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Switchgrass (Panicum virgatum L.) is a perennial C4 grass native to North America and successfully adapted to diverse environmental conditions. It offers the potential to reduce soil surface carbon dioxide (CO2) fluxes and mitigate climate change. However, information on how these CO2 fluxes respond to changing climate is still lacking. In this study, CO2 fluxes were monitored continuously from 2011 through 2014 using high frequency measurements from Switchgrass land seeded in 2008 on an experimental site that has been previously used for soybean (Glycine max L.) in South Dakota, USA. DAYCENT, a process-based model, was used to simulate CO2 fluxes. An improved methodology CPTE [Combining Parameter estimation (PEST) with "Trial and Error" method] was used to calibrate DAYCENT. The calibrated DAYCENT model was used for simulating future CO2 emissions based on different climate change scenarios. This study showed that: (i) the measured soil CO2 fluxes from Switchgrass land were higher for 2012 which was a drought year, and these fluxes when simulated using DAYCENT for long-term (2015-2070) provided a pattern of polynomial curve; (ii) the simulated CO2 fluxes provided different patterns with temperature and precipitation changes in a long-term, (iii) the future CO2 fluxes from Switchgrass land under different changing climate scenarios were not significantly different, therefore, it can be concluded that Switchgrass grown for longer durations could reduce changes in CO2 fluxes from soil as a result of temperature and precipitation changes to some extent.

On March 24, 2015, a political bureau meeting of the Communist Party of China Central Committee first proposed the political task of "greening" and placed unprecedented importance on the construction of an ecological civilization, aiming to guide China's economy and society toward green and low carbon development. This study aims to examine the impact of this "greening" policy on China's climate change mitigation. First, from an emissions reduction perspective, this study interprets greening as the process of constantly strengthening society's awareness and willingness regarding emissions reduction. Then, this study incorporates a carbon abatement willingness factor into a nonparametric model, and quantitatively simulates the impact of greening on carbon dioxide (CO2) emissions reduction in China. The results show that China can rapidly decrease its CO2 emissions in the early stages of greening. However, when greening passes a certain stage, it no longer affects CO2 emissions. Thus, the willingness to reduce emissions has a diminishing marginal effect on emissions reduction. Additionally, throughout the greening process, China is expected to reduce its CO2 emissions by 36.08%, or 3718.50 million tons. Finally, the impact of greening on China's CO2 emissions exhibits spatial variation, as its undeveloped western region can achieve greater CO2 emissions reductions by promoting greening. Base on the above results, corresponding policy implications are also provided at the end of this paper.

Abstract Bioenergy systems are expected to expand over the coming decades due to their potential to address energy security and environmental pollution challenges. Nevertheless, any renewable energy project can only survive if approved environmentally superior to its conventional counterparts. Life cycle assessment (LCA) is an internationally standardized and validated methodology to evaluate and quantify the environmental impacts of bioenergy systems. However, due to its methodological scope, the LCA method measures only the environmental consequences of the target products of energy systems. The LCA approach can neither allocate the environmental impacts at the component level nor measure the environmental impacts of intermediate products. These challenges can be substantially resolved by systematically integrating the LCA approach with the thermodynamically-rooted exergy, offering a powerful environmental sustainability assessment tool known as “exergoenvironmental analysis“. Due to the unique methodological and conceptual characteristics of exergoenvironmental analysis in revealing the possibilities and trends for improvement, it has recently received increasing attention to mitigate the environmental impacts of bioenergy systems. Therefore, this review is aimed to thoroughly summarize and critically discuss the evaluation of sustainability aspects of bioenergy systems based on exergoenvironmental analysis. The pros and cons of using exergoenvironmental analysis in bioenergy research are also outlined to identify possible future directions for the field. Overall, exergoenvironmental analysis can offer more detailed information on the environmental consequences of each flow and component of bioenergy production plants, thereby diagnosing the breakthrough points for additional environmental improvements.

