•The fruitwood biochar could enhance methane production substantially.•The transformation of substances was accelerated by biochar.•The buffering capacity of anaerobic digestion system was enhanced ...by biochar.
This study investigated the impact of different types of biochar on the anaerobic digestion (AD) of chicken manure. Wheat straw, discarded fruitwood, and air-dried chicken manure were pyrolysed at 350, 450, and 550 °C to generate biochar. A lab-scale batch anaerobic digestion experiment was conducted at 35 ± 1 °C. Substantial improvements in methane production were observed for all nine types of biochar. With the production of 294 mL CH4/g VSadded, fruitwood char pyrolysed at 550 °C increased the methane yield by 69% from the control. Characteristic analysis indicated that fruitwood char pyrolysed at 550 °C exhibited the largest specific surface area and highest total ammonia nitrogen reduction capacity. The buffering capacity of the AD system was improved by the biochar through accelerating the transformation of macromolecular substances to dissolved substrates and reducing the contents of soluble salts, total ammonia nitrogen, and free ammonia.
Biochar produced by pyrolysis of biomass can be used to counter nitrogen (N) pollution. The present study investigated the effects of feedstock and temperature on characteristics of biochars and ...their adsorption ability for ammonium N (NH4(+)-N) and nitrate N (NO3(-)-N). Twelve biochars were produced from wheat-straw (W-BC), corn-straw (C-BC) and peanut-shell (P-BC) at pyrolysis temperatures of 400, 500, 600 and 700°C. Biochar physical and chemical properties were determined and the biochars were used for N sorption experiments. The results showed that biochar yield and contents of N, hydrogen and oxygen decreased as pyrolysis temperature increased from 400°C to 700°C, whereas contents of ash, pH and carbon increased with greater pyrolysis temperature. All biochars could sorb substantial amounts of NH4(+)-N, and the sorption characteristics were well fitted to the Freundlich isotherm model. The ability of biochars to adsorb NH4(+)-N followed: C-BC>P-BC>W-BC, and the adsorption amount decreased with higher pyrolysis temperature. The ability of C-BC to sorb NH4(+)-N was the highest because it had the largest cation exchange capacity (CEC) among all biochars (e.g., C-BC400 with a CEC of 38.3 cmol kg(-1) adsorbed 2.3 mg NH4(+)-N g(-1) in solutions with 50 mg NH4(+) L(-1)). Compared with NH4(+)-N, none of NO3(-)-N was adsorbed to biochars at different NO3(-) concentrations. Instead, some NO3(-)-N was even released from the biochar materials. We conclude that biochars can be used under conditions where NH4(+)-N (or NH3) pollution is a concern, but further research is needed in terms of applying biochars to reduce NO3(-)-N pollution.
•Microalgae cultivation using liquid digestate showed promising results.•Integrated flocculation-biological contact oxidation had the lowest water footprint.•Sealed storage and optimized processes ...can enhance microalgae scenarios.•Digestate direct use under controlled condition is most environmentally favorable.
The direct use of digestate on farmlands as soil amendment is becoming an uneconomic option for farmers. Moreover, there are serious environmental concerns about its oversupply in regions with intensive biogas plants. Downstream technologies, offering innovative upcycling methods to handle huge amounts of digestate, have absorbed great interest in this context. In this study, three digestate treatment technologies were compared from a life cycle assessment perspective to combine the environmental impacts from pig manure transportation to biogas plants, biogas production, different digestate treatment technologies, and the use of final products. The results showed that scenario including digestate fractionation into solid and liquid, and their use for compost production and microalgae cultivation, respectively, would be a suitable downstream strategy with lower impacts on human health, ecosystem quality, and climate change damage categories, however future improvements still required. The results showed that sealed storage system or fast-continuous downstream processes as well as shorter distances between biogas plants and farms can significantly enhance the environmental performance of coupled anaerobic digestion and microalgae production. The high energy payback also signified that co-digestion of pig manure and microalgae would be energetically favorable in this context. However, having compared the results with a baseline scenario demonstrated that the direct use of digestate on farmlands, under controlled conditions to avoid its over application, is still the most environmentally favorable option, despite being a costly option for farmers. The results achieved in the present study suffered some uncertainties because technologies under consideration are at their infancy stage, thus further research still is required to find the most sustainable solutions.
