Changes in the Material Characteristics of Maize Straw during the Pretreatment Process of Methanation

Pretreatment technology is important to the direct methanation of straw. This study used fresh water, four bacterium agents (stem rot agent, “result” microbe decomposition agent, straw pretreatment composite bacterium agent, and complex microorganism agent), biogas slurry, and two chemical reagents (sodium hydroxide and urea) as pretreatment promoters. Different treatments were performed, and the changes in the straw pH value, temperature, total solid (TS), volatile solid (VS), and carbon-nitrogen ratio (C/N ratio) under different pretreatment conditions were analyzed. The results showed that chemical promoters were more efficient than biological promoters in straw maturity. Pretreatment using sodium hydroxide induced the highest degree of straw maturity. However, its C/N ratio had to be reduced during fermentation. In contrast, the C/N ratio of the urea-pretreated straw was low and was easy to regulate when used as anaerobic digestion material. The biogas slurry pretreatment was followed by pretreatments using four different bacterium agents, among which the effect of the complex microorganism agent (BA4) was more efficient than the others. The current study is significant to the direct and efficient methanation of straw

Microbial traits determine soil C emission in response to fresh carbon inputs in forests across biomes

Soil priming is a microbial-driven process, which determines key soil–climate feedbacks in response to fresh carbon inputs. Despite its importance, the microbial traits behind this process are largely undetermined. Knowledge of the role of these traits is integral to advance our understanding of how soil microbes regulate carbon (C) emissions in forests, which support the largest soil carbon stocks globally. Using metagenomic sequencing and C-glucose, we provide unprecedented evidence that microbial traits explain a unique portion of the variation in soil priming across forest biomes from tropical to cold temperature regions. We show that microbial functional profiles associated with the degradation of labile C, especially rapid simple sugar metabolism, drive soil priming in different forests. Genes involved in the degradation of lignin and aromatic compounds were negatively associated with priming effects in temperate forests, whereas the highest level of soil priming was associated with β-glucosidase genes in tropical/subtropical forests. Moreover, we reconstructed, for the first time, 42 whole bacterial genomes associated with the soil priming effect and found that these organisms support important gene machinery involved in priming effect. Collectively, our work demonstrates the importance of microbial traits to explain soil priming across forest biomes and suggests that rapid carbon metabolism is responsible for priming effects in forests. This knowledge is important because it advances our understanding on the microbial mechanisms mediating soil–climate feedbacks at a continental scale.This work were financially supported by the National Natural Science Foundation of China (41907031), the Chinese Academy of Sciences “Light of West China” Program for Introduced Talent in the West, the National Natural Science Foundation of China (31570440, 31270484), the Key International Scientific and Technological Cooperation and Exchange Project of Shaanxi Province, China (2020KWZ-010), the 2021 First Funds for Central Government to Guide Local Science and Technology Development in Qinghai Province (2021ZY002), the i-LINK +2018 (LINKA20069) from CSIC, and a Ramón y Cajal grant from the Spanish Ministry of Science and Innovation (RYC2018-025483-I

Research on the Food Security Condition and Food Supply Capacity of Egypt

Food security is chronically guaranteed in Egypt because of the food subsidy policy of the country. However, the increasing Egyptian population is straining the food supply. To study changes in Egyptian food security and future food supply capacity, we analysed the historical grain production, yield per unit, grain-cultivated area, and per capita grain possession of Egypt. The GM (1,1) model of the grey system was used to predict the future population. Thereafter, the result was combined with scenario analysis to forecast the grain possession and population carrying capacity of Egypt under different scenarios. Results show that the increasing population and limitations in cultivated land will strain Egyptian food security. Only in high cultivated areas and high grain yield scenarios before 2020, or in high cultivated areas and mid grain yield scenarios before 2015, can food supply be basically satisfied (assurance rate ≥ 80%) under a standard of 400 kg per capita. Population carrying capacity in 2030 is between 51.45 and 89.35 million. Thus, we propose the use of advanced technologies in agriculture and the adjustment of plant structure and cropping systems to improve land utilization efficiency. Furthermore, urbanization and other uses of cultivated land should be strictly controlled to ensure the planting of grains

Household biogas use in rural China: A study of opportunities and constraints

As a renewable energy, biogas is not only an important part of the development of rural new energy, but also an important aspect of sustainable development in China. The development process and present status of household biogas, specifically the opportunities and constraints of household biogas in rural China, are discussed in this paper. Only about 19% of the biogas potential has been utilized in rural China. There are several opportunities for household biogas development in rural China, including the problem of rural household energy consumption, the availability of biogas fermentation materials, national financial subsidies, legal and international clean development mechanisms. Also, more research needs to be done in straw fermentation and cold fermentation technology. Training should be conducted to raise the level of biogas customers in comprehensive biogas utilization. Measures should be taken to improve the follow-up services and management of biogas plants. The information presented in this paper will be helpful not only to the sustainable development of household biogas in rural China, but also to the development of biogas in similar countries around the world.Household biogas Renewable energy Sustainable development

