This study clearly demonstrates the feasibility of using less expensive crude glycerol to grow R. arrhizus and produce fumaric acid. It was found that crude glycerol was more suitable than glucose for R. arrhizus forming smaller pellet. By the co-fermentation of crude glycerol and glucose, fumaric acid production (22.81 g/L) and glycerol consumption were both significantly enhanced, and the production cost of fumaric acid was reduced by approximately 14% compared to glucose fermentation. Therefore, the co-fermentation strategy proposes a cost-effective way for fumaric acid production, while helping to solve the problem of waste glycerol disposal.