Lignin represents the most abundant natural source of aromatic scaffolds. The majority of lignin is obtained as byproduct from industrial pulping. However, since lignin is often burned after pulping for energy purposes, its real potential as renewable resource for the production of aromatic compounds or polymeric applications is not fully exploited. In this literature review, recent advancements in the field of lignin modification are addressed. In particular, methods for the insertion of different functional groups onto lignin (amines, epoxides, carboxylic acids, esters, multiple bonds and hydroxyl groups) are discussed, focusing on sustainability and safety of the employed procedures and on applications of the respective modifications. The E-factor was chosen as green metric for the evaluation of sustainability, for its clarity and ease of application to different methodologies, together with a careful evaluation of toxicity and hazardousness of the used substances. This review thus provides an overview on lignin modification and applications possibilities and, importantly, quantitatively compares all discussed literature procedures in terms of sustainability.

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从废物到资源：可持续木质素改性的进展

木质素是芳香支架最丰富的天然来源。大部分木质素是作为工业制浆的副产品获得的。然而，由于木质素在制浆后经常被燃烧以用于能源目的，因此其作为生产芳香族化合物或聚合物应用的可再生资源的真正潜力尚未得到充分开发。在这篇文献综述中，讨论了木质素改性领域的最新进展。特别是，讨论了在木质素上插入不同官能团（胺、环氧化物、羧酸、酯、多重键和羟基）的方法，重点关注所采用程序的可持续性和安全性以及相应改性的应用。 E-因子被选为评估可持续性的绿色指标，因为它的清晰度和易于应用于不同的方法，以及对所用物质的毒性和危险性的仔细评估。因此，本综述概述了木质素改性和应用的可能性，重要的是，在可持续性方面定量比较了所有讨论的文献程序。