Comparative net energy ratio analysis of pellet produced from steam pretreated biomass from agricultural residues and energy crops

A process model was developed to determine the net energy ratio (NER) for the production of pellets from steam pretreated agricultural residue (wheat straw) and energy crops (i.e., switchgrass in this case). The NER is a ratio of the net energy output to the total net energy input from non-renewable energy sources into a system. Scenarios were developed to measure the effects of temperature and level of steam pretreatment on the NER of steam pretreated wheat straw and switchgrass pellets. The NERs for the base case at 6 kg h⁻¹ are 1.76 and 1.37 for steam-pretreated wheat straw and switchgrass-based pellets, respectively. The reason behind the difference is that more energy is required to dry switchgrass pellets than wheat straw pellets. The sensitivity analysis for the model shows that the optimum temperature for steam pretreatment is 160 °C with 50% pretreatment (i.e. 50 % steam treated material is blended with the raw biomass and then pelletised). The uncertainty results for NER for steam pretreated wheat straw and switch grass pellets are 1.62 ± 0.10 and 1.42 ± 0.11, respectively.     

山西省农业机械普查情况分析

农业机械普查是全面收集农业机械化基础资料的一种统计方法。开展农业机械化普查,有助于了解掌握农业机械的数量、使用情况、作业情况、经营效益情况等基础数据,能够为各级农机部门制定发展政策、实施宏观引导提供参考依据。文章分析了山西省农业机械普查的意义、背景、模式,普查情况和存在的问题,以及可以采取的措施,并对开展农业机械普查的必要性及普查模式进行了探讨。     

Assessment of the energetic and mechanical properties of pellets produced from agricultural biomass

This paper presents an assessment of the energetic and mechanical properties of pellets produced from agricultural biomass. For the production of pellets the following raw materials were used: wheat straw, rape straw, and maize straw. Additionally, the mixtures of wheat-rape straw, wheat-maize straw, and rape-maize straw (each accounting for 50% of the mass) were applied. The studied resources were ground with the use of a universal shredder driven by a 7.5 kW electric engine. A pelleting machine fitted with a fixed flat matrix with two driven thickening rolls was used to produce the pellets. Analyses of the moisture and calorific value of resources as well as the bulk density and mechanical strength of pellets were performed according to biding standards. The moisture of resources ranged from 16.5% to 18.5% for rape and maize straw, respectively. The average calorific value fluctuated between 15.3 MJ kg⁻¹ for a mixture of wheat and rape straw to 16.2 MJ kg⁻¹ for maize straw. The bulk density and mechanical strength of pellets depended on the type of resources used. The lowest bulk density was recorded for wheat straw pellets (386–420 kg m⁻³), and the highest (561–572 kg m⁻³) for maize straw pellets. The lowest mechanical strength of pellets was noted for rape (95.4–96.8%), whereas the highest was for pellets made from a wheat and maize straw mixture (96.8–98.9%).     

Integrating social and value dimensions into sustainability assessment of lignocellulosic biofuels

The paper clarifies the social and value dimensions for integrated sustainability assessments of lignocellulosic biofuels. We develop a responsible innovation approach, looking at technology impacts and implementation challenges, assumptions and value conflicts influencing how impacts are identified and assessed, and different visions for future development. We identify three distinct value-based visions. From a techno-economic perspective, lignocellulosic biofuels can contribute to energy security with improved GHG implications and fewer sustainability problems than fossil fuels and first-generation biofuels, especially when biomass is domestically sourced. From socio-economic and cultural-economic perspectives, there are concerns about the capacity to support UK-sourced feedstocks in a global agri-economy, difficulties monitoring large-scale supply chains and their potential for distributing impacts unfairly, and tensions between domestic sourcing and established legacies of farming. To respond to these concerns, we identify the potential for moving away from a one-size-fits-all biofuel/biorefinery model to regionally-tailored bioenergy configurations that might lower large-scale uses of land for meat, reduce monocultures and fossil-energy needs of farming and diversify business models. These configurations could explore ways of reconciling some conflicts between food, fuel and feed (by mixing feed crops with lignocellulosic material for fuel, combining livestock grazing with energy crops, or using crops such as miscanthus to manage land that is no longer arable); different bioenergy applications (with on-farm use of feedstocks for heat and power and for commercial biofuel production); and climate change objectives and pressures on farming. Findings are based on stakeholder interviews, literature synthesis and discussions with an expert advisory group.     

