Inoculação de microrganismos como aceleradores no processo de compostagem de resíduos sólidos agroindustriais

Brazil is considered one of the countries with the highest potential of agricultural production in the world, however, it is the fourth largest consumer of nutrients for formulating mineral fertilizers in the world. At the same time, the projections point to the increase in demand for food and the growth of the agroindustrial sector, as consequence of which there is also an increase in the generation of waste and the pressure on natural resources. Composting emerges as an interesting strategy for the treatment and recovery of these wastes, because it allows them to be transformed into organic compost capable of improving soil quality and reducing the use of mineral fertilizers, however it is a time-consuming process, which can take up to 180 days, depending on the raw material used and operational control. Since inoculation of microorganisms may intensify the degradation process, the present study aimed to produce an inoculum of microorganisms and to evaluate its efficiency in accelerating the process composting of organic agroindustrial solid wastes. The solid wastes used were sludges from the wastwater treatment plants from industry potato and corn chips and dairy, bovine ruminal residue and coffee silverskin. The research was developed at the Biocomp composting plant located in the municipality of Papagaios, MG, from February to August 2017. The inoculum of microorganisms was prepared based on the method of capture of effective microorganisms (EM). Therefore, as substrate for catching the microorganisms was used 3 kg of rice cooked in unsalted water and left for 10 days in the forest near the composting yard, then transferred to an aerobic reactor mounted in a water tank of 3000 liters with a recirculation system with pump. As culture medium for the microorganisms was used sugar cane molasses powder and organic foliar fluid fertilizer. In the mounting procedure of the compost heap, the initial mixture of agroindustrial residues had a C/N 19 ratio and a moisture content of 66.8%. Two treatments with 5 replicates were used, being treatment A without addition of inoculum of microorganisms and treatment B with addition of inoculum of microorganisms. During the composting process the physical-chemical parameters were monitored: temperature, humidity, pH, electrical conductivity, total nitrogen, total organic carbon and C / N ratio. To confirm the maturity of the organic compounds germination tests were performed with lettuce (Lactuta sativa). The collected data were submitted to non-parametric statistical tests that allowed to compare the median values of the treatments at the level of 5% of significance. A multivariate linear regression with robust standard errors was used to verify the effect of composting days and treatment type about temperature. It was verified that the inoculum of microorganisms promoted a greater biological activity to the composting process increasing the temperature and the pH, with faster reduction of the temperature. For the other parameters observed, there was no significant statistical difference between treatments, indicating that treatment B produced organic compound with similar qualities to treatment A, but with 46% less time. The germination index (GI)> 80% indicated the absence of phytotoxic substances that inhibit the germination and growth of the plants at 65 days of composting.