COMPARISON OF TWO CHEMICAL PRETREATMENTS OF RICE STRAW FOR BIOGAS PRODUCTION BY ANAEROBIC DIGESTION

Lignocellulosic biomass is considered the most abundant renewable resource that has the potential to contribute remarkably in the supply of biofuel. Previous studies have shown that chemical pretreatment prior to anaerobic digestion (AD) can increase the digestibility of lignocellulosic biomass and methane yield. In the present study, the effect of rice straw pretreatment using ammonium hydroxide (NH3•H2O) and hydrogen peroxide (H2O2) on the biogasification performance through AD was investigated. A self-designed, laboratory-scale, and continuous anaerobic biogas digester was used for the evaluation. Results showed that the contents of the rice straw, i.e. the lignin, cellulose, and hemicellulose were degraded significantly after the NH3•H2O and H2O2 treatments, and that biogas production from all pretreated rice straw increased. In addition, the optimal treatments for biogas production were the 4% and 3% H2O2 treatments (w/w), which yielded 327.5 and 319.7 mL/gVS, biogas, respectively, higher than the untreated sample. Biogas production from H2O2 pretreated rice straw was more favorable than rice straw pretreated with same concentration of ammonia, ranking in the order of 4% ≈ 3% > 2% > 1%. The optimal amount of H2O2 treatment for rice straw biogas digestion is 3% when economics and biogas yields are considered

Effects of temperature and carbon-nitrogen (C/N) ratio on the performance of anaerobic co-digestion of dairy manure, chicken manure and rice straw: focusing on ammonia inhibition.

Anaerobic digestion is a promising alternative to disposal organic waste and co-digestion of mixed organic wastes has recently attracted more interest. This study investigated the effects of temperature and carbon-nitrogen (C/N) ratio on the performance of anaerobic co-digestion of dairy manure (DM), chicken manure (CM) and rice straw (RS). We found that increased temperature improved the methane potential, but the rate was reduced from mesophilic (30∼40°C) to thermophilic conditions (50∼60°C), due to the accumulation of ammonium nitrogen and free ammonia and the occurrence of ammonia inhibition. Significant ammonia inhibition was observed with a C/N ratio of 15 at 35°C and at a C/N ratio of 20 at 55°C. The increase of C/N ratios reduced the negative effects of ammonia and maximum methane potentials were achieved with C/N ratios of 25 and 30 at 35°C and 55°C, respectively. When temperature increased, an increase was required in the feed C/N ratio, in order to reduce the risk of ammonia inhibition. Our results revealed an interactive effect between temperature and C/N on digestion performance

Seeking sustainable solutions for human food systems

Sustainable food system development is the cornerstone of global human survival and development. This research briefly analyzes the challenges facing the current food system, summarizes the directions of food system transformation, expounds the role of geography in the transformation of food system, and discusses the future paths to promote the sustainable development of food system. The main conclusions are as follows: 1) The interaction of factors such as regional conflicts, climate change, slowdown in development, raging epidemics, and resource and environmental constraints pose multiple challenges to the global food system. 2) The food system should be high-quality, efficient, nutritious and healthy, green and low-carbon, inclusive and inclusive transformation. 3) Geography can provide solutions for the transformation of food systems. 4) The transformation paths of the food system includes: establishing a global food system with benefit sharing, cleaner production, and fair participation, improving the innovation capability of the food system, and establishing an effective organizational guarantee system

Stratification of carbon fractions and carbon management index in deep soil affected by the Grain-to-Green Program in China.

Conversion of slope cropland to perennial vegetation has a significant impact on soil organic carbon (SOC) stock in A horizon. However, the impact on SOC and its fraction stratification is still poorly understood in deep soil in Loess Hilly Region (LHR) of China. Samples were collected from three typical conversion lands, Robinia psendoacacia (RP), Caragana Korshinskii Kom (CK), and abandoned land (AB), which have been converted from slope croplands (SC) for 30 years in LHR. Contents of SOC, total nitrogen (TN), particulate organic carbon (POC), and labile organic carbon (LOC), and their stratification ratios (SR) and carbon management indexes (CMI) were determined on soil profiles from 0 to 200 cm. Results showed that the SOC, TN, POC and LOC stocks of RP were significantly higher than that of SC in soil layers of 0-10, 10-40, 40-100 and 100-200 cm (P<0.05). Soil layer of 100-200 cm accounted for 27.38-36.62%, 25.10-32.91%, 21.59-31.69% and 21.08-26.83% to SOC, TN, POC and LOC stocks in lands of RP, CK and AB. SR values were >2.0 in most cases of RP, CK and AB. Moreover, CMI values of RP, CK, and AB increased by 11.61-61.53% in soil layer of 100-200 cm compared with SC. Significant positive correlations between SOC stocks and CMI or SR values of both surface soil and deep soil layers indicated that they were suitable indicators for soil quality and carbon changes evaluation. The Grain-to-Green Program (GTGP) had strong influence on improving quantity and activity of SOC pool through all soil layers of converted lands, and deep soil organic carbon should be considered in C cycle induced by GTGP. It was concluded that converting slope croplands to RP forestlands was the most efficient way for sequestering C in LHR soils

Optimization of the Alkaline Pretreatment of Rice Straw for Enhanced Methane Yield

The lime pretreatment process for rice straw was optimized to enhance the biodegradation performance and increase biogas yield. The optimization was implemented using response surface methodology (RSM) and Box-Behnken experimental design. The effects of biodegradation, as well as the interactive effects of Ca(OH)2 concentration, pretreatment time, and inoculum amount on biogas improvement, were investigated. Rice straw compounds, such as lignin, cellulose, and hemicellulose, were significantly degraded with increasing Ca(OH)2 concentration. The optimal conditions for the use of pretreated rice straw in anaerobic digestion were 9.81% Ca(OH)2 (w/w TS), 5.89 d treatment time, and 45.12% inoculum content, which resulted in a methane yield of 225.3 mL/g VS. A determination coefficient (R2) of 96% was obtained, indicating that the model used to predict the anabolic digestion process shows a favorable fit with the experimental parameters

El control de la marginalidad en la Castilla del Siglo de Oro : el caso de Toledo

<p>Values are presented as the mean ±standard error of three replicates (n = 3). Vertical bars represent LSD at the 5% level.</p