Prediction of the biomass to fuel conversion by NIR

Lignocellulosic biomass has long been recognized as a potential sustainable source of mixed sugars for fermentation to biofuels, however in order to achieve sustainable energy production, it will be necessary to overcome the chemical and structural properties that have evolved in biomass to prevent its disassembly also known as "biomass recalcitrance." [1]. Equally important is the ability to predict the biomass to fuel conversion. There are many different potential uses of wheat straw from soil incorporation, animal feed and bioenergy. For most of these purposes degradability and ash content are important determinants of quality. Degradability of straw is of importance in relation with the fermentation process for bioethanol production whereas the ash content is of importance for its suitability for incineration. Therefore, a fast method for assessment of straw quality could be very useful to determine the price and help choosing between different applications. In this study, the ability of near infrared (NIR) spectroscopy to predict the degradability of different cultivars of wheat straw grown at nine different sites is investigated [2]
NIR spectroscopy has proven useful for characterising straw characteristics and quality in several connections. Bruun et al. [2] successfully predicted the results of an assay developed to determine digestibility in ruminants. However, caution should be exercised when developing predictive models of digestibility based on NIR spectra to make sure that the models are transferable. In the interpretation of the calibrations, generally published on advanced biofuels, it is not possible to distinguish the ethanol potential of total sugars from the potential of the monomeric sugars (C6, glucose from glucan in cellulose and C5, xylose from xylan in the hemicelluloses). Since there is yet no commercial ethanol production from C5 sugars, a more refined interpretation of the calibration is needed for the true estimation of potentials of these interrelated variables. Furthermore, the possible discovery of any information in the reference method (chemical bonds in the NIRspectra) uniquely related to the predictions of either of the specific monomers will contribute new knowledge to the topic of biomass conversion. In this study, we are comparing wheat straw digestibility in terms of released glucose and xylose, which are highly correlated. Advanced chemometrics is used to isolate the effect of each carbon source in order to develop a more reliable, interpretable and transferable prediction model.

[1] ME:Himmel, SY Ding, DK Johnson, WS Adney, MR Nimlos, JW Brady, TD Foust, D Thomas D. Biomass recalcitrance: Engineering plants and enzymes for biofuels production, Science (2007), 315, 804-807
[2] S. Bruun, J.W. Jensen, J. Magid, J. Lindedam & S.B. Engelsen, Prediction of the degradability and ash content of wheat straw from different cultivars using near infrared spectroscopy, Industrial Crops and Products (2010), 31(2), 321-326.