The multi‐feedstock biorefinery – Assessing the compatibility of alternative feedstocks in a 2G wheat straw biorefinery process

Abstract

For second‐generation (2G) bioethanol refineries, the feedstock supply is one of the important parameters in terms of cost and consistency. Biorefineries are in most cases designed for a specific type of feedstock. For some biorefineries, the use of multiple feedstocks is an option, but how would such feedstocks perform when used in a process designed and optimized for a specific feedstock? There is no “one‐size‐fits‐all” processing package, due to variations in composition and structure of different feedstock types, but due to the size of commercial biorefineries, only minor adjustments of the processing parameters are practically feasible. In this study, 16 alternative feedstocks were characterized and compared to the benchmark feedstock wheat straw under identical processing conditions. The alternative feedstocks studied were as follows: barley straw, rye straw, grass straw, oat straw, Norway spruce sawdust, mixed softwood sawdust, oat wrap, biogas fiber, deep litter, washed deep litter, ryegrass fiber, lucerne fiber, ryegrass chaff, mixed grain chaff, rapeseed press cake, and beer production mash. These biomasses varied in carbohydrate content and accessibility after hydrothermal pretreatment. Applying a hydrothermal pretreatment under identical conditions, the subsequent enzymatic convertibility of these biomasses ranged from 0.5% to complete conversion based on their glucan content. Water retention value was determined and correlated with enzymatic convertibility, which provided a simple method for indirect measurement of biomass recalcitrance. Ethanol potentials were estimated based on carbohydrate release from enzymatic hydrolysis, and yeast toxicity test was performed on liquid fractions from hydrothermal pretreatment. Furthermore, a number of key processing indicators, including market price, logistics and availability, were taken into consideration based on a proposed full‐scale 2G ethanol plant in Denmark. The overall results show that while some feedstocks had inferior performance compared to wheat straw, identical or even superior performance was observed from barley, oat, and ryegrass feedstocks.

Enzymatic processing of lignocellulosic biomass: principles, recent advances and perspectives

“…While some pretreatment technologies aim to increase plant cell wall accessibility via reorganization of plant cell wall polymers without removal of matrix polymers (AFEX, ARP), other technologies increase enzymatic accessibility of cellulose via fractionation of the biomass by separating lignin (e.g., alkali and sulfite pulping), hemicellulose (steam explosion) or both (ionic liquid or organosolv pretreatment) from cellulose. Detailed analysis of pretreated biomass with glycome profiling and immunolabeling of plant cell wall polymers indicate that not even the most efficient pretreatment technologies, such as hydrothermal pretreatment [86,397], AFEX [264] and extractive ammonia pretreatment [13], can completely separate cellulose from the other cell wall polymers. Indeed, studies on the optimization of enzymatic biomass saccharification have revealed the need for a wide-spectrum enzyme cocktail, including cellulases and hemicellulases, to achieve complete saccharification of pretreated biomass, and the composition of the optimal enzyme cocktail depends on pretreatment and biomass type [21,61,168].…”

Downscaling of agricultural market impacts under bioeconomy development to the regional and the farm level—An example of Baden‐Wuerttemberg

“…Beside PBC cultivation, the unused grassland could also be a potential biomass feedstock for biorefineries and, in this way, used for new value chains in the bioeconomy (Mandl, ). However, biomass resources with a high water content in the harvested product have relatively high transport costs, which therefore must be given a particular consideration (Zhang et al, ). In accordance with other studies, the decreasing use of grassland in marginal regions seems likely due to the decreased competiveness of cattle farming in those regions (Ketzer, Rösch, & Haase, ).…”

The hydrogen gas bio-based economy and the production of renewable building block chemicals, food and energy

“…Second-generation biorefineries allow the production of renewable chemicals from organic waste streams, such as crop residues [6], with multiple viable full-scale systems in Denmark [7], Brazil [8], Canada [9], the USA, and China [10]. In this way, a broad range of building block chemicals, not only ethanol, but also others, such as succinic acid, lactic acid, glycerol and sorbitol [10][11][12], can be produced, while avoiding competition with the agricultural food supply chain [13].…”