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In this study, dairy manure was converted into solid and liquid products via hydrothermal carbonization (HTC) to determine optimal reaction conditions to retain the greatest amounts of inorganic nutrients. The influence of three parameters, reaction temperature (150–270 °C), residence time (0.5–6 h) and manure/water ratio (5/200–25/200 g/mL), on the total nutrient content (TNC) in the solid and liquid products were investigated using a 5-level, 3-factor orthogonal test and principal components analysis (PCA). Also, the distribution characteristics of inorganic nutrients were determined using single factor tests. The maximum TNC of the solid product was 22.92 mg/g, obtained at manure/water ratio of 20/200 g/mL and performed at 240 °C for 6 h. For obtaining the maximum TNC of liquid product, the most optimal conditions were 150 °C, 1 h and 20/200 g/mL which produced TNC of 1619.55 mg/L. The proportion of ammonium (NH 4 + -N) and orthophosphate (PO 4 3− ) were also analyzed in the liquid product. The amount of NH 4 + -N increased with reaction temperature increasing and manure/water ratio decreasing, the main form of phosphorus (P) was PO 4 3− in the liquid product, and most of the potassium (K) were also dissolved in the liquid product. These results indicate that the HTC could be a promising approach for the utilization of dairy manure as inorganic fertilizer in the future. [ABSTRACT FROM AUTHOR]

Nitrogen, as a common element, is widely present in biomass. The effects of nitrogenous substances on the same origin pyrolysis of biomass and the consequences of N-containing biochar on the catalytic process of volatiles are important for further analyzing the pyrolysis mechanism of biomass. In this research, N-containing biochar was prepared under different conditions, and the interaction between N-containing biochar and biomass pyrolysis volatiles at 400–700 °C was studied. The results show that N-containing biochar can simultaneously participate in reactions as adsorbents, catalysts, and reactants. Its catalytic effect is obviously different for various N configurations. Pyridinic N and pyrrolic N can promote the cracking of lignin into methoxy phenol compounds and promote the further cracking of 5-hydroxymethylfurfural. Graphitic N and oxidized N can promote the further decomposition of phenol and the conversion of D-xylose into small-molecule ketones. In addition, oxidized N can also inhibit the cracking of lignin to produce guaiacol. In the long-term interaction, the highly active pyridinic N tends to convert to a more stable graphitic N. [Display omitted] • N-containing biochar and volatile interaction under biomass pyrolysis was studied. • Urea as the N source has about 10% increase for the bio-oil yield. • N had the most significant effect on the conversion of cellulose to furans. • The conversion of pyridinic N to graphitic N affects catalytic behavior obviously. • Catalytic mechanism of N-containing biochar for same origin pyrolysis was proposed. [ABSTRACT FROM AUTHOR]

Wheat straw is rich in organic matter and nutrients and has the potential to replace peat as the primary raw material in organic nurseries. Using straw as a peat substitute can also aid in reducing the CO 2 emissions that result from peat mining. Furthermore, this can avoid resource wastage and eliminate the practice of burning wheat straw, thereby causing pollution. The conventional composting treatment has a long cycle and inability to control substrate properties in a targeted manner. Thus, this study analyzed the physicochemical properties, material science properties, and biological toxicity of straw substrate at the end of fermentation to achieve rapid and targeted regulations of the substrate's overall performance. Wheat straw treated with two types of fermentation (aerobic/anaerobic) and five chemical conditioners (1% CH 3 COOH, 1% H 2 SO 4 , 1% NaOH, 1% K 2 CO 3 , and H 2 O) under different temperature conditions was used. Adjusting the pH of straw substrate to acidic levels (4.47–6.51) reduced the organic matter consumption by 0.27–5.82% under anaerobic digestion than under aerobic composting. Meanwhile, aerobic composting retained more nitrogen (0.12–8.23 mg/g) than anaerobic digestion. The co-fermentation of wheat straw pretreated with 1% H 2 SO 4 resulted in 14.18–46.12% hemicellulose degradation. Co-aerobic straw composting with H 2 SO 4 and K 2 CO 3 at 35 °C reduced the crystallinity of the straw substrate by 6.66 and 7.33%, respectively, as compared to other conditioning agents. CH 3 COOH lowered the electrical conductivity values of the straw substrate at the end of fermentation (2.33–3.49 mS/cm). Overall, the findings revealed that CH 3 COOH-cooperative aerobic composting pretreatment at 35 °C is a suitable replacement for the traditional composting process as a method of utilizing straw substrate. [Display omitted] • Alternative organic substrates are required to replace peat, as it is rare. • Properties of different straw pre-treatments were tested as a peat alternative. • Pre-treated with different additives/temperatures produces different end products. • Anaerobic digestion facilitates pH adjustment and organic matter retention. • The best treatment has excellent properties that facilitate its use in horticulture. [ABSTRACT FROM AUTHOR]

