IntroductionHuman dependence on these fuels is increasing day by

IntroductionHuman beings are consuming conventional sources which comprise higher carbon content, e.g. coal, petroleum reserve based fuels, and natural gas for energy generation. Especially, petroleum oil reserves are the major source of fuels for transportation all over the world. These non-renewable fuels are available in limited amount, and our dependence on these fuels is increasing day by day. The conventional sources of energy for fuel generation are diminishing in an extensive manner with the passage of time and emit higher percentage of pollutant gases in our environment which accelerates global warming and other harmful effects on human habitation. In the last few decades, depletion of fossil fuels, emissions of pollutant gases, and the growing demand for energy generation have received increasing attention for searching new technologies and fuels which can provide high-efficiency energy use. It is imperative to explore ways to produce more efficient, effective, and attractive nonconventional energy fuels in order to suppress the economic and environmental impacts associated with conventional fuel utilization.Significance of HydrogenFuel cells are “power generation devices” which can generate electricity by an electrochemical reaction between hydrogen and oxygen and are considered as promising devices for meeting future global energy expectations. In general, the fuel cell as the clean and green cell works without polluting the atmosphere and generates power 2–3 times more than conventional power plants (combustion based). An established power plant normally generates electricity with 33–35% thermal efficiency, while fuel cells can produce power up to 60% and higher thermal efficiency using cogeneration. Hydrogen can be utilized as a potential feed for fuel cell operations due to its plenteous, attractive, effective, and environmentally friendly attributes. It can be considered as an important part of present as well as future energy systems (e.g. fuel cell systems). Also, hydrogen is the most copious element present on earth, which modulates easily with other chemical substances and exists as a part of various chemical compounds such as alcohols, hydrocarbons, and water. It is also found in biomass-consisting living organisms such as animals and trees. Because of this attribute, H2 is distinguished as an energy carrier but not as an energy source.Production of HydrogenHydrogen is produced by various feedstocks such as nuclear, coal, natural gas, and other types of renewable energy sources. These different sources make hydrogen a promising and a vital factor for energy security. Hydrogen is also used for the manufacturing of plastics, pharmaceuticals, and various quality chemicals such as methanol, glycerol, ethanol, dimethyl ether, methane, biodiesel, butanol, and ammonia on a large scale. Moreover, hydrogen is produced by using various non-reforming technologies, namely, electrolysis, biomass gasification, photoelectrolysis, and thermochemical water splitting, and reforming processes such as steam reforming (SR), dry reforming (DR), aqueous phase reforming (APR), oxidative steam reforming/autothermal reforming (OSR/ATR), and supercritical water reforming (SCWR).The estimated hydrogen production is approximately 55 million tons per annum with respect to its consumption, which is increasing by around 6% every year. Almost 48–50% of H2 is produced from methane SR, around 30% from naphtha/oil reforming process from a refinery, 18% from coal gasification technique, 3.9% from water electrolysis process, and the remaining 0.1% from other sources. Processing of gaseous, liquid, and solid fuels for hydrogen production.Butanol as an Emerging source of HydrogenRecently, butanol has been introduced as the most abundant renewable feedstock because it comprises a higher composition of hydrogen as compared to other fuels such as methanol and ethanol. It is a non-conventional source of energy processed by fermentation of several feed stocks such as ligno-cellulosic biomass, wheat, sugar beets, corn, sugar cane, agricultural wastes, aqueous phase of biomass pyrolysis liquids, and micro-algae. Butanol as an important raw material is in great demand for various chemical and petrochemical industries. Its expected market has been estimated approximately 5 million tons in 2015 globally. China seems to be a major consumer nowadays utilizing around 34% of the world’s total demand, whereas Europe and North America consume 25% and 24%, respectively. Besides, butanol has superior tolerance capacity to water contamination, better safety measures like combustible but not flammable in nature, and lower vapor pressure which minimizes the risk of vapor lock. Butanol and its isomers are used as solvents for paints, resins, and dyes; ink ingredient; perfumes; composite of ethanol; additives of gasoline; etc. It is also known as a potential biofuel in internal combustion engines with 85% strength. It can be blended at a higher amount in petrol and diesel directly without retrofitting vehicles for reducing soot emissions. There are some advantages and disadvantages of butanol discussed below:1. Higher heating value: Butanol contains 25% more energy than low-carbon alcohols like methanol and ethanol. Due to this reason, better energy efficiency can be achieved with less fuel consumption.2. Low volatility: The saturation pressure (volatility) of butanol is lower than methanol and ethanol, which means butanol will have less cavitation and vapor lock problems.3. Less ignition problems: The autoignition temperature of butanol is low as compared to methanol and ethanol which creates less ignition problems.4. Intersolubility: Butanol has better intersolubility quality than other low-carbon alcohols. It can easily blend with gasoline and diesel without adding any other cosolvents.5. Higher viscosity: The kinematic viscosity is much higher rather than that of motor spirit and diesel, which makes butanol a suitable fuel for a fuel pump.6. Safer: Butanol has low vapor pressure point which makes it a potential and the safest fuel for high temperature reforming processes as compared to lowcarbon alcohols.7. Easier distribution: Butanol is less corrosive than lowcarbon alcohols like methanol and ethanol. Due to this quality, butanol can be distributed easily through pipelines as compared to other alcohols which can be transported by using railways or truck services. Production of Butanol from Biomass