Characterisation of agricultural residues used as a source of fibres for fibre-cement production

Nowadays, certain components of non-wood annual plants such as corn stalk and industrial hemp core are considered waste materials or used in low value applications; both by-products have a very low cost. On the other hand, given the large quantities of these materials generated worldwide and their renewable character, it is reasonable to explore new routes for their exploitation. The aim of this paper is to study the potential of both corn stalk (Zea Mays L.) and industrial hemp core (Cannabis Sativa L.) fibres as a renewable source of cellulose fibres in the production of fibre-cement. For each source of fibres, a number of chemical cooking treatments were studied. The morphological properties of the fibres were determined using a scanning electron microscope and a fibre and pulp morphological analyser. Pulp refining was carried out in a PFI mill to improve the characteristics of the fibres. In the case of corn fibres, different degrees of refining were applied. The fibre flocculation process was investigated using several polyacrylamides. The process was studied by monitoring the chord size distribution in real time by means of a focused beam reflectance measurement probe.The results indicated that both pulps can be used for the production of fibre-cement, having the two types of pulp morphological similarities with the pine fibres currently used.Through the flocculation process it was concluded the floc size depends on the length of the fibres.     

Effects of cross-linking on mechanical and physical properties of agricultural residues/recycled thermoplastics composites

Maleated graft polyolefins as cross-linking agents (CAs) are widely used to improve properties of wood thermoplastic composites made by melt extrusion process. In this study, novel CAs, free isocyanate group (NCO)-terminated urethane pre-polymers (UPs) were synthesized and used in manufacturing wheat straw (WS)/recycled polyethylene (PE) composites. The composites using polymeric diphenylmethane diisocyanate (pMDI) as a CA were also made in comparison. The relationship between composite properties and the level of CA and its content as well as the composite density and hot pressing time were investigated based on wood based board processes. The results show that the internal bonding (IB) strength, the IB after soaked in boiling water for 2 h (2hWIB), the modulus of rupture (MOR), the modulus of elasticity (MOE) and the 24 h thickness of swell after absorption of water (24hTS) of the composites are significantly improved with increased CA contents and composite densities. The optimal hot pressing time is 1.1 min/mm at 180°C. The cross-linking function is attributed to the reaction between free NCOs of CA molecules with hydroxyls of WS and the moisture in the raw materials, as well as the interaction between weak polar chain segments in the CA molecules to the non-polar PE. It is highly feasible to manufacture high quality composite using WS and recycled PE as raw materials when cross-linked with just 2.5% of UPs.     

The use of lignocellulosic hybrid filler in alternative FGRP configurations

The aim of this study was to develop an alternative fiberglass-reinforced plastic (FGRP) configuration. A hybrid composite, composed of a polyester-based matrix reinforced with fiberglass was conceived, in both continuous strand (roving) and mats forms, along with an alternative hybrid filler, derived from two different types of industrial residue: from the furniture industry and from the Cocos nucifera Linn (coconut palm) food derivative industry. The initial aim was to determine the feasibility of using residues, mainly of dry endocarp, without the need of prior selection, because it is more resistant and harder than wood residues. To that end, the following tests were performed: X-ray diffraction, differential thermal analysis (DTA), thermogravimetric analysis (TGA) and microstructural analysis of micrographic studies. The mechanical properties of strength and stiffness were studied using tensile uniaxial and three-point bending tests in dry and saturated moisture states. The graphics were obtained using Microsoft Oringin 6.0 software.     

Characteristics of lignocellulosic fibers from hardwood pulp by laccase-catalyzed TEMPO oxidation

There is a challenge to find an effective and eco-friendly method to achieve the modification of fibers. The effect of laccase-TEMPO system on the properties of the bleached eucalyptus kraft pulp was investigated in this work. The results were demonstrated by the decreases in curl values and kink index. In addition, carboxyl and aldehyde groups were introduced in this reaction system. Compared with initial pulp, the contents of aldehyde and carboxyl groups of the treated pulp were increased from 42.6 μmol/g, 8.4 μmol/g to 125.4 μmol/g, 26.3 μmol/g respectively. However, the treatment had a detrimental effect on the thermal stability of pulp fibers. Moreover, the crystallinity index was slightly increased (from 82.1 % to 83.8 %) after the TEMPO-mediated oxidation, but the native crystalline structure was nearly unchanged. Furthermore, after the oxidation treatment, the relatively smooth film surface became textured, the carbon and oxygen bonds were changed, which were investigated by scanning electron microscope and X-ray photoelectron spectroscopy.     

