The environmental-friendly and sustainable solutions for fully utilizing the tobacco wastes

Tobacco is one of the most important economic crops worldwide for mainly producing cigarettes, accompanying with millions of tons of tobacco wastes in agricultural fields every year. Owing to the increasing concerns for human health and agricultural ecology, tobacco wastes containing the bioactive compounds such as nicotine are commonly recognized to be hazardous and urgently required to be handled carefully. Therefore, the full utilization of tobacco wastes seems to be an ideal goal for not only avoiding their negative effects but also providing the sustainable resources. The microwave-assisted hydrothermal treatment is proposed to be the first solution for extracting the carbohydrate from the wasted leaves and stalks. A high efficiency more than 90% and solid content higher than 50 g/L could be achieved at 120-130 ^oC in only 20 min. The preliminary economic analysis shows 10 times benefit of the crude carbohydrate output compared with the consumption of energy input. Specifically, the carbohydrate could be also used as the coating material for promoting the germination of wheat seeds. Then pyrolysis is proposed to be the second solution for transforming the residual biomass solid into high-value aromatic compounds and by-products biochar. A relatively high level of phenols and even some benzenes that are difficult to generate could be obtained after the hydrothermal treatment of tobacco wastes. More interestingly, the introduction of seawater would result in the preferred production of benzenes and phenols in all identified compounds, which may be attributed to the facilitation of chloride element. These products should be separated by distillation technology for further industrial usage. The by-product biochar could be also employed in adsorbing environmental contaminant and other applications. These solutions may pave the way for sustainable agricultural development.