This experiment examined the forage potential of hemp (Cannabis sativa) and kenaf (Hibiscus cannabinus). The objectives were to evaluate yield and forage nutritive value (i.e. NDF, ADF, ADL, IVTD, and CP) fluctuations over the course of a growing season based on planting date, morphological composition, and management. Three types of hemp (grain, fiber, and a dual- purpose type) and kenaf were planted on two dates and were sampled approximately every two weeks throughout the growing season at the University of Kentucky (UK) Research Farm in Lexington, KY. Subsamples were separated into morphological components (i.e. leaf, flowers, stem, core fiber, and bast fiber) while the remainder of the sample was ground for laboratory analysis. All samples were scanned in Foss 6500 NIRS and wet chemistry analytical methods were utilized on a subset of samples to develop equations to predict the nutritive value of the remaining samples. Significant interactions for forage type, planting date, and harvest time were observed for yield, % floral components, % bast, and ADL. Significant interactions occurred between planting date and harvest date as well as type and harvest date for NDF, ADF, digestibility, crude protein, % leaf, % core, and % stem. Overall, forage nutritive value declined with increased plant maturity. The later planting date reduced the vegetative growth period, resulting in reduced leaf content, yield, and forage nutritive value. The performance of kenaf in this study indicates that it may be a better alternative forage than hemp due to remaining vegetative longer and having superior nutritive value. Better selection and the development of new hemp varieties with different photoperiod requirements could lengthen the vegetative state and may result in yields and nutritive values that are more competitive with kenaf and other typical forages.

Natural fibers have drawn attention of researchers as an environmentally-friendly alternative to synthetic fibers. Developing natural fiber reinforced bio-composites are a viable alternative to the problems of non-degrading and energy consuming synthetic composites. This study focuses on (i) the application of kenaf fiber as a potential reinforcement and, (ii) determining the tensile properties of the randomly oriented short kenaf fiber composite both experimentally and numerically. Kenaf fiber micro-structure and its Young's modulus with varying gage length (10, 15, 20, and 25.4 mm) were investigated. The variation in tensile strength of kenaf fibers was analyzed using the Weibull probability distribution function. It was observed that the Young's modulus of kenaf fiber increased with increase in gage length. Fabrication of randomly oriented short kenaf fiber using vacuum bagging techniques and hand-lay-up techniques were discussed and the tensile properties of the specimens were obtained experimentally. The tensile modulus of the composite sample at 22% fiber volume fraction was found to be 6.48 GPa and tensile strength varied from 20 to 38 MPa. Numerical models based on the micro mechanics concepts in conjunction with finite element methods were developed for predicting the composite properties. A two-step homogenization procedure was developed to evaluate the elastic constants at the cell wall level and the meso-scale level respectively. Von-Mises Fisher probability distribution function was applied to model the random orientation distribution of fibers and obtain equivalent modulus of composite. The predicted equivalent modulus through numerical homogenization was in good agreement with the experimental results.

Kenaf fibers have mechanical properties making them a good candidate to replace glass fibers in composites. This research investigates kenaf fiber-reinforced composites, examining the effect of cure time, density, matrix hardener ratio, surface treatment, and fiber length on the mechanical properties of the composite material such as natural frequency, damping loss factor, and tensile modulus. These are essential characteristics for many manufacturing parts and products, but are not well known for natural fiber-reinforced composite materials since interest in utilizing natural fibers for composites is in the infancy phase and determining properties is difficult. Natural fibers display properties similar to glass fibers, and present a more environmentally friendly option for manufacturing composite materials. By studying published research on the topic and experimenting with different methods, a consistent procedure for manufacturing composites was developed and several samples were created for testing these parameters. These samples were subjected to a vibrational test using an impact hammer and accelerometer. Through the half-power bandwidth method and other relationships, mechanical properties were extracted from the test to study the effect of each manufacturing process. Samples were found to exhibit repeatable mechanical properties after approximately 150 hours following removal from the oven. Increasing the pressure applied during the cure cycle results in higher densities, which increases loss factors and tensile moduli, and lowers natural frequencies. The matrix hardener ratio also affects these properties in a similar way. High hardener ratios result in a more brittle material that dampens less but generally has a higher stiffness. Models predict that a chemical surface treatment should decrease the loss factor due to a better fiber-matrix bond, resulting in less sliding and friction. However, testing showed the opposite result with treated fibers exhibiting higher amounts of damping. Fiber length was also tested, though the results showed a less prominent effect.

