Bioaugmentation as a strategy to improve the compost quality in the composting process of agro-industrial wastes

The most common way to inoculate composting piles in composting plants is using commercial inoculum which besides increasing production costs can also have its efficiency compromised given the peculiar characteristics of each type or combination of wastes. We aimed to evaluate the efficiency of an inoculum that can be produced in its composting plant using samples from the piles collected during the different phases of the process. Four piles of 525 kg each were conducted and inoculated once a week with 0, 10, 5, and 2.5 L of inoculum, respectively, during the thermophilic phase (38 days). We submitted the main control parameters of the process and some important final compost characteristics to the Multivariate Analysis tools which demonstrated preliminary but promising results of the inoculum usage advantages. FTIR analysis also demonstrated that the inoculum usage accelerates the humification process. After the thermophilic phase, the composts remained in the maturation phase and were sampled on days 0, 30, and 60. Only some chemical parameters (pH, EC, and soluble nitrogen) were affected by both, the dose and the maturation time. To evaluate the efficiency of the composts compared to a commercial substrate (CS), we also conducted an assay of seedling production (lettuce and tomato). All the characteristics of the obtained composts were better than the CS, excepted pH, and EC. For the tomato seedling which is less sensitive to EC than lettuce, the effect of the inoculum usage was more evident, considering the quality seedling index. (C) 2021 Elsevier B.V. All rights reserved.