The Chinese electric power industry, including its coal industry and other energy industries that are not efficient, contributes to China’s serious energy shortages and environmental contamination. The governing authority considers energy conservation to be one of the most prominent national targets, and has formulated various plans for decarbonizing the power system. Applying the trans-log cost function, this paper examined the trans-log cost function to analyze the potential inter-factor substitution among energy, capital and labor. We also investigated what role human capital played in energy substitution for the electric power sector during the period from 1981 to 2017. Three key results were derived: (1) energy is price-insensitive, (2) there exists large substitution sustainability between both capital and labor with energy, and (3) human capital input not only enhances the extent of energy substitutability with capital and labor but also is a substitute to energy itself. These findings imply that the liberalization of the electric price mechanism is conducive to lessening energy use and augmenting non-energy intensiveness, and that energy conservation technology could become more sustainable by investing more capital in the electricity sector, thereby achieving a capital–energy substitution and a decrease of CO2 emissions. We further suggest that the priority for the Chinese electric power industry should be to attach more importance to increasing human capital input.

Abstract The United States Department of Defense (DoD) is considering replacing the 2.8 billion gallons of petroleum jet fuel consumed within the continental United States (CONUS) annually with alternative jet fuels to reduce vulnerability to price and supply fluctuations and improve sustainability. We evaluate the feasibility of replacing DoD CONUS jet fuel with alternative jet fuel from domestic feedstocks and assess the cost, greenhouse gas (GHG) emissions, energy balance, land, water, and fertilizer impacts of nine alternative jet fuel pathways. The feedstocks include terrestrial crops (soy, corn, wood, and grass), marine microalgae, and by-products (forestry residue, municipal solid waste, and waste oil) converted by extraction, fermentation, or thermo-chemical conversion, paired with upgrading steps. We found that domestic biomass feedstocks can meet the DoD CONUS jet fuel demand without significantly affecting food supply. Alternative pathways cost more than petroleum jet fuel ($0.78 l-1 and emitting 89 g CO2 equivalent (CO2e) MJ−1), but many lowered GHG emissions. The forestry residue and waste oil pathways yielded the lowest costs ($0.92 and $0.82 l-1, respectively), decreased emissions (23 and 35 g CO2e MJ−1, respectively), and had negligible effects on land, water, and fertilizer resources. Tradeoffs among sustainability metrics are further explored with a sensitivity analysis and by evaluating carbon-cost scenarios.

IntroductionThe industrial yeast Pichia pastoris is widely used as a cell factory to produce proteins, chemicals and advanced biofuels. We have previously constructed P. pastoris strains that overexpress protein disulfide isomerase (PDI), which is a kind of molecular chaperone that can improve the expression of an exogenous protein when they are co-expressed. Chicken cystatin (cC) is a highly thermostable cysteine protease inhibitor and a homologous protein of human cystatin C (HCC). Wild-type cC and the two mutants, I66Q and ΔW (a truncated cC lacking the á-helix 2) represent proteins with different degrees of stability.MethodsWild-type cC, I66Q and ΔW were each overexpressed in P. pastoris without and with the coexpression of PDI and their extracellular levels were determined and compared. Transcriptomic profiling was performed to compare the changes in the main signaling pathways and cell components (other than endoplasmic reticulum quality control system represented by molecular chaperones) in P. pastoris in response to intracellular folding stress caused by the expression of exogenous proteins with different stabilities. Finally, hub genes hunting was also performed.Results and discussionThe coexpression of PDI was able to increase the extracellular levels of both wild-type cC and the two mutants, indicating that overexpression of PDI could prevent the misfolding of unstable proteins or promote the degradation of the misfolded proteins to some extent. For P. pastoris cells that expressed the I66Q or ΔW mutant, GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analyses of the common DEGs in these cells revealed a significant upregulation of the genes involved in protein processing, but a significant downregulation of the genes enriched in the Ribosome, TCA and Glycolysis/Gluconeogenesis pathways. Hub genes hunting indicated that the most downregulated ribosome protein, C4QXU7 in this case, might be an important target protein that could be manipulated to increase the expression of foreign proteins, especially proteins with a certain degree of instability.ConclusionThese findings should shed new light on our understanding of the regulatory mechanism in yeast cells that responds to intracellular folding stress, providing valuable information for the development of a convenient platform that could improve the efficiency of heterologous protein expression in P. pastoris.

