查看更多>>摘要：There is an urgent need for building energy services that are not only low-carbon but reliable. District energy systems (DES) have the potential to meet building power, heating and cooling needs efficiently and reliably, but further research is needed to understand their coupling with local renewable energy sources such as biomass. Here we assess the cost and greenhouse gas implications of using bioenergy from local organic waste to power DES in California communities. We describe a set of possible scenarios for bioenergy integration into DES, including fuel switching and retrofitting of existing systems and DES expansion through new projects. In all locations, DES have higher combined capital and operating expenses (ranging from $5-12 million) than conventional fossil fuel building thermal systems. However, the net amortized annual cost of DES can reach as low as 70% that of the conventional system from the sale of excess electricity. Bioenergy-powered DES can offer a cost of carbon abatement on par with distributed solar-powered building thermal systems (50% less to 34% more). Furthermore, upgrading existing DES from fossil to renewable natural gas represents an immediate economical path to decarbonize buildings.
查看更多>>摘要：Responding to the global crises - Covid19 and climate change - governments around the world are formulating green recovery plans to stimulate economic growth, boost clean energy technologies and cut emissions. Potential transition pathways for low carbon energy systems, however, remain as open questions. Generally, the simulation of biomass in the grid models is limited in their tempo-spatial resolution, transition pathways description, and/or biomass feedstock supply representation. This study aims to provide spatio-temporal highly resolved grid configurations featuring disaggregated biomass feedstocks, to assess Australia's potential energy transition pathways and 100% renewable electricity supply scenarios under various biomass bidding strategies and cost assumptions. We find that, as carbon prices increase, bioelectricity will prove to be a cost-effective flexible option compared to other low-carbon (such as CSP) and fossil-based flexible options (e.g. coal and gas), with its generation share reaching ~9%-12% at higher carbon price scenarios. Biomass power plants can be well suited for operating in gap-filling mode to provide flexible power generation and to facilitate grid stability and load balancing. In light of the high biomass resource potential in Australia, keeping bioelectricity in the generation mix is beneficial for reducing system capacity and cost by 32% and 21%, respectively, under a future renewabledominated Australian grid system.
de Gussem, EwoudVerstraete, WillyRyberg, MortenValverde-Perez, Borja...
11页
查看更多>>摘要：Carbon and nitrogen present in residual water streams can be converted into microbial protein and used as animal feed in aquaculture. While microbial protein is thought to be more environmentally sustainable when compared to proteins made from fish residues or plants, nothing is known about how it performs in an absolute sustainability perspective, relative to planetary boundaries. Here, a systems-oriented analysis using life cycle assessment (LCA) linked to the planetary boundaries framework was conducted to assess environmental performance of a pilot-scale microbial protein production from starch-rich process water using aerobic heterotrophs. Results showed that while this microbial-protein indeed performed significantly better than just fishmeal or soybean meal for impacts related to nitrogen (N) and phosphorus (P) flows, none of the three feeds were found sustainable in relation to all planetary boundaries. This constitutes an opportunity for technology developers when the microbial protein production is scaled up and matures.
查看更多>>摘要：With the periodic goals of reaching carbon emission peak before 2030 and achieving carbon neutrality before 2060 ("dual carbon" goals), China shows its unprecedented determination to coal power phaseout. This research takes Jilin Province to showcase possible pathways of coal power units' phaseout on provincial level. We set up four different coal power phaseout scenarios, under which their transition cost and effectiveness would be calculated, respectively. In terms of natural resource endowment and electricity demand, Jilin Province would achieve a complete coal power phaseout by 2045 or even by 2040. However, after assessing the effectiveness of power transition under the four coal development scenarios, we found out that the transition costs for the earlier coal power phaseout scenario is CNY 6-47 billion lower than the normal coal power retirement scenario. In addition, after 2040, compared to the normal coal power retirement scenario, the average unit cost of electricity generation for the coal power earlier phaseout scenario is 11-40 CNY/MWh higher. However, the earlier coal power phaseout scenario would save 168 to 220 million tons of coal and reduce 449 - 614 million tons of CO2 emissions, significantly better than the normal coal power retirement scenario. Therefore, a clean transition and achieving the "dual carbon" goal requires a practical course of action that fully considers the power transition's cost-effectiveness and reasonably spreads the transition costs by improving the design of the electricity market mechanism.
