Guayule Bagasse Research Articles

Guayule bagasse to make mycelium composites: An alternative to enhance the profitability of a sustainable guayule crop

Parthenium argentatum Gray, known as Guayule is recognized for its quality latex production. For this reason, the cultivation of this plant generates an important economic interest. Although this crop thrives in arid climates, its production has not been extended due to a high production cost per hectare compared to other rubber sources. To alleviate this difference in market prices and make Guayule rubber production competitive, several options have been proposed. One of them is the use of bagasse, which has been used to produce biofuels and refractory bricks, among other alternatives. Mycelium composites are a novel type of material with physical-mechanical characteristics similar to some types of expanded polystyrene with the additional advantage of being fully compostable. In this article, we successfully manufactured a Mycelium-based bio-composite using bagasse from guayule and a wild strain of Ganoderma curtisii by a simple pressed method, which is cost-effective, eco-friendly, and fully compostable. The composite G. curtisii/guayule showed excellent insulating ability with a K factor value of 0.0792 Btu/(h•ft•°F). In the same way, compressive strength and density values obtained were 0.740 MPa and 0.469 gcm−3, respectively. The composite G. curtisii/guayule manufactured in this work, has a low cost of manufacture and is environmentally friendly. Subsequent explorations for its use in various industrial applications like packing, building insulation, and interior design, could make more profitable the cultivation of guayule plant.

Guayule stems fractionation and sugars recovery by different pretreatment technologies

The bagasse of guayule, obtained after extraction of natural rubber and resins, can be used to produce 2nd generation fermentable sugars and lignin. For this purpose, four pretreatment technologies were applied to deconstruct the guayule bagasse: diluted acid (DA), steam explosion (SE), organosolv (OS), and the steam explosion followed by alkaline washing (AW). The obtained lignocellulosic pulp underwent enzymatic hydrolysis (EH) to produce glucose. The conditions that gave the highest hydrolysis yield were assessed. A mass balance was elaborated for all processes which were compared on the basis of sugars yield, water and chemical consumption, and energy expenditure footprint. The greatest amount of glucose (133 g kg−1 of dry guayule bagasse, corresponding to 71% enzymatic hydrolysis yield) was obtained using SE followed by AW, whereas SE and OS had lower yields (104 g and 106 g kg−1, respectively). The highest overall monomeric sugars yield, including xylose, was obtained by DA (317 g kg−1) followed by OS (243 g kg−1) pretreatment, although the sugar streams must be purified in both processes by removing the acid and the solvent, respectively. SE is a process with a limited requirement of chemicals and energy input, which are significantly higher for AW and for OS, respectively.

Economic and environmental sustainability assessment of guayule bagasse to fuel pathways

Guayule (Parthenium argentatum A. Gray) is a desert-dwelling crop that can produce hard rubber for tires and has the potential to help meet the water conservation needs of arid regions such as the Southwest U.S. Previous work has quantified the cost and environmental impact from guayule rubber production. However, establishing the economic viability of a domestic guayule industry requires identifying value-added products from the residual non-rubber guayule biomass, referred to as bagasse. Using guayule bagasse for bioenergy production is one potential solution, but the best pathway for thermochemical conversion of bagasse to fuels has yet to be defined. In this work, process models of pyrolysis and pelletization of bagasse are developed to inform a path to commercialization. A facility processing 200 tonnes of guayule bagasse per day is considered with a system boundary defined from biomass cultivation to fuel combustion. The materials and energy inventory results enabled the first comparative assessment of bagasse to fuels by concurrently performing techno-economic analysis and well-to-wheels life cycle assessment on both pathways. The minimum fuel selling price for the bagasse to fuels pathway was $0.076 per MJ ($9.26 per gallon of gasoline equivalent) and the minimum selling price of pellets from bagasse was $176 per tonne. This work compares the economic and life cycle results of both processes to make conclusions about the economic potential of bagasse and environmental impact of its conversion, areas to reduce production cost of biofuels, and potential for greenhouse gas emissions reduction compared with conventional fuels. In addition, the work identifies areas where future research may optimize production costs such that these fuels can be integrated alongside guayule rubber into a successful bioeconomy for the Southwest United States.

