Novel strategy for efficient energy recovery and pollutant control from sewage sludge and food waste treatment.

Considering the high organic matter contents and pollutants in sewage sludge (SS) and food waste (FW), seeking green and effective technology for energy recovery and pollutant control is a big challenge. In this study, we proposed a integrated technology combing SS mass separation by hydrothermal pretreatment, methane production from co-digestion of hydrothermally treated sewage sludge (HSS) centrate and FW, and biochar production from co-pyrolysis of HSS cake and digestate with heavy metal immobilization for synergistic utilization of SS and FW. The results showed that the co-digestion of HSS centrate with FW reduced the NH4+-N concentration and promoted volatile fatty acids conversion, leading to a more robust anaerobic system for better methane generation. Among the co-pyrolysis of HSS cake and digestate, digestate addition improved biochar quality with heavy metals immobilization and toxicity reduction. Following the lab-scale investigation, the pilot-scale verification was successfully performed (except the co-digestion process). The mass and energy balance revealed that the produced methane could supply the whole energy consumption of the integrated system with 26.2 t biochar generation for treating 300 t SS and 120 t FW. This study presents a new strategy and technology validation for synergistic treatment of SS and FW with resource recovery and pollutants control.

Multidirectional Fate Path Model to Connect Phosphorus Emissions with Freshwater Eutrophication Potential.

Excessive anthropogenic phosphorus (P) emissions put constant pressure on aquatic ecosystems. This pressure can be quantified as the freshwater eutrophication potential (FEP) by linking P emissions, P fate in environmental compartments, and the potentially disappeared fraction of species due to increase of P concentrations in freshwater. However, previous fate modeling on global and regional scales is mainly based on the eight-direction algorithm without distinguishing pollution sources. The algorithm fails to characterize the fate paths of point-source emissions via subsurface pipelines and wastewater treatment infrastructure, and exhibits suboptimal performance in accounting for multidirectional paths caused by river bifurcations, especially in flat terrains. Here we aim to improve the fate modeling by incorporating various fate paths and addressing multidirectional scenarios. We also update the P estimates by complementing potential untreated point-source emissions (PSu). The improved method is examined in a rapidly urbanizing area in Taihu Lake Basin, China in 2017 at a spatial resolution of 100 m × 100 m. Results show that the contribution of PSu on FEP (62.6%) is greater than that on P emissions (58.5%). The FEP is more spatially widely distributed with the improved fate modeling, facilitating targeted regulatory strategies tailored to local conditions.

An optimized crop-livestock system can achieve a safe and just planetary boundary for phosphorus at the sub-basin level in China.

The contribution of crop and livestock production to the exceedance of the planetary boundary for phosphorus (P) in China is still unclear, despite the country's well-known issues with P fertilizer overuse and P-related water pollution. Using coupled models at sub-basin scales we estimate that livestock production increased the consumption of P fertilizer fivefold and exacerbated P losses twofold from 1980 to 2017. At present, China's crop-livestock system is responsible for exceeding what is considered a 'just' threshold for fertilizer P use by 30% (ranging from 17% to 68%) and a 'safe' water quality threshold by 45% (ranging from 31% to 74%) in 25 sub-basins in China. Improving the crop-livestock system will keep all sub-basins within safe water quality and just multigenerational limits for P in 2050.

Relationship of black soldier fly larvae (BSFL) gut microbiota and bioconversion efficiency with properties of substrates.

