Microbial oil is one important bio-product for its important function in energy, chemical, and food industry. Finding suitable substrates is one key issue for its industrial application. Both hydrophilic and hydrophobic substrates can be utilized by oleaginous microorganisms with two different bio-pathways (“de novo” lipid fermentation and “ex novo” lipid fermentation). To date, most of the research on lipid fermentation has focused mainly on only one fermentation pathway and little work was carried out on both “de novo” and “ex novo” lipid fermentation simultaneously; thus, the advantages of both lipid fermentation cannot be fulfilled comprehensively. In this study, corncob acid hydrolysate with soybean oil was used as a mix-medium for combined “de novo” and “ex novo” lipid fermentation by oleaginous yeast Trichosporon dermatis. Both hydrophilic and hydrophobic substrates (sugars and soybean oil) in the medium can be utilized simultaneously and efficiently by T. dermatis. Different fermentation modes were compared and the batch mode was the most suitable for the combined fermentation. The influence of soybean oil concentration, inoculum size, and initial pH on the lipid fermentation was evaluated and 20 g/L soybean oil, 5% inoculum size, and initial pH 6.0 were suitable for this bioprocess. By this technology, the lipid composition of extracellular hydrophobic substrate (soybean oil) can be modified. Although adding emulsifier showed little beneficial effect on lipid production, it can modify the intracellular lipid composition of T. dermatis. The present study proves the potential and possibility of combined “de novo” and “ex novo” lipid fermentation. This technology can use hydrophilic and hydrophobic sustainable bio-resources to generate lipid feedstock for the production of biodiesel or other lipid-based chemical compounds and to treat some special wastes such as oil-containing wastewater.

Biochar application is considered an effective method for reducing nitrous oxide (N₂O) emissions from soil. However, the mechanisms underlying the influence of various biochar dosages on soil N₂O emissions and the duration of one-time biochar application remain unclear. The effects of different biochar application rates and a one-time application on soil N₂O emissions in the Huanghuaihai Plain of China were investigated through a field experiment from 2020 to 2022. In the wheat and maize rotation system, six treatments were administered: no biochar (C0); 2 (C1), 4 (C2), 8 (C3), and 12 t/hm² biochar (C4) applied annually; and a one-time application of 12 t/hm² biochar (CS) in 2018. Our results indicate that, compared with C0, biochar significantly inhibited soil N₂O emissions, particularly in the C3 and C4 treatments, with reductions of 31.36–56.21% and 36.92–52.45%, respectively. However, CS did not significantly affect soil N₂O emissions during the study period. These findings suggest that the biochar’s inhibitory effect on soil N₂O emissions is contingent upon the dosage and frequency of application. A structural equation model revealed that biochar decreases soil N₂O emissions by enhancing the reduction in N₂O during denitrification. Under the conditions of this experiment, based on a logistic ecological model, a one-time application of 12 t/hm² biochar was projected to significantly reduce soil N₂O emissions for approximately 1.77 years. On the whole, biochar reduces soil N₂O emissions mainly by regulating N₂O production through denitrification, and the duration of this inhibition of N₂O emissions mainly depends on the application amount and frequency of biochar application.

Polyacrylamide (PAM), a widely utilized flocculant in sewage treatment, typically finds its way into sewage sludge (SS) and undergoes transformation during the SS treatment process. Despite its prevalence and potential implications, the transformation of PAM during SS treatment has scarcely been documented in the literature. This study investigated the transformation of PAM during two prevalent thermal treatment processes of SS: hydrothermal carbonization (HTC) and pyrolysis. To comprehensively analyze the transformation products, LC-MS/MS was employed to examine the liquid products obtained from the HTC treatment of PAM, while TG-FTIR was utilized to analyze the pyrolysis gas. Upon subjecting PAM to HTC treatment in the temperature range of 150–240 °C, a detailed analysis of the water quality characteristics of the liquid phase derived from PAM was conducted. The analysis successfully identified a total of 81 components, consisting of 35 carbonaceous and 46 nitrogenous compounds. Notably, when the reaction temperature remained below 150 °C, the decomposition of both the side chains and the backbone of PAM was relatively mild. However, as the temperature exceeded 180 °C, the deamination process was significantly enhanced. Concurrently, the pH of the liquid phase decreased, which could be attributed to the decomposition of high molecular polybasic acids into low-molecular weight organic acids. The TG-FTIR analysis of PAM revealed that the mass loss during the pyrolysis of PAM at 30–1,000 °C could be distinctly divided into five stages. The initial mass loss stage was primarily attributed to the removal of adsorbed water and organic solvents. The second mass loss stage was hypothesized to be a result of intramolecular decomposition accompanied by the elimination of CHx and C=C groups. The subsequent third, fourth, and fifth mass loss stages were predominantly due to the release of amides and CO₂. Additionally, it was observed that CO was generated through the reduction of CO₂ by the carbon present in the solid residues. The conclusion of this study presents a comprehensive discussion of environmental implications based on the results of HTC and pyrolysis treatments of PAM.

