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In this study, bagasse from two arid land plants, grindelia and rabbitbrush, were hydrothermally carbonized (HTC) along with their raw biomass at 200−260 °C for 5 min. Prior to HTC, biocrude was extracted from grindelia (Grindelia squarrosa), whereas rubber was extracted from rabbitbrush (Ericameria nauseosa). Solid hydrochars and HTC process liquids of extracted feedstocks were characterized by ultimate, proximate, fiber, FTIR, higher heating value (HHV), and GC−MS analyses and the results were compared with their corresponding unextracted conditions. Hydrochars were pelletized in a single-press pelletizer and mass and energy densities of the pellets were measured. From the proximate, ultimate, FTIR, and fiber analyses, the bagasse show similar properties of the raw biomass, although the HHV was slightly increased with crude extraction from grindelia and decreased with rubber extraction from rabbitbrush. With the increase of HTC temperature, solid mass yield was decreased up to 44% for grindelia bagasse and 57% for rabbitbrush bagasse. HHV increases for all the feedstocks up to about 26 MJ kg −1 , regardless of biomass type, when treated at 260 °C. HTC process liquid becomes acidic in the presence of short-chain organic acids with HTC temperature.

BACKGROUND: Taraxacum kok-saghyz (TK) is a rubber-producing plant being developed as a commercial alternative source of natural rubber (NR). The objective of this study was to investigate processes to extract high quality NR at high yield and purity from TK. Rubber is formed in the roots of TK and exists in mostly solid form. Previously used mechanical processes extract NR from TK roots at low purity (< 90%) that does not meet industry standards (≥ 99.8%). To improve this, the effects of root chopping, enzymatic hydrolysis, pebble milling and alkaline pretreatment and purification on NR yield, purity and quality were investigated. RESULTS: Enzymatic digestion (with and without alkaline pretreatment), yielded rubber at the highest yield (∼80%) and purity (99.4%). Alkaline pretreatment of roots improved NR yield and did not adversely affect quality. More rubber was extractable from chopped roots than whole roots, but the rubber was less pure. Alkaline purification of the extracted crude rubber further increased rubber purity but reduced rubber molecular weight. CONCLUSION: Enzymatic digestion with or without alkaline pretreatment forms the basis of aqueous processes that could be used for large-scale, efficient extraction of TK rubber at high yield, purity and quality to meet industry standards for NR.

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