Treating food waste using black soldier fly larvae (BSFL) is widely regarded as a promising nature-based measure. This study explored the influence of food waste particle sizes on substrate properties and its subsequent effects on bioconversion efficiency and gut microbiota. The results indicated that particle sizes mainly ranging from 4 mm to 10 mm (T1) significantly increased the weight loss rate of food waste by 35 % and larval biomass by 38 % compared to those in T4 (particle sizes mostly less than 2 mm) and promoted the bioconversion of carbon and nitrogen into larvae and gases. Investigation of substrates properties indicated that the final pH value of T1 was 7.79 ± 0.10, with Anaerococcus as the predominant substrate microorganism (relative abundance: 57.4 %), while T4 exhibited a final pH value of 5.71 ± 0.24, with Lactobacillus as the dominant microorganism (relative abundance: 95.2 %). Correlation analysis between substrate chemical properties and microbial community structure unveiled a strong relationship between substrate pH and the relative abundance of Anaerococcus and Lactobacillus. Furthermore, beneficial microorganisms such as Lactobacillus and Enterococcus colonized the BSFL gut of T1, while pathogenic bacterium Morganella, detrimental to BSFL gut function, was enriched in T4 (relative abundance: 60.9 %). Nevertheless, PCA analysis indicated that alterations in the gut microbial community structure may not be attributed to the substrate microorganisms. This study establishes particle size as a crucial parameter for BSFL bioconversion and advances understanding of the relationship between gut microbiota and substrate microbiota.

Remarkable Spatial Disparity of Life Cycle Inventory for Coal Production in China.

Coal is the primary energy source in China, and its life cycle inventory (LCI) is widely used as background data for life cycle assessment studies. Previous research indicates that the inventory of coal production varies regionally. However, the development of complete regionalized LCIs for coal production is quite limited. Here, we establish the first provincial-level LCIs of local coal production and market for coal in China, based on a database of 6,122 coal mines and developed models. In the inventory results of local coal production, the coefficients of variation (CVs) of nine indicators exceed 0.5, especially SO2 and particulate matter emission factors (CVs > 1). Compared with that, the interprovincial coal trade homogenizes the provincial production inventory of market for coal relatively, despite four indicators with CVs exceeding 0.5. Therefore, the regionalized inventory with remarkable spatial differentiation can provide more accurate fundamental data for future research such as electricity production. Furthermore, CH4 emissions from coal production account for 24% of China's total methane emissions, highlighting its significance in mitigating global warming. Moreover, through the increasing coal trade, the significant and implicit plunder of water resources from the three coal net-exporting provinces, located in water-scarce areas, should be noted.

Investing in mini-livestock production for food security and carbon neutrality in China.

Future food farming technology faces challenges that must integrate the core goal of keeping the global temperature increase within 1.5 °C without reducing food security and nutrition. Here, we show that boosting the production of insects and earthworms based on food waste and livestock manure to provide food and feed in China will greatly contribute to meeting the country's food security and carbon neutrality pledges. By substituting domestic products with mini-livestock (defined as earthworms and insects produced for food or feed) protein and utilizing the recovered land for bioenergy production plus carbon capture and storage, China's agricultural sector could become carbon-neutral and reduce feed protein imports to near zero. This structural change may lead to reducing greenhouse gas emissions by 2,350 Tg CO2eq per year globally when both domestic and imported products are substituted. Overall, the success of mini-livestock protein production in achieving carbon neutrality and food security for China and its major trading partners depends on how the substitution strategies will be implemented and how the recovered agricultural land will be managed, e.g., free use for afforestation and bioenergy or by restricting this land to food crop use. Using China as an example, this study also demonstrates the potential of mini-livestock for decreasing the environmental burden of food production in general.

Revealing the effects of fermented food waste on the growth and intestinal microorganisms of black soldier fly (Hermetia illucens) larvae.

The escalating global food waste (FW) issues necessitate sustainable management strategies. Black soldier fly larvae (BSFL) offer a promising solution for FW management by converting organic matter into insect protein. However, the fermentation of FW during production, collection, and transportation induces changes in FW's physicochemical properties and bacterial communities, requiring further exploration of its impact on BSFL growth and gut microbiota. The results showed that feeding FW fermented for different durations (0-10 d) slightly affected the BSFL yield. Feeding FW fermented for 8 d, characterized by a lower pH and higher biodiversity, resulted in a slight increase in larval biomass (222 mg/larvae). Nearly all groups harvested the peak larval biomass after 10 day's bioconversion. The fermentation significantly altered the microbial community of FW, with an increase in the abundance of unclassified_f_Clostridiaceae and a decrease in Lactobacillus abundance. As bioconversion progressed, intricate and mutualistic microbial interactions likely occurred between the BSFL gut and FW substrate, restructuring each other's microbial community. Specifically, the abundance of unclassified_f_Clostridiaceae increased in the BSFL gut, while its abundance in the initial larval gut was extremely low (<1 %). Despite the substrate microbial changes and interactions, a stable core gut microbiota was identified across all BSFL samples, primarily composed of nine genera dominated by Enterococcus and Klebsiella. This core gut microbiome may play a crucial role in facilitating the adaptation of BSFL to various environmental conditions and maintaining efficient FW bioconversion. These findings enhance our understanding of the role of BSFL gut microbiota in FW bioconversion.

