AbstractThe acid hydrolysis of lignocellulosic material (LM) is one of the most widely studied and important subprocess in the LM biorefinery. After acid hydrolysis, LM can be converted to various biofuels, biochemicals, and biomaterials through chemical or biochemical methods. However, conventional LM acid hydrolysis is not regarded as a cost-effective and environmentally-friendly process because it has drawbacks such as difficulties in acid recovery, equipment corrosion, and chemical wastes from the neutralization of acid and the removal of LM degradation products. Use of ionic liquids and solid acids during LM hydrolysis has provided potential technical tools to overcome these problems and has given new life to the LM acid hydrolysis process in the biorefinery. This editorial will discuss the role of the LM acid hydrolysis process in the LM biorefinery, provide an analysis of the conventional LM acid hydrolysis process, and briefly discuss new developments in the LM acid process.