Effect of the addition of the Bacillus sp., Paenibacillus sp. bacterial strains on the co-composting of green and food waste

Composting is an alternative for the recovery and recycling of green waste (GW) with the potential to generate a product of high agricultural value. However, composting is affected by the high content of slowly degradable lignocellulosic substances that prolong processing time and impact end-product quality. Adding food waste (FW) and bacterial inocula are strategies that can increase the degradation rates of green waste. This study determined the effect of adding a bacterial inocula composed of Bacillus sp. F3x3 and Paenibacillus sp F1A5 and co-substrates on the GW composting processes and end-product quality. Three treatments were evaluated: i) TGW: 100% GW (p/p) without bacterial inocula, ii) TI: 50% GW, 32.5% unprocessed FW (UPFW), 2.5% processed FW (PFW), 13% sawdust (SW) and 2% phosphoric rock (PR) with bacteria inocula during the cooling phase and iii) TNI: mixture 50% GW, 32.5% UPFW, 2.5% PFW, 13% SW and 2% PR without any bacterial inocula. Results showed that bacterial inocula with the co-substrates accelerated the degradation rate of organic matter (TIkG 0.14d(-1); TNIk(G): 0.1d(-1); TGWk(G): 0.1d(-1)), lignocellulose (TI: 31.7%; TNI:23.1%; TGW:15.5%) and increased germination indexes (TI:98.8%; TNI:86.03%; TGW:75.5%). Likewise, the respirometric index (RI) was lowered in TI (3.4 +/- 0.1 gCO(2) d-1) which indicates a high stability of the end-product. The addition of the bacterial inocula reduced the cooling phase duration by 63% and 20% for TGW and TNI, respectively. The end-product obtained from the TI treatment is considered suitable for use as a soil amendment.