Comparative Analysis of Pyrolysis Products from a Variety of Herbaceous Canadian Crop Residues

Interest in recovering and valorizing agricultural biomass residues has increased in recent years in response to emerging economic opportunities and the potential for more sustainable use of renewable and nonrenewable resources. Agricultural crop residues are a major source of lignocellulose, with considerable potential for use as a renewable resource and lignin’s polyphenolic structure makes it a potential source of high value products such as fine chemicals. To achieve this requires characterization of the chemical composition of biomass and in this study we determined the lignin and structural carbohydrate content of various sources of agricultural biomass such as flax shives, wheat straw, wheat bran, triticale straw, triticale bran, barley straw, oat straw and mustard straw along with selected lignin samples that were isolated using an environmentally benign ionic liquid (1-ethyl-3-methylimidazolium acetate ([emim]Ac)). Pyrolysis-GC/MS was used to determine the thermal degradation products of the select biomass and lignin samples. The main phenolic compounds obtained from pyrolysis included catechol, guaiacol, 4-vinyl guaiacol, eugenol, vanillin and isoeugenol. We quantified the lignin content of the select biomass samples directly from pyrolysis-GC/MS measurements. Lignin values obtained from pyrolysis-GC/MS (Py-lignin) were compared against conventional acid insoluble lignin values and good correlation was found between lignin values obtained from pyrolysis-GC/MS and acid insoluble lignin content within species (R =0.98). Also a good correlation was established between species (R =0.97). This work 2 2 provides information that demonstrates that pyrolysis is a depolymerization technology capable of producing high value phenolic molecules from crop residues. This work also provides information demonstrating that analytical pyrolysis can be used to assess the lignin content in monocotyledonous and dicotyledonous herbaceous crop residues.