BackgroundBioethanol can be produced from sugar-rich, starch-rich (first generation; 1G) or lignocellulosic (second generation; 2G) raw materials. Integration of 2G ethanol with 1G could facilitate the introduction of the 2G technology. The capital cost per ton of fuel produced would be diminished and better utilization of the biomass can be achieved. It would, furthermore, decrease the energy demand of 2G ethanol production and also provide both 1G and 2G plants with heat and electricity. In the current study, steam-pretreated wheat straw (SPWS) was mixed with presaccharified wheat meal (PWM) and converted to ethanol in simultaneous saccharification and fermentation (SSF).ResultsBoth the ethanol concentration and the ethanol yield increased with increasing amounts of PWM in mixtures with SPWS. The maximum ethanol yield (99% of the theoretical yield, based on the available C6 sugars) was obtained with a mixture of SPWS containing 2.5% water-insoluble solids (WIS) and PWM containing 2.5% WIS, resulting in an ethanol concentration of 56.5 g/L. This yield was higher than those obtained with SSF of either SPWS (68%) or PWM alone (91%).ConclusionsMixing wheat straw with wheat meal would be beneficial for both 1G and 2G ethanol production. However, increasing the proportion of WIS as wheat straw and the possibility of consuming the xylose fraction with a pentose-fermenting yeast should be further investigated.

SUMMARY Background

In this work, Norway spruce stem wood, stump and bark were torrefied in a bench scale tubular reactor at 225, 275 and 300 °C with two residence times (30 and 60 minutes). The effects of torrefaction process conditions and feedstock type on the physical properties, chemical composition and grindability of torrefied biomass samples were investigated. Furthermore, information was also obtained by conducting scanning electron microscopy (SEM) analysis to gain insights into changes of microstructure and morphology of biomass samples upon torrefaction at different conditions. Higher heating value and fixed carbon content of torrefied biomass samples increased with increased torrefaction severity. Torrefaction caused decrease of hydrogen-to-carbon (H/C) and oxygen-tocarbon (O/C) atomic ratios with increasing temperature and residence time, which results in increase of energy density of torrefied biomass samples. Chemical compositions of torrefied biomass samples considerably changed with increase of torrefaction severity.For the stem wood and stump, the relative hemicellulose content significantly decreased from 42.3% and 29.8% to less than 1% after torrefaction at 300 °C for 60 minutes, *Manuscript Click here to view linked References respectively. The hemicellulose content of untreated bark decreased from 27.5% to 0.14% after torrefaction at the same conditions. Additionally, the cellulose content of the torrefied bark drastically decreased already to half the initial value at a torrefaction temperature of 275 °C, with only trace amounts left in the 300 °C torrefied products. The grindability of stem wood and stump were substantially improved after torrefaction treatment. The energy required for grinding stem wood and stump torrefied at 225 °C decreased to respectively 87 and 70 kwh/ton, which are less than 50% of the energy needed for grinding the untreated samples. For raw bark, much less grinding energy is required compared to those for raw stem wood and stump, and torrefaction has minor effects on the grindability of bark. The ground torrefied biomass samples have much smaller particles than those of the untreated ones. The improvement of grindability of torrefied biomass samples can be coupled to the weakening of the fibre bonds indicated by change in chemical compositions. SEM analysis results show that particles from ground torrefied samples lose their fibrous structure with decrease of length-to-diameter ratios, compared to untreated biomass samples. It explains the shift in particle size distribution curves towards smaller particles as obtained from the sieving tests.

L+SScF 232 ABSTRACT 1 A techno-economic analysis was conducted for a simplified lignocellulosic ethanol 2 production process developed and proven by the University of Florida at laboratory, pilot, and 3 demonstration scales. Data obtained from all three scales of development were used with 4 Aspen Plus to create models for an experimentally-proven base-case and 5 hypothetical 5 scenarios. The model input parameters that differed among the hypothetical scenarios were 6 time of L+SScF, enzyme loading, enzymatic conversion, solids loading, and overall process 7 yield. The minimum ethanol selling price (MESP) varied between 50.38 and 62.72 US 8 cents/L. The feedstock and the capital cost were the main contributors to the production cost, 9 comprising between 23-28% and 40-49% of the MESP, respectively. A sensitivity analysis 10 showed that overall ethanol yield had the greatest effect on the MESP. These findings suggest 11 that future efforts to increase the economic feasibility of a cellulosic ethanol process should 12 focus on optimization for highest ethanol yield.

On-site cellulase enzyme fermentation in a softwood-to-ethanol process, based on SO2-catalysed steam pretreatment followed by simultaneous saccharification and fermentation, was investigated from a techno-economic aspect using Aspen Plus© and Aspen Icarus Process Evaluator© softwares. The effect of varying the carbon source of enzyme fermentation, at constant protein and mycelium yields, was monitored through the whole process. Enzyme production step decreased the overall ethanol yield (270 L/dry tonne of raw material in the case of purchased enzymes) by 5–16 L/tonne. Capital cost was found to be the main cost contributor to enzyme fermentation, constituting to 60–78% of the enzyme production cost, which was in the range of 0.42–0.53 SEK/L ethanol. The lowest minimum ethanol selling prices (4.71 and 4.82 SEK/L) were obtained in those scenarios, where pretreated liquid fraction supplemented with molasses was used as carbon source. In some scenarios, on-site enzyme fermentation was found to be a feasible alternative.