Adsorption of pharmaceuticals from aqueous solutions using biochar derived from cotton gin waste and guayule bagasse

Biochars produced from cotton gin waste (CG) and guayule bagasse (GB) were characterized and explored as potential adsorbents for the removal of pharmaceuticals (sulfapyridine-SPY, docusate-DCT and erythromycin-ETM) from aqueous solution. An increase in biochar pyrolysis temperature from 350 οC to 700 οC led to an increase in pH, specific surface area, and surface hydrophobicity. The electronegative surface of all tested biochars indicated that non-Coulombic mechanisms were involved in adsorption of the anionic or uncharged pharmaceuticals under experimental conditions. The adsorption capacities of Sulfapyridine (SPY), Docusate (DCT) and Erythromycin (ETM) on biochar were influenced by the contact time and solution pH, as well as biochar specific surface area and functional groups. Adsorption of these pharmaceutical compounds was dominated by a complex interplay of three mechanisms: hydrophobic partitioning, hydrogen bonding and π–π electron donor–acceptor (EDA) interactions. Despite weaker π–π EDA interactions, reduced hydrophobicity of SPY− and increased electrostatic repulsion between anionic SPY− and the electronegative CG biochar surface at higher pH, the adsorption of SPY unexpectedly increased from 40% to 70% with an increase in pH from 7 to 10. Under alkaline conditions, adsorption was dominated by the formation of strong negative charge-assisted H-bonding between the sulfonamide moiety of SPY and surface carboxylic groups. There seemed to be no appreciable and consistent differences in the extent of DCT and ETM adsorption as the pH changed. Results suggest the CG and GB biochars could act as effective adsorbents for the removal of pharmaceuticals from reclaimed water prior to irrigation. High surface area biochars with physico-chemical properties (e.g., presence of functional groups, high cation and anion exchange capacities) conducive to strong interactions with polar-nonpolar functionality of pharmaceuticals could be used to achieve significant contaminant removal from water.Graphic

Characterization and evaluation of guayule processing residues as potential feedstock for biofuel and chemical production

In the processing of guayule (Parthenium argentatum) for bulk rubber production using solvent extraction, two residue streams are produced: a complex resin-rich liquid and a ground, dry woody bagasse. In order to enhance the economic viability of guayule as an industrial crop, value-added use of the residues is needed and has the potential to reduce gross rubber production costs. The main objective of this research is the characterization of these two residues using analytical techniques to identify potential value-added components and applications. Here, guayule bagasse and resin were characterized by CNHS/O elemental analysis, bomb calorimetry, thermogravimetric analysis, Fourier-transform infrared spectrometry (FT-IR), X-ray diffractometry (XRD), gas chromatography–mass spectrometry (GC–MS), and high-resolution Fourier transform ion cyclotron resonance mass spectroscopy (FT-ICR MS). Guayule bagasse has high energy content (22–24 MJ/kg), less moisture (0.5–1.5 wt.%) and ash (3.7–4.1 wt.%), low cellulose crystallinity (29–34 %), and abundant carbohydrates (36–38 wt.%) and lignin (22–23 wt.%) relative to plenty of other lignocellulosic biomass, indicating bagasse’s potential for thermochemical conversion to fuels. By FT-ICR MS with negative ionization mode, the most abundant classes among the 7200 heteroatom-containing compounds detected in guayule resin were O3, followed by O4 and O2. Identified compounds included fatty acids, steroids, triterpenoids, and sesquiterpene esters, some of which have never been reported, as potential precursors of industrial chemicals.Characterization of guayule bagasse and resin guides exploring potential applications of waste streams, beneficial for enhancing techno-economic feasibility of guayule rubber-derived tires manufacturing industry.

