The influence of pyroligneous acid on fermentation parameters, CO2 production and bacterial community of rice straw and stylo silage

CO2 is known as a primary greenhouse gas and the main cause of global warming. It could be produced during ensiling, a method of moist forage preservation applied all over the world, because of respiration of plant cells and microorganisms. However, limited information about CO2 emission and mitigation during ensiling is available. Pyroligneous acid, a by-product of plant biomass pyrolysis, has strong antibacterial capacity. To investigate the CO2 production and the influence of pyroligneous acid, fresh stylo and rice straw were ensiled with or without 1% and 2% pyroligneous acid. The dynamics of fermentation characteristics, CO2 production and bacterial community during ensiling were analyzed. Results indicated that pyroligneous acid increased (P < 0.05) lactic acid content and decreased (P < 0.05) weight losses, pH value, ammonia-N, butyric acid contents and coliform bacteria number. It also increased the relative abundance of Lactobacillus and decreased that of undesirable bacteria like Enterobacter and Lachnoclostridium. The addition of pyrolytic acids reduced gas production, especially CO2 production. It increased the relative abundance of CO2 producing genera and increased that of genera with potential for CO2 fixation. In conclusion, the fermentation quality of these two silages was improved by adding pyroligneous acid. During ensiling, CO2 production correlated with bacterial community. Using pyroligneous acid could alter bacterial community to reduce CO2 production during ensiling. Given the huge production and demand for silage around the world, the application of pyroligneous acid could be an effective way to mitigate global warming by greenhouse gas emission.