查看更多>>摘要：Analysis of in-use metal stocks provides information on the potential quantity and quality of the generated waste and secondary metals and an understanding of metal demands. Previous studies have analyzed the in-use metal stocks mainly considering their volume and final products. However, an end-use sector where a final product is used (e.g., household, industry) is essential for information on the waste origin and recycling route. Therefore, in this study, the historical trends of in-use stocks and waste flows of copper in Japan until 2015 are comprehensively identified with high resolution of both the final products and end-use sectors based on input-output and dynamic material flow analysis. The results show that in-use copper stocks in manufacturing, infrastructure-related sectors, and household already peaked and decreased until 2015, while those in real estate and residence continued to increase. The in-use total copper stock peaked in 2008 (22.5 Tg) and later decreased, with 21.1 Tg in 2015, while the total copper waste flows increased, resulting in 1.0 Tg in 2015. Our analysis of copper waste flows indicates that the household was a significant end-use sector for copper recycling with unrecycled copper flows of 60.6 Gg in 2015. Furthermore, our analysis suggests that the Japanese in-use copper stocks per capita for some end-use sectors decreased as per capita GDP increased, and some country-specific factors affected the in-use copper stock growth. The findings will help future demand forecasts and develop resource policies and recycling strategies toward sustainable metal management.
Rostek, L.Espinoza, L. A. TerceroGoldmann, D.Loibl, A....
10页
查看更多>>摘要：Accurate and up-to-date accounting of material stocks and flows is an important quantitative basis for current Circular Economy discussions. Herein, we describe the application of dynamic material flow analysis to model the global anthropogenic zinc cycle in the period 1900 to 2019 and yielding results for 1980-2019. Results show that approx. 250 Mt of zinc were globally in use in 2019, which equals the 19-fold mine production of the same year. Between 2010 and 2019, 34 Mt of Zn in fabrication and manufacturing scrap (new scrap) and 77 Mt of Zn in end-of-life products (old scrap) became available for recycling. Of these, approx. 52 Mt of zinc were recycled, the majority (42 Mt) via direct reuse in production processes and a smaller part via refineries. The recycling input rate of 29% and the end-of-life recycling rate of 27%, both averaged between 2010 and 2019, point to opportunities for increased circularity. Nearly half of the overall cycle losses occur in the end-of-life waste collection, so that measures for more circularity should be taken at this lifecycle phase. Further considerable zinc losses arise within steel recycling, where zinc transfers to steel mill dusts. These dusts are more and more used for zinc recycling, but still underutilized. Despite existing recycling challenges, the overall modeling results show that recycling flows and recycling rates rose in the last decade.
查看更多>>摘要：Cement Treated Base (CTB) is a mixture of aggregates, Portland cement and water that hardens through curing to create a strong and durable material that is widely used as a base course in road pavement construction. This layer can be used in either flexible or rigid pavements, and the range of possible materials used in CTB has been recently expanded to include Reclaimed Asphalt Pavement (RAP). Despite the considerable use of CTB in road pavements, there is only limited information regarding its environmental performance, especially when RAP is added. This paper presents a comparative assessment of the environmental performance of sixteen CTB mixtures, with and without RAP, with different cement percentages, different production methods and different recycling procedures. The thickness of the pavement layers required for a given purpose was calculated for each CTB mixture using a pavement design tool (KENPAVE (R)) and data obtained from laboratory tests (both primary and secondary data). The environmental sustainability assessment used the Life Cycle Assessment (LCA) methodology combined with uncertainty analysis. The functional unit (FU) consisted of a road pavement structure corresponding to a 1 km stretch of 22 m wide major urban road including a CTB layer that would enable a specified volume of traffic to drive safely over a 20-year lifespan. A cradle-to-gate system boundary was adopted. The characterisation modelling to quantify the potential environmental impacts of each pavement structure was carried out using the CML v. 4.4 2015 impact assessment method at midpoint level. The analysis shows that having higher percentages of cement in the CTB mixture allows a thinner base-course layer, thereby compensating for the increased environmental burdens related to the production of cement and transport. The uncertainty analysis shows that including RAP in the mixture leads to greater spread in the LCA results. Further, the results of a real case study show, regardless of the CTB composition, that mixed-in-place production substantially reduces the environmental impacts compared to central-plant-mixed production. Overall, this research increases the knowledge on the environmental performance of CTB layers containing high percentages of recycled materials and produced using alternative construction methods.