Techno-economic analysis of guayule (Parthenium argentatum) pyrolysis biorefining: Production of biofuels from guayule bagasse via tail-gas reactive pyrolysis

The tire industry is currently considering natural rubber from guayule (Parthenium argentatum Gray) as a viable alternative to imported Hevea natural rubber, or petroleum-based synthetics, to meet expanding materials needs of the industry. However, only 5–10% of the harvested guayule plant is converted into rubber latex. For economic sustainability, the industry must identify viable uses for the balance residual, termed bagasse. Bioenergy production has been considered, but conversion facilities must be co-located to avoid additional costs in transportation of the bagasse. This study investigated the economics of processing a minimum of 200metric ton per day (MTPD) of guayule bagasse to produce biofuels in a biorefinery co-located with a guayule latex processing facility. A unique aspect of the simulated process was the use of the tail gas reactive pyrolysis (TGRP) technology that formulates an intermediate bio-oil with less oxygenates and therefore requires only mild upgrading to fuel products. This achieved a yield of 16.2%, distributed in the gasoline (9.7%), jet fuel (5.6%), and diesel (0.9%) carbon ranges. The capital cost was estimated at $58.74 million (MM), and the annual operating cost was estimated at $14.19MM. A discounted cash flow rate of return (DCFROR) analysis was conducted to evaluate the economic feasibility based on a 30-year plant life and 10% internal rate of return. The minimum fuel selling price (MFSP) calculated was 1.88$/L for gasoline, 1.84$/L for jet fuel and 1.91$/L for diesel fuel, clearly showing the limitations imposed by economies of scale of the current guayule bagasse availability. However, there is a potential to reduce the MFSP by increasing the facility capacity and utilizing the valuable co-products that accompany guayule pyrolysis biorefining. Sensitivity analysis indicates the MFSP of gasoline can be lowered to 0.96$/L considering the most optimistic scenario, comprising an integrated large facility of 2000MTPD, lower cost of hydrogen, and the sale of a premium-quality residual guayule biorefinery coke.

Thermomyces lanuginosus STm: A source of thermostable hydrolytic enzymes for novel application in extraction of high-quality natural rubber from Taraxacum kok-saghyz (Rubber dandelion)

Hydrolytic enzymes from a newly isolated strain of the thermophilic fungus Thermomyces lanuginosus were used to extract rubber from Taraxacum kok-saghyz commonly known as rubber (or Russian or Kazak(h)) dandelion. The fungus was isolated from garden soil and identified as Thermomyces lanuginosus STm based on 18S rRNA gene sequence analysis. The isolate produced considerable amounts of extracellular hydrolytic enzymes on lignocellulosic substrates at 55°C incubated for 8days in 150mL shake flask experiments. The maximum enzyme activities on wheat straw and guayule bagasse were: xylanase (167.41; 130.1U/mg), inulinase (69.8; 34.1U/mg), cellulase (carboxymethyl cellulase) (16.7; 4.8U/mg), filter paper assay (FPase) (14.2; 5.5FPUg−1) and pectinase (7.2; 3.2U/mg), respectively. In addition, alkali-pretreated roots of Taraxacum kok-saghyz (TK), incubated with crude enzyme extracts from T. lanuginosus STm grown on guayule bagasse, subsequently yielded more natural rubber (90mg/g dry TK root) than previously established protocols, Eskew process (24mg/g) and commercial-enzyme-combination process (45mg/g). Rubber purity in the T. lanuginosus STm treatment was 71.7%, greater than the Eskew process at 37.5%. However, the crude T. lanuginosus STm enzyme treatment at 91.6% rubber purity approached the purity of the commercial-enzyme-combination process at 94.1% purity.

QUANTIFICATION OF THE CONTRIBUTION OF FILLER CHARACTERISTICS TO NATURAL RUBBER REINFORCEMENT USING PRINCIPAL COMPONENT ANALYSIS

ABSTRACTPractical statistical models were developed to quantify individual contributions from characteristics of conventional and non-conventional fillers and predict resulting mechanical properties of both hevea and guayule natural rubber composites. Carbon black N330 and four different agro-industrial residues, namely, eggshells, carbon fly ash, processing tomato peels, and guayule bagasse, were used in this study. Filler characteristics were used as explanatory variables in multiple linear regression analyses. Principal component analysis was used to evaluate correlations among explanatory variables based on their correlation matrices and to transform them into a new set of independent variables, which were then used to generate reliable regression models. Surface area, dispersive component of surface energy, carbon black, and waste-derived filler loading were found to have almost equal importance in the prediction of composite properties. However, models developed for ultimate elongation poorly explained variability, indicating the dependence of this property on other variables. Agro-industrial residues could potentially serve as more sustainable fillers for polymer composites than conventional fillers. This new modeling approach for polymer composites allows the performance of a wide range of different waste-derived fillers to be predicted with minimum laboratory work, facilitating the optimization of compound recipes to address specific product requirements.

