Innovative approaches for volatile fatty acids recovery from wastes

有机废物产生量的增加和对其最终处置的监管要求在整个加拿大都是严重的经济和环境问题。有机废物的填埋对环境和公众健康构成重大风险。加拿大各地的许多市政当局已经制定了积极的废物转移目标，以减少当前废物管理做法的环境足迹。因此，人们越来越重视开发先进和可靠的生物能源技术和废物增值资源，这可以提供废物转移和创收的双重好处。厌氧消化是迄今为止应用最广泛的将废物转化为富含甲烷的沼气的生物能源技术。厌氧消化过程中产生的沼气可以转化为热能和电能。厌氧消化过程依赖于复杂有机物的微生物分解。在第一阶段，有机物被降解为各种挥发性有机酸，这一阶段称为产酸发酵阶段。然后，这些有机酸在第二阶段被转化为甲烷和二氧化碳。近年来，在发酵阶段后终止该过程并回收挥发性有机酸的可能性受到了特别的关注。这些挥发性有机酸可用作各种高附加值产品的原料，包括生物塑料、生物能源、液态碳氢化合物、用于生产生物柴油的脂类、用于生物营养去除的电子供体。目前，挥发性有机酸是通过化学(羧化和氧化)和生物过程从化石燃料和纯糖中生产出来的。拟议的研究计划集中在开发一种新型的产酸发酵系统，该系统集成了真空和水热技术。真空技术的应用可以提供多方面的好处，如最大限度地提高工艺稳定性，通过连续去除发酵产物来获得高质量的挥发性有机酸。此外，水热过程提供了一个极好的机会，通过增溶来提高原料的生物转化潜力。该项目产生的先进知识将加强加拿大在开发尖端可再生能源和资源收获技术以实现低碳未来方面的持续努力。

The increased organic waste generation and the requirements regulating their ultimate disposal are serious economic and environmental concerns across Canada. Landfilling of organic wastes poses significant risks to the environment and public health. Many municipalities across Canada have already set aggressive waste diversion goals to reduce the environmental footprint of current waste management practices. Thus, there has been growing attention to developing advanced and reliable technologies for bioenergy and value-added resources from waste, which can provide dual benefits of waste diversion and revenue generation. Anaerobic digestion is by far the most widely implemented waste-to-bioenergy technology for converting waste to methane-rich biogas. The biogas produced during anaerobic digestion can be converted into heat and electricity. The process of anaerobic digestion relies on the microbial breakdown of complex organic matter. Organic matter is degraded to various volatile organic acids in the first stage, known as the acidogenic fermentation stage. Then, these organic acids are converted to methane and carbon dioxide in the second stage. In recent years, the possibilities of terminating the process after the fermentation stage and recovering volatile organic acids have received particular attention. These volatile organic acids can be used as a feedstock for various high value-added products, including bioplastics, bioenergy, liquid hydrocarbons, lipids for biodiesel production, electron donors for biological nutrient removal. Currently, volatile organic acids are commercially produced through chemical (carboxylation and oxidation) and biological processes from fossil fuels and pure sugars. The proposed research program focuses on developing a novel acidogenic fermentation system integrating vacuum and hydrothermal technologies. The application of vacuum technology can provide multiple benefits, such as maximizing the process stability, high-grade volatile organic acids with higher yield by continuously removing fermentation products. Moreover, the hydrothermal process provides an excellent opportunity to boost the bioconversion potential of feedstock via solubilization. The advanced knowledge generated from this project will strengthen the continuous efforts of Canada in developing cutting-edge renewable energy and resource harvesting technologies to achieve a low-carbon future.