Saline-alkali soil has poor fertility and low organic matter content, which are key factors that limit agricultural productivity. Intercropping systems can enhance biodiversity in farmlands, thereby increasing the organic matter content. During this process, soil microorganisms respond to environmental changes. Therefore, we conducted a three-year intercropping enhancement experiment using saline-alkali soil. To avoid nutrient and microbial differences caused by the varying nutrient demands of different crop types, we systematically sampled the tillage layer of the soil (0–20 cm) from the subsequent crop (wheat season) in the intercropping systems. We found that compared to the control group, the three intercropping systems significantly increased the nutrient content in saline-alkali soil, including total nitrogen, total phosphorus, total potassium, organic matter, available nitrogen, and available potassium. Notably, there were significant increases in total nitrogen, organic matter, and available potassium. The intercropping systems had varying effects on the alpha and beta diversities of soil bacteria and fungi. Specifically, the effect of intercropping on fungal alpha diversity was significantly greater than that on bacterial alpha diversity, whereas its effect on bacterial beta diversity was greater than that on fungal beta diversity. Additionally, intercropping influenced microbial community composition, increasing the abundance of Acidobacteria and Gemmatimonadetes and decreasing the abundance of Actinobacteria. It also increased the abundance of Ascomycota and Mortierella and decreased the abundance of Basidiomycota. Total nitrogen and soil organic matter were identified as the primary environmental factors that significantly affected bacterial community composition; however, they had no significant impact on fungal communities. Intercropping had different effects on the fungal and bacterial networks. It increased the stability and complexity of the bacterial network. However, although it improved the stability of the fungal network, intercropping reduced its complexity. In summary, intercropping with leguminous plants is an effective way to enhance soil nutrients, particularly organic matter, in saline-alkali soils. Simultaneously, intercropping affects the soil microbial community structure of subsequent crops; however, the responses of bacteria and fungi to intercropping are significantly different. The results of this study provide data support for improving saline-alkali land through planting systems.

Agri-environmental subsidies had been implemented to promote sustainable agriculture in regions such as the EU and the U.S. prior to the year 2000. Contract-Based Agri-Environmental Schemes (AESs) are designed to promote green, sustainable agriculture by employing environmentally friendly farming practices (EFFPs) to reduce pollution and meet other environmental goals. A central challenge, however, is the limited inclusion of small farmers, who are key to agricultural sustainability and form the backbone of production, particularly in developing countries. This study aims to investigate the preferences and participation of small farmers in AESs to enable effective policy design. Using discrete choice experiments (DCEs) and a latent class model (LCM) on survey data collected in 2017 from three key rice-producing counties in China—Fangzheng (Heilongjiang), Qingtongxia (Ningxia), and Yixing (Jiangsu)—allowed us to identify two distinct preference classes: “experienced adopters” and “potential adopters”. The results confirmed (1) a high participation rate of small farmers in AESs. Compensation can further motivate them to sign a contract. (2) There is significant heterogeneity among small farmers’ preferences on various EFFPs, so flexible and modulated schemes are needed; (3) those with experience in EFFPs are more likely to participate in AESs; and (4) the modular AES contract with progressive subsidy ties makes payments directly based on EFFP adoption, addressing the shortcomings of China’s current area-based subsidy system. The results of this paper can help policymakers fine-tune farming policies that effectively engage smallholders, thereby alleviating tensions over production–pollution cycles and fostering a more targeted and sustainable agricultural policy system.