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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A fibre optimisation index developed from a material investigation of Eucalyptus grandis for the Kraft pulping process.

Du Plessis, Marius 03 1900 (has links)
Thesis (PhD (For))--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A primary reason for the existence of the forest industry is to provide a renewable and natural resource for much needed timber and fibre products. Substantial improvements in management practices are required to increase forest volume and pulp yields for increased demand. Eucalyptus grandis clonal trees of age 6.75 years, grown in a Nelder 1a spacing experiment, were sampled and analysed to describe the effect of planting density on i) growth and yield, ii) wood properties and iii) pulp and paper quality. The main objective was to populate a fibre productivity index (FPI) which would be suitable from technical and economical perspectives. A material study was conducted on the wood and in addition, two methods were developed to further describe the variability of the forest resource to i) separate growth rings by means of wood density peaks from gamma-ray densitometry and ii) calibrate near infrared (NIR) prediction models. The results indicated that planting density did not influence the variability of wood density but mechanisms affecting available soil water are important. NIR prediction models were developed to rapidly and reliably assess wood properties on a non-destructive basis. The validation models for wood density, total pulp yield, kappa number and insoluble lignin returned high predictive ability. When applied to predict chemical properties from an independent data set, the outcomes were accurate in comparison with measured data. Growth and yield functions were developed for tree survival, dominant height and basal area. They accurately predicted outcomes as demonstrated by the goodness of fit and their logical behaviour tested over the range of planting densities. When the most extreme stand density treatments, 6809 and 275 trees per hectare (TPH) were evaluated for wood and fibre properties, the larger trees grown at 275 TPH, produced wood of better quality for pulp processing; basic wood density at 0.520 g cm–3 (21 % higher), fibre cell wall thickness at 2.10 μm (18.6 % thicker) and fibre lumen diameter at 8.16 μm (9.9 % lower) than for 6809 TPH. Intra-specific tree variability of wood and product properties increased from diameter at breast height (DBH) to 35 % and then decreased to 65 % of tree height. The effect of planting density was carried throughout the product value chain up to the paper manufacturing phase. Paper with higher bulk mass and thickness and more porous sheets is most likely to be made from lower planting densities (801 and 275 TPH), and stronger, smoother and denser paper is most likely to be made with trees at high planting densities (6809 or 2336 TPH). From the growth and yield and materials investigation, technical indicators identified to populate a fibre productivity index were: i) mean annual increment (MAI) as a forestry growth indicator, ii) wood density, summarising the composition of wood and, iii) pulp yield, the indicator of the amount of fibre processed through a chemical cooking process. Delivered cost of timber to the mill, was identified as the most suitable economic indicator which included fixed costs elements, variable costs and aspects of mill efficiency. The product of the technical and economic indicators concluded in a profit/loss scenario of producing 1 ton of pulp was deemed the best index to describe the entire and integrated value chain. This index, termed the Fibre Productivity Index (FPI) at the Mill, denoted as FPMill, is an integrated index that is easy to interpret in the realms of a forestry - pulp manufacturing, and can be used for differential pricing of timber for wood quality. / AFRIKAANSE