Building waste and disposable packaging are a major component in today's landfills. Most of these are structural or thermally insulative polymer foams that do not degrade over a long period of time. Currently, there is a push to replace these foams with thermoplastic or biodegradable foams that can either be recycled or composted. We propose the use of compostable soy-based polyurethane foams (PU) with kenaf core modifiers that will offer the desired properties with the ability to choose responsible end-of-life decisions. The effect of fillers is a critical parameter in investigating the thermal and mechanical properties along with its effect on biodegradability. In this work, foams with 5%, 10%, and 15% kenaf core content were created. Two manufacturing approaches were used: the free foaming used by spray techniques and the constrained expansion complementary to a mold cavity. Structure-property relations were examined using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal conductivity, compression values, scanning electron microscopy (SEM), x-ray micro-computed tomography (micro-CT), and automated multiunit composting system (AMCS). The results show that mechanical properties are reduced with the introduction of kenaf core reinforcement while thermal conductivity and biodegradability display a noticeable improvement. This shows that in application properties can be improved while establishing a responsible end-of-life choice.

Decreasing the carbon footprint through use of renewable materials has environmental and societal impact. Foams are a valuable constituent in buildings by themselves or as a core in sandwich composites. Kenaf is a Southeast USA plant that provides renewable filler. The core of the kenaf is porous with a cell size in a 5-10 micrometer range. The use of kenaf core in foams represents a novel multiscalar cellular structural composite. Rigid polyurethane foams were made using free foaming expansion with kenaf core as filler with loadings of 5, 10 and 15 %. Free foaming was found to negatively affect the mechanical properties. An innovative process was developed to introduce a constraint to expansion during foaming. Two expansion ratios were examined: 40 and 60 % (decreasing expansion ratio). MicroCT and SEM analysis showed a varying structure of open and closed cell pores. The mechanical, thermal insulation, acoustic properties were measured. Pure PU foam showed improved cell size uniformity. Introducing kenaf core resulted in decreasing the PU performance in the free expansion case. This was reversed by introducing constraints. To understand the combined impact of having a mixed close cell and open cell architecture, finite element modeling was done using ANSYS. Models were created with varying percentages of open, closed, and bulk cells to encompass entire range of foam porosities. Net zero energy building information modelling was conducted using EnergyPlus was conducted using natural fiber composite skins. Environmental impacts for instance global warming potential, acidification, eutrophication, fossil fuel consumption, ozone depletion, and smog potential of the materials used in construction was studied using life cycle assessment. The results showed improvement on energy consumption and carbon footprint.

This study evaluates the pre-treatment of cellulose from kenaf plant to yield sugar precursors for the production of ethanol or butanol for use as biofuel additives. In order to convert the crystalline cellulosic form to the amorphous form that can undergo enzymatic hydrolysis of the glycosidic bond to yield sugars, kenaf pulp samples were subjected to two different pre-treatment processes. In the acid pre-treatment, the pulp samples were treated with 37.5% hydrochloric acid in the presence of FeCl 3 at 50 °C or 90 °C whereas in the alkaline method, the pulp samples were treated with 25% sodium hydroxide at room temperature and with 2% or 5% sodium hydroxide at 50 °C. Microwave-assisted NaOH-treatment of the cellulose was also investigated and demonstrated to be capable of producing high glucose yield without adverse environmental impact by circumventing the use of large amounts of concentrated acids i.e., 83-85% phosphoric acid employed in most digestion processes. The treated samples were digested with the cellulase enzyme from Trichoderma reesei. The amount of glucose produced was quantified using the QuantichromTMglucose bioassay for assessing the efficiency of glucose production for each of the treatment processes. The microwave-assisted alkaline pre-treatment processes conducted at 50 °C were found to be the most effective in the conversion of the crystalline cellulose to the amorphous form based on the significantly higher yields of sugar produced by enzymatic hydrolysis compared to the untreated sample.

