The depletion of fossil fuels, which are the primary source of energy on a global scale, will pose a grave threat to energy security and the environment in order to satisfy ever-increasing demand (Ali et al., 2024; Jiao et al., 2024a). In addition, there has been a global transition in focus from short-term economic development to sustainable economic expansion (Ali et al., 2022a; Jiao et al., 2024b). Environmental pollution is an additional issue of concern, given that the combustion of fossil fuels generates toxic pollutants (mercury, polycyclic hydrocarbons, and volatile compounds) and greenhouse gases (GHGs), which contribute to global warming and have numerous detrimental impacts on human health (Ali et al., 2022b, Ali et al., 2022c; Madadi et al., 2023a, Madadi et al., 2023b; Priya et al., 2023). Finding alternative energy sources that are renewable, sustainable, and environmentally favorable is necessary to meet future energy demands in light of the numerous obstacles that must be overcome. To reduce environmental pollution, attention can be directed towards the advancement of process technologies that utilize waste biomass as substrates (Ali et al., 2021a, Ali et al., 2022b; Mastropetros et al., 2022; Sun et al., 2024). Life–cycle assessment (LCA) refers to the systematic collection and evaluation of data regarding the inputs, outputs, and potential environmental impacts of a process or product system over its complete life cycle (Nwodo and Anumba, 2019). LCA is a standardized global process utilized to calculate all relevant GHG emissions and resource consumption. One of the principle factors behind the energy transition is the reduction of GHG emissions (Shobande et al., 2024).

Bioenergy is an environmentally sustainable and economically viable solution that satisfies the current development landscape by harnessing the power of replenishable organic matter, known as biomass (Madadi et al., 2023a, Madadi et al., 2023b; Zakoura et al., 2022). It provides numerous benefits, including the mitigation of GHG emissions. The key factors motivating the production of bioenergy using biorefineries as viable alternatives to fossil fuels are the depletion of non-renewable fuel resources, increasing energy use, and the significant environmental impact caused by pollution (Ali et al., 2023a; Danso et al., 2022; Jiao et al., 2024a). From this standpoint, several viable and sustainable biorefineries have been constructed, showcasing notable advancements in using natural biomass as a renewable source for hydrogen (H2) production (Ahmed et al., 2022; Jiao et al., 2024a). H2 has the capability to produce electricity through the utilization of carbon-neutral biomass and renewable energy sources such as solar and wind power (Koivunen et al., 2023).

Biohydrogen (BioH2) is regarded as one of the most energy-efficient and environmentally friendly biofuels (Sahrin et al., 2022). It can be produced through a range of technological processes, including dark fermentation, photofermentation, and thermochemical reactions (pyrolysis and gasification) of biomass (Cheng et al., 2019; Chong et al., 2022a, Chong et al., 2022b). Thermochemical conversion techniques, including pyrolysis, incineration, and gasification, are frequently used to recover energy from waste at high temperatures. Pyrolysis refers to the process by which substances decompose at elevated temperatures into syngas, biofuels, and biochar while oxygen is absent (Amenaghawon et al., 2021). Gasification is the conversion of waste into syngas (AlNouss et al., 2020). Incineration involves the oxidation of the waste material, resulting in a highly exothermic reaction that generates heat, flue gas, and ash (Thabit et al., 2022). Although the application of chars yields several advantageous results and is consistent with the tenets of a circular economy, contemporary research has also identified adverse consequences associated with their use (Ali et al., 2022b, Ali et al., 2023a, Ali et al., 2024). The primary issues revolve around the possibility of self-heating in the processed biomass and the limitations imposed by the substantial ash content when biomass is valorized to produce char or tar (Bahadar et al., 2022; Chen et al., 2021a, Chen et al., 2021b).

