Biomass, yield stress

Corn stover, a well-known example of lignocellulosic biomass, is a potential renewable feed for bioethanol production. Dilute sulfuric acid pretreatment removes hemicellulose and makes the cellulose more susceptible to bacterial digestion. The rheologic properties of corn stover pretreated in such a manner were studied. The Power Law parameters were sensitive to corn stover suspension concentration becoming more non-Newtonian with slope n, ranging from 0.92 to 0.05 between 5 and 30% solids. The Casson and the Power Law models described the experimental data with correlation coefficients ranging from 0.90 to 0.99 and 0.85 to 0.99, respectively. The yield stress predicted by direct data extrapolation and by the Herschel-Bulkley model was similar for each concentration of corn stover tested. 

FIGURE 4.2 Yield stress evolution through the course of enzymatic hydrolysis of pretreated com stover, starting at 20% insoluble solids content and varying enzyme loading (mass enzyme/mass cellulose), as afunction of biomass conversion. The predictive model is described by Roche et al. (2009a). 

Roche CM, Dibble CJ, Knutsen JS, Stickel JJ, Liberatore MW. (2009a). Particle concentration and yield stress of biomass slurries during enzymatic hydrolysis at high-sohds loadings. Biotechnol Bioeng, 104(2), 290-300. 

Drought is perhaps one of the most complex examples to choose but it illustrates well the possibilities of, and pitfalls to, progress. Drought affects almost every facet of plant function and we are faced with the paradox that yield and evapotranspiration are intimately linked. In general, increases in yield when water supply is limiting are likely to result from characteristics which increase the available water supply, increase water use efficiency or increase biomass allocation to the economically useful plant parts (Pass-ioura, 1986). Additionally, features which maintain cell viability and protect metabolism in water-stressed tissue and allow rapid recovery after dry periods will contribute yield under some circumstances. 

Conde, J.R., Tonorio, J.L., Rodrfguez-Maribona, B., and Ayerbe, L, Tuber yield of Jerusalem artichoke (Helianthus tuberosus L.) in relation to water stress, Biomass Bioenergy, 1, 137-142, 1991. 

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