Environmental life-cycle assessment of waste-coal pellets production

Industrial decarbonization is crucial to keeping the global mean temperature <1.5°C above pre-industrial levels. Although unabated coal use needs to be phased out, coal is still expected to remain an important source of energy in power and energy-intensive industries until the 2030s. Decades of coal exploration, mining and processing have resulted in ~30 billion tonnes of waste-coal tailings being stored in coal impoundments, posing environmental risks. This study presents an environmental life-cycle assessment of a coal-processing technology to produce coal pellets from the waste coal stored in impoundments. It has been shown that the waste-coal pellets would result in the cradle-to-gate global warming of 1.68–3.50 kgCO2,eq/GJch, depending on the source of electricity used to drive the process. In contrast, the corresponding figure for the supply of conventional coal in the US was estimated to be 12.76 kgCO2,eq/GJch. Such a reduction in the global-warming impact confirms that waste-coal pellets can be a viable source of energy that will reduce the environmental impact of the power and energy-intensive industries in the short term. A considered case study showed that complete substitution of conventional coal with the waste-coal pellets in a steelmaking plant would reduce the greenhouse-gas emissions from 2649.80 to 2439.50 kgCO2,eq/tsteel. This, in turn, would reduce the life-cycle greenhouse-gas emissions of wind-turbine manufacturing by ≤8.6%. Overall, this study reveals that the use of waste-coal pellets can bring a meaningful reduction in industrial greenhouse-gas emissions, even before these processes are fully decarbonized.

Exergy-aided environmental life cycle assessment of propylene oxide production

Purpose Propylene oxide (PO) is one of the useful chemicals that is predicted to experience a compound annual growth rate of 3.9% from 2020 through 2027. The environmental burdens of the current PO production process and its corresponding utility system including power generation system need to be determined quantitatively as a response to increasing demands for its environmentally sustainable production process in the energy transition period from fossil fuels towards renewable energy resources. Methods A new methodology is proposed to study the PO production process called exergy-aided environmental life cycle assessment (EELCA), using the US National Renewable Energy Laboratory’s database known as life cycle inventory (LCI) database. EELCA is dedicated to LCA studies of processes in the energy transition period and is aided by Monte Carlo simulation (MCS) as a tool for discernibility analysis which brings another dimension to the EELCA because MCS was often used to assess uncertainty in LCA studies. EELCA impact categories are classified into two classes: (i) emission-dependent impact categories addressed by ReCiPe and (ii) resource-dependent impact categories covered by cumulative exergy demand (CExD). The alternative energy like bioenergy is evaluated through the stepwise scenarios assisted by MCS, which are employed in openLCA with 10,000 iterations. Results and discussion The cumulative exergy depletion of the base scenario is 6.1898 MJ (CExD). The human health and ecosystem impacts are 3.65E-06 DALY and 1.58E-08 species.yr, respectively. Human health-total (2.7E-4 DALY) is the most important category, where the power generation system by residual fuel oil (33.19%) is on top of the list. By analysing statistically discernible scenarios using EELCA, it has been proven that natural gas is not a proper choice for energy mix in the energy transition period. This is because natural gas-based scenarios present more burden compared to residual fuel oil-based scenarios especially regarding human toxicity, freshwater ecotoxicity, marine ecotoxicity, terrestrial acidification, and particulate matter formation. This study shows that the reduction in environmental impacts without changes in the production process technology is feasible through implementing bioenergy scenarios. Conclusions Having applied successfully EELCA, this study shows that PO production in the present configuration is not sustainable at all. The statistically discernible scenarios regarding energy mix selection help to enhance sustainability of the PO production process. Moreover, by examining the application of CExD along with LCA analysis, it is proved that by using the concept of CExD, we were able to represent the environmental impacts of the entire system with one figure, which tremendously facilitates the calculations in MCS.