Comparative assessment of Chinese mitten crab aquaculture in China: Spatiotemporal changes and trade-offs.

The increasing human demand for high-quality animal protein has provided impetus for the development of aquaculture. Chinese mitten crab (Eriocheir sinensis) is a catadromous species rapidly being cultured in China but scientific literature documenting its life cycle environmental and economic consequences remains scarce. This study aims to address this gap by examining the spatio-temporal evolution of crab aquaculture in China since the 2000s and evaluating the environmental and economic characteristics along its life-cycle stages: megalopa, juvenile crab, and adult crab cultivation. The geostatistical analysis shows a more dispersed pattern of crab aquaculture nationally as crab grows, with coastal provinces that have brackish water for megalopa cultivation but wider spatial coverage for juvenile and adult crab cultivation. Our findings reveal that the production of 1 ton of live-weight crab results in 7.65 ton of CO2 equivalent of greenhouse gas emissions, surpassing previous estimates for finfish fish production by approximately 50%. Most environmental pressures occur during the adult crab cultivation stage, with significant contributions from upstream processes such as electricity and feed production. By comparing between different production systems, our study shows that crab aquaculture in lake systems performs better than pond systems in terms of most global environmental impact categories and economic considerations. This work contributes to the existing literature by elucidating the spatio-temporal changes of crab aquaculture boom in China and constructing a representative life cycle data pool that broadens the benchmark knowledge on its environmental and economic characteristics. We highlight the trade-offs between environmental and economic performance as well as the balance between global and local environmental impacts to promote sustainable growth in the aquaculture industry.

Agricultural trade impacts global phosphorus use and partial productivity.

The spatio-temporal distribution, flow and end use of phosphorus (P) embedded in traded agricultural products are poorly understood. Here we use global trade matrices to analyse the partial factor productivity of P (output per unit of P input) for crop and livestock products in 200 countries and their cumulative contributions to the export or import of agricultural products over 1961-2019. In these six decades, the trade of agricultural P products has increased global partial factor productivity for crop and livestock production and has theoretically saved 67 Tg P in fertilizers and 1.6 Tg P in feed. However, trade is now at risk of contributing to wasteful use of P resources globally due to a decline in trade optimality, as agricultural products are increasingly exported from low to high partial factor productivity countries and due to P embedded in imported agricultural products mainly lost to the environment without recycling. Integrated crop-livestock production systems and P-recycling technologies can help.

Uncovering the spatio-temporal dynamics of crop-specific nutrient budgets in China.

Nitrogen (N) and phosphorus (P) are two critical nutrients for agroecosystems. In meeting food demands, human use of both nutrients has crossed planetary boundaries for sustainability. Further, there has been a dramatic shift in their relative inputs and outputs, which may generate strong N:P imbalances. Despite enormous efforts on agronomic N and P budgets, the spatio-temporal characteristics of different crop types in using nutrients are unknown as are patterns in the stoichiometric coupling of these nutrients. Thus, we analyzed the annual crop-specific N and P budgets and their stoichiometric relations for producing ten major crops at the provincial level of China during 2004-2018. Results show that, China has generally witnessed excessive N and P input over the past 15 years, with the N balance remaining stable while the P balance increasing by more than 170%, thus resulting in a decline in the N:P mass ratios from 10.9 in 2004 to 3.8 in 2018. Crop-aggregated nutrient use efficiency (NUE) of N has increased by 10% in these years while most crops have shown a decreasing trend of this indicator for P, which reduced NUE of P from 75% to 61% during this period. At the provincial level, the nutrient fluxes of Beijing and Shanghai have obviously declined, while the nutrient fluxes of provinces such as Xinjiang and Inner Mongolia have increased significantly. Although N management has made progress, P management should be further explored in the future due to eutrophication concerns. More importantly, N and P management strategies for sustainable agriculture in China should take account of not only the absolute nutrient use, but also their stoichiometric balance for different crops in different locations.