Hyperspectral imaging to classify and monitor quality of agricultural materials

Hyperspectral imaging has been acknowledged as an emerging technology for monitoring quality parameters and improving grading of agricultural materials, such as field crops (e.g., cereals, pulses, oil seeds) and horticultural crops (e.g., apples, strawberries). It has become a popular research tool that facilitates thorough non-destructive analyses by simultaneous acquisition of both spectral and spatial information of agricultural samples. The technique is an extension of multispectral imaging, which provides a large data set by applying conventional imaging, radiometry, and spectroscopic principles when acquiring images. Hyperspectral imaging was initially used for remote sensing applications, but now has been developed to facilitate complete and reliable analyses of intrinsic properties and external characteristics of samples. This paper reviews applications of using hyperspectral imaging for routine grain industry operations such as grading, classification, and chemometric analyses of major constituents of agricultural materials.     

柴河水库流域主要种植类型非点源污染试验研究

为研究水稻田、玉米地和苗木地三种重要耕作类型的非点源污染产生规律,分别选取了柴河水库流域内地理位置相近、土壤特性相似的三块试验田进行了非点源污染类型源试验,分析了不同试验田的产污特征及其影响因素。结果表明,在相同降雨条件下三种耕作类型试验田的污染物输出特征各不相同;相同试验田在不同降雨条件下的产污规律也会发生相应变化;耕作类型、降雨特征和施肥状况都是影响农田非点源污染的重要因子。     

Load Modeling Approach for Evaluating Selenium Stream Standards Compliance

Elevated selenium concentrations have been observed in several rivers in the western United States and are a concern for healthy aquatic systems. Water quality modeling is a valuable tool for quantifying the importance of sources and assessing management alternatives for stream standards compliance in basins with impaired water quality. This modeling study uses a relatively simple approach to describe a water distribution system and processes that drive loading of dissolved selenium and salts from the naturally occurring Cretaceous shale soils in the extensively irrigated Uncompahgre and Gunnison River Basins in Western Colorado. Calibrated model output characterizes processes that load an average total of 4,130?kg (9,100?lb) of selenium and 2.9×108?kg (316,000?t) of salts per year from agricultural subbasins to the Uncompahgre River. Simulations of best management practices predict that extensive implementation of methods to minimize seepage and constituent loading would be required to reduce selenium concentrations to comply with the current water quality standards.     

Hydrogenative pyrolysis of waste tyres: kinetic analysis

A kinetic model for the hydrogenative liquid-solid pyrolysis of waste tyres is presented. The model is tested with available experimental data obtained by running the pyrolysis of tyre particles (size < 500 μm) in a stirred batch reactor, in the presence of tetralin (as hydrogen donor), under a nitrogen atmosphere, and in the temperature range 345–430°C. Because a huge number of products is formed during the pyrolysis process, the compounds have been classified into homogeneous groups. On the basis of the proposed model, a reaction network which describes the evolution of these groups has been set. The kinetic constants of the reactions entering the network have been evaluated at 345, 393, and 430°C. The analytical equations obtained from the model fit the data satisfactorily.

The results of the investigation indicate that the first step of the pyrolysis is the rupture of weak bonds which leads to the dissolution of the tyre particles as large aggregates of molecules, in a time which is of the order of 1 min. Then, much more slowly, lighter products are released from these aggregates. At T = 430°C the large aggregates are completely transformed into stable compounds, detectable by GC, in about 250 min. At lower temperatures, T = 345°C, after 250 min 40% of the loaded tyre is still present as macromolecules not detectable by GC.     

药物分子设计研究新方法

介绍了ＬＣＣ近年来进行计算机辅助药物分子设计所建立的新方法，通过应用这些方法，同药物开发与合成者开展了一系列的合成研究，取得一些可喜的进展，并探索出一条计算机辅助药物分子设计，及开发新先导化合物合理的，可行的，高效的途径。     

短路波导法的新应用

本文介绍一种测定不能进行机械加工的“固体材料”（农产品或矿物）微波介电特性的新方法。将这类材料研碎，成为“空气－粒子”混合物，应用短路波导方法，对几种不同的“松密度”混合物测量其介电特性（介电常数和损耗因子）。当已知待测材料的“固体密度”时，利用这些测得特性与混合物“松密度”的线性函数关系进行“外推”，从而获得“固体密度”下的农产品（或矿物）的微波介电特性。