OPSOMMING: 'n Primêre rede vir die bestaan van die bosbouindustrie is om ‘n hernubare, natuurlike hulpbron vir hout en vesel te voorsien. Aansienlike verbeterings in bestuurspraktyke is nodig om die houtvolume en pulpopbrengste vir die toename in aanvraag te verhoog. Eucalyptus grandis klonale bome met ‘n ouderdom van 6.75 jaar en wat in 'n Nelder 1a spasiëring eksperiment gegroei is, is versamel en ontleed om die effek van opstandsdigtheid te beskryf op a) groei en opbrengs, b) houteienskappe en c) pulp- en papiergehalte. Die hoofdoel was om 'n veselproduktiwiteitsindeks (FPI), wat geskik sou wees in terme van tegniese en ekonomiese perspektiewe, te ontwikkel. 'n Materiaalkundigestudie is op hout uitgevoer. Twee metodes is ontwikkel om die variasie in hout as natuurlike hulpbron te beskryf deur a) vroeëhout- en laathoutdigtheidspieke deur gammastraal-densitometrie van mekaar te skei en variasie in groeiringe te beskryf en b) daarstelling van naby-infrarooispektroskopiese (NIR) voorspellingsmodelle. Die resultate het aangedui dat aanplantingsdigtheid nie ‘n invloed het op die variasie van houtdigtheid nie, maar dat meganismes wat beskikbare grondwater bepaal, belangrik is. NIR-voorspellingsmodelle is ontwikkel om houteienskappe op 'n nie-destruktiewe manier betroubaar te kan evalueer. Die validasiemodelle vir houtdigtheid, pulpopbrengs, kappanommer en onoplosbare lignien, openbaar akkurate voorspellingsvermoë. Wanneer dit toegepas word om chemiese eienskappe van 'n onafhanklike datastel te voorspel, was die resultate akkuraat in vergelyking met gemete data. Groei- en opbrengsfunksies is ontwikkel vir mortaliteit, dominante boomhoogte en basale area. Akkurate voorspellingsuitkomste is verkry soos gedemonstreer deur die logiese gedrag wat getoets is vir alle plantdigthede. Toe die mees ekstreme opstansdigtheidbehandelings vir hul hout- en veseleienskappe geëvalueer is, was die hout van die groter bome, teen 275 stamme per hektaar (SPH), van beter gehalte. Dit was veral prominent vir houtdigtheid van 0.520 g cm-3 (21 % hoër), veselselwanddikte van 2.10 μm (18.6 % dikker) en vesellumendeursnit van 8.16 μm (9.9 % laer) as by die hoër (6809) SPH. Intra-spesifieke boomvariasie van hout- en produkeienskappe het toegeneem van deursnee op borshoogte (DBH) tot 35 % en dan weer afgeneem tot 65 % van die boomhoogte. Die effek van plantdigtheid is regdeur die produkwaardeketting tot by die papiervervaardigingstadium sigbaar. Papier met hoër basismassa en dikte, en meer poreuse papiervelle kan meer waarskynlik van laer aanplantdigtheid (801 en 275 TPH) bome gemaak kan word. Papier wat sterker, gladder en digter is, kan waarskynlik gemaak word van hout van bome teen hoë aanplantdigthede (6809 of 2336 SPH). Die veselproduktiwiteitindeks wat ontwikkel is uit die materiaalondersoek en tegniese aanwysers wat geïdentifiseer is sluit in i) gemiddelde jaarlikse aanwas, as 'n bosbou groei-indikator, ii) houtdigtheid, wat ‘n opsomming van die samestelling van hout is, en iii) pulpopbrengs; die aanduiding van die hoeveelheid vesel verwerk deur 'n chemiese verpulpingsproses. Gelewerde koste van hout by die pulpmeul is geïdentifiseer as die mees geskikte ekonomiese aanwyser wat vaste kosteelemente, veranderlike koste en aspekte van die meul se doeltreffendheid insluit. Die produk van die tegniese en ekonomiese aanwysers is saamgevat in 'n wins / verlies opsie vir die vervaardiging van 1 ton pulp, en is beskou as die mees geskikte indeks om die geïntegreerde waardeketting te beskryf. Dié indeks, die sogenaamde Vesel Produktiwiteitsindeks (VPI) by die Pulpmeul, aangedui as VPMeul, is 'n geïntegreerde indeks wat maklik is om te interpreteer in 'n bosbou - pulpvervaardigingsopset, en kan gebruik word in die differensiële prysbepaling van hout waarby die kwaliteit in ag geneem word.
2

Thes-economic impact of the phasing out of plantations in the Western and Southern Cape regions of South Africa : a case study of three plantations.

