Production of green adhesives from sustainable proteins derived from municipal wastewater treatment plant sludges and potential enhancements from soy protein amending.

In recent years, wood-based composites bonded with adhesives of conventional resins containing formaldehyde have raised concerns as corporations are becoming environmentally conscious and fossil fuels are in high demand. A new generation of adhesives are being developed from natural renewable biomass resources with considerable protein concentrations. In this study, wastewater treatment plant-activated sludge and biosolids are formulated into bio-adhesives via protein denaturation. Three urban-based biomass sources, consisting of waste-activated sludge, biosolids, and dewatered biosolids, were used to produce adhesives via alkaline denaturation of the present proteins. The mechanical properties of the produced adhesive were evaluated via lap shear testing. A fiberboard material was also generated using the formulated adhesives to analyze the practical application of the adhesives as binding materials. It was found that the waste adhesives possess significant bonding strength in relation to single lap shear testing, for each of the waste sludge feedstocks resulting in adhesive strengths nearing 700-1200 kPa which signifies potential as an applicable protein-based adhesive. Through small soy additions, the waste sludge adhesive formulations neared 2500 kPa detailing a lessened environmental burden of crops utilized for protein-based adhesive formulations. The prepared fiberboard also contained flexural mechanical properties in comparison to soy-based formulations, resulting in an average modulus of elasticity of 187 MPa, an average modulus of rupture of 5.6 MPa, and an average internal bond strength of 39.6 kPa. Although strength was sensitive to denaturant concentration as well as sample location, the resultant fiberboard has the potential for further application.