Guayule (Parthenium argentatum) pyrolysis biorefining: Fuels and chemicals contributed from guayule leaves via tail gas reactive pyrolysis

Guayule (Parthenium argentatum), a woody desert shrub cultivated in the southwestern United States, is a source of natural rubber and organic resins that promises to revolutionize the tire and rubber industry. Some 20,000kgha−1yr−1 is reported to be harvested worldwide and expected to grow due to renewed interest in guayule to replace imported Hevea rubber. We have recently reported the use of guayule bagasse, the residual biomass after latex extraction, as feedstock in a pyrolysis process that employs a reactive gas environment to formulate a special intermediate bio-oil product that is easily distillable and readily synthesized to hydrocarbon (drop-in) fuels (Boateng et al., 2015). This submission reports on the use of the same pyrolysis process for the leaves of the guayule plant and the array of fuels and chemicals that the leaves can contribute to a co-located guayule biorefinery at a latex plant that could utilize the entire biomass residue value chain. The composition of the guayule leaves is different from the bagasse, with the main differences being lower resin content along with higher ash (>16wt%) and higher nitrogen (2.6wt%, dry ash free, daf) contents resulting from the higher concentration of the plant proteins (16.4wt% (daf)). Since the former two components have exhibited a drastic influence on pyrolysis product distribution in the past, it was incumbent upon us to explore whether the resin content would provide additional synergistic effects and influence product selectivity pathways to bio-based chemicals. We found that the combined effect of the tail gas reactive pyrolysis process, the proteinaceous nature of the guayule leaf and resin combine to create a complex mechanism that results in an interesting bio-oil intermediate product from which a slew of fuel and commodity chemical compounds can be synthesized upon mild upgrading.

Novel Mineral and Organic Materials from Agro-Industrial Residues as Fillers for Natural Rubber

Bio-based materials are being developed, increasingly, because of the need for sustainable, environmentally friendly, processes and products. We have made natural rubber composites containing low cost fillers derived from agro-industrial wastes, namely, eggshells, carbon fly ash, processing tomato peels and guayule bagasse. Composites manufactured with 35 phr (parts per hundred rubber) of carbon black (particle size 108 ± 31 nm) were used as a reference filled material. The amount of carbon black was gradually replaced by a specific waste-derived macro (<300 µm diameter) or micro (<38 µm diameter) filler. Despite differences in particle size distribution and surface chemistry, the tensile properties of micro sized tomato peels composite were similar to those of the carbon black reference composite. Composites manufactured using micro sized particles at low loadings (5 and 10 phr) of carbon fly ash and eggshells, as co-fillers with carbon black, also demonstrated comparable tensile results to those of composites manufactured solely with carbon black. Hierarchical cluster analysis partitioned the data into five groups of composites having statistically similar mechanical properties. Composites containing micro sized particles at low loadings (5 and 10 phr) were grouped in clusters 1, 2 and 5. These clusters gathered composites with the highest tensile strength and 300 % modulus. As the amount of non-carbon black filler increased above 10 phr and up to 35 phr (maximum filler loading used), the composites became weaker than the carbon black filled composites and modulus decreased.

Guayule (Parthenium argentatum) pyrolysis biorefining: Production of hydrocarbon compatible bio-oils from guayule bagasse via tail-gas reactive pyrolysis

