest residue is unused and adds a penalty of GHG emissions due to microbial decay. When forest residues are available, their use is recommended before considering willow production. Investment in bioenergy‐based DH with carbon capture and storage and natural‐gas‐based DH with carbon capture and storage (CCS) technology is considered to assess their influence on RF. Its implementation further improves the net carbon mitigation potential of DH despite the carbon and energy cost of CCS infrastructure. Soil carbon sequestration from willow production reduces RF overall, specifically when grown on land converted from cropland to pasture, hay, and grassland. The study places initial GHG emissions spikes from infrastructure and land‐use change into a temporal framework and shows a payback within the first 5 years of operation for DH with forest residues and willow. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Decentralized approaches to managing urban stormwater are gaining increased attention within the contexts of urban sustainability, climate change adaptation, and as a means of reducing combined sewer overflows (CSOs). This study applied a life cycle assessment (LCA) to comparing the environmental efficiency of three means of equivalently reducing CSOs to the Bronx River (Bronx, NY, USA). Strategy 1 featured decentralized green infrastructure technologies, while 'grey' strategies 2 and 3 detained, and detained and treated, respectively, excess flows at the end of pipe. We estimated greenhouse gas emissions (in metric tons of carbon dioxide equivalents [t CO2-eq]) over the construction, operation, and maintenance phases, including energy consumed at the wastewater treatment plant (WWTP), carbon sequestered, and shading provided by vegetation (in the case of the green approach) over a 50-year analysis period. The study area comprised the entire drainage area contributing to New York State permitted CSO discharge points associated with the Hunts Point WWTP. The analysis was performed using a hybrid of process and economic input-output (EIO) LCA methods. The decentralized green strategy outperformed the two grey strategies in terms of this set of environmental metrics. The net emissions of the green strategy over 50 years was 19,000 t CO2-eq, whereas the grey strategies emitted 85,000 t CO2-eq (detention) and 400,000 t CO2-eq (detention and treatment). These results were significantly influenced by the emissions associated with the operation and maintenance activities required for strategies 2 and 3, and the carbon sequestered and shading provided by the vegetation in strategy 1, and suggest that watershed managers who seek to reduce CSOs and reduce carbon footprints would opt for the green approach. [ABSTRACT FROM AUTHOR]

Abstract: Lignocellulosic ethanol holds promise for addressing climate change and energy security issues associated with personal transportation through lowering the fuel mixes’ carbon intensity and petroleum demand. We compare the technological features and life cycle environmental impacts of near- and mid-term ethanol bioconversion technologies in the United States. Key uncertainties in the major processes: pre-treatment, hydrolysis, and fermentation are evaluated. The potential to reduce fossil energy use and greenhouse gas (GHG) emissions varies among bioconversion processes, although all options studied are considerably more attractive than gasoline. Anticipated future performance is found to be considerably more attractive than that published in the literature as being achieved to date. Electricity co-product credits are important in characterizing the GHG impacts of different ethanol production pathways; however, in the absence of near-term liquid transportation fuel alternatives to gasoline, optimizing ethanol facilities to produce ethanol (as opposed to co-products) is important for reducing the carbon intensity of the road transportation sector and for energy security. [Copyright &y& Elsevier]

The retirement of aging concrete infrastructure is resulting in significant material flows of concrete debris in the economy. A proposed outlet for this debris is new concrete: the debris can be crushed into small particles and used in place of virgin aggregate. This form of recycling lessens use of aggregate resources, but its consequences are less clear in terms of energy use and greenhouse gas emissions. To examine these impacts, we develop life-cycle inventory models of the manufacturing of recycled concrete aggregate from debris. Results from these models are then used in life-cycle models of nonstructural concretes containing varying proportions of recycled concrete aggregate. For scenarios in which virgin and recycled aggregates are locally available, only 20% recycled aggregate substitution is beneficial. This corresponds to a modest reduction in energy use and greenhouse gas emissions: up to 15 MJ/m3 and 1.20 kg CO2-eq./m3 of concrete, respectively. Only when virgin aggregate must be transported large distances are higher levels of substitution beneficial, in terms of the metrics studied. [ABSTRACT FROM AUTHOR]

Utilizing domestically produced cellulose-derived ethanol for the light-duty vehicle fleet can potentially improve the environmental performance and sustainability of the transport and energy sectors of the economy. A life cycle assessment model was developed to examine environmental implications of the production and use of ethanol in automobiles in Ontario, Canada. The results were compared to those of low-sulfur reformulated gasoline (RFG) in a functionally equivalent automobile. Two time frames were evaluated, one near-term (2010), which examines converting a dedicated energy crop (switchgrass) and an agricultural residue (corn stover) to ethanol; and one midterm (2020), which assumes technological improvements in the switchgrass-derived ethanol life cycle. Near-term results show that, compared to a RFG automobile, life cycle greenhouse gas (GHG) emissions are 57% lower for an E85-fueled automobile derived from switchgrass and 65% lower for ethanol from corn stover, on a grams of CO2 equivalent per kilometer basis. Corn stover ethanol exhibits slightly lower life cycle GHG emissions, primarily due to sharing emissions with grain production. Through projected improvements in crop and ethanol yields, results for the mid-term scenario show that GHG emissions could be 25-35% lower than those in 2010 and that, even with anticipated improvements in RFG automobiles, E85 automobiles could still achieve up to 70% lower GHG emissions across the life cycle. [ABSTRACT FROM AUTHOR]