•Recent achievements in enhanced anaerobic digestion profit by biochar are reviewed.•Biochar enhanced methanogenesis through stimulated direct electron transfer.•Biochar accelerated the generation ...and degradation of volatile fatty acids.•Ammonia control and acids-buffering can be realized by biochar.
Anaerobic digestion (AD) and pyrolysis are two promising technologies used worldwide for waste biomass treatment. Interests on intensification techniques of AD has been increasing to obtain sufficient and sustainable methane production with stable digester performance. For instance, considerable attention has been devoted to the coupling of AD with biochar, which is produced by biomass thermochemical conversion. This manuscript presents a comprehensive review about recent achievements in enhancing AD efficiency with the utilization of biochar. The key roles of biochar include enhancing and equilibrating hydrolysis, acidogenesis-acetogenesis, and methanogenesis, as well as alleviating inhibitor stress were summarized. Biochar can promote biomethane process mainly by serving as a provision for bioelectrical connections between fermentative bacteria and methanogens, a support for microbial colonies, and a reinforcer for buffer capacity. Through an overview of the early applications, this paper aims to pinpoint the potential mechanism and future explorative directions of biochar enhancing AD performance.
Soil pH is a key factor that controls soil nutrient availability, soil microbial activities, and crop growth and development. However, studies on the soil pH variations of cultivated lands in ...different horizons at the regional scale remain limited. In this work, 348 soil samples were collected from three soil horizons (A, B, and C) at 120 sites over the hilly region of Chongqing, southwestern China. Six topographic indicators, four climate parameters, and parent material were considered. Classification and regression trees (CARTs) were applied to investigate the relationships between soil pH and the variables in the A, B, and C horizons. Model performances were evaluated by root mean square error (RMSE), relative root mean square error (RRMSE), and coefficient of determination (R2). Results showed that soil pH increased obviously from the A to C horizons. Soil pH was predicted well by the forcing factors with the CART models in all horizons. RMSE, RRMSE, and R2 varied between 0.37 and 0.435, between 5.93 and 7.23%, and between 0.71 and 0.80, respectively. The relative importance of the studied variables to soil pH differed with the horizons. Annual temperature range (ATR), terrain wetness index (TWI), and Melton ruggedness number were critical factors that controlled soil pH variability in the A horizon. Parent material, precipitation of warmest quarter (PWQ), ATR, and TWI were important variables in the B horizon. Parent material, PWQ, ATR, and precipitation were key factors in the C horizon. The results are expected to provide valuable information for designing appropriate measurements for agricultural practices and preventing soil acidification.
Farm size plays a critical role in agricultural sustainability. This may have far-reaching consequences for the economic and environmental performance of agricultural production, resulting, for ...instance, in an excessive use of mineral fertilizers. However, the magnitude of such effects and their main causes are not well understood, while being essential for effective policy development, especially for countries like China where the agricultural sector is still largely dominated by smallholder farms. In this paper, we review the current understanding of how farm size affects agricultural sustainability using China's crop farming as an example from economic, environment and social aspects. We analyze impacts from both a Chinese and a global perspective to identify intervention points to improve agricultural performance. We found that increasing farm size has a positive impact on farmer's net profit, as well as economic, technical and labor efficiency with mean coefficients of 0.005, 0.02 and 2.25, respectively. Nevertheless, the relationships between farm size and overall productivity, total factor productivity and allocative efficiency are still not well understood and therefore require more research. Meanwhile, increase in farm size is associated with statistically significant decrease in fertilizer and pesticide use per hectare, showing clear benefits for environmental protection. In line with the experiences documented for the evolution of agricultural practices in developed countries, the expansion of large-scale farming is a critical path for modernizing agricultural production and ensuring sustainable food production from the social perspective. Measures concerning farm size should be implemented in an interaction between farmers and the government to promote the green development of agriculture.