Abstract Guayule (Parthenium argentatum) is a woody desert shrub cultivated in the southwestern United States as a source of natural rubber, organic resins, and high energy biofuel feedstock from crop residues. We used guayule bagasse, the residual biomass after latex extraction as feedstock in a pyrolysis process that employs a reactive gas environment to formulate a special intermediate bio-oil product that allows use of conventional hydrotreating with conventional noble metal catalysts and a simple distillation process to synthesize hydrocarbon (drop-in) fuels. The said guayule-bagasse tail gas reactive pyrolysis (TGRP) process comprises pyrolyzing the guayule bagasse in a fluidized-bed reactor in the presence of a reactive and flammable tail gas (comprising CO ∼ 30%, CH4 ∼ 16%, CO2 ∼ 40%, H2 ∼ 10%, C2H4 ∼ traces) generated in the pyrolysis process and without the use of catalyst to produce bio-oil with C/O molar ratio of 14/1 in organic yields of 34–40 wt% having an energy content of 31–37.5 MJ/kg. When we further processed the said bio-oil by centrifugation, we obtained 85 wt% yield and further 50–65 wt% yields following a continuous hydrotreatment over common noble metals (Pt, Ru or Pd) on a carbon support. Distillation of this mixture yielded >95 wt% hydrocarbon liquid fuel mixture comprising 30.4% gasoline (C5–C7), 37% jet (C8–C12) and 24% diesel (C13–C22). Analysis of a composite mixture of the hydrotreated product from the bagasse showed the majority of the sample (66%) was C12 and below, which falls within the gasoline (naphtha) range with the greatest fraction of naphtha falling within the C8–C10 range. Beyond C12, the molecular weights increased through the diesel range (34%), with C37 being the highest observable molecular weight. The product met several ASTM standards for drop-in fuels, but the sulfur content (primarily due to latex extraction additives) was relatively high at around 300 ppm, indicating that hydrodesulfurization may be required to be infrastructure ready.

Statistical optimization of operating conditions for supercritical carbon dioxide-based pretreatment of guayule bagasse

A central composite design (CCD) was used to find the optimal temperature, pressure, moisture and duration for the supercritical CO2-based pretreatment of guayule, a desert shrub for commercial production of hypoallergenic latex. The pretreatment involved: adding water to the biomass, raising system temperature, pressurizing with supercritical CO2, holding the system for a period of time, and exploding the biomass by rapidly opening the vent valve. The pretreated biomass was then hydrolyzed at 30 °C for 72 h in an enzyme solution with 5% (w/v) solid loading. The yields of released glucose and pentose were determined and used as the CCD response variables. Statistical analysis of results led to the following recommended condition: 175 °C, 26.2 MPa (3800 psi), 60% moisture and 30 min. The corresponding glucose and pentose yields were 56% and 61%. X-ray diffraction analysis was done to get the crystallinity index of the bagasse before and after pretreatment. Scanning electron microscopy was also used to examine the structural changes caused by pretreatment. These characterizations indicated that at milder conditions, the pretreatment exposed cellulose and hemicellulose for subsequent enzyme attack; at harsher conditions, the pretreatment destroyed cellulose crystallinity and gave higher glucose yields. To isolate the explosion effect (caused by instantaneous pressure drop, ΔP) from the reaction (pressure) effect, a series of experiments was made with the bagasse pretreated at the same condition (27.6 MPa) but exploded against different back pressures. The explosion needed to be severe enough (with ΔP > 17 MPa) to give a sugar yield of over 50%.

Termite resistance of biobased composition boards made from cotton byproducts and guayule bagasse

Large quantities of cotton gin byproducts (CGB), also known as cotton gin trash or cotton gin waste, are being produced across the cotton belt of the United States annually. Similarly, guayule wastes after rubber latex production is expected to increase as this industry begins to expand. Use of these waste materials in value-added products can help the economics of the crops and aid in alleviating waste management issues and environmental problems. Conventional wood preservatives used to protect wood from insect and microbial damage are of concern to human health and the environment. Guayule bagasse (GB) has been shown to have termite control properties, and a combination of cotton gin and guayule wastes could also have such valuable properties. An initial study evaluating the physical and mechanical properties of boards produced from these two biomasses was published in 2009, this study is a continuation focusing on the termite resistance of boards produced. Thus, the objective of this research was to determine the termite resistance property of experimental composition boards made from CGB and GB. Composition boards were made from five different ratios of CGB to GB: 100:0, 75:25, 50:50, 25:75 and 0:100 (C100, C75–G25, C50–G50, C25–G75, and G100, respectively). Additionally, three-layered boards (3-layer) consisting of 25% GB (upper layer), 50% CGB (middle layer), and 25% GB (bottom layer) were made. For comparison, a commercial southern pine lumber board (SPB), a commercial oriented strandboard (OSB), and a commercial preservative treated medium density fiberboard (MDF) were included in the testing. This testing was an extension of a previous study where the mechanical properties of the CGB and GB composition boards were compared to select commercial standards. Five specimens were cut from each of the nine different board treatments and tested using Eastern subterranean termites. Weight loss, termite survival days, and visual grade of each specimen were determined according to testing standards. Results confirmed good termite control quality for boards made from GB alone. Boards containing CGB to GB ratios of 75–25 and 50–50 obtained similar termite resistance as the commercial OSB based on the total weight loss and one-week termite mortality rate. Visual grading of tested specimens revealed all six CGB and GB composition boards and the treated MDF showed better rating than the commercial OSB and pine lumber. No differences were noted among the total termite surviving days for the six CGB and GB composition boards. Overall, the biobased CGB and GB boards showed promise with the boards containing GB exhibiting improved termite resistance properties than SPB and OSB.