• GHG impact and cost of alternative polymer materials compared for long-lived pipe assets. • LCA of recycled HDPE/nanoclay composite material compared with pristine polymer. • Pipe service life predictions from experiments integrated with stochastic LCA models. • Maintaining functional equivalency requires larger mass of polymer for recycled blends. • Bio-HDPE reduces costs and environmental impacts for long-lived pipe assets. 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. [ABSTRACT FROM AUTHOR]

Electric vehicles are being promoted worldwide in an attempt to mitigate greenhouse gas emissions and improve air-quality in cities. Yet, alternative propulsion systems could allow meeting climate change and air-quality policy goals while not raising other environmental burdens. This study offers a glimpse into the mobility solutions aside from traditional battery-electric vehicles (BEVs). A feasibility study of the novel combined electro-thermo-chemical (CETC) propulsion technology composed of a fuel-cell (FC), an internal-combustion engine (ICE) and thermochemical recuperation (TCR) of waste heat is performed based on a life-cycle assessment. A comprehensive comparison between the proposed technology and the BEV is conducted across multiple categories of environmental impacts from the stage of manufacturing, through vehicle use and vehicle end-of-life. Our findings showed for the first time that a technology comprising an internal combustion engine can assure a better environmental performance compared to BEV. Moreover, we demonstrate that the climate-change benefits of the suggested CETC technology over BEV are more pronounced when the share of renewable energy use increases. The study results show that the new CETC technology outperforms the battery electric propulsion for the majority of environmental impacts, including climate-change, air-pollution, human-health and ecological impacts by up to 22%, 62%, 60% and 43%, respectively. It is found that the environmental advantages of the CETC technology over the BEV stem mainly from the vehicle manufacturing stage, affected by the BEV's higher weight and resource-intensive production. These encouraging findings call for further examination and research into BEV alternatives, such as the discussed hybrid CETC powertrain. The latter has promising prospects for future implementation in both mobile and stationary applications. • We proved that a technology comprising ICE can assure a better environmental performance compared to BEV • Climate-change benefits of CETC technology over BEV are more pronounced when the share of a renewable energy use increases • CETC emits less GHG, less target pollutants and has lower ecological impacts than BEV • The overall energy demand from well-to-wheel is lower for the CETC-driven vehicle • CETC powertrain enables achieving higher power at the same efficiency than fuel cell [ABSTRACT FROM AUTHOR]

[Display omitted] • Promising corn-to-aviation fuel GHG emission LCA presented. • Pathway opportunity to meet sustainable aviation fuel policy targets. • CCS and agricultural best management needed to mitigate induced LUC. • Average fuel carbon intensity (AFCI) ranges from 5 to 36 gCO 2 e/MJ fuel. • Retrofitting 1st generation bio-refineries can benefit low C aviation fuel markets. This paper investigates options to produce low carbon and renewable aviation fuel through existing commercial first generation biorefineries, which could be strategic given the rapid growth of the electric vehicle market for personal mobility. We evaluate the environmental impact of retrofitting a first generation biorefinery to produce aviation fuel through chemical process simulation. The analysis investigates the potential for reducing greenhouse gas (GHG) emissions and displacing fossil fuel (petroleum-based jet kerosene) in the aviation fuel industry through using corn feedstocks in dry grind biorefineries to convert sugars to 1,4-dimethylcyclooctane (DMCO), which qualifies as renewable jet-A fuel blend and is infrastructure compatible. The average life cycle GHG emissions for a baseline case and a scenario with carbon capture and storage (CCS) of fermentative CO 2 are 36 and 5 g CO 2 e/MJ DMCO, respectively. Investment in CCS at the biorefinery and adoption of crop best management practices on farms are essential for mitigating the risks of induced land use change GHG emissions for existing corn biorefineries. DMCO as a low-carbon aviation fuel could be a strategic fuel product for retrofitting existing corn dry grind facilities. For aviation fuel supply, corn dry grind facilities could displace about 12 % of jet fuel demand in the near term, which would meet sustainable aviation fuel policy targets. We conclude that corn-to-DMCO shows promise for near-term low-carbon fuel markets in the aviation industry and as a bridge to developing biomass-based jet fuel in the future. [ABSTRACT FROM AUTHOR]