With a growing interest in sustainable issues and ecofriendliness,the textile industry is now faced with the challenges of developing eco-friendly textile products with enhanced sustainability.Efforts have been made in the field of wet processing of textile products.However,another equallyimportant aspect of producing more sustainable textile product is to select eco-friendly and low-cost raw materials,as well as to control the textile manufacturing processes in regard to energy and labour savings.An increasing recognition of hemp as more sustainable cellulose fibres has to be accompanied by an improvement in some comfort performances,aesthetics and,last but not least,by cost effectiveness.Apart from the environmental benefits of hemp in comparison to cotton,which is elaborated in the introduction section,the average prices of hemp fibre are 1.0e2.1 US$/kg while the cotton prices are between 2.1 and 4.2 US$/kg.However,the approximate prices for plain hemp textiles range from 5 to 13 US$/kg.In addition to these aspects,modern consumers expect high standard of performance even after a number of care cycles.Low cost and efficient production of synthetic fibres,together with their easy care and shape-retention properties can contribute to hemp based textiles to fulfil these requirements.In this context,acrylic fibres offer some benefits one of which is low specific gravity that allows yarns and fabrics to be made with a high bulk to weight ratio enabling improved softness.Other one is the simple and effective on-line coloration capability of acrylic fibre technology by which any further wet processing for finishing fabrics and garments does not need.This is not only extremely cost-effective,but very environmentally competitive route to market.In addition,avoiding any chemical treatment of hemp based fabrics with softeners to improve the tactile comfort performance is important from both economic and ecological aspects of sustainability.This elaboration,along with the results obtained and references given in the introduction section,clearly indicate that the use of hemp instead of cotton,mobile vertical rack and the use of acrylic to integrate with hemp yarn during knitting offer possibility of improving several sustainability aspects for cellulose based textiles.

However,some efforts are continuously made to achieve the reduction in cost and environmental impact in the range from the crop stage to the hemp product development stage.A new approach to a decrease in the environmental impact involves a reduction in eutrophication in the crop production.In fibre processing step,the research is aimed at improving fibre extraction processes so as to increase fibre quality and reduce labour requirements and price.Attempts have been made to improve hemp yarn production by developing new and more productive equipment and reducing energy costs.The avoidance of additional chemical treatments in this project is extremely important bearing in mind that a large amount of energy,water and chemicals are used for processing,finishing and dyeing of fibres,yarns and fabrics.The current trend towards improving sustainability of these processes goes in a direction of using eco-friendly substances and dyes.The recyclability and degradability of enzymes has stimulated research into their application to hemp fibre processing.Dyeing by natural dyes extracted from various plants,as well as agricultural wastes utilization for dyeing of textile fabrics,have been investigated in recent studies in order to meet the challenges of improving sustainability of production processes.In addition to production technology,new products development is also very important so as to meet market demand.We believe that hemp based textile product developed in our project presents a useful contribution to up to-date hemp textile product range,offering the textile engineers,designers and decision makers in textile companies the way to balance the cellulose based product performance,environmental concerns and costs at the current level of technological development.The utilisation of wood resources for energy production makes up the demand for the development of new technologies in the area of the chemical processing of agricultural residue.

The increasing demand for products derived by the chemical industry also increases the demand for furfural,which is exclusively produced from hemicelluloses-containing biomass.There is no synthetic route available for furfural production in the chemical industry.The production of furfural belongs to environmentally friendly technologies,although it has chemical properties similar to those of petrochemicals.It is used for the production of a wide range of important non-petroleum derived chemicals such as furan,tetrahydrofuran and furfuryl alcohol.It is also used as an extractive,a fungicide,in oil refineries,as well as in the plastics,food,pharmaceutical and agricultural industries.For example,it can be introduced during fibril formation to enhance the thermal and mechanical stability of collagen.At the moment,in the European Union,furfural is an imported products,although potential raw material resources are in a sufficient amount.During hydrothermal pre-treatment,the dehydration of xylose to furfural in water typically proceeds at 150–220 °C,and the reaction rate is small under neutral conditions,increases during autocatalysis by acetic acid,which originates from the biomass,and is accelerated further by the addition of catalysts,especially strong acids such as sulphuric acid or solid acid catalysts such as H-Beta zeolite.The costs and inefficiency of separating these catalysts from the products make their recovery impractical,resulting in large volumes of acid waste,which must be neutralised and disposed of.Other drawbacks include corrosion and safety problems.Al23 as a hydrolysis catalyst has been considered in some publications related to obtaining levulinic acid from biomass,but there are no scientific publications about the use of Al23 in furfural production from lignocellulosic biomass by hydrothermal pre-treatment.Furfural production from hemp shives has not been investigated until now as well,while the high content of hemicelluloses shows that the hemp fibre production byproduct has great potential.Also,this valuable raw material is concentrated in one place at the fibre production manufacturer’s site.The hemp species are an approved and rapidly expanding crop in Latvia,with a yield from 150 ha in 2009 to 1200 ha in 2013.Hemp shives are the woody inner part of the hemp stalk separated from the fibres,making up to 75 % of the oven dry stalk.

