AbstractThe increasing cost and depletion of fossil-based energy combined with the problems of global warming is driving the development of bio-based energy products from plant biomass as renewable energy. The utilization of biofuel co- product (BCP) in new industrial applications should be investigated to increase the profitability of bio-based products and the bio-energy business. One such area of high-impact application is the stabilization of low quality roadbed soils with sulfur-free lignins found in BCPs. Recently, researchers are taking interest in investigating the viability and use of biofuel derived sulfur-free lignins for soil stabilization.This study aims to investigate the utilization of biofuel co-products (BCPs) containing lignin in pavement geomaterials stabilization. Laboratory tests were conducted to evaluate the effect of BCP addition on strength performance for a wide range of soils encountered in Iowa. Two different sulfur-free lignins were investigated: Co-product A is a liquid material with higher lignin content and co-product B is a powder material with lower lignin content.For all soil types, a significant increase in compressive strength was observed once 12% BCP B was added to pure soil. The compressive strength values were increase up to two times for Soil 2 (CL-ML) and four times for Soil 4 (ML). The results of these study indicated that the BCP has excellent potential for stabilizing low quality materials for use in road construction.