A transition from a fossil-based to a bio-based economy is a major objective for the industry to reduce greenhouse gas emissions. Lignocellulosic biomass is of particular interest as a plant-based feedstock for the production of biofuels, biochemicals and biomaterials. However, current lignocellulosic feedstock suffers from a relatively low processing efficiency, mainly because of the presence of the recalcitrant lignin polymer. To overcome this problem, biomass crops can be engineered to make less lignin. However, lignin-modified plants that have the largest reduction in lignin content and, hence, the highest improvement in processing efficiency, typically suffer from a biomass penalty. CINNAMOYL-CoA REDUCTASE (CCR) is an enzyme involved in lignin biosynthesis. Plants mutated in the CCR gene have strongly reduced lignin levels and, consequently, a very high saccharification efficiency, but they produce less biomass. We recently discovered that mutation of the complete UDP glycosyltransferase (UGT) 72E gene family in CCR-deficient Arabidopsis partially restored the lignin levels and fully restored the biomass. To explore the valorization potential of this finding, we will investigate (i) whether the observed effects in Arabidopsis can be translated to poplar, (ii) whether mutation of the UGT72E gene family also restores the growth of other low-lignin mutants, and (iii) what is the molecular cause of the observed biomass recovery.