Is solar heating an appropriate choice in rural areas of northern China? Evidence from numerical simulation and life cycle assessment.

Solar heating is generally regarded as a clean and low-carbon heating method, while its high initial investment hinders its promotion in economically underdeveloped areas. With the implementation of the clean heating policy and the proposal of the carbon neutralization target, rural bulk coal heating in northern China is restricted. The Chinese government proposes to widely adopt solar heating to meet the heating demands of rural residents. In this research, the application of solar assisted heat pump systems in Beijing, Tianjin, Hebei and its surrounding areas in China is numerically simulated. A new evaluation method under the same initial investment constraint is proposed to verify its benefits throughout the entire life cycle. The results indicate that although solar thermal heating has the lowest environmental impact and carbon emissions among various heating methods, it is not the best solution to rural clean heating. The reason is that equal investment in other projects can bring much more benefits, such as roof solar photovoltaic. In contrast to the air source heat pump and photovoltaic panel scheme with the same initial investment, solar heating has obvious negative environmental impact, 53.3 % higher economic cost, 35.9 tons more carbon emissions, and 105.9 % higher roof area occupation. The sensitivity analysis of solar fraction, geographical coordinates, and energy price also supports the above findings. The recommendation is proposed to promote air source heat pumps or solar photovoltaic, rather than solar thermal collectors, so as to reduce the cost of rural clean heating and carbon emission reduction.

Estimation of Emission Factors from Purchased Electricity for European Countries: Impacts on Emission Reduction of Electricity Storage.

To evaluate the reduction brought about by energy storage technology, it is essential to first have accurate data on carbon emissions from electricity consumption. However, when gathering this data by evaluating marginal emission factors (MEFs), previous research measured only generation emissions and direct transfer emissions while ignoring the impact of embodied emissions from the cross-grid transfer. To gather more accurate data, this study constructs an electricity network composed of 28 European countries in 2019 and compares the difference between the MEFs when considering the network-wide emissions and the MEFs when only considering generation emissions and direct transfer emissions for electricity trade (neglecting the indirect emissions in purchased electricity). Three energy storage strategies are adopted to evaluate the carbon emission reduction benefits of energy storage. The results show that the errors in emission accounting and MEF calculation are 7% and 10%, respectively, if the impact of electricity trade is not taken into account. When disregarding the indirect emissions from electricity trade, the errors in emission accounting and MEF calculation are 1%. Implementing wind curtailment reduction strategies for energy storage systems could effectively reduce electricity carbon emissions, more than 200 gCO2/kWh in most countries with 100% storage efficiency. The accuracy of MEFs has a significant impact on the results of energy storage benefits, and the choice of storage strategies has different effects on electricity emissions in the same country. Our methods have general applicability for other regions and countries.

Carbon footprint and embodied carbon transfer at the provincial level of the Yellow River Basin.

The ecological conservation and high-quality development of China's Yellow River Basin is a national strategy proposed in 2019. Under China's goal of achieving a carbon peak by 2030 and carbon neutrality by 2060, clarifying the carbon footprint of each province and the transfer paths of embodied carbon emissions is crucial to the carbon reduction strategy for this region. This paper uses input-output model and multi-regional input-output model to account for the carbon footprint of nine provinces in the Yellow River Basin, and to estimate the amount of embodied carbon transfer between provinces and industrial sectors. Social network analysis is applied to identify the critical industries in the inter-provincial embodied carbon emission transfers from the three major industries. We found that the per capita carbon footprint of the Yellow River Basin decreased by 23.4% in 2017 compared to 2012. Among the sectoral composition of the carbon footprint of each province, "Processing and manufacturing of petroleum, coking, nuclear fuel, and chemical products", "Construction", "Other services", and "Metal processing and metal, non-metallic products" are the four sectors with a higher proportion of emissions. The embodied carbon emission transfer between the provinces in middle and lower reaches of the Yellow River Basin is much higher than that between the upstream provinces. Among carbon emission transfer network of three major industries in nine provinces，the secondary industry in Shaanxi has the highest centrality and is the most critical industry. This study provides a theoretical basis and data support for formulating carbon emission reduction plans in the Yellow River Basin.

Reducing the life cycle environmental impact of electric vehicles through emissions-responsive charging.

Electric vehicles (EVs) are currently being promoted to reduce transport emissions. We present a life cycle assessment of EV charging behaviors based on marginal emissions factors. For Great Britain, we find that electricity consumption accounts for the highest proportion of life cycle carbon emissions from EVs. We highlight the potential life cycle carbon emissions reduction brought by charging during periods when the grid mix produces relatively low emissions. While our study focuses on Great Britain, we have applied our methodology to several European countries with contrasting electricity generation mixes. Our analysis demonstrates that countries with a high proportion of fossil energy will have reduced benefits from deploying EVs, but are likely to achieve increased benefits from smart charging approaches. We conclude that using marginal emissions factors is essential to understanding the greenhouse gas impacts of EV deployment, and that smart charging tied to instantaneous grid emissions factors can bring benefits.

Topological analysis of type 3 secretion translocons in native membranes.