The underestimated importance of fertilizer in aquacultural phosphorus budget: Case of Chinese mitten crab.

China's reliance on aquaculture has intensified to satisfy the growing human demand for high-quality animal protein, making it the only country whose aquaculture production has greatly exceeded that of capture fishery for a long time. Previous studies have shown that phosphorus (P) is a limiting nutrient for freshwater eutrophication; therefore, the quantification of P flows in freshwater aquaculture is of great importance for improving aquaculture efficiency and reducing environmental pollution. In this study, life cycle assessment (LCA) and substance flow analysis (SFA) are combined to develop a life cycle P flow model for Chinese mitten crab (Eriocheir sinensis) culture and calculate the P inputs, outputs and net change in stock. The results show a relatively low P use efficiency (4 %) in Chinese mitten crab. Among all life-cycle stages, the maximum P input occurs during adult crab cultivation, when feed is continuously added to maintain appropriate nutrition levels and increase body weight. In addition, fertilizer is often neglected in the existing accounts but accounts for 24 % of the total P inputs. On the output side, approximately 86 % of the P accumulates in sediment, indicating the potential of sediment recycling as a nutrient source in agriculture. This study provides an updated quantitative method for describing nutrient flows within freshwater aquaculture systems and will contribute to decision-making in pollution control of intensive freshwater aquaculture activities.

Improving food waste composting efficiency with mature compost addition.

This study investigated the impact of mature compost addition on food waste composting physicochemical properties, bacterial community succession and corresponding metabolic function. Analytical results from two pilot-scale composting treatments with (C20) or without (C0) mature compost demonstrated that mature compost amendment increased the reduction rate of volatile solids by 71.4% and shortened the composting period by 7 days. Microbial dynamics analysis revealed that mature compost addition increased the bacteria abundance related to maturity during the initial stage, and these bacteria (mainly SBR1031 and Actinomarinales) were easier to grow again during cooling stage, thus promoted the maturity of compost. Mature compost addition increased the abundance of Ureibacillus, Lysinibacillus, Limochordaceae and Tepidimicrobium by providing an appropriate temperature environment, which enhanced the amino acid and carbohydrate metabolism function and promoted the degradation of organic matter. Together, these findings revealed the underlying mechanisms of bacterial community succession with mature compost addition.

Advancing greenhouse gas emission factors for municipal wastewater treatment plants in China.

Estimations of greenhouse gas (GHG) emissions from municipal wastewater treatment plants (MWTPs) remain significant uncertainties in China owing to a lack of reliable emission factors (EFs). This study developed a framework to obtain multi-level (technology, province, and nation) GHG EFs of MWTPs using a database containing 3107 MWTPs in China and published site-specific monitoring data. Results show that GHG EFs of different technologies range widely from 180.0 to 615.7 g CO2-eq/t wastewater, and significant differences are also observed among different provinces in China (190.5-600.3 g CO2-eq/t wastewater), which are generally lower than the previous estimates. It confirms the importance of more detailed technology classification and considering the technological disparity of different provinces in refining GHG estimations of MWTPs. To test the feasibility of the developed EFs, we compared GHG emissions from MWTPs based on multi-level EFs at different spatial and temporal scales. Similar estimation results imply that selecting corresponding EF depending on the availability of activity data would simplify GHG estimations of MWTPs without sacrificing much accuracy. This study contributes a set of well-developed EFs to improve the estimates of GHG emissions from MWTPs, and also offers a method to develop GHG EFs for other sectors.

Environmental impacts of hydrometallurgical recycling and reusing for manufacturing of lithium-ion traction batteries in China.

