Fossil fuels, such as natural gas and coal, can be converted to produce hydrogen, and the use of carbon capture, utilization, and storage (CCUS) can reduce the carbon footprint of these processes.

CCUS technologies remove carbon dioxide (CO2) from industrial and power plant emissions, transport it, usually by pipeline, and then securely store it. Possible storage sites include depleted oil or gas fields, rocks containing unpotable saline water, or storage in oilfields during enhanced oil recovery operations, which differs from fracking.

Captured CO2 can be used directly or as a feedstock in industrial or chemical processes to produce valuable carbon-containing products. This can result in a portion of the CO2 being permanently stored, for example, in concrete that has been cured using CO2, says Andy Lane, vice president of CCUS solutions at the British petroleum company bp.

Hydrogen can also be produced from low carbon and renewable resources such as biomass grown from non-food crops, and by splitting water using renewables for electricity.

One kilogram of hydrogen has the same energy content as one gallon of gasoline, on a lower heating value basis.

A colorless gas, hydrogen is labeled by color to indicate how it was produced.

Green hydrogen is made by using clean electricity from surplus renewable energy sources, such as solar or wind, to electrolyze water. This electrochemical reaction splits water into its components of hydrogen and oxygen, emitting none of the greenhouse gas carbon dioxide in the process.

Green hydrogen currently makes up a small percentage of the overall hydrogen produced in the United States, because production is expensive. Just as energy from wind power has gone down in price, green hydrogen is expected to come down in price as it becomes more common.

Blue hydrogen is produced mainly from natural gas, using a process called steam reforming. The output is hydrogen, and carbon dioxide is produced as a by-product. So, the definition of blue hydrogen includes the use of carbon capture and storage.

Blue hydrogen is sometimes described as low-carbon hydrogen, as the steam reforming process doesn’t actually avoid the creation of greenhouse gases.

Currently, the most common form of hydrogen production is labeled grey hydrogen. This hydrogen is produced from natural gas, or methane, using steam methane reformation but without capturing the greenhouse gases emitted by the process. Grey hydrogen is essentially the same as blue hydrogen, but without the use of carbon capture and storage.

To see the characteristics of the other hydrogen color labels: black or brown, pink, turquoise, yellow, and white, click here to visit the Society of Professional Engineers.

Natural Gas Reforming: Hydrogen can be produced from natural gas using high-temperature steam. This process, called steam methane reforming, accounts for about 95 percent of the hydrogen used today in the United States. 

Another method, called partial oxidation, produces hydrogen by combusting methane in air. Both produce a synthesis gas or syn gas, which is then reacted with more steam to produce a higher hydrogen content gas stream.

Gasification: Coal or biomass is converted into gaseous components by applying heat under pressure and in the presence of air/oxygen and steam. A series of chemical reactions produces syn gas, which is then reacted with steam to produce a gas stream with an increased hydrogen concentration that can be separated and purified.

With carbon capture and storage, hydrogen can be produced directly from coal with near-zero greenhouse gas emissions. Since growing biomass consumes carbon dioxide from the atmosphere, producing hydrogen through biomass gasification results in near-zero net greenhouse gas emissions without carbon capture and storage.

Renewable Liquid Reforming: Biomass can be processed to make renewable liquid fuels, such as ethanol or bio-oil, which are convenient to transport and can be reacted with high temperature steam to produce hydrogen at or near the point of use.

Electrolysis: An electric current splits water into hydrogen and oxygen. To minimize greenhouse gas emissions, electricity generation using renewable energy technologies such as wind, solar, geothermal, and hydroelectric power, nuclear energy, or natural gas and coal with carbon capture, utilization, and storage are preferred.

Heat from industrial processes such as a nuclear reactors can be used to improve the efficiency of electrolysis to produce hydrogen. By increasing the temperature of the water, less electricity is required to split it into hydrogen and oxygen, which reduces the total amount of energy required.

Solar Thermochemical Water-Splitting: Another water-splitting method uses high temperatures generated by solar concentrators – mirrors that focus and intensify sunlight – to drive a series of chemical reactions that split water into hydrogen and oxygen. All of the intermediate process chemicals are recycled within the process.

Photoelectrochemical: Hydrogen can be produced directly from water using sunlight and a special class of semiconductor materials that absorb sunlight and use the light energy to directly split water molecules into hydrogen and oxygen.

Biological: Certain microbes, such as green algae and cyanobacteria, produce hydrogen by splitting water in the presence of sunlight as a byproduct of their natural metabolic processes. Other microbes can extract hydrogen directly from biomass.

Cost is the Challenge

The greatest hurdle for hydrogen production from renewable resources is providing hydrogen at lower cost. For transportation fuel cells, hydrogen must be cost-competitive with conventional fuels and technologies on a per-mile basis. This means that the cost of hydrogen, regardless of the production technology, must be less than $4/gallon gasoline equivalent (0.98 euros per litre) untaxed and dispensed.

To reduce overall hydrogen cost, research is focused on improving the efficiency and lifetime of hydrogen production technologies as well as reducing the cost of capital equipment, operations, and maintenance.

Research Directions

Hydrogen production technologies are in various stages of development. Some technologies, such as steam methane reforming, are already commercial and can be used in the near-term. Others, such as solar thermochemical water-splitting, Photoelectrochemical, and biological are in early stages of laboratory development and considered potential pathways for the longer term.

Related research includes developing new hydrogen delivery methods and infrastructure, improving carbon sequestration technology to ensure that coal-based hydrogen production releases almost no greenhouse gas emissions, and improving biomass growth, harvesting, and handling to reduce the cost of biomass resources used in hydrogen production.

Gasification of biomass, plastics, common household garbage and other wastes – coupled with carbon capture and storage strategies to address greenhouse gas emissions – is expected to be a low-cost, environmentally friendly route to producing clean hydrogen.

The selected projects focus on advancing hydrogen systems that convert a variety of waste feedstock materials into clean energy with superior environmental performance to help achieve the Biden-Harris Administration’s ambitious decarbonization goals.

The U.S. Nationally Determined Contribution as part of the Paris Agreement commits the country to achieve 50-52 percent reductions in economy-wide net greenhouse gas emissions by 2030 relative to 2005 levels. Reaching this goal requires the U.S. to roughly triple the rate of decarbonization compared to reductions in the previous 15 years, according to the Electric Power Research Institute in its White Paper, “Strategies and Actions for Achieving a 50% Reduction in U.S. Greenhouse Gas Emissions by 2030.”

The six projects selected by the U.S. Energy Department under this latest funding opportunity are expected to advance the performance, reliability, and flexibility of existing and novel methods to produce, transport, store, and use hydrogen.

These six projects were chosen for funding:

GTI Energy, located in the Chicago suburb of Des Plaines, Illinois, will demonstrate a gasifier feed control system that produces clean hydrogen from biomass and waste feedstocks.

A recent rebrand of the Gas Technology Institute, GTI Energy is an American nonprofit research and development organization focused on the natural gas industry.

GTI Energy specializes in Regional Clean Hydrogen Hubs (H2Hubs) that will serve as the foundation for a national network of commercially viable hydrogen while delivering cleaner air and improved public health, high-paying jobs, and community-based grants for business growth in disadvantaged areas.

Funded by President Joe Biden’s Bipartisan Infrastructure Law, the seven H2Hubs are expected to kickstart a national network of clean hydrogen producers, consumers, and connective infrastructure supporting the production, storage, delivery, and use of clean hydrogen.