The chemical components of the hemp variety “Bialobrzeskie” shives used for experiments testify that the material also has the potential for the production of composites.Up until now,however,the main utilisation of hemp as a crop has been for its bast fibres.To utilise the leftover lignocellulose after obtaining furfural,binder-less panels could be made without the use of any additional adhesives during the panels’ production process.The panels made from the shives after the catalysed pre-treatment may have improved water resistance of the panel because hemicelluloses are the most water absorbing component and,after pre-treatment,their content is significantly diminished.Furthermore,steam explosion treatment transforms the lignin structure in the plant matrix and promotes the binder-less composite moulding in the following hot-pressing process.The objective of the study was to investigate the preliminary technological parameters of obtaining furfural and binder-less panels depending on the hydrothermal pre-treatment temperature,steam explosion treatment and pressing conditions.The pre-treatment process reference criteria for optimal parameters were chosen by the furfural yield and cellulose destruction degree in the leftover lignocellulose,which affects the obtained panel’s mechanical properties.The panel’s evaluation criteria were the panel quality and the maximal values of the tested properties – modulus of rupture and modulus of elasticity.The holocellulose content in the raw material was 75.5 wt% and,after the pre-treatment process,it decreased to 34.2 wt% at 160 °C and 27.7 wt% at 180 °C,calculated on the oven dry hemp shives’ mass.This means that,during the catalytic pre-treatment in the presence of Al23,not only is hemicelluloses converted to furfural,but also some part of cellulose has started to degrade.By increasing the hydrothermal pre-treatment process temperature up to 180 °C,the cellulose content significantly decreased from 31.4 wt% to 22.2 wt%,calculated on the oven dry raw material,vertical grow rack taking into account the yield of lignocellulose.The leftover lignocellulose after the hydrothermal pre-treatment contained ~ 50 wt% moisture content; therefore,it was dried to a 10–15 wt% moisture content at 25°C.

With increasing temperature of the pre-treatment process,the moisture content of residual lignocellulose was higher at the drying stage.This can be explained by the increasing of the surface of the raw material particles due to the degradation of cellulose at elevated temperatures in the presence of the Al23 catalyst.The obtained panels are very different from the outside.The Ref 1 and Ref 2 panels are light enough in colour like the raw shives and similar to conventional OSB panels.The panels from the shives after the catalysed hydrothermal pre-treatment process are slightly darker in colour,compared to the reference panels.The panels from the pre-treated and steam-exploded shives are very dark in colour,with an apparent degraded morphology of shives on the surface.Most of the panels from the pretreated and steam-exploded shives have gaps on the surface and on the inside parallel to the surface.These observations allow concluding that the lignocellulosic material after the steam explosion treatment is significantly degraded.However,the degradation level of lignocelluloses depends on both pre-treatment and treatment,and the treatments conditions should be optimised.Cutting edges are another property of the panel quality that was observed,although only qualitatively.The panels made of untreated shives at 160 °C have unstable edges,which drop off.However,the cut edges of the panels made at 200 °C are stable enough.The panels made of pre-treated shives have cut edges similar to those of the untreated ones,although look more stable.Generally,the cut edges of the obtained panels are poor in quality.This is probably due to the too high moisture content of the pressing material and due to the too high steam explosion temperature that results in the too high severity factor of the material and degradation of cellulose.However,we believe that this could be improved by optimising the panel moulding process that is the next goal of the research.Some studies state that it is possible to make a high quality binder-less panel from agricultural species.The density range of all panels obtained was from 800 kg/m3 to 1250 kg/m3.85 % of the differences in density are explained by the panel’s thickness,which varies from 6 to 8 mm as shown in Fig.4.On the other hand,such different thickness obtained means that the same pressure used at pressing for all samples shows that the samples are different as materials,and different pressures should be used for each of them to obtain the same density.

The MOR values of the panels vary from 2 to 12 N mm-2,depending on all included factors.However,the strength difference is not significant.The low MOR values could be explained by the high enough severity factor of the lignocelluloses and,possibly,the fact that the pressing temperature was too low to achieve the lignin flowing and then the glass transition necessary to form a rigid material.The MOE values of the panels vary from 141 to 3250 N mm-2,also depending on the same factors as in the MOR performance.The obtained maximal MOE value is high enough and demonstrates that the material can be used for panel production.However,the MOR values are too low and should be improved by optimising the panel moulding conditions.In spite of the low mechanical properties,an excellent correlation was obtained between the MOE and MOR values,which means that the strength of the composites could be predictable.Temperature and relative humidity are important parameters influencing perceived indoor air quality and human comfort.High moisture levels can damage construction and inhabitant’s health.High humidity harms materials,especially in case of condensation and it helps moulds development increasing allergic risks.Consequently,several researchers have studied the use of various hygroscopic materials to moderate indoor humidity levels.The material that absorbs and desorbs water vapor can be used to moderate the amplitude of indoor relative humidity and therefore to participate in the improvement of the indoor quality and energy saving.Vegetal fiber materials are an interesting solution as they are eco materials and have low embodied energy.Hemp concrete is one of these materials which is more and more recommended by the eco-builders for its low environmental impact.The physical properties of hemp concrete has been measured by many authors.It is highlighted that the one presents high moisture buffering capacity and a good compromise between insulation and inertia materials.To investigate the hygrothermal behavior of building envelope,a simulation should be done because it is cheaper and more detailed than the test in situ.For this to be done,many simulation tools have been developed.Hygrothermal properties are required for all Heat,Air and Moisture transfer models.Many models and simulation tools for predicting the hygrothermal behavior of building envelope are represented in the Annex 41 of the International Energy Agency’s.For the building envelope,the main difference in HAM-transfer modeling is made by the dimension of represented phenomena and they can be classed by the granularity and complexity†.