查看更多>>摘要：Aggregates are the most extracted material resources by weight worldwide. As an important resource for buildings and infrastructure, aggregates, however, are now facing shortages and are associated with negative environmental and social impacts. More attention is now paid to the sand and gravel issues, however, recent investigations are often found ambiguous in definition or adopting over-simplified accounting methodology. To bridge the knowledge gap, first, we conducted a detailed literature investigation to clarify the associated terms. Then we established a systematic material flow and stock accounting framework to map the social metabolism of aggregate resources for the largest aggregates consumer and producer-China. Our results show during 1978-2018, the inflows of China's aggregates increased by 13 times (1.3 to 17.3 billion tons) and the stocks increased by 15 times (18.3 to 285.5 billion tons). We observed both aggregate inflows and stocks have shown a relative decoupling from economic growth. Around 2014, inflows entered a platform area and the dominated consuming sector shifted from buildings to infrastructure. Due to supply shortages and policy interventions, the source of primary supply sees a sustainable transition: manufactured aggregates (instead of natural aggregates) gradually dominated, accounting for 78% of the total primary supply in 2018. Additionally, regarding accumulated stocks of aggregates, it is expected to see rapid growth of aggregate waste in the near future. It is essential to foster a well-functioned circular system to achieve the sustainable development of the aggregate industry.
Chandrashekharaiah, P. S.Gupte, YashPrasad, ShyamSanyal, Debanjan...
13页
查看更多>>摘要：The synergistic interaction between algae and bacteria can be exploited to develop the next-generation waste-water treatment systems as the traditional activated sludge process are expensive, time-consuming, and release several greenhouse gasses. Thus, the protocooperation of algae bacterial consortia was studied during bioremediation of Pb2++Cd2+, followed by a bioassay study with bioremediated stream using Sorghum bicolor. Bacterial [Bacillus sp., (NCBI Acc. No. MK999907), Bacillus sp. (NCBI Acc. No. MN005950) and Micrococcus sp. (NCBI Acc. No. MN005949)]-algal [Scenedesmus acutus (NCIM 5584) and Chlorella pyrenoidosa (NCIM 2738)] consortium was constructed in such as way, which can tolerate and efficiently remove 200 ppm Pb2+ +1.5 ppm Cd2+. The individual consortia showed higher bioremediation attributes when they were mixed in equal quantities. However, the algae-bacterial consortia in the protocooperation study showed similar to 30-33% higher bioremediation than individual consortia of algae/bacteria. Due to positive protocooperation 30% higher algal AFDW, 13% higher bacterial CFU mL(-1), 82% lower dissolved oxygen, and 62% higher bicarbonates were reported as compared to individual consortia systems. For reuse of water, Sorghum plants were treated with bioremediated mixed metal stream (amino acid rich) reported higher total chlorophyll, Fv/Fm, and dry weight. The FTIR signal patterns and SEM-EDX images of Sorghum roots treated with bioremediated mixed metal stream were found negative for presence of any metals, whereas the seedlings treated with mixed metal showed deposition of Pb2+ and Cd2+. Therefore, algal bacterial consortia-based bioremoval approaches can be adopted as an efficient tool for metal bioremediation and reuse of wastewater.
Neo, Edward Ren KaiYeo, ZhiquanGoodship, VannessaLow, Jonathan Sze Choong...
15页
查看更多>>摘要：Mismanagement of plastic waste globally has resulted in a multitude of environmental issues, which could be tackled by boosting plastic recycling rates. Chemometrics has emerged as a useful tool for boosting plastic recycling rates by automating the plastic sorting and recycling process. This paper will comprehensively review the recent works applying chemometric methods to plastic waste sorting. The review begins by introducing spectroscopic methods and chemometric tools that are commonly used in the plastic chemometrics literature. The spectroscopic methods include near-infrared spectroscopy (NIR), mid-infrared spectroscopy (MIR), Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS). The chemometric tools include principal component analysis (PCA), linear discriminant analysis (LDA), partial least square (PLS), k-nearest neighbors (k NN), support vector machines (SVM), random forests (RF), artificial neural networks (ANNs), convolutional neural networks (CNNs) and K-means clustering. This review revealed four main findings. (1) The scope of plastic waste should be expanded in terms of types, contamination and degradation level to mirror the heterogeneous plastic waste received at recycling plants towards understanding potential application in the recycling industry. (2) The use of hybrid spectroscopic method could potentially overcome the limitations of each spectroscopic methods. (3) Develop an open-sourced standardized database of plastic waste spectra would help to further expand the field. (4) There is limited use of more novel machine learning tools such as deep learning for plastic sorting.
NSTL
Elsevier