Abstract
AbstractMiscanthus and poplar are very promising second‐generation feedstocks due to the high growth rates and low nutrient demand. The aim of the study was to develop a systematic approach for choosing suitable pretreatment methods evaluated with the modified severity factor (log ). Optimal pretreatment results in a high delignification grade, low cellulose solubilization and increased accessibility for enzymatic hydrolysis while revealing minimal log values. In order to do so, several reaction approaches were compared. Acid‐catalyzed organosolv processing carried out for miscanthus and poplar revealed the highest delignification grade leading to a relatively high glucose yield after enzymatic saccharification. In both cases, a design of experiments approach was used to study the influence of relevant parameters. Modeling the data resulted in the identification of optimum pretreatment conditions for miscanthus with concentrations of 0.16% H2SO4 and 50% EtOH at 185°C for a retention time of 60 min. Experimental validation of these conditions revealed an even higher delignification degree (88%) and glucose yield (85%) than predicted. 0.19% H2SO4 and 50% EtOH were determined as optimum concentrations, 182°C and 48 min identified as optimum pretreatment conditions for poplar; the delignification degree was 84% and the resulting glucose yield 70%.
Highlights
Earlier approaches using renewable resources to gain energy or to produce basic chemicals utilized first‐generation feedstocks as sugars from corn, potatoes, or sugar cane
The development and characterization of suitable pretreatment methods for miscanthus and poplar wood is presented
After selecting the preferred pretreatment method, optimum reaction conditions were identified with DoE and response surface methodology (RSM)
Summary
Earlier approaches using renewable resources to gain energy or to produce basic chemicals utilized first‐generation feedstocks as sugars from corn, potatoes, or sugar cane. Since lignin acts as natural barrier to prevent cellulose and hemicellulose degradation, pretreatment should result in a higher accessibility of the carbohydrates and a higher degree of delignification for efficient enzymatic hydrolysis. This was approved by Adams, Winters, Hodgson, and Gallagher (2018) demonstrating that high carbohydrate:lignin ratios of different miscanthus species increase the glucose release by the means of enzymes. The introduction of the modified severity factor log R′0′ offered the opportunity to implement pH, temperature, and residence time in one reaction ordinate (Overend & Chornet, 1987; Pedersen & Meyer, 2010) This enables the comparison of different chemical and physical–chemical methods with strongly deviating reaction parameters. A subsequent DoE approach was used to further identify the quantitative relations between the influencing parameters and glucose yield as well as the degree of delignification for the pretreatment of the two feedstocks
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