Hydrogen - Energy Policy Analysis: A Conceptual Framework - page 192

competitive price using small-scale water electrolysis without the usual platinum catalyst, using
significantly lower-cost membrane materials and a new one-step assembly process that facilitates
mass production. Development of cost-competitive small-scale, residential electolyzers could be a
game-changer, because it may allow hydrogen to be widely used without the need for major new
transportation and distribution infrastructure (Ekins, Hawkins, and Hughes 2010, 35).
Nuclear High-Temperature Electrolysis
Heat from a nuclear reactor can be used to improve the efficiency of water electrolysis to produce
hydrogen. By increasing the temperature of the water, less electricity is required to split it into
hydrogen and oxygen, which reduces total energy required (USDOE 2006). Nuclear reactors
operate at higher temperatures than most electric generators and produce substantial excess heat
that can be used in this manner.
High-Temperature Thermochemical Water-Splitting
Another water-splitting method uses high temperatures generated by solar concentrators (mir-
rors that focus and intensify sunlight) (Rand and Dell 2008, 124) or nuclear reactors to drive a
series of chemical reactions to split water into hydrogen and oxygen. All intermediate process
chemicals are recycled within this process (USDOE 2006). This process allows utilization of what
would otherwise be considered waste heat from solar power plants or nuclear reactors. Advanced
nuclear-fueled thermochemical processes are currently unproven, but may provide low per-unit
production costs for hydrogen production in the future (USEIA 2008b).
Gasification
Gasification is a process in which coal or biomass is converted into gaseous components by ap-
plying heat under pressure in the presence of oxygen and steam, producing hydrogen and carbon
monoxide. This syngas can be used directly in electric power production, as a chemical feedstock
for production of synthetic chemicals and fuels, or for hydrogen production. If used for hydrogen
production, the syngas is chemically cleaned to remove hydrogen sulfide, coal ash, and other
impurities before a water-gas shift reaction is used to produce hydrogen and carbon dioxide.
Carbon dioxide is removed using pressure-swing adsorption, leaving virtually pure hydrogen. In
commercial hydrogen production, CO 2 is usually vented to the atmosphere (Ekins, Hawkins, and
Hughes 2010, 32). With carbon capture and storage, hydrogen might be produced directly from
coal with near-zero greenhouse gas emissions. Since growing biomass removes carbon dioxide
from the atmosphere, producing hydrogen through biomass gasification releases near-zero net
greenhouse gases (USDOE 2006). Biomass gasification can use a variety of feedstocks, includ-
ing nonfood fuel crops like willow and switch grass or biomass residues like peanut shells and
sugarcane waste (Ekins, Hawkins, and Hughes 2010, 32).
Biological
Certain microbes, such as green algae and cyanobacteria, produce hydrogen by splitting water
in the presence of sunlight as a by-product of their natural metabolic processes. Other microbes
can extract hydrogen directly from biomass (USDOE 2006). Hydrogen produced by electrohy-
drogenesis may be able to achieve greater efficiencies than other biological hydrogen production