(270c) Qualitative and Quantitative Characterization of Biomass Using FT-IR Microspectroscopy and X-Ray Diffraction

The ability to quickly and accurately determine key quality characteristics of biomass prior to processing in a thermochemical biorefinery is critical in determining the types of products, and co-products, which will be produced in the conversion process. Proximate (moisture, ash, fixed carbon, volatiles) and ultimate (C, H, N, O, S) analyses and chemical composition (e.g., cellulose, hemicellulose, lignin) result in quality parameters of importance to thermochemical conversions. For example, oxygen content causes low heating value and corrosiveness, while cellulose, hemicellulose, and lignin each convert to unique products during thermochemical conversion for both pyrolysis and hydrothermal liquefaction. Rapid screening models based upon FT-NIR and FT-IR spectroscopy are being developed to rapidly predict fixed C, H, N, O, volatiles, and total ash of select feedstocks to avoid the long analysis times and high costs of current methods.

In addition, FT-IR microscopy offers the potential to analyze biomass for proximate, ultimate, and chemical composition at spatial scales as small as 5 µm. ¹ In this work, models based upon FT-NIR and FT-IR are developed and validated to predict fixed C, H, N, O, volatiles, and total ash in switchgrass samples, as well as glucan, xylan, and lignin for a set of mixed feedstock types. These models are then applied to FT-IR microscopy data to predict the local variability of specific properties at scales of 100 µm or smaller. A focal plane array (FPA) detector with a pixel resolution less than 5 µm is used to rapidly create chemical composition maps of select regions of the sample surface. This technique promises new methods to investigate the chemical composition of biomass materials at the cell and tissue level as well as track how preprocessing operations impact those properties at the microscale.

Finally, biomass ash structure has been probed for various types of woody biomass, at various stages of pyrolytic conversion, using x-ray diffraction (XRD). Investigation of the biomass ash structure at various stages of pyrolysis allows for determination of the structural changes that could take place during processing at a thermochemical biorefinery. Knowledge of the inorganic content of the biomass will enhance the ability to determine useful co-products from what is now considered waste material, such as the use of biomass ash in the production of cement based materials.²         

1              Allison, G. G. et al. Measurement of key compositional parameters in two species of energy grass by Fourier transform infrared spectroscopy. Bioresource technology 100, 6428-6433 (2009).

2              Rajamma, R. et al. Characterisation and use of biomass fly ash in cement-based materials. Journal of hazardous materials 172, 1049-1060 (2009).