Sustainable agriculture is a crucial factor to be considered in order to meet the growing demand for food production. The need for low cost and highly functional materials to provide the most efficient cultivation process has led the agriculture industry to consume petrochemical and mineral based material in an enormous amount. Thus, disposal of the used mulch materials has become a serious environmental issue. In this work, the possibility of using wood pulp fibre in two distinct applications in agriculture is investigated. First, agricultural mulching is the subject of the study and second, we focus on using wood pulp fibre as growing medium in greenhouses. Mulching in agriculture is an essential practice in order to have high crop yield, healthy products, and more efficient cultivation process. Over the years, agricultural mulch has been made out of a variety of materials. The most common of all is plastic mulch due to its low price and high functionality. However, the problems associated with applying and removing the enormous load of plastic and their disposal have made it an option far from ideal. Therefore, there is a need to develop mulches based on biodegradable materials. Paper-based mulch is one of the candidates, In the first chapter of this work, with a review of previous works in this area, we attempt to develop a new spray-able mulch based on wood pulp fibre. A novel foam forming method is utilised to deposit wood pulp fibres in combination with other chemicals as an evenly distributed fibre network on a porous bed. Currently available paper based-mulch is of a very high basis weight. In first part of this work, application of a foam formed low basis weight paper-based mulch is investigated. Whereas, in the second chapter, the use of wood pulp fibres in a similar function as “rockwool” in soilless greenhouse farming is investigated. Rockwool is named after fibres made of melted minerals at temperatures as high as 2000°C. Rockwool is used as blocks for seeds growth and propagation and as an alternative for soil in greenhouses. The feasibility of microenvironment control of the rockwool blocks in crop production plus its low cost have made is popular. However, their disposal has always been an environmental issue. The biodegradability of wood pulp fibres is a great advantage over mineral fibres used in rockwool. In the second chapter of current work, we study the possibility of using wood pulp fibres as carriers for agriculturally beneficial chemicals. Specifically, we focus on binding and release properties of small organic molecules from wood pulp fibres. The goal is to achieve an understanding of the capability of wood pulp fibres to be used in building biodegradable growing medium blocks in greenhouses. / Thesis / Master of Applied Science (MASc)

This study explores the performance of porous Paptic paper materials composed of a mixture of softwood and lyocell fibers. The investigation involves laboratory experiments and numerical simulations to analyse the impact of various parameters on the paper's characteristics. Tensile and hygroexpansion tests were conducted on sheets with different binder quantities and drying methods. VTT aided in the analysis of mechanical properties using tomography images. The objective was to determine the optimal binder content, to understand the behaviour of the paper under different drying conditions and to optimise the pulp mixture through numerical simulations. Experimental tests involved producing paper sheets with varying binder amounts and different drying methods. Tensile tests were conducted to assess the elastic stiffness, strength, and strain at break. Constrained dried and freely dried papers were compared to evaluate the influence of drying conditions. Hygroexpansion tests were performed to examine the water storage behaviour of papers with added binders. Tomography measurements provided the density profile, which was replicated in the numerical sheets. A micro-mechanical model was employed for numerical simulations, representing each fiber as a beam. The model was calibrated using stress-strain data from VTT's tensile testing of the paper with the highest binder content. The influence of altering the amount and length of lyocell fibers was examined to optimise the pulp. From the tensile tests, an optimal binder content was identified that yielded the highest elastic stiffness while considering the density increase caused by binders. Further additions of binders did not enhance elastic stiffness. However, no optimal value was found for strength and strain at break, as both parameters continued to increase with additional binders. Tensile tests comparing constrained dried and freely dried papers showed similar behaviour, suggesting inadequate constraint in