Kenaf (Hibiscus cannabinus L.) is a highly productive crop that is cultivated worldwide for its fibre content which may be used to produce various commodities. The kenaf crop was commercially cultivated in South Africa in the 1950’s, but production was discontinued from the 1960’s up to the mid 2000’s. Production commenced again and kenaf emreged as a “new” fibre crop with the first kenaf processing factory in the country going into production in 2006 in KwaZulu-Natal. Due to the importance of kenaf in manufacturing of various commodities, there was a need to investigate the agronomic practices thereof to ensure sustainable yield. Therefore a two year study (2008/09 and 2009/10 summers) was conducted in Pretoria to investigate the influence of nitrogen, plant population, row spacing and water treatments on kenaf growth, yield, chemical quality and microscopic analysis of the fibre. In total, four field trials were conducted at the Hatfield Experimental Farm of the University of Pretoria. In 2008/09 a trial was conducted to investigate effects of plant population (200,000; 300,000 and 400,000 plants ha-1), nitrogen level (0, 50, 100 and 150 kg ha-1) and row spacing (0.17, 0.34 and 0.50 m) under rainfed conditions. Sampling for growth parameters were done at 85, 113 and 126 days after planting (DAP). The biomass and chemical analysis of bark fibre were conducted only at or after the final harvest, at 126 DAP. In general, no clear effect of different treatment was observed on either parameter studied. During 2009/10 three experiments were conducted. The first two had the same nitrogen levels as in the previous season, but were grown either under rainfed or irrigated conditions. The nitrogen was applied as two dressings of 0 and 50 kg ha-1 at planting and 0, 50 and 100 kg ha-1 at thinning (35 DAP). The third experiment investigated combinations of plant population (main plots) and row spacing (sub plots) under rainfed conditions. Due to increasing stem yield with increasing plant population during 2008/09, the lowest population of 200,000 plants ha-1 was left out and 500,000 and 600,000 plants ha-1 were added. The same three row spacings as in 2008/09 were used. Nitrogen was applied at 150 kg ha-1, with 50 kg ha-1 at planting and 100 kg ha-1 at thinning. Growth and biomass parameters, water use efficiency (WUE) (nitrogen trial only) were subsequently measured up to the end of the growth cycle. The chemical characteristics of bark fibre and nutrient removal (nitrogen trial only), nutrient use efficiency as well as the nitrogen contents of leaves and stems were determined only once at final harvest. The number of fibre rings and fibre bundles were assessed only once during the growth cycle. Growth and biomass parameters, WUE and both nutrient removal and nutrient use efficiency generally tended to increase with increase in nitrogen level under both rainfed and irrigated conditions. On the other hand, increasing plant population tended to result in a decrease in all growth parameters, while it increased biomass yield per hectare. Finally, the effect of row spacing was inconsistent for the same parameter from one sampling to another one, and from one parameter to another. The chemical characteristics of bark fibre showed inconsistent responses to all agronomic practices. The number of fibre rings and fibre bundles increased with increasing nitrogen level, decreased as plant population increased, but did not show clear trends with regard to row spacing. In general the plants grown under irrigated conditions performed better than those grown under rainfed conditions. The results of this study revealed that under the environmental conditions of Pretoria, nitrogen levels above 100 kg ha-1 applied in two dressings should result in best plant performance, but most benefit could be obtained under irrigated conditions. A plant population of 500,000 plants ha-1 or higher and row spacing wider than 0.34 m proved to be most suitable for both growth and biomass parameters. / Dissertation (MScAgric)--University of Pretoria, 2015. / tm2015 / Plant Production and Soil Science / MScAgric / Unrestricted

