Hydrothermal carbonization: Sustainable pathways for waste-to-energy conversion and biocoal production

Hydrothermal carbonization (HTC) technology emerges as a sustainable method to convert wet biomass, including food waste and municipal solid waste into high-energy dense biocoal. This process, conducted at temperatures ranging from 180 to 260°C and pressures of 10–50 bar, effectively transforms the organic material in wet biomass into solid, liquid, and gaseous outputs. The solid product, biocoal, possesses a high carbon concentration and heating values on par with lignite coal, presenting a cleaner alternative to traditional fossil fuels. Despite operational commercial-scale HTC facilities globally, further adoption across various feedstocks can improve waste management and energy production. The process can achieve energy yields up to 80%, particularly at temperatures favoring the generation of secondary char with higher heating values. HTC not only aids in reducing greenhouse gas emissions through carbon sequestration in solid waste but also promotes environmental sustainability by yielding nutrient-rich by-products for agriculture. As a versatile and energy-efficient solution, HTC technology is a pivotal innovation in waste-to-energy conversion, addressing the imperative for sustainable waste management. Other supplementary benefits are presented; they include higher employability, reduction of a nation's reliance on imported energy, and better waste control, therefore considering all pillars of sustainability. Future research should focus on optimizing process efficiency and exploring the broader applicability of HTC to various biomass feedstocks, enhancing its role in the global pursuit of sustainable energy solutions.