Antibiotic residues pose a risk to the agricultural application of liquid digestate. In our previous study, photocatalysis was employed to degrade the antibiotics in liquid digestate and observed that the removal efficiency of TC, OTC, and CTC was up to 94.99%, 88.92%, and 95.52%, respectively, at the optimal experimental level, demonstrating the feasibility of this technology. In this study, the liquid digestate after photocatalysis was analyzed to evaluate the effect of photocatalysis on the nutrients, phytotoxicity, and bacterial community of liquid digestate. The results showed that photocatalysis had little effect on the major nutrients TN, TP, and TK in liquid digestate. However, photocatalysis could cause an increase in tryptophan substances as well as soluble microbial by-products and a decrease in humic acid substances in the liquid digestate. The toxicity of liquid digestate after photocatalysis exhibited an increasing trend followed by a decreasing trend, and the liquid digestate after photocatalysis for 2 h had a promoting effect on seed germination and root growth. The richness, diversity, and evenness of bacterial communities in liquid digestate were decreased as a result of photocatalysis. The dominant species in the liquid digestate was dramatically changed by photocatalysis, and the antibiotic concentration also had a major effect on the dominant species in the liquid digestate after photocatalysis. After photocatalysis for 2 h, the dominant species in the liquid digestate changed from Firmicutes to Proteobacteria. [Display omitted] • Photocatalysis has little effect on the main nutrient content of liquid digestate. • Photocatalysis can reduce the toxicity of liquid digestate and antibiotics. • Richness, diversity and evenness of bacterial community reduced after photocatalysis. [ABSTRACT FROM AUTHOR]

Graphite is a widely used industrial material, which experienced a marked shortage caused by the growing demand for electrode anode material and the increased costs for raw material. Graphitic carbon from biomass is a promising approach that will result in low-cost and efficient preparation. Herein, Fe(NO 3) 3 was selected as the catalyst for pine sawdust, and the effects of temperature and iron content on the graphitization of biochar were investigated. Additionally, the formation mechanism of the graphitic crystallite structure was explored. Results showed that the formation of pyrolysis gas increased with the increase in the amount of catalyst added or pyrolysis temperature. The change in pyrolysis gas, such as H 2 and CO, was a critical auxiliary factor reflecting the conversion process. As temperature was increased from 600 °C to 800 °C, the solid products showed high graphitization and low solid yield. Graphite structure mainly formed at 700 °C because of the formation of Fe nanoparticles. The increase in the amount of catalyst could provide more reaction sites and promote the contact between Fe and C, showing that amorphous carbon is dissolved on Fe nanoparticles and precipitated into ordered graphitic carbon. On this basis, a mechanism of "carbon dissolution-precipitation" was proposed to explain the formation of graphite structure, and the whole pyrolysis process included the transformation of the iron element were analyzed. [Display omitted] • Low-temperature catalytic of iron nitrate on graphitization of sawdust was studied. • Fe nanoparticles promote graphitization of sawdust. • Temperature affects the graphitization degree by changing the morphology of Fe. • Reaction mechanism of biomass catalytic pyrolysis graphitization was proposed. [ABSTRACT FROM AUTHOR]

The cellulose content in vegetable waste (VW) is high and cannot be directly digested by black soldier fly larvae (BSFL). In this study, in order to treat VW using BSFL composting, kitchen waste (KW) is used as the only nutritional supplement for VW to analyze the effects of the different contents of crude protein (CP), crude fat (EE), carbohydrate (3C), compost thickness (CT), and treatment time on the larval weight (LW), survival rate (SR), dry matter reduction rate (DMR), bioconversion rate (BCR), physical and chemical properties of BSFL sand and changes in the microbial community. Our results showed that when the average 3C content increased by 40%, the average LW increased by 47.6%, and the SR, DMR, BCR, and organic matter (OM) content increased by 16.82%, 8.5%, 4.77%, and 3.86%, respectively. In contrast, when the average compost thickness increased by 5 cm, the average weight of BSFL decreased by 22.64%, while the SR of larvae, DMR, BCR, OM, and total nutrients (TN + P 2 O 5 + K 2 O) decreased by 5%, 5.2%, 4.42%, 9.6%, and 0.78%, respectively. Germination test showed that BSFL sand alone could not be used as soilless culture substrate. After BSFL treatment, we found that the dominant phyla in BSFL sand were Firmicutes (95.77%), Proteobacteria (2.54%), Actinobacteria (0.74%), and Chloroflexi (0.6%). Our results indicate that BSFL composting is an effective method of treating VW, and 3C content and CT have a significant effect on BSFL composting. [Display omitted] • 3C content and CT had significant effects on LW, SR, DMR, BCR and FCR. • 3C (129.34 g), CT (5 cm) and time (10 days) are suitable for BSFL composting. • BSFL sand cannot be directly used as soilless culture substrate. • Firmicutes (95.77%) was the most abundant gate in the BSFL sand. [ABSTRACT FROM AUTHOR]