• Energy Research

Abstract Biomass resources could be used in the Northeastern U.S. in centralized district heating networks supplied by combined heat and power (CHP) plants to reduce consumption of petroleum resources (fuel oil), generate renewable electricity, and cost-effectively reduce greenhouse gas (GHG) emissions when supplying buildings with space and water heating. Alternatively, the CHP plants could be powered by natural gas, which would reduce GHG emissions relative to conventional, individual heating solutions owing to the improved efficiency of cogeneration. To assess the potential for investment in these technologies, hourly heat load demand in residential and commercial buildings in all New England and New York state towns (populations > 5000) was estimated and used to optimize the energy efficiency of district heating networks using MODEST software. All of the 116 studied locations without access to natural gas distribution infrastructure showed negative carbon abatement costs, the majority between −$250 and −$38 per Mg CO2 equivalents (eq.), when biomass-fed district heating was implemented due to significantly reduced operational costs and life cycle GHG emissions. Similarly, almost all (465 out of 467) locations connected to the natural gas grid were found to have negative GHG abatement costs, ranging from −$4500 to −$400 per Mg CO2 eq., demonstrating strong economic feasibility for district heating. Natural has an economic advantage over biomass in district heating due to its combined cycle CHP plants being able to generate more electricity per heat unit compared to biomass CHP plants and its lower O&M costs. District heating in all locations could abate 2.6 billion Mg of CO2 eq. at an economic surplus over 30 ears of continuous operation. Using a framework that integrated spatial tools, optimization, LCA, and cost evaluation, this study uniquely identified promising locations in the U.S. where district heating could be both environmentally and economically beneficial. This framework can be applied to other global regions that have significant space heating needs, for CHP implementation, and as a tool for identifying alternative building energy investments, such as improved insulation or individual space heating solutions, which in some cases could yield higher GHG reductions per dollar.

Abstract Feed-in tariffs and Renewable Portfolio Standards (RPS) are among the most prominent policies to address anthropogenic influence on climate change. Implementation of RPS favorably affects renewable energy supply and rural development while reducing the land available for meeting demand for food and feed resulting from global population growth. Even in the vast Great Plains of the United States, land requirements are primary considerations between increasing renewable energy capacity and food and feed production. This study applied life cycle assessment (LCA) and project economics to estimate and compare the land intensity and profitability of anaerobic digestion and wind energy projects in the Great Plains. The results show that significantly more energy and revenue can be generated per hectare of land using wind versus anaerobic digestion. Economically, the benefit-to-cost ratios of wind farms were almost twice as favorable as anaerobic digester facilities. Wind farms have consistent benefit-to-cost ratios of 2.15 while the anaerobic digester facilities benefit to cost ratios range from 1.2 to 1.25. Legislature changes to RPS could incentivize increasing the number of anaerobic digesters while also assisting in reversing the current trend of diminishing dairy farms while reducing climate change risks and creating new economic opportunities for renewable energy.

The scale-up of mechanochemical methods could play a transformative role in making manufacturing processes in the pharmaceutical industry greener by eliminating solvent use and recovery. Combined with energy-efficient continuous processing that consolidates reaction steps, mechanochemistry’s environmental and economic benefits may translate across product supply chains. Here, we evaluate numerous sustainability and green chemistry metrics for producing nitrofurantoin, an active pharmaceutical ingredient (API), via mechanochemical continuous twin-screw extrusion (TSE) and conventional solvent-batch synthesis methods. We find a significant reduction in all metrics for TSE including energy, climate change, and human and ecological health, as well as cost due to reducing excess reactant consumption and eliminating solvents while maintaining high product selectivity. In addition, replacing the direct energy source to drive the chemical reaction from mostly thermal to electrical sources does not increase the net life cycle energy consumed to produce functionally equivalent API. We conclude that mechanochemical synthesis via TSE holds multiple sustainability benefits for manufacturing APIs and potentially other chemical products.

