The organic fraction of municipal solid waste (OFMSW), mainly composed of lignocellulosic polymers, is extremely complex. Therefore, it is necessary to apply pretreatments to remove the lignin content and decrease the cellulose crystallinity in order to use the OFMSW for gas biofuels production in the context of biorefineries from waste. This work focused on critically reviewing the conventional pretreatments applied to OFMSW, with the goal of improving the H 2 production, as well as other biofuels in modern biorefineries. There are a wide variety of pretreatments that have successfully been used, mainly alkaline, milling and dilute acid. In addition, some research has focused on the recovery and reutilization of the alkali, acid or solvents after the pretreatment, to be incorporated into new cycles of production, minimizing the environmental impacts. Moreover, it would be necessary to incorporate analytical tools, in order to determine the sustainability of the biorefinery project. It is concluded that waste pretreatments could significantly contribute to increased yields of biogas fuels in organic waste-based biorefineries. Therefore, establishing preliminary stages for conditioning biomass or wastes is essential to improve the degradation of wastes and bio-product generation. 938 www.soci.org L Romero-Cedillo et al. db dry basis wb wet basis wrm wet reactor mass J Chem Technol Biotechnol 2017; 92: 937-958 /jctb , [56.76 j , 2.53 k ] 104 J Chem Technol Biotechnol 2017; 92: 937-958 Steam explosion Steam explosion, also known as hydrothermal, promotes the formation of soluble lignin compounds, such as HMF, due to high temperatures that stimulate the breakdown of sugars. 121 In this process, HMF and other inhibitor compounds are generated, such as furans from pentoses and HMF from hexoses. 122 Interestingly, HMF can be finally degraded into levulinic and formic acids. In contrast, even when a pretreatment did not necessarily remove lignin, it was hypothesized that high temperatures had a significant J Chem Technol Biotechnol 2017; 92: 937-958 /jctb J Chem Technol Biotechnol 2017; 92: 937-958