Environmental life cycle assessment and operating cost analysis of a conceptual battery hybrid-electric transport aircraft

Noise and greenhouse gas emission targets set by e.g., the EU commission, NASA, and ICAO oblige the aviation industry to reduce its environmental footprint. Battery-powered hybrid-electric aircraft are currently being investigated in this regard as they can potentially reduce in-flight greenhouse gas emissions and noise. However, most studies to date have focused on the CO2 emission reduction potential instead of considering the total life cycle environmental impact. Hence, within this study an environmental life cycle assessment method for a hybrid-electric aircraft is developed and applied, supplemented by a direct operating costs analysis. This allows the simultaneous evaluation of the environmental impact reduction potential and the economic consequences for aircraft operators. This demonstrates the faced trade-off and contributes to a meaningful review process. A single-aisle transport aircraft (A320 class) serves as a use case for the established methodology. It consists of the conceptual aircraft design, the environmental life cycle assessment, and the direct operating costs analysis for a conventional reference aircraft and a hybrid-electric aircraft with a discrete parallel powertrain architecture. It should be noticed that the focus of this study is the comparison of conceptual aircraft designs of the same fidelity on system level, in lieu of the detailed modeling of a hybrid-electric aircraft. Results show that for a degree of hybridization of 0.3, the environmental impact of the hybrid-electric configuration increased by $$15.1\%$$ 15.1 % , while the operating costs increased by $$41.0\%$$ 41.0 % compared to a conventional reference aircraft. For a future scenario, favourable for hybrid-electric aircraft with i.a. renewable electricity production, the environmental impact could be reduced by $$7.0\%$$ 7.0 % compared to the reference aircraft. At the same time, the operating costs gap between both configurations decreases to $$+ 26.8\%$$ + 26.8 % . Hybrid-electric aircraft should therefore be investigated further as a potential solution to reduce the environmental impact of aviation, if simultaneously to developing them the expansion of renewable energies is fostered. Nevertheless, this reduction in environmental impact involves a high direct operating costs penalty.

Environmental life cycle assessment of yellow mealworm (Tenebrio molitor) production for human consumption in Austria – a comparison of mealworm and broiler as protein source

Purpose Global food production needs to increase to provide enough food for over 9 billion people living by 2050. Traditional animal production is among the leading causes for climate change and occupation of land. Edible insects might be a sustainable protein supply to humans, but environmental life cycle assessment (LCA) studies on them are scarce. This study performs an LCA of a small-scale production system of yellow mealworms (Tenebrio molitor) in Central Europe that are supplied with organic feedstuff. Methods A combined ReCiPe midpoint (H) and CED method is used to estimate the potential environmental impacts from cradle-to-gate. Impact categories include global warming potential (GWP), non-renewable energy use (NREU), agricultural land occupation (ALOP), terrestrial acidification potential (TAP) and freshwater eutrophication potential (FEP). The robustness of the results is tested via sensitivity analyses and Monte Carlo simulations. Results and discussion Impacts related to the production of 1 kg of edible mealworm protein amount to 20.4 kg CO2-eq (GWP), 213.66 MJ-eq (NREU), 22.38 m2 (ALOP), 159.52 g SO2-eq (TAP) and 12.41 g P-eq (FEP). Upstream feed production and on-farm energy demand related to the heating of the facilities are identified as environmental hot-spots: Depending on the impact category, feed supply contributes up to 90% and on-farm heating accounts for up to 65% of overall impacts. The organic mealworm production system is contrasted with a selected Austrian organic broiler production system, to which it compares favourably (18–72% lower impacts per category), with the exception of freshwater eutrophication (6% higher impacts). Conclusions This case study shows that the Austrian mealworm production system compares favourably to traditional livestock systems. Compared to LCAs from large-scale T. molitor rearing facilities in France and in the Netherlands, however, the Austrian production system cannot compete for the reasons of production scale, feed conversion efficiency and type of production system. Nevertheless, the investigated mealworms represent a sustainable protein alternative that should be added to the Western diet.