Wood Chips Components Separation with a New Wet-Milling Process Compared to Chemical Depolymerization: A Technical, Economic, and Environmental Comparison

Abstract

This article evaluates two processes, wet milling and chemical depolymerization, for the end-of-life of wood waste in terms of environmental performance (ex ante life cycle assessment), energy balance, and economic analysis of the operating costs. Cellulose, hemicellulose, and lignin are essential components with numerous applications. The study provides valuable insights for industry stakeholders, policymakers, and researchers of the wet milling process (WMP), which is scarcely reported in the literature. The chemical depolymerization process (CDP) is discontinuous and more energy-intensive, while the WMP is a continuous reaction demanding milder conditions and shorter times. However, the milling process requires a pretreatment to reduce the wood chip size. Economic analysis shows that the CDP has lower operational costs when considering the average European electricity price in 2019. This is a result of the price differences between steam and electricity. For lower electricity prices such as in France or using utility-scale solar photovoltaics, the WMP has lower operational costs. The WMP also outperforms the CDP in most environmental indicators, such as global warming potential, particularly when using green electricity technologies.