Biohydrogenation is a prospective strategy for meeting future energy needs due to its sustainability, regenerative capacity, cost-effectiveness, and devoid of any detrimental impact on the environment in comparison to conventional approaches (Chong et al., 2022a, Chong et al., 2022b; Jiao et al., 2024b; Ram et al., 2024). Biological hydrogen production methods are characterized by extended reaction periods and reduced yields (4 mol of H2 per mol of glucose) (Akhlaghi and Najafpour-Darzi, 2020). Nevertheless, these methodologies exhibit a greater level of H2 production selectivity and provide sustainable, environmentally conscious, and cost-effective benefits (Kazmi et al., 2024). It has been demonstrated that the most effective way to increase bioprocessing efficiency and Bio-H2 production is through the incorporation of microorganisms. Fermentative and photosynthetic microorganisms are indispensable to the Bio-H2 production process (Jiao et al., 2024b).

Lignocellulosic biomass (LB) is an abundant and cost-effective raw material (Ali et al., 2019a, Ali et al., 2023b; Al-Tohamy et al., 2023). It is mainly composed of cellulose (33–55 wt%), hemicellulose (20–40 wt%), and lignin (10–25 wt%), as depicted in Fig. 1. Biomass is primarily hindered by its refractory character, which stems from its intricate composition and the presence of lignin. This impedes the enzymes' ability to reach hydrolyzable sugars (Wang et al., 2020). The utilization of waste biomass for the production of Bio-H2 has been recognized as a crucial step in the process of bioremediation and the development of environmentally friendly energy. LB serves as an all-encompassing scavenger, providing an ongoing stream of electrons that can be utilized in the production of fuel (Fig. 2). The primary components of polysaccharides, which make up a substantial portion of LB, are glucose and xylose. The conversion of xylose and glucose during the pretreatment stage produces compounds, including furfural and 5-hydroxymethyl furfural (HMF). In the realm of microbial conversion, furfural and HMF are widely acknowledged for their inhibitory effects (Upare et al., 2023). Consequently, they operate as impediments to the final process of Bio-H2 production. Prior to fermentation, LB need pretreatment (Ali et al., 2017; Ali and Sun, 2015). In order to reduce the recalcitrance of biomass, a number of different pretreatment approaches have been documented (Ali and Sun, 2019; Arıç et al., 2024). The effective digestion of material without prior preparation is a significant hurdle for continuous Bio-H2 production by biological means (Ali et al., 2021a). With inoculum pre-treatments, hydrogenotrophic methanogenic archaea, which are H2-consumers, are eliminated in order to enrich the community with H2-producing organisms (Toledo-Alarcón et al., 2020; Sahrin et al., 2022).

Dark fermentation is a highly regarded process for producing biobased Bio-H2 (Dangol et al., 2022). H2 production occurs during dark fermentation through the utilization of organic waste and water by anaerobic microorganisms, including, Clostridium sp., Enterobacter sp., and Bacillus sp. (Sarangi and Nanda, 2020). As determined by microorganisms and operating conditions, dark fermentation of LB produces Bio-H2 and additional byproducts (e.g., butyrate, lactate, and ethanol) (Ahmad et al., 2024). Anaerobic conditions facilitate the entry of pyruvate produced through glycolysis into the acidogenic pathway, which is coupled with H2 production. Volatile fatty acids (VFAs) and methane (CH4) are produced as a consequence (Ali et al., 2019b; Wainaina et al., 2019). The production of Bio-H2 is influenced by various factors, including the operational conditions, available nutrients, and the type of raw materials (Arun et al., 2022). Scientists are implementing novel techniques, such as mixed microbial cultures, mixed substrates, and utilizing nanomaterials, to enhance the development of microbes and optimize the performance of enzymes responsible for Bio-H2 production (Bosu and Rajamohan, 2022).

This review paper expands upon previous reviews by harnessing recalcitrant LB for enhanced Bio-H2 production. Consequently, this study aimed to conduct a comprehensive literature review to clarify the current state of knowledge by identifying important research gaps and, therefore, potential limitations in Bio-H2 production from LB to date. Various methods involved in converting LB to Bio-H2 are reviewed. Recent advances in pretreatment technologies for the production of Bio-H2 are described. Additionally, recent strategies employed to increase Bio-H2 production are reviewed. Furthermore, challenges encountered in the process of Bio-H2 production from LB are suggested.