Nowadays, there is an increased demand for energy, the access to which, however, is limited due to the decreasing of fossil sources and the need to reduce emissions, especially carbon dioxide. One possible remedy for this situation is using hydrogen as a source of green energy. Hydrogen is usually bound to other chemical elements and can be separated via energy-intensive few-step conversion processes. A few methods are involved in separating H₂ from biomass, including biological and thermochemical (TC) ones. Such methods and possible hazards related to them are reviewed in this study.

Hydrogen is applied to supply various internal combustion engines but also to the fuel cells, which are used in various vehicles. The goal of the present study was to review state of art ralative to application of H2 in automotive industry. The reviewy is focused on out-of-engine studies on the effect of H2 combustion process, internal combustion engines supplied with H2 and vehicles utilizing fuel cells. Challenges in applying fuel cells to actual vehicles include limited flexibility in controlling power flow in the PEMFC + B setup, significant power flow losses, complicating the management of energy systems in case of . The PEMFC + B + UC configuration, as well as a low power density of batteries. A drawback of H2 engines is the emission of NOx, which can be lowered by exhaust gas treatment. Fuel cell vehicles (FCVs) can be a clean energy alternative to gasoline-powered cars. However, their development depends on H2 fuel availability and more refueling infrastructure.

The present study reviews the state-of-art regarding the application of H2 in the automotive industry. This part focuses on dual-fuel (DF) internal combustion engines (ICEs) supplied with fuel and H2. This is a continuation of the earlier part, which focused on out-of-engine studies on the effect of H2 combustion processes, ICEs supplied with H2, and vehicles powered by fuel cells (FCs). Using H2 in diesel engines via the DF strategy enables a decrease in diesel fuel consumption and a reduction in harmful exhaust emissions. Using H2 in diesel engines powered by diesel/biodiesel mixtures also allows for reducing reliance on fossil fuels. Also, incorporating nanomaterials or oxygen-containing compounds into diesel fuel formulations may enhance the combustion efficiency of H2-powered diesel engines, thereby increasing thermal efficiency and reducing fuel consumption. However, additional studies are required on this subject.