Liquefaction of lignocellulose at high‐solids concentrations

Abstract

To improve process economics of the lignocellulose to ethanol process a reactor system for enzymatic liquefaction and saccharification at high-solids concentrations was developed. The technology is based on free fall mixing employing a horizontally placed drum with a horizontal rotating shaft mounted with paddlers for mixing. Enzymatic liquefaction and saccharification of pretreated wheat straw was tested with up to 40% (w/w) initial DM. In less than 10 h, the structure of the material was changed from intact straw particles (length 1-5 cm) into a paste/ liquid that could be pumped. Tests revealed no significant effect of mixing speed in the range 3.3-11.5 rpm on the glucose conversion after 24 h and ethanol yield after subsequent fermentation for 48 h. Low-power inputs for mixing are therefore possible. Liquefaction and saccharification for 96 h using an enzyme loading of 7 FPU/gÁDM and 40% DM resulted in a glucose concentration of 86 g/kg. Experiments conducted at 2%-40% (w/w) initial DM revealed that cellulose and hemicellulose conversion decreased almost linearly with increasing DM. Performing the experiments as simultaneous saccharification and fermentation also revealed a decrease in ethanol yield at increasing initial DM. Saccharomyces cerevisiae was capable of fermenting hydrolysates up to 40% DM. The highest ethanol concentration, 48 g/kg, was obtained using 35% (w/w) DM. Liquefaction of biomass with this reactor system unlocks the possibility of 10% (w/w) ethanol in the fermentation broth in future lignocellulose to ethanol plants.

Biomethane production from starch and lignocellulosic crops: a comparative review

“…Preliminary data are showing a moderate potential for raw switchgrass, at 0.125 m 3 CH 4 / kg VS. 45 Its high solid content (400 kg VS/ wet ton) places it at an estimated 650 m 3 CH 4 / ha, which is much lower than for the other crops, however there is a lot of room for improvement considering that this was obtained from less than 35% VS conversion. 46 In most of the aforementioned literature, there is no specii c pre-treatment of the crop prior to its anaerobic digestion, excepted particle size reduction (chopping, shredding, 51 Ensiling has been shown to have a positive impact most of the time, and may result in up to 31% more methane production from the crops. 23 h e particle size reduction had a dif erent ef ect on sugar and starch or cellulosic crops and lignocellulosic crops.…”

Partial Simultaneous Saccharification and Fermentation at High Solids Loadings of Alkaline-pretreated Miscanthus for Bioethanol Production

“…3b), corresponding to theoretical ethanol yields of 93.0 % and 90.9 %, respectively. This phenomenon appeared in many other studies, due to inefficient mixing and mass transfer with increased solids concentration (Jørgensen et al 2007;Han et al 2011).…”

“…Enzymatic saccharification or fermentation with high solids generally induces a lack of available water, high viscosity, and thereby an insufficient transfer of biomass and heat in reaction. Therefore, the rapid liquefaction of pretreated biomass is a key factor in determining fermentation productivity and yield (Jørgensen et al 2007). Thus, the impeller was characterized according to mixing behavior; the use of the plate-and-frame, doublecurved-blade impeller, and peg mixer was at first avoided because of limited power input and structure in the 5-L fermenter (Modenbach and Nokes 2012).…”

Improved Ethanol Production Based on High Solids Fed-Batch Simultaneous Saccharification and Fermentation with Alkali-Pretreated Sugarcane Bagasse

“…Moreover, high solids loading increased the concentrations of inhibitors such as organic acids (Fig. 2B) and other accumulated by-products (Jorgensen et al 2007). The produced acids may change the osmotic pressure of the yeast cells, and the sensitivity of the yeast to fermentation byproducts (Fig.…”