De Beer, Margareta Caterine 03 1900 (has links)
Thesis (MScFor)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This study sought to determine the possible socio-economic impacts of the phasing out of nearly 22 500 ha of plantations within the Southern and Western Cape regions of South Africa as a result of a decision made by Government in September 2000. None of the previous studies undertaken focussed on the socio-economic impacts within the specific regions and plantations, but were based on wider environmental and economic considerations. Data was collected in 2007 from three plantations managed by Mountain to Ocean Forestry (MTO) (PTY) LTD: one located in Grabouw (Western Cape) and two in George (Southern Cape), among three different plantation stakeholder groups. These three groups were: (i) Forest Dependent Communities, (ii) Stakeholders among the forestry value chain and (iii) Indirect stakeholders. Within the first group, a total of 70 persons representing households were interviewed. A total of 26 primary and secondary processing company respondents were interviewed. Information on all of the indirect stakeholder groups was gathered, either through interviews with the stakeholders or from data received from MTO. This study indicated that there are significant differences between the potential impacts within the Southern Cape and Western Cape regions. The data collected showed that among communities within the Western Cape, the dependency on the plantations in terms of employment, income and fuelwood is low. This is in stark contrast to the communities within the Southern Cape, who are dependent on the plantations for their employment and income, and as a result will be affected greatly by the phasing out process. Company respondents in the Western Cape were less concerned than their Southern Cape counterparts about the future decrease in timber supply and indicated that they will source timber from elsewhere, whereas companies within the Southern Cape indicated that they would likely have to shut down. The dependency of indirect stakeholders on the plantations to be phased out, and the resulting impact was found to be minimal. The study concluded with an evaluation of an existing nine step plan for the implementation of social and economic actions within natural resource planning. Three main aspects were identified that need to be addressed namely: (i) To increase public awareness and participation among communities and companies to be impacted on by the phasing out process, (ii) Provide necessary training and thus increased skills level of workers who face unemployment; and (iii) The identification of alternative employment opportunities for the unemployed affected by the phasing out process. / AFRIKAANSE OPSOMMING: Hierdie studie het die potensiële sosio-ekonomiese impak van die uitfasering van plantasies in die Suid- en Wes-Kaap gebiede van Suid-Afrika ondersoek. Die besluit om 22 500 ha plantasies uit te faseer is in September 2000 deur die Suid-Afrikaanse Regering geneem. Geen vorige studies wat onderneem is het gefokus op die moontlike sosio-ekonomiese impakte in die spesifieke gebiede en plantasies nie, maar was gebaseer op groter omgewings- en ekonomiese oorwegings. Data insameling het in 2007 geskied in drie Mountain to Ocean Forestry (MTO) plantasies: een geleë in Grabouw (Wes-Kaap) en twee in George (Suid-Kaap), en onder drie verskillende plantasie belangegroepe. Hierdie drie groepe was (i) Gemeenskappe afhanklik van plantasies; (ii) Belangegroepe in die Bosbou-waardeketting en; (iii) Indirekte belangegroepe. ‘n Totaal van 70 huishoudings in die eerste groep is ondervra, en 26 primêre en sekondêre verwerkingsmaatskappye in die tweede groep is ondervra. Inligting oor al die indirekte belangegroepe is ingesamel, hetsy deur middel van onderhoude of deur data wat van MTO ontvang is. Die studie het aangedui dat daar betekenisvolle verskille tussen die potensiële impakte binne die Suid-Kaap en Wes-Kaap streke bestaan. Die versamelde data het getoon dat die afhanklikheid van gemeenskappe in die Wes-Kaap op die plantasies in terme van werk, inkomste en brandhout laag is. Dit is in skrille kontras met die gemeenskappe in die Suid-Kaap, wat afhanklik is van die plantasies vir hul werk en inkomste, en as gevolg daarvan grootliks geraak sal word deur die uitfasering proses. Maatskappy respondente in die Wes-Kaap was minder bekommerd as hulle eweknieë in die Suid- Kaap oor die toekomstige afname in die saaghoutvoorraad en het aangedui dat hulle saaghout van elders sal bekom, terwyl maatskappy respondente in die Suid-Kaap aangedui het dat hulle waarskynlik hul deure sal moet sluit. Die afhanklikheid van indirekte belanghebbendes op die plantasies wat uitgefaseer word, en die gevolglike impak blyk minimaal te wees. Die studie is afgesluit met 'n evaluering van ‘n bestaande nege stap plan vir die implementering van maatskaplike en ekonomiese kwessies in natuurlike hulpbron beplanning. Die drie belangrikste aspekte is geïdentifiseer wat aangespreek moet word naamlik: (i) Die verhoging van openbare bewustheid van en deelname tussen gemeenskappe en maatskappye wat deur die uitfasering proses geraak sal word, (ii) Die verskaffing van nodige opleiding en dus die verhoging van die vaardighede van werkers wat werkloosheid in die gesig staan; en (iii) Die identifisering van alternatiewe werksgeleenthede vir die werkloses wat deur die uitfasering proses geraak sal word.

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