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University of Nevada, Reno (2017)

Biofuels and Biomaterials from an Arid Lands Plant, Grindelia squarrosa

Neupane, Bishnu Prasad

Titre : Biofuels and Biomaterials from an Arid Lands Plant, Grindelia squarrosa

Auteur : Neupane, Bishnu Prasad

Etablissement de soutenance : University of Nevada, Reno,

Grade : Doctor of Philosophy (PhD) 2017

Résumé partiel
Grindelia squarrosa, commonly called curlytop gumweed, can potentially be cultivated for biofuel production in the semiarid and arid lands of western USA. It can be grown on marginal land with less than 25 cm of water annually and has low nutrient requirements. The average amount of dry biomass that was produced by growing gumweed in plots in the agricultural experimental field stations of University of Nevada Reno was approximately ten tons per hectare 9950 kilogram per hectare (kg/ha). The germination success was approximately 87% in the greenhouse and 61% in the field, where germination requires damp conditions. The biennial plant blooms for 1.5 months with an initial milky stage of the pre bloom, followed by yellow flowers in August of the second year of planting. The buds produce a diterpene carboxylic acid, grindelic acid, as the primary component along with additional carboxylic acids and various terpenes. Constraints on production of the crop include various weeds and occasional fungal infections. _ The biofuel potential is greatest when the plant contains 50% flowers, and can be harvested, field dried and then ground/milled with a hammer mill. Acetone extraction of the ground gumweed biomass produced an average of 12.5% biocrude using a pilot scale bioreactor, while a more complete soxhlet extraction produced 15.5% biocrude. The carboxylic acid fraction was 68% of the weight of the biocrude. The average amount of biocrude production on a biennial basis was 1,260 kg/ha while the average amount of carboxylic acid fraction production was 816 kg/ha.
Acid-catalyzed methylation of biocrude produced about 72.5% hexane-extractable materials, consisting primarily of methyl esters of the carboxylic acids and various terpenes. When the carboxylic acid fraction of the biocrude was isolated and methylated, the hexane extract contained 85% of the weight. Those hexane-extracted materials are the materials examined for biofuel values. Although the methylated components produced a viscous liquid, this fraction could be mixed with petroleum diesel fuel up to 20%. The blend met the biofuel standards, despite its slightly higher viscosity. A single peak of grindelic acid methyl ester (GAME) was observed by gas-chromatography mass spectrometry (gc-ms) using diazomethane as the methylation agent, while the acid catalyzed methylation produced an additional peak, also identified by gc-ms as GAME. The differences in structure of the two compounds were not determined. While the average amount of useful biofuel production from gumweed was about 865 liter per hectare (L/ha) (92 gallons per acre (gal/ac)), the best plots suggested that it could be produced up to 1290 L/ha on a biennial basis, which is equivalent to 138 gal/ac in every two years

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Page publiée le 13 septembre 2017, mise à jour le 1er octobre 2017