the former. Hygroexpansion tests confirmed the similarities between the two drying methods and revealed that papers with added binders stored less water at a given humidity. Additionally, the drying-moistening cycling exhibited an unusual behaviour not observed in conventional paper, with irreversible expansion occurring during the first drying cycle. Numerical simulations using a micro-mechanical model demonstrated that higher amounts of lyocell fibers improved performance, increasing strength and strain at break. However, varying fiber length did not yield significant improvements in these parameters, although stiffness showed a slight increase. While the literature suggests that the addition of long lyocell fibers decreases paper strength, this study found that when maintaining constant bulk, strength increased under the assumption that the bonding strength was unaffected by lyocell fibers. Furthermore, numerical simulations indicated that an even density profile throughout the paper thickness resulted in higher strength and strain at break. The tomography data revealed that the density profile is affected by the binder quantity. With the addition of binders, the thickness decreased even though the grammage increased. The density is high on the top and bottom surface of the papers which contain more binders while the density is lower in the middle. This difference in density is more pronounced with higher amounts of binders. / Denna studie undersöker prestandan hos porösa pappersmaterial från Paptic som består av en blandning av barrträd och lyocell-fibrer. Undersökningen innefattar laboratorieexperiment och numeriska simuleringar för att analysera effekten av olika parametrar på papperets egenskaper. Drag- och hygroexpansionstester utfördes på ark med olika mängder bindemedel och torkningsmetoder. VTT hjälpte till med analysen av mekaniska egenskaper genom tomografibilder. Målet var att bestämma optimalt innehåll av bindemedel, att förstå papperets beteende under olika torkningsförhållanden och att optimera pappersmassan genom numeriska simuleringar.  De experimentella testerna innefattade framställning av pappersark med varierande mängder bindemedel och olika torkningsmetoder. Dragtester utfördes för att bedöma elastisk styvhet, styrka och töjning vid brott. Inspännt samt fritt torkade papper jämfördes för att utvärdera inflytandet av torkningsförhållanden. Hygroexpansionstester utfördes för att undersöka vattenlagringsbeteendet hos papper med tillsatt bindemedel. Tomografimätningar gav papprens densitetsprofilen, som återskapades i de numeriska arken. En mikromekanisk modell användes för de numeriska simuleringarna, där varje fiber representeras som en balk. Modellen kalibrerades med hjälp av spännings-töjnings-data från VTT:s dragprovning av papperet med högst mängd bindemedel. Inflytandet av att ändra mängden och längden på lyocell-fibrer undersöktes för att optimera pappersmassan.  Från dragtesterna identifierades en optimal mängd bindemedel som gav högst elastisk styvhet när den densitetsökning som orsakas av bindemedel har tagits till hänsyn. Ytterligare tillsatser av bindemedel förbättrade inte den elastiska styvheten. Dock hittades ingen optimal värde för styrka och brottsträckning, eftersom båda parametrarna fortsatte öka med ytterligare bindemedel. Dragtester som jämförde inspännt och fritt torkat papper visade liknande beteende, vilket tyder på otillräcklig begränsning i det förstnämnda fallet. Hygroexpansionstester bekräftade likheterna mellan de två torkningsmetoderna och avslöjade att papper med tillsatt bindemedel lagrade mindre vatten vid en given luftfuktighet. Dessutom uppvisade torknings-fuktnings-cykeln ett ovanligt beteende som inte observerats i konventionellt papper, där irreversibel expansion inträffade under den första torkningscykeln. Numeriska simuleringar med en mikromekanisk modell visade att högre mängder lyocell-fibrer förbättrade prestandan genom att öka styrka och töjning vid brott. Ändringar i fibrernas längd gav dock inte märkvärda förbättringar i dessa parametrar, även om styvheten visade en liten ökning. Medan litteraturen föreslår att tillsatsen av långa lyocell-fibrer minskar papperets styrka, fann denna studie att när densiteten hålls konstant ökar styrkan under antagandet att bindestyrkan inte påverkas av lyocell-fibrer. Dessutom indikerade de numeriska simuleringarna att en jämn densitetsprofil genom papperets tjocklek resulterade i högre styrka och töjning vid brott. Tomografidata visade att densitetsprofilen påverkas av mängden bindemedel. När mängden bindemedel ökade, minskade tjockleken trots att ytvikten ökade. Densiteten är hög på papperets över- och undersida, medan densiteten är lägre i mitten. Skillnaden i densitet är mer uttalad med högre mängder bindemedel.