Recycling lithium-ion batteries from electric vehicles is considered an important way to tackle the future supply risks of virgin materials, but the actual environmental impact of traction battery recycling is controversial. This study conducted a process-based life cycle assessment to quantify the environmental impacts of hydrometallurgical recycling of two common lithium-ion traction batteries (lithium nickel manganese cobalt oxide and lithium iron phosphate battery) and reusing materials in their manufacturing in China. The results show that recycling can cause net environmental benefits of the two traction battery types for the considered impact categories, but the net benefits for direct recycling technology are higher because of fewer requirements of chemicals and energy. Reusing recovered materials in battery manufacturing would reduce the impacts in comparison to no recycling, but the reduction potential of greenhouse gas emission and energy demand is not significant. Sensitivity analysis shows that recycling benefits are highly dependent on recovering efficiency and electricity used for manufacturing and recycling. Comprehensive management strategies are necessary to improve the end-of-life traction battery management, such as using carbon-free energy sources, designing batteries with less metal, and developing recycling technology using fewer chemicals. This study contributes by offering transparent life cycle inventory for hydrometallurgical recycling lithium-ion traction batteries and providing scientific knowledge to improve their sustainable management.

Bioprocess potential of Eco-friendly fungal isolates converting organic waste to bioresource.

This study aims to present indigenous fungal diversity in the soil sample collected from solid waste disposal site. The synthesis of cellulase enzymes via in laboratory scale study has been performed using indigenous fungus isolates. Additionally; its impact has been evaluated on the basis of the bioconversion of organic waste treated employing screened potential cellulase producer fungi which is further used for primary and secondary screening of cellulolytic. The findings advised that, a total of 27 fungal isolates belonging to twenty-four genera were reported as most potential fungal strains. The findings indicates a highest exo-ß-glucanase (C1) enzymatic action was observed by fungal strains T. harzianum, T. viride , A. niger. These isolates are promising and could be suitable candidate for biodegradation of organic waste due to its's well established extraordinary ability. Therefore, these fungal isolates are suggested for more in depth research in order to use for recycling of organic waste.

Assessment of end-of-life electric vehicle batteries in China: Future scenarios and economic benefits.

A better understanding of the waste of end-of-life batteries from electric vehicles (EVs) is a basis for their sustainable management. This study aims to estimate the waste of end-of-life EV batteries during 2006-2040 in China and to analyze the opportunities and challenges of subsequent utilization, based on a developed numerical model, real market data, and elaborately developed scenarios. The result shows that end-of-life batteries would increase from 0.1 to 7.8 thousand tons during 2012-2018, and then to 1500-3300 thousand tons in 2040. Of the waste streams, around 50% are estimated to be metal materials, representing great opportunities for battery recycling for material recovery. Economically, battery recycling for energy storage is estimated to create more economic benefits compared with that for material recovery solely (147.8 versus 76.9 billion US dollars). However, the supply of end-of-life batteries can hardly meet the demand for renewable energy storage in the near future, and a spatial mismatch of the supply and demand of energy storage capacity exists between the eastern and western regions in China. Accordingly, this study highlights national coordination for the rational layout of the collection, disassembly, and remanufacture facilities for the second use of end-of-life EV batteries in China.

Aeration rate improves the compost quality of food waste and promotes the decomposition of toxic materials in leachate by changing the bacterial community.

The effect of aeration rates on maturity, leachate and bacterial community succession during a pilot-scale food waste composting were evaluated. Out of the four aeration rates (0.44, 3.25, 6.50 and 11.65 L kg-1 DM initial min-1 for T1, T2, T3 and T4, respectively) that were conducted, results found T2 to be the recommended ventilation rate considering the quality of compost and the leachate utilization. Higher ventilation increased germination index of diluted leachate. The abundance of Proteobacteria in mesophilic stage (35.5%) and Actinobacteria in cooling stage (30.6%) in T4 were higher than in other groups (7.9%-17.5%), suggesting the formation of a select community categorized by the capacity of degrading the organic matter and promoting maturity. The key bacteria of aeration-shaped bacterial communities such as Sporosarcina, Pseudomonas and Thermobifida were identified and they could be manipulated by increasing NH4+, NO3- contents and pH in the initial stage of composting.

[Evolution of Material Metabolism in China's Pulp and Paper Industry].