Guayule as a feedstock for lignocellulosic biorefineries using ammonia fiber expansion (AFEX) pretreatment

Natural rubber latex extraction from guayule leaves behind greater than 90% (by weight) of agricultural residue as a feedstock suitable for conversion to biofuels via a thermochemical or biochemical route. Untreated guayule shrub and bagasse (after latex extraction) has shown to be very recalcitrant to enzymatic hydrolysis, necessitating application of a chemical pretreatment to enhance cellulase accessibility. The objective of this work was to carry out detailed compositional analysis, ammonia fiber expansion (AFEX11AFEX: ammonia fiber expansion.) pretreatment, enzymatic hydrolysis and ethanol fermentation for various guayule-derived biomass fractions. Plant feedstocks tested were derived from two sources; (a) a mature 2007 AZ-2 whole guayule shrub plant obtained from USDA/ARS22USDA/ARS: United States Department of Agriculture/Agricultural Research Service. research fields, and (b) the guayule latex-extracted commercial grade bagasse (62505) from Yulex Corporation. Compositional analysis and enzymatic hydrolysis were carried out using standard NREL33NREL: National Renewable Energy Laboratory. protocols (www.nrel.gov/biomass/analytical_procedures.html). AFEX pretreatment was carried out using concentrated ammonium hydroxide at elevated temperatures for desired residence times in a pressurized reactor. Yeast fermentations on biomass hydrolyzates were carried out micro-aerobically using Saccharomyces cerevisiae (424A strain) in shake flasks.AFEX pretreatment was found to substantially improve overall enzymatic digestibility by 4–20 fold for both untreated guayule shrub and latex-extracted bagasse. Maximum glucan and xylan conversion achieved for the latex-extracted bagasse was 40% and 50%, respectively. The yeast was readily able to ferment both glucose and xylose to ethanol from the guayule bagasse hydrolyzate with or without external nutrient supplementation (i.e., yeast extract and tryptone). Our results highlight the possible utilization of guayule as a feedstock for lignocellulosic refineries co-producing natural rubber latex and biofuels. However, further process improvements (e.g., lignin/resin extraction and cellulose decrystallization using a modified AFEX process) are necessary to increase the effectiveness of ammonia-based pretreatments for further enhancing enzymatic digestibility of guayule-derived hardwood biomass.

Properties of thermoplastic composites with cotton and guayule biomass residues as fiber fillers

This study was conducted to evaluate the suitability of using residual plant fibers from agricultural waste streams as reinforcement in thermoplastic composites. Three groups of plant fibers evaluated included cotton burrs, sticks and linters from cotton gin waste (CGW), guayule whole plant, and guayule bagasse. The plant fibers were characterized for physical (bulk density and particle size distribution) and chemical properties (ash, lignin and cellulose contents). A laboratory experiment was designed with five fiber filler treatments, namely control (oak wood fiber as the filler – OWF), cotton burr and sticks (CBS), CBS with 2% (by weight) second cut linters (CBL), CBS with 30% (by weight) guayule whole plant (CGP), and CBS with 30% (by weight) guayule bagasse (CGB). The composite samples were manufactured with 50% of fiber filler, 40% of virgin high-density polyethylene (HDPE), and 10% other additives by weight. The samples were extruded to approximately 32 × 7 mm cross-sectional profiles, and tested for physico-mechanical properties. The CBS and CBL had considerably lower bulk density than the other fibers. Cotton linters had the highest α-cellulose (66.6%), and lowest hemicellulose (15.8%) and lignin (10.5%) of all fibers tested. Guayule whole plant had the lowest α-cellulose and highest ash content. Both CBS and guayule bagasse contained α-cellulose comparable to OWF, but slightly lower hemicellulose. Evaluation of composite samples made from the five fiber treatments indicated that fibers from cotton gin byproducts and guayule byproducts reduced the specific gravity of the composites significantly. However, the CBS and CBL samples exhibited high water absorption and thickness swelling, but the addition of guayule bagasse reduced both properties to similar levels as the wood fiber. The CGP exhibited significantly lower coefficient of thermal expansion. Composite samples with the five different fiber fillers showed similar hardness and nail holding capacity, yet oak fibers imparted superior strength and modulus under flexure and compression with the exception of the compressive modulus of CGB composites. In general, both cotton ginning and guayule processing byproducts hold great potential as fiber fillers in thermoplastic composites.

