Second-generation biofuel production from grassland biomass is getting more and more popular as a research topic. A zero-to-low waste production strategy is one of the core ideas in the technology design. Biogas production from lignocellulose is one of the promising components in technology development, which can solve the upcoming remaining lignocellulose problems. This study is looking into lignocellulose leftovers after sugar extraction as a substrate for anaerobic digestion enhancing the fermentation process with surfactant usage. Biomethane potential tests were used to test the remaining biomass. It has relatively high biomethane potential up to 378.31 mlCH4·gVS-1, but enzymatic hydrolyses leftovers show the substrate toxicity characteristics at a concentration higher than 2.5% from total volatile solids loaded. The biomethane formation inhibition process can be related to an increase in phenol concentration, ethic was measured using the colorimetric analyses method, although it is not the only factor that is leaving an influence on the fermentation process. The study shows biodegradable surface-active substance positive influence on the used substrate biomethane potential increasing it on average by 50%. There was no evidence found on the different positive effects for surfactants with different chemical structures. © 2021 Latvia University of Life Sciences and Technologies. All rights reserved.