An Exploratory Study on the Use of Biobinder Derived from Brewer's Spent Grains as an Asphalt Modifier

The production of asphalt concrete depends on the use of nonrenewable resources, such as asphalt binder and crushed rocks. Nowadays, technologies exist to convert biomass into biofuels and other by-products, which are an alternative to traditional sources of energy. The by-products of biomass conversion are similar to those of petroleum distillation. Several researchers have investigated the use of bio-oils from biomass as asphalt additives, but the potential use of brewery waste has not been considered. In this project, spent grains from a local brewery were converted into bio-oil using an auger reactor. The water in the bio-oil was removed, and the biobinder was analyzed. It was found that the biobinder derived from brewer's spent grain has an elemental composition similar to other biomass-derived biobinders. Fourier transform infrared (FTIR) spectroscopy identified multiple polar functional groups in the biobinder, including high nitrogen content (4.6% by weight). Also, thermogravimetric analysis and gas chromatography showed a higher thermal degradation rate of the biobinder and loss of volatile components. The biobinder was used to create six blends with 5%, 8%, 10%, 15%, 20%, and 25% replacement of asphalt. The performance of each of the six blends was compared with the performance of control unmodified samples. The modified binder characterization indicated that the biobinder makes the material more susceptible to permanent deformation at high temperatures, and it showed higher aging of the short-term aged residue. However, the biobinder seems to improve relaxation properties at low temperatures, which could be attributed to its high nitrogen content. The findings of this preliminary study suggest that production and use of brewer's spent grain biobinder are feasible and could be considered a potential feedstock for further development of asphalt biomodifiers.