Physicochemical and adsorptive properties of fast‐pyrolysis bio‐chars and their steam activated counterparts

AbstractBACKGROUND: This study investigated steam‐activation as a technology for adding value to fast‐pyrolysis bio‐chars. Due to short residence times in the fluidized‐bed pyrolyzer, required to maximize bio‐oil production, the bio‐char structure tends to be underdeveloped thereby impacting its full potential application as a value‐added co‐product.RESULTS: The bio‐chars of several substrates from a fluidized‐bed fast pyrolyzer and their respective corresponding steam‐activated counterparts were characterized for their surface areas and metal ion adsorption (copper, cadmium, nickel and zinc). Surface areas increased with activation from negligible to 136–793 m2 g−1 of material, with concomitant pore development evidenced by scanning electron microscopy and mathematical modeling. Affinity to Cu2+ was highest with adsorption efficiencies for 1 mmol L−1 solutions ranging from 60–85%. Metal ion adsorption performance was feedstock dependent and increased with activation, possibly due to improved access to highly reactive adsorption sites associated with the inorganic material in the feedstock.CONCLUSION: Because of their higher yields and metal ion uptake, broiler litter and alfalfa stems could be the feedstock of choice when considering upgrading fast pyrolysis bio‐char for metal ion uptake. However, if the development of large surface areas is required, guayule bagasse and soybean straw could be the preferred feedstock. Published 2010 by John Wiley and Sons, Ltd.

Guayule ( Parthenium argentatum) pyrolysis and analysis by PY–GC/MS

Economic and sustainable biofuel production requires high process efficiency. The choice of biomass and the conversion technology employed to produce renewable fuels determine the product yields, fuel quality and consequently the process efficiency. Guayule, a perennial shrub native to the southwestern United States, is currently cultivated as a source of natural rubber latex. However, after latex extraction, about 90% of the crop is used for low value biomass markets or simply goes to waste. Residual biomass from guayule presents an opportunity as a solid fuel resource that is already collected, on-site, and is a suitable ligno-cellulosic conversion feedstock. Using Py–GC/MS, we characterized the starting material of whole guayule shrub (G1) and solid waste streams, including ground bagasse from the industrial latex extraction process (G4), ground whole shrub minus resin (G2), and ground whole shrub minus resin and rubber (G3). These waste streams contain varying amounts of resin and rubber compounds. We measured the energy content of these streams and compared their compositions based on Py–GC/MS pyrograms. Catalytic and non-catalytic pyrolysis reactions were performed. It was found that the stem-derived latex-extracted guayule bagasse (G4) is the material with the most thermochemical energy potential. Whole shrub (G1) is the next in energy content. The gross energy content declined as resin is removed (G2) and further declined with the removal of resin and rubber (G3). The pyrograms showed fragmentation of the biomass polysaccharides and lignin polymers to compounds that have chemical energy, which provides support to the gross energy profiles.

