Respirometric index and biogas potential of different foods and agricultural discarded biomass

The biological stability of biomass is an important parameter for treatment plant design, process control or compost use. Measuring the biological reactivity of waste with the help of indicators such as respirometric indexes (RI) becomes an important tool to prevent the significant environmental impact of biodegradable wastes in accordance with European legislation. The aim of this paper is to show the importance of the RI technique as a tool to establish further uses of biomass such as fertilizer or biogas. The respirometric process length for different types of biomass (grape marc, apple pomace and olive pomace) was quantified. Higher moisture content seemed to favor the biological activity during the respirometric experiments and shorten the length of the process. The duration of olive pomace respirometry did not exceed 3 days, while the respirometric activity of apple scraps the lasted approximately 2 days. The highest RI values were encountered for the apple pomace, 4888 mgO2·kgVS−1·h−1. The majority of the discarded biomasses are categorized in the third class of stability materials in the course of degradation. This technique is important to detect the biodegradability of substrates, as well as to gain insight into the quantity and generation rate of biogas produced, information that is important from an engineering management perspective.