Renewable fuel standards for biofuels have been written into policy in the U.S. to reduce the greenhouse gas (GHG) intensity of transportation energy supply. Biofuel feedstocks sourced from within a regional market have the potential to also address sustainability goals. The U.S. Mid-Atlantic region could meet the advanced fuel designation specified in the Renewable Fuel Standard (RFS2), which requires a 50% reduction in GHG emissions relative to a gasoline baseline fuel, through ethanol produced from winter barley (Hordeum vulgare L.). We estimate technology configurations and winter barley grown on available winter fallow agricultural land in six Mid-Atlantic states. Using spatially weighted stochastic GHG emission estimates for winter barley supply from 374 counties and biorefinery data from a commercial dry-grind facility design with multiple co-products, we conclude that winter barley would meet RFS2 goals even with the U.S. EPA’s indirect land use change estimates. Using a conservative threshold for soil GHG emissions sourced from barley produced on winter fallow lands in the U.S. MidAtlantic, a biorefinery located near densely populated metropolitan areas in the Eastern U.S. seaboard could economically meet the requirements of an advanced biofuel with the co-production of CO2 for the soft drink industry.

Abstract Lead halide perovskites (LHP) are an emerging class of photovoltaic (PV) materials that have drawn intense interest due to their power conversion efficiencies above 23% and their potential for low-cost fabrication. However, the toxicity of lead causes concern about its use in LHP-PV at large scales. Here, we quantified lead intensity and toxicity potential of LHP-PV in potential commercial production. Lead intensity in LHP-PV life cycles can be 4 times lower and potential toxic emissions can be 20 times lower than those in representative U.S. electricity mixes, assuming that PV operational lifetimes reach 20 years. We introduce the metric “toxicity potential payback time”, accounting for toxic emissions in the life cycle of energy cycles, and showed that it is

Mechanochemical methods are currently under investigation as alternative approaches to conventional solvent-batch synthetic chemistry. Environmental life cycle assessment (LCA) is needed to evaluate and compare chemical products made through mechanochemical processes with those from conventional production routes, using “cradle-to-gate” system boundaries. However, chemical supply chains involved in product manufacturing are often unknown, and synthesis tracing of these chemicals is needed to create life cycle environmental profiles. Herein, we trace the synthesis of the chemicals required to produce Pigment Black 31, a perylene diimide (PDI) organic dye, based on two main principles: maximum reaction yield and minimum synthetic steps. This approach facilitates comparing the environmental life cycle impact of producing Pigment Black 31 via twin-screw extrusion (TSE) with a conventional solvent-batch process, wherein similar reactants are used in both systems. The production of Pigment Black 31 via the TSE process affords a roughly order-of-magnitude reduction across global warming and human and ecological health life cycle environmental impacts following ReCiPe 2016 methods, mainly due to solvent reduction and elimination compared with production via the solvent-batch process. Interestingly, this reduction is found despite the need for a methanol extraction step in the purification of Pigment Black 31 made by TSE. We conclude that while LCA data sets may not be available for other organic dyes produced similarly through TSE processes, the life cycle environmental impacts for Pigment Black 31 can be used to approximate those of similar organic dyes, such as Pigment Black 32.

AbstractDistrict 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.

Biofuels vary greatly in their carbon intensity, depending on the specifics of how they are produced. Policy frameworks are needed to ensure that biofuels actually achieve intended reductions in greenhouse gas emissions. Current approaches do not account for important variables during cultivation that influence emissions. Estimating emissions based on biogeochemical models would allow accounting of farm-specific conditions, which in turn provides an incentive for producers to adopt low emissions practices. However, there are substantial uncertainties in the application of biogeochemical models. This paper proposes a policy framework that manages this uncertainty while retaining the ability of the models to account for (and hence incentivize) low emissions practices. The proposed framework is demonstrated on nitrous oxide (N2O) emissions from the cultivation of winter barley. The framework aggregates uncertainties over time, which (1) avoids penalizing producers for uncertainty in weather, (2) allows for a high degree of confidence in the emissions reductions achieved, and (3) attenuates the uncertainty penalties borne by producers within a timescale of several years. Results indicate that with effective management, N2O emissions from feedstock cultivation may be 20% of the carbon intensity of gasoline. If these emissions reductions are monetized, the framework can provide up to $0.002 per liter credits (0.8 cents per gallon) to fuel producers, which could incentivize emissions mitigation practices by biofuel feedstock suppliers, such as avoiding fall N application on silty clay loam soils. The conservatism in the current approach fails to incentivize the adoption of biofuels, while the lack of specificity fails to incentivize site-level mitigation practices. Improved uncertainty accounting and consideration of farm-level practices will incentivize mitigation efforts at landscape to global scales.