Multiple use of plants: Studies on selenium incorporation in some agricultural species for the production of organic selenium compounds

The technique of spraying plants with inorganic forms of selenium can be employed for phytochemical production of organic selenium compounds. Fractionation of the plant material makes it possible to produce a highly concentrated and well defined selenium supplement with potential use in animal and human nutrition. The fractionation also gives opportunities to combine production of organic selenium compounds with other products, for example plant fibres. Multiple use of plants can contribute to a more efficient utilization of land area (in comparison to monocultures solely adapted to food production). It also gives the opportunity to develop systems suitable for long term fixation of carbon, as long as the plant material is not reoxidised to carbon dioxide. Plant fibres could provide raw material for the production of paper or building materials in combination with the production of organic selenium compounds preferentially accumulated in another fraction of the processed plant.     

秸秆热解液化制备生物油技术

介绍了秸秆快速热解液化技术及其动力学研究现状、生物油的性质与精制,提出了秸秆快速热解液化技 术存在主要问题及未来研究目标和建议。     

Delineation of agricultural drought-prone zones considering irrigation capacities of agricultural facilities under climate change

Paddy and Water Environment - This study was conducted to delineate agricultural drought-prone zones with respect to each agricultural watershed in South Korea, considering irrigation capacity of...     

Production of carboxymethylcellulose fibers from waste lignocellulosic sawdust using NaOH/NaClO2 pretreatment

In this study, waste lignocellulosic sawdust was converted to carboxymethylcellulose (CMC) by the combination process of an inorganic base (NaOH) and a weak acid (monochloroacetic acid, MCA). Optimum conditions for the pretreatment were studied on the basis of lignin and hemicellulose removal. NaOH and MCA concentration, reaction time, and operating temperature were the parameters studied to acquire the optimized conditions for the production of CMC. Degree of substitution (DS) and solubility were greatly influenced by the changes in the experimental conditions. DS increased on increasing the concentration of NaOH and MCA but the effect was more profound during the NaOH loading. A maximum DS of 0.5 was obtained on the treatment with 20 % NaOH and 20 % MCA concentration at 50 °C, 150 rpm for 4 h. 1.28 g CMC/g cellulose was obtained at the optimized set of conditions. Structural information of cellulose and CMC was obtained using IR spectroscopy and the surface morphology was studied using field emission scanning electron microscopy (FESEM). Carboxymethylcellulose showed lower crystallinity than the native cellulose extracted from sawdust which was studied using X-ray diffraction.     

农务短信系统的应用

农务短信系统,通过电脑自动化实现了农务信息传递管理的最基本功能,其中包括从砍蔗票证的发放、报运、派车、过磅再到蔗款结算实现一条龙短信服务和手机短信查询功能.     

8-Lump reaction pathways of cornstalk liquefaction in sub- and super-critical ethanol

The objective of this work was to develop appropriate reaction pathways to explain the liquefaction behavior of cornstalk in sub- and super-critical ethanol. This reaction system was divided into gas lump, water-soluble oil lump, heavy oil lump, volatile organic compounds lump and residue lump based on the characteristics of cornstalk and liquefaction products, and the residue was further separated into carbon, hydrogen, oxygen and nitrogen. Results showed that the reversible reaction between heavy oil and volatile organic compounds occurred in the liquefaction process, and the decrease in the water-soluble oil yield was mainly attributed to the conversion of water-soluble oil to gas in the sub- and super-critical ethanol. The GC/MS analysis showed that the volatile organic compounds, water-soluble oil and heavy oil comprised a mixture of organic compounds of 6-10, 3-12 and 8-20 carbons, respectively, which mainly included esters, phenols, acids, furans and their derivatives.     

Comparative study of conventional and microwave-assisted liquefaction of corn stover in ethylene glycol

A comparative study on conventional and microwave-assisted liquefaction of corn stover has been carried out using ethylene glycol (EG) as liquefacient and sulfuric acid as catalyst. Microwave dramatically increased the liquefaction extent and rate compared to conventional heating. The liquefied products and residues in both methods have been investigated using gel permeation chromatography (GPC), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). The GPC results show that the molecular weight of liquefied products with conventional heating is significantly greater than those of microwave-assisted liquefaction. The FTIR spectra indicate that there are significant differences in the hydroxyl and carbonyl group contents in the liquefied products with the two methods. The residue from microwave-assisted liquefaction mainly consisted of mineral matter. Many granules appeared on the surface of microwave liquefied residue according to SEM observation.     

