Determination of chemical oxygen demand of agricultural wastes by combining acid hydrolysis and commercial COD kit analysis

Chemical oxygen demand (COD) is an essential parameter in waste management, particularly for monitoring bioprocess such as anaerobic digestion. Indeed, chemical oxygen demand (COD) is a key parameter that can prove useful for the evaluation of waste biodegradability and to evaluate mass and energetic balances of the overall process. In this study, an adapted method to determine the COD of solid agricultural wastes was developed. This method combined a double acid hydrolysis of the solid waste materials followed by commercial COD tubes analysis. This method was compared to direct sampling after a standard dilution (3.5 g TS.L^-1) and analysis in commercial COD tubes. The method developed in this study allowed the COD of nine agricultural wastes to be accurately predicted, with an absolute error of 7% compared to the theoretical COD. In comparison, the method with only a prior water dilution resulted in higher absolute errors of 36% and 31% when sampling was performed with pipette tips and cut pipette tips, respectively.