Energy-dense liquid fuel intermediates by pyrolysis of guayule ( Parthenium argentatum) shrub and bagasse

Guayule is a perennial shrub grown in the southwestern United States that is used to produce high quality, natural rubber latex. However, only about 10% of the plant material is used for latex production; the remaining biomass, called bagasse, can be used for renewable fuel production. Fast pyrolysis of guayule, both whole shrub and bagasse was performed. From both feedstocks a very viscous, high energy content (∼30 MJ/kg) pyrolysis liquid (bio-oil) was produced in yields averaging over 60% without any catalyst. The properties and compositions of the bio-oils were found to be similar in the two feedstocks. Co-products, charcoal (20–30 wt%) and non-condensable gas (5–15%), were also dense and had a high energy content. Of the two feedstocks, the whole shrub yielded higher quantities of charcoal that also had a higher energy content than the charcoal produced from bagasse. As a result, the energy recovery, estimated as the percentage of the energy products, to energy input into the reactor was lower (60%) for guayule bagasse than for the whole shrub (73%). This notwithstanding, the bagasse is a more attractive feedstock for thermochemical conversion, not only because it is a residue from a primary process (latex extraction) that is on-site, but also because it has a high energy content. Moreover, it produces high quality pyrolysis products. Co-production of latex rubber from the whole shrub and renewable fuels from the residual bagasse by pyrolysis should improve the already positive economics of the guayule latex rubber industry.

Latex yield and quality during storage of guayule ( Parthenium argentatum Gray) homogenates

Extraction and purification of latex from guayule ( Parthenium argentatum Gray) require that harvested shrub first be homogenized in an alkaline aqueous buffer. The stability of the latex was investigated in a variety of homogenates and under different storage conditions. Neither the length of post-harvest storage (up to 5 weeks) nor branch diameter affected the concentration of the latex in homogenates. Latex concentration was not affected by the length of grinding time used to make the homogenate. However, latex concentration declined in acidic pH, and the initial latex concentration in homogenate prepared from defoliated shrub was below 4 mg/ml. This decline was less apparent in homogenates made from leafy shrub, suggesting a protective effect derived from the leaves. Storage at 4 °C prevented latex loss under all treatments. The quality of the rubber polymers in the latex fraction was investigated using size exclusion chromatography/multiangle laser light scattering detection. Polymer molecular weight and molecular radius declined in parallel, but both declined faster in the dilute homogenate generated from the second grind of the guayule bagasse than in the more concentrated homogenate from once-ground shrub. Degradation was greatly slowed in all treatments when the homogenates were stored refrigerated. Polydispersity values were low in all treatments, only slightly increasing over time, with the exception of homogenate generated by the second grind of shrub in the presence of leaves and stored at 24 °C. The relatively rapid polymer degradation of the latex fraction in this homogenate led to an increase in polydispersity followed by a decrease as the latex fraction was degraded to below detection levels. We conclude that guayule homogenate provides a stable environment for latex yield and quality, even at room temperature, for at least 13–16 weeks provided that the pH is basic and the concentration of rubber particles is at least 4 mg/ml. This is in contrast to the extractable latex content of harvested branches, which is prone to rapid coagulation and degradation in situ unless the branches are stored hydrated and refrigerated.

Guayule as a wood preservative

Conventional wood preservatives used to protect wood from insect and microbial damage are presently of major concern to human health and the environment. Finding alternative and economical preservatives has not been successful. Studies have shown that the resin material extracted from the guayule plant ( Parthenium argentatum, Gray) has both insect and microbial resistant properties. Unfortunately, this finding has not been applied commercially. However, large quantities of guayule waste wood and resin material could become available with the domestication of guayule to produce hypoallergenic rubber latex. Thus, opportunities exist in using this natural source of biologically resistant resinous chemicals. The objective of this preliminary study was to determine the effects of latex-extracted wood residues or bagasse and resin extracts on termite and decay resistance properties of wood products. Two types of test materials were used. One was wood impregnated with organic solvent-extracted resin material from the plant. The other was composite board fabricated using the bagasse residue or whole plant and a plastic binder, which was used to improve the physical properties of the composite. Accelerated laboratory tests were conducted to determine the resistance of the wood products against an Eastern subterranean termite and wood fungi (brown-rot). The wood and stem of the guayule plant, wood treated with the resin extract, and particle and composite boards made from ground guayule bagasse exhibited termite and wood fungal resistance. Because the guayule plant is drought tolerant and its product can reduce the need to harvest trees for replacing wood damage, its cultivation as an alternative crop will help conserve water and forest resources world-wide.