Effects of agricultural use of municipal composts

In Switzerland over 2 million tons of solid municipal waste are produced every year. On average, this is equal to one kg per inhabitant per day. More than 75% of the total municipal waste is burned and most of the generated energy is utilized. Only 3% of the total municipal waste is composted normally together with dewatered sewage sludge. The largest fraction of the municipal compost is utilized in vineyards. The beneficial effects of organic matter, nitrogen, phosphorus and calcium and possible harmful effects of heavy metals present in municipal compost on soils are discussed. Constructive suggestions for curative and preventive measures to reduce the metal content of composts and to avoid the problems of irreversible enrichment of heavy metals in soils are discussed.     

秦皇岛市农业生态旅游经济发展现状探析

分析秦皇岛市农业生态旅游经济的主要特点和效益现状，并与相似城市进行比较；针对秦皇岛市农业生态旅游市场发展中存在的问题，提出农业生态旅游经济发展的思路与对策。     

浅谈农业土壤的污染和防治

农业土壤为自然资源,是人类食物来源的生命支持系统.良好的土壤环境能给人们提供安全的食物.随着人口的快速增长,人们过渡索取,大量使用化肥、农药、三废的污染及自然环境的变化,是农业土壤污染的根本原因,而农业增长方式落后是农业污染的催化剂.要从根本上防治农业土壤污染是发展可持续农业的重要保障.     

大石桥市农业可持续发展问题思考

针对“十五”期间全面建设小康社会的要求和加入WTO的挑战,结合大石桥市农业具体情况,阐述了大石桥市农业发展的三点措施。指出,发展六项优势产业,把农业结构调整作为切入点,加强农业质量标准体系,抓好农业人才素质、技能培训,激励技术创新,是解决大石桥市农业可持续发展问题的良好途径。     

The potential use of Ricinus communis L. (Castor) stalks as a lignocellulosic resource for particleboards

Castor (Ricinus communis L.) stalks, which are a readily available by-product of this plant mainly cultivated for seed production, derived from experimental plantations grown in Northern Greece during the period April–October 1996 were assessed for their suitability as feed stocks for direct substitution of wood in particleboard. The average stalk yield of castor reached about 10 dry t/ha, which is higher than the average yield of forest in temperate zones. After harvesting, castor stalks were dried in a greenhouse to about 12% moisture content, and chipped by an automobile chipper and re-chipped in a hammermill. Castor particles and industrial wood particles mixed in various proportions were used as raw material for one-layer and for the middle layer of three-layer particleboards. A commercial E₂ grade UF-resin was used as binder. Castor particles were characterized by a lower slenderness ratio and lower bulk density than industrial wood particles. The evaluation of the mechanical and hygroscopic properties of panels showed the following results: Partial substitution of wood by castor stalks resulted in the deterioration of all board properties. The presence of the unlignified pith and the configuration of castor particles seem to be responsible for the deleterious effect of castor stalks on board properties. However, comparing the properties of the boards produced in this study to relevant European and American Standards, it was found that, with the exception of screwholding strength for three-layer boards, the experimental one layer-, and three-layer boards containing up to 25% and 75% castor particles respectively meet or exceed the Standards requirements for interior boards.     

浅谈湖南农业结构调整

通过对世界农产品贸易和世界农业发展形势的简要分析 ,结合湖南农业结构调整的现状 ,提出了加入 WTO后我省农业结构调整要扬长避短 ,因势利导 ,树立整体观念 ,加强环境保护 ,大力发展有机食品和绿色食品生产的几点建议。     

茶渣综合利用研究进展

本文就茶渣的来源、茶渣的成分、茶渣综合利用的研究现状进行综述,并提出开发和利用茶渣生产饲料和肥料的前景及意义。     

加入WTO后农业政策性银行的改革

入世后,中国经济正在发生深刻的变化,一个重要领域是向外资开放金融市场,随之而来的是更激烈的竞争以及中国金融业为应对挑战而进行的自身改革与完善。农业政策性银行自然不在例外。根据加入世贸组织对我国农业政策性银行的影响,我们应采取积极的对策,确保发挥农业政策性银行职能作用,促进农村经济的全面发展。1　入世对农业政策性银行的影响1 1　粮食市场全面放开　随着粮食生长的发展和中国入世,粮食不再是特殊商品,而是竞争性的商品。按照世贸组织国民待遇原则,竞争性商品,任何法人组织都可以经营。因此,粮食购销市场将全面放开,农业政策…