Cellulosic fibers sized from the macro-scale to the nano-scale were prepared hierarchically from kenaf bast fibers using chemicals. The process began with a hermetical alkaline retting followed by a bleaching treatment. The bleached fibers were hydrolyzed using inorganic acid, from which microfibers and cellulose nanowhiskers (CNWs) were fabricated. Inorganic nanoparticle impregnation (INI) was used to treat the retted fibers for the improvement of the interfacial compatibility between the fiber and polypropylene (PP) matrix. The retted fibers and INI-treated fibers were used as reinforcement for the PP polymer composites. Film casting process was used to make CNW/PVA composites. The hermetical retting process used in this study produced fibers with high cellulose contents (81-92%) by removing the lignin and hemicelluloses. Higher retting temperature resulted in higher fiber surface hardness and elastic moduli. The tensile strengths and tensile moduli of the fibers decreased as the temperature increased. The SEM images showed the micropores in the cell wall structure for the fibers retted at over 130°C, providing the possibility to anchor nanoparticles into the cell wall. Surface morphology of the INI-treated fibers was examined with SEM, and showed that the CaCO3 nanoparticle crystals grew onto the fiber surface. Energy-dispersive X-ray spectroscopy (EDS) was used to verify the CaCO3 particle deposits on the fiber surface. As the size scale of the fibers decreased, the fiber crystallinity increased from 49.9% (retted fibers) to 83.9% (CNWs). About 23% á-cellulose in the raw kenaf bast fibers had been converted into CNWs. The retted fibers without INI treatment had poor compatibility with the polypropylene matrix. The INI treatment improved the compatibility between the fibers and the PP matrix, resulting in an improvement in kenaf fiber/PP composite tensile moduli and tensile strengths. The CNWs prepared from kenaf bast fiber gave excellent reinforcement for PVA composites. A nine percent increase of CNWs in the CNW/PVA composites yielded significant improvements in tensile strength and modulus of about 46% and 152%, respectively, compared with pure PVA.

In this research, the adsorptive capacities of kenaf, peat moss, hay, and peanut hulls were evaluated for the removal of TNT and 2,4-DCP from aqueous solutions. Adsorbent loading capacities determined by batch studies were verified by continuous column experiments. It was found that the adsorption capacity of the candidate adsorbents were significantly lower than granular activated carbon (GAC). The impact of surface modification techniques, such as surface oxidation, were evaluated to study the effect on adsorption capacity. At lower equilibrium concentrations of the adsorbate (less than 10 ppb), surface oxidation by ozone showed an increase in the adsorption capacity. The same trend was not observed with peroxone and ultrasound pretreatment. The adsorbent requirement for treating water contaminated with TNT and 2,4-DCP were calculated based on the adsorptive capacity of the adsorbents. Though the adsorbent requirements for the candidate adsorbents were considerably higher than granular activated carbon, the adsorbent requirement costs for most of the candidate adsorbents tested were competitive when compared to GAC costs.

Natural disasters are affecting a significant number of people around the world. Sheltering is the first step in post-disaster activities towards the normalization of the affected people's lives. Temporary housing is being used in these cases until the construction of permanent houses are done. Disposal of temporary housing after use is leading to a significant environmental impact because most of them are filled with thermally insulative polymer foams that do not degrade in a short period. To reduce these problems this work proposes to use foams made with compostable thermoplastic polylactic acid (PLA) and degradable kenaf core as filler materials; these foams are made using CO2 as blowing agent for insulation purposes. Foams with PLA and 5%, 10% and 15% kenaf core were tested. Different properties and their relations were examined using differential scanning calorimetry (DSC), thermal conductivity, mechanical properties, scanning electron microscopy (SEM), x-ray μ-computed tomography (μ-CT) and building energy simulations were done using Energy Plus by NREL. The results show that mechanical properties are reduced with the introduction of kenaf core reinforcement while thermal conductivity display a noticeable improvement.