Waste straw biomass is an abundant renewable bioresource raw material on Earth. Its stubborn wooden cellulose structure limits straw lignocellulose bioconversion into value-added products (e.g., biofuel, chemicals, and agricultural products). Compared to physicochemical and other preprocessing techniques, the steam explosion method, as a kind of hydrothermal method, was considered as a practical, eco-friendly, and cost-effective method to overcome the above-mentioned barriers during straw lignocellulose bioconversion. Steam explosion pretreatment of straw lignocellulose can effectively improve the conversion efficiency of producing biofuels and value-added chemicals and is expected to replace fossil fuels and partially replace traditional chemical fertilizers. Although the principles of steam explosion destruction of lignocellulosic structures for bioconversion to liquid fuels and producing solid biofuel were well known, applications of steam explosion in productions of value-added chemicals, organic fertilizers, biogas, etc. were less identified. Therefore, this review provides insights into advanced methods of utilizing steam explosion for straw biomass conversion as well as their corresponding processes and mechanisms. Finally, the current limitations and prospects of straw biomass conversion with steam explosion technology were elucidated.

Design and test of the key components for a combing-type tobacco harvester

The input of exogenous organic matter could affect the transformation of soil carbon (C) and nitrogen (N), and their C- and N-priming effects (CPE and NPE) play a key role in the balance of soil C and N. However, little is known about how the interaction effect between straw and straw biochar regulates CPE and NPE. Therefore, we conducted a 90-day incubation experiment, which included five treatments: no straw and straw biochar (CK), 1.5% straw (S), 0.53% straw biochar (B), 1.5% straw + 0.53% straw biochar (SB), and 1.5% straw + 1.06% straw biochar (SB1). Our findings revealed that cumulative soil CO₂ emissions were increased by 95.52–216.53% through the short-term input of exogenous organic matter input; however, this trend gradually weakened with decreasing dissolved organic C (DOC) content. The cumulative NPE generated by the addition of exogenous organic matter was much smaller than the cumulative CPE. Under the B and S treatments, the cumulative CPE and NPE were negative throughout the entire incubation period. The SB treatment remarkably boosted the microbial biomass nitrogen (MBN) content; however, the SB1 treatment was more effective in inhibiting soil C and N mineralization processes than SB treatment. Moreover, the cumulative CPE and NPE were mainly regulated by N. We conclude that the combination of straw and straw biochar preferentially stimulated soil C mineralization, but that this effect decreased with time, which may be due to the consumption of labile DOC caused by the initial positive CPE, while soil N mineralization had a lag effect.

Biochar application has received much attention because biochar can be used as an organic amendment. The nutrient release patterns and interactions in straw biochar produced at different temperatures are not well understood. In this study, we observed the release patterns of carbon (C), nitrogen (N), phosphorus (P), and potassium (K) and the interaction between released C, N, P, and K from straw biochar prepared from 225 to 600 °C through a 180-day degradation experiment. The results showed that the degradation rate of the two kinds of straw biochar was faster in the first 30 days at different temperatures, and that of the straw biochar prepared before 300 °C was more rapid, indicating that 300 °C is an important turning point. The rule of nutrient release in the straw biochar showed that the K release rate was the highest and most rapid and was more than 60% in the first 30 days. The nutrient release rates for the two kinds of straw biochar were in the order K > N > P > C. The release of nutrients accompanied the decomposition of the straw biochar, and there was an exponential relationship between the amount of nutrients released from straw biochar and its degradation mass. There were collaborative or similar release processes indicated by significant positive correlations between the released C and N (R² = 0.96) and P and K (R² = 0.94) in the tobacco straw biochar and an obvious correlation between the released C and N (R² = 0.76) in the rice straw biochar. These results indicated that the released C and N, P, and K in tobacco straw biochar, as well as C and N in rice straw biochar, have synergistic effects and the same degradation path. The application of straw biochar can provide a source of P and N in the short term and a source of P and C in the long term. This study suggests that returning straw biochar to the soil could appropriately reduce the input of K fertilizer in the early stage.

Numerical simulation and experimental study of the extrusion process for rice straw powder based on EDEM