Abstract Global environmental change is driven by food production. Biogas from food waste is a better source of clean energy. Ghana’s energy strategy targets a 10% increase in renewable energy and modern biomass in the national electricity generation mix. Studies on the assessment of electricity generation potential and economic feasibility of biogas to electricity projects in Ghana’s major cities are scarcely available. This study assesses the electricity generation potential of biogas from food waste through anaerobic digestion technology. The municipal solid waste generation potential of Accra and Kumasi was estimated from 2020 to 2039. The potential theoretical methane yield from food waste was calculated using Buswell’s equation. The study analyzed anaerobic digestion projects’ economic feasibility using the total life cycle cost, net present value, investment payback period, levelized cost of energy, and internal rate of return methods. A sensitivity analysis based on two scenarios (optimistic and pessimistic) was performed to analyze the influence of changes in the composition of food waste, per capita waste generation rate, population growth rate, per capita GDP growth rate, discount rate, capacity factor, electricity generation efficiency, waste collection efficiency, and methane production potential on the economic feasibility of the projects. The main findings indicate that the amount of waste generation in Accra during the project life cycle is 899,000 t/y to 3,359,000 t/y, while that of Kumasi is 915,000 t/y to 3,159,000 t/y. The power generation potential of the project in Accra ranges from 80.43 to 300.49 GWh/y, and in Kumasi ranges from 60.63 to 209.31 GWh/y. Economically, the project is feasible in Accra and Kumasi. The net present value of the project in Accra and Kumasi is $217,800,000 and $156,100,000. The sensitivity analysis shows that the project is infeasible in all the cities with a discount rate exceeding 20%. When the discount rate exceeds 20%, the project becomes highly infeasible in Accra compared to Kumasi. This study will offer itself as scientific guidance for investment in biogas to electricity projects in Ghana’s cities.

Abstract Domestic wind turbine manufacturing sector in China has experienced development stages starting from scratch to mass production. During the 11th FYP period (2006–2010), the main goal of wind power policy in China is to promote the commercialization of wind power by large-scale deployment of wind farms. This goal has been realized to a great extent and now the cost of wind power generation is nearly comparable to coal-fired power generation in China. The industry policy, which devotes to mass production of domestic wind turbines, is also largely successful. The purpose of the paper is to provide an overview on wind turbine manufacturing sector in China. The policy evolution in different stages, achievements and challenges pertinent to the sector are addressed in the paper. Key findings are that the misleading industry policy, which provides strong incentive to blind entrance and “competition for scale and price” and restrains innovation as well, is the key obstacle for the sustainable development of the sector. Deficient technology standard and qualification system and the misplaced franchise bidding system also indulge vicious competition and oversupply. Creating a level playground for all turbine supplies, providing strong incentive to innovative manufacturers, establishing thorough and practicable standard and qualification system, and fine-tuning the directive of the franchise bidding system towards technology and service are the primary policy implications proposed by our study.

Senses are the primary channel by which travelers enjoy tourism, and the sensory experience of tourists is very important to the quality of their tourism experience. In this study, 385 questionnaires were distributed to tourists visiting the first batch of characteristic towns classified by the China National Forestry and Grassland Administration as national towns with forest characteristics. SPSS software was used for regression analysis to test the differences in the impact of sensory experience on the experience quality and future loyalty of forest town tourists. The results show that: (1) vision makes the highest contribution to the quality of tourist experience; (2) olfactory experience makes the lowest contribution to the quality of tourist experience and has no significant impact on it; (3) auditory experience has a significant impact on the quality of tourism experience but has no significant impact on the loyalty index. The study further confirms that, when a single sensory experience of tourists is insufficient, satisfaction can be achieved through the other senses. It is of great significance for forest town managers to design a sensory landscape according to the combined components of a destination’s characteristics and the tourists’ physical identities.