This comprehensive review explores recent developments in Proton Exchange Membrane Fuel Cells (PEMFCs) and evaluates their alignment with the ambitious targets established by the U.S. Department of Energy (DOE). Notable advancements have been made in developing catalysts, membrane technology advancements, gas diffusion layers (GDLs), and enhancements in bipolar plates. Notable findings include using carbon nanotubes and graphene oxide in membranes, leading to substantial performance enhancements. Innovative coatings and materials for bipolar plates have demonstrated improved corrosion resistance and reduced interfacial contact resistance, approaching DOE targets. Nevertheless, the persistent trade-off between durability and cost remains a formidable challenge. Extending fuel cell lifetimes to DOE standards often necessitates higher catalyst loadings, conflicting with cost reduction objectives. Despite substantial advancements, the ultimate DOE goals of USD 30/kW for fuel cell electric vehicles (FCEVs) and USD 600,000 for fuel cell electric buses (FCEBs) remain elusive. This review underscores the necessity for continuous research and innovation, emphasizing the importance of collaborative efforts among academia, industry, and government agencies to overcome the remaining technical barriers.

Development of a substitute fuel for conventional fuels, such as wood, coal, charcoal and Liquefied Petroleum Gas LPG, is important. Briquette production technology, a kind of unpolluted coal technology, will facilitate to prevent global warming and serve to conserve forest resources. The main ingredients of biomass briquettes are agricultural wastes (such as straw, sugarcane bagasse, maize stalk, coconut husks and leaves, groundnut shells and rice husk), sawdust and the waste papers from the municipal waste, which mainly act as a binding agent. Briquettes are very cheap as they are manufactured from waste. They are additionally used as a substitute fuel for cooking purposes and several other heating processes. The experimental work focuses on developing a method to manufacture briquettes of consistent quality at low pressures by employing a wet technique. The impact of process variables like shape, density, moisture content and calorific value on briquettes with different combinations were studied. The usage of briquettes instead of firewood results in preventing deforestation and reducing green house effect. In this situation, briquettes could potentially offer a means of waste management while providing a new fuel business opportunity for the local economy.

Tamanu-based biodiesel can be used as a non-conventional fuel blended with conventional fuel in a compression ignition engine without any need for modification in engine design. The three main processes involved in production of biodiesel are removal of OH group by H₂SO₄ (acid) and KOH (base), and removal of soapy water. The molar ratios tried in this process were 4:1 to 10:1 and the yield was maximum at 6:1 (86.15%). In this present study, production of biodiesel from Tamanu oilseeds, its performance analysis and emission characteristics in a CI engine were extensively studied. Prepared Tamanu-based biodiesel was used in a four-stroke CI engine and performance analysis was done. The blend proportions used in the diesel engine were 10–40 wt.% biodiesel (B10, B20, B30 and B40). Analysis of emissions such as NO_X, CO, and HC from a CI engine has shown that the biodiesel blends produced fewer emissions than that of commercial diesel. Results revealed that there is a substantial reduction of emissions and an increase in performance of the biodiesel blends tested. Moreover, the amounts of toxic pollutants emitted from the biodiesel blends are significantly less when compared to commercial diesel.

Bio-fuels are proved to be very good substitutes for the existing petroleum fuels. Blends of biodiesel extracted from Tamanu oil (B100, B80, B60, B40, and B20) along with induction of biogas with constant mass flow of 2.313 * 10