The pulp and paper industry is an important industry that is closely related to national socioeconomic development. To understand the historical trends of resource consumption and environmental pollution, we conducted an economy-wide material flow analysis and quantitatively evaluated the dynamic characteristics of input-output balances, material metabolism intensity, and resource recycling rate of China's pulp and paper industry, from 2005 to 2017. The results indicate downward trends in the material inputs and outputs of China's pulp and paper industry from 2005 to 2017, with water contributing over 90% of the totals. In recent years, with the continuous optimization of the raw material structure of the paper industry, the proportion of non-wood pulping has dropped from 42% to 13% and has been replaced by mainly waste paper pulping and wood pulping. Resource consumption can still be greatly reduced. In 2017, the amount of direct material input per ton of paper and paperboard had decreased by 67% from 2005 to 26 t. The consumption of fresh water per ton of paper and paperboard dropped by approximately 69% over the study period, whereas the water recycling rate increased significantly, reaching 77% in 2017. At present, the production of paper and paperboard is increasingly dependent on the input of domestic waste paper and imported wood, the proportions of which have increased from 21% and 9% in 2005 to 60% and 31% in 2017, respectively. However, the rate of domestic waste paper recycling is relatively low, and measures such as strengthening the construction of the recycling system and educating the residents about recycling are needed to alleviate the shortage of raw materials caused by restrictions on waste paper imports.

Identifying hotspots based on high-resolution emission inventory of volatile organic compounds: A case study in China.

The emission of volatile organic compounds (VOCs) makes a substantial contribution in the formation of secondary organic aerosols (SOAs) and ground-level ozone, which could deteriorate air quality and cause damage to human health. To help inform local VOCs management decisions, we compiled a speciated and high spatial resolution anthropogenic VOCs emission inventory for Huai'an City in 2017, using investigated human activity data and the latest emission factors. Furthermore, the ozone formation potential (OFP) was estimated to understand the contributions of different VOC species to ozone formation. The results show that Huai'an City emitted about 36 kt of VOCs in 2017, mainly from industrial processes, e.g. petroleum refining and iron & steel industry, and solvent use, e.g. pesticide use and asphalt paving, accounting for 41% and 32% of the total emissions, respectively. The high emissions were spatially located in the areas where there is an intensive cluster of industrial enterprises, with the top 20 VOCs emitting enterprises contributing to 43% of the city's total. These anthropogenic VOCs emissions, especially m/p-xylene, ethylene, propene, toluene, have the potential to form about 102 kt ozone in the lower atmosphere. Different from the hotspots identified based on physical weights, solvent use became the largest constituent and m/p-xylene was the leading VOC species. By investigating the spatial distribution of anthropogenic VOCs emissions and the OFP, this work highlights the necessity to consider VOC species and different effects they might have on ozone formation in future hotpot identification, which could lay a more scientific basis for local VOCs emission mitigation strategies.

Environmental burdens of small-scale intensive pig production in China.

Small-scale intensive pig production systems account for over a half of the total number of pig farms in China, of which concerns have been raised relating to their environmental performances. This study explores the cradle-to-slaughterhouse gate environmental impacts using life cycle assessment (LCA) approach, with the purpose of identifying major hotspots to formulate mitigation strategies. The functional unit is defined as 1000 kg of pig carcass weight. Consistent with previous research, feed production makes up the largest contribution (56-95%) to all the six selected impact categories based on the ReCiPe 2016 framework. Of the feed ingredients, maize is identified as the principal hotspot mainly due to the large consumption as well as the heat usage in grain steaming to enhance availability of starch digestion. The results also indicate that changes of feed consumption and composition along the lifetime growth reveal a much higher contribution from the grower-finisher stage. Marked differences are observed in terms of greenhouse gas emissions from pig production between developing (including China) and developed countries. With lots of studies showing feasibilities, improvements suggested for small-scale intensive pig production systems include the optimization of feed formulas, the introduction of new feed technologies, and the upgrade of manure management system. Our results provide valuable and practical insight for the Chinese pig supply chain to mitigate environmental burdens and achieve future environmental sustainability.