Hydrogen - Energy Policy Analysis: A Conceptual Framework - page 191

including fuels, such as coal, natural gas, and biomass, or by using nuclear energy and renewable
energy sources, such as wind, solar, geothermal, and hydroelectric power to split water. More than
95 percent of hydrogen is produced from fossil fuels, in a variety of processes, some of which
generate carbon dioxide in addition to hydrogen. Only about 4 percent of hydrogen is produced
by electrolysis of water, a much more expensive process used only when high-purity hydrogen is
needed (Armaroli and Balzani 2011, 281).
Hydrogen can be produced almost anywhere, at large central plants, or in small distributed units
located at or near the point of use, such as at gasoline refueling stations or stationary power sites.
It can even be produced onboard a transportation vehicle. A wide range of technologies is being
developed to produce hydrogen economically from a variety of resources (USDOE 2006).
Natural Gas Reforming
Hydrogen can be produced from the methane in natural gas using high-temperature steam. Steam
methane reforming accounts for about 95 percent of the hydrogen used today in the United States.
In steam-methane reforming, methane reacts with heated steam (700°C-1000°C) under pressure in
the presence of a catalyst to produce hydrogen, carbon monoxide, and a small amount of carbon
dioxide. Subsequently, in what is called a water-gas shift reaction, the carbon monoxide and steam
are reacted using a catalyst to produce carbon dioxide and more hydrogen. In a final process step
called pressure-swing adsorption, carbon dioxide and other impurities are removed from the gas
stream, leaving essentially pure hydrogen (USDOE 2006). Steam methane reforming is considered
the least expensive way to produce hydrogen (Ekins, Hawkins, and Hughes 2010, 31).
Biofuel Reforming
Biomass can be processed to make renewable liquid fuels, such as ethanol or bio-oil, which are
relatively convenient to transport and can be reacted with high-temperature steam to produce
hydrogen at or near the point of use. A variation of this technology is known as aqueous-phase
reforming (USDOE 2006).
Electrolysis
Electrolysis uses an electric current to separate water into hydrogen and oxygen. Required elec-
tricity can be generated using any of a number of resources. However, to minimize greenhouse
gas emissions, electricity generation using renewable energy technologies, such as wind, solar
photovoltaics, geothermal, or hydroelectric power might be preferred (USDOE 2006). A well-to-
wheels energy use study showed hydrogen produced by wind-powered electrolysis, from coal with
CO 2 sequestration, and from natural gas with CO 2 sequestration generates very low amounts of
greenhouse gas emissions compared to advanced internal combustion engine vehicles and hybrid
vehicles (Ogden 2004, 81). Carbon sequestration is a risky, expensive technology with which there
has not been much experience (White et al. 2003). Presumably hydrogen produced with electrolysis
powered by solar photovoltaics, geothermal, or hydroelectric power would produce comparably
low emissions of greenhouse gases, without the expense and risks of sequestration. Moreover,
carbon sequestration for the purpose of emissions reduction has not yet been demonstrated on a
commercial scale, so its costs and long-term viability remain speculative (Ekins, Hawkins, and
Hughes 2010, 31).
In 2009 ITM Power, a British company, announced it had produced hydrogen at a commercially