•Farm size plays an important role in the performance of agriculture.•Increasing farm size shows clear benefits for environmental protection.•Large-scale farming is a critical path for modernizing and sustaining agriculture.•Smallholders prefer to use more non-fixed inputs to increase yields.
Dietary protein and its metabolites, amino acids, are essential nutrients for humans and animals. Accumulated research has revealed that the gut microbiota mediate the crosstalk between protein ...metabolism and host immune response. Gut microbes are involved in the digestion, absorption, metabolism and transformation process of dietary protein in the gastrointestinal tract. Amino acids can be metabolized into numerous microbial metabolites, and these metabolites participate in various physiological functions related to host health and diseases. The components of dietary protein impact the gut microbiota composition and microbial metabolites. The source, concentration, and amino acid balance of dietary protein are primary factors which contribute to the composition, structure and function of gut microbes. A suitable ratio between protein and carbohydrate or even a low protein diet is recommended over a diet with protein in excess of requirements. Greater levels and undigested protein lead to an increase of pathogenic microorganism with associated higher risk of metabolic diseases. Herein, the crosstalk between dietary protein and gut microbiota composition and function is summarized, which will help to reveal the potential mechanism of gut microbes on the gastrointestinal tract health.
All-inorganic perovskite solar cells (PVSCs) have drawn increasing attention because of their outstanding thermal stability. However, their performance is still inferior than the typical ...organic-inorganic counterparts, especially for the devices with p-i-n configuration. Herein, we successfully employ a Lewis base small molecule to passivate the inorganic perovskite film, and its derived PVSCs achieved a champion efficiency of 16.1% and a certificated efficiency of 15.6% with improved photostability, representing the most efficient inverted all-inorganic PVSCs to date. Our studies reveal that the nitrile (C-N) groups on the small molecule effectively reduce the trap density of the perovskite film and thus significantly suppresses the non-radiative recombination in the derived PVSC by passivating the Pb-exposed surface, resulting in an improved open-circuit voltage from 1.10 V to 1.16 V after passivation. This work provides an insight in the design of functional interlayers for improving efficiencies and stability of all-inorganic PVSCs.
Transition-metal sulfide SnS2 has aroused wide concern due to its high capacity and nanosheet structure, making it an attractive choice as the anode material in sodium-ion batteries. However, the ...large volume expansion and poor conductivity of SnS2 lead to inferior cycle stability as well as rate performance. In this work, FeS2 was in situ introduced to synchronously grow with SnS2 on rGO to prepare a heterojunction bimetallic sulfide nanosheet SnS2/FeS2/rGO composite. The composition and distinctive structure facilitate the rapid diffusion of Na+ and improve the charge transfer at the heterogeneous interface, providing sufficient space for volume expansion and improving anode materials’ structural stability. SnS2/FeS2/rGO bimetallic sulfide electrode boasts a capacity of 768.3 mA h g–1 at the current density of 0.1 A g–1, and 541.2 mA h g–1 at the current density of 1 A g–1 in sodium-ion batteries, which is superior to that of either single metal sulfide SnS2 or FeS2. TDOS calculation further confirms that the binding of FeS2/SnS2–Na is more stable than FeS2 and SnS2 alone. The superior electrochemical performance of the SnS2/FeS2/rGO composite material makes it a promising candidate for sodium storage.
Sign languages are developed around the world for hearing-impaired people to communicate with others who understand them. Different grammar and alphabets limit the usage of sign languages between ...different sign language users. Furthermore, training is required for hearing-intact people to communicate with them. Therefore, in this paper, a real-time motion recognition system based on an electromyography signal is proposed for recognizing actual American Sign Language (ASL) hand motions for helping hearing-impaired people communicate with others and training normal people to understand the sign languages. A bilinear model is applied to deal with the on electromyography (EMG) data for decreasing the individual difference among different people. A long short-term memory neural network is used in this paper as the classifier. Twenty sign language motions in the ASL library are selected for recognition in order to increase the practicability of the system. The results indicate that this system can recognize these twenty motions with high accuracy among twenty participants. Therefore, this system has the potential to be widely applied to help hearing-impaired people for daily communication and normal people to understand the sign languages.
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