PFPs (Pore-forming proteins) perforate cellular membranes to create an aqueous pore and allow the passage of ions and polar molecules. The molecular mechanisms for many of these PFPs have been elucidated by combining high resolution structural information of these proteins with biochemical and biophysical approaches. However, some PFPs do not adopt stable conformations and are difficult to study in vitro. An example of these proteins are the bacterial Type 3 Secretion (T3S) translocators. The translocators are secreted by the bacterium and insert into the target cell membrane to form a translocon pore providing a portal for the passage of T3S toxins into eukaryotic cells. Given the important role that the T3S systems play in pathogenesis, methods to study these translocon pores in cellular membranes are needed. Using a combination of protein modifications and methods to selectively permeate and solubilized eukaryotic membranes, we have established an experimental procedure to analyze the topology of the Pseudomonas aeruginosa T3S translocon using P. aeruginosa strain variants and HeLa cell lines.

Integrated assessment of the environmental and economic effects of "coal-to-gas conversion" project in rural areas of northern China.

Northern China suffers from serious air pollution especially in winter, much of which derives from solid fuel used for domestic heating in rural areas. In order to reduce pollution emissions in the heating season, the Chinese government has introduced a "coal-to-gas conversion" policy, promoting a switch to natural gas which is much cleaner than the coal normally used for winter heating. The "coal-to-gas conversion" project will cover more than 1.8 billion m2 of heated built floor area and affect more than 12 million heat users in Beijing, Tianjin, Hebei, and the surrounding areas. Life cycle assessment and life cycle cost methods are applied to compare and analyze the environmental impact and economic cost of household energy usage for the whole year under 5 scenarios before and after "coal-to-gas conversion." In the three scenarios after "coal-to-gas conversion," the environmental impact decreases by around 50% while the total economic cost increases by around 80%. Particulate emissions responsible for air pollution are considerably reduced with accompanying benefits for human health, though significant, but reduced, impacts on freshwater and marine ecotoxicity remain. Improving thermal efficiency through natural gas utilization, implementing an energy-saving retrofit of rural housing, and promoting straw utilization yield benefits for people and the environment in rural areas of northern China.

Life cycle assessment of autoclaved aerated fly ash and concrete block production: a case study in China.

With the rapid development of construction industry, consumption of concrete block has increased rapidly in China. As a kind of green building material and resource comprehensive utilization product, autoclaved aerated fly ash and concrete block have better performance in terms of heat preservation, sound insulation, and fire resistance. However, some typical issues are associated with autoclaved aerated fly ash and concrete block production process such as energy and material consumption as well as pollutant emissions. To examine the environmental and economic impacts of its production process is imperative. Choosing 1 m3 of autoclaved aerated fly ash and concrete block product as functional unit and "cradle to gate" as system boundary, a life cycle inventory is developed. The key processes and key materials with significant environmental impact are identified. Results show that the top four environmental impact categories are marine ecotoxicity, freshwater ecotoxicity, freshwater eutrophication, and human toxicity. Key processes are fly ash slurry production, lime grinding, and steam curing processes. These processes account for 46.58%, 26.00%, and 19.62% of the total environmental load respectively. The key materials are cement, lime, and natural gas, which account for 44.91%, 22.79%, and 20.61% respectively of overall environmental impact. Sensitivity analysis shows that the fly ash slurry production should be optimized preferentially, followed by lime grinding and steam curing processes. These findings are helpful to facilitate the sustainable production of autoclaved aerated fly ash and concrete block.

The Pseudomonas aeruginosa type III secretion translocator PopB assists the insertion of the PopD translocator into host cell membranes.

Many Gram-negative bacterial pathogens use a type III secretion system to infect eukaryotic cells. The injection of bacterial toxins or protein effectors via this system is accomplished through a plasma membrane channel formed by two bacterial proteins, termed translocators, whose assembly and membrane-insertion mechanisms are currently unclear. Here, using purified proteins we demonstrate that the translocators PopB and PopD in Pseudomonas aeruginosa assemble heterodimers in membranes, leading to stably inserted hetero-complexes. Using site-directed fluorescence labeling with an environment-sensitive probe, we found that hydrophobic segments in PopD anchor the translocator to the membrane, but without adopting a typical transmembrane orientation. A fluorescence dual-quenching assay revealed that the presence of PopB changes the conformation adopted by PopD segments in membranes. Furthermore, analysis of PopD's interaction with human cell membranes revealed that PopD adopts a distinctive conformation when PopB is present. An N-terminal region of PopD is only exposed to the host cytosol when PopB is present. We conclude that PopB assists with the proper insertion of PopD in cell membranes, required for the formation of a functional translocon and host infection.

Type 3 Secretion Translocators Spontaneously Assemble a Hexadecameric Transmembrane Complex.

A type 3 secretion system is used by many bacterial pathogens to inject proteins into eukaryotic cells. Pathogens insert a translocon complex into the target eukaryotic membrane by secreting two proteins known as translocators. How these translocators form a translocon in the lipid bilayer and why both proteins are required remains elusive. Pseudomonas aeruginosa translocators PopB and PopD insert pores into membranes forming homo- or hetero-complexes of undetermined stoichiometry. Single-molecule fluorescence photobleaching experiments revealed that PopD formed mostly hexameric structures in membranes, whereas PopB displayed a bi-modal distribution with 6 and 12 subunits peaks. However, individually the proteins are not functional for effector translocation. We have found that when added together, the translocators formed distinct hetero-complexes containing 8 PopB and 8 PopD molecules. Thus, the interaction between PopB and PopD guide the assembly of a unique hetero-oligomer in membranes.