SPECTROPHOTOMETRIC METHODS FOR QUALITY ASSESSMENT OF BIOFUEL MATERIALS DERIVED FROM OIL FLAX STEMS: IMPLICATIONS FOR SUSTAINABLE DEVELOPMENT

Abstract

The study is devoted to the development of a spectrophotometric methodology for evaluating biofuel materials produced from non-conditioned oil flax (Linum usitatissimum L.) stems. Solid biofuel briquettes with different ratios of flax biomass and sapropel binder (L70/S30, L50/S50, L100) and a control wood sample were investigated. Aqueous extracts of combustion residues were analyzed using spectrophotometry in the wavelength range of 200–1100 nm. The obtained transmission spectra demonstrated similar overall patterns for all samples, indicating comparable structural features of combustion residues. A pronounced minimum at a wavelength of 975 nm was identified for all investigated samples. This spectral feature is attributed to the second overtone of O–H stretching vibrations and reflects the presence of hydroxyl-containing compounds and bound water in the analyzed systems. Comparative analysis showed that the differences in transmission values between flax-based biofuels and the control wood sample do not exceed 3–4%, indicating a high degree of similarity in the chemical composition of their combustion residues. The use of sapropel as a binder does not significantly affect the overall spectral characteristics, although it increases absorption intensity due to higher mineral content. The results confirm the feasibility of using oil flax stem biomass for the production of solid biofuels and demonstrate that spectrophotometric analysis can be applied as a rapid diagnostic tool for assessing their quality and environmental safety.