The Minority Mix: Blue and Green Hydrogen
August 25, 2021
The Minority Mix: Blue and Green Hydrogen
Increased attention to carbon emissions and a demand for more eco-friendly industrial products has put a spotlight on hydrogen and its production methods. In our last blog, we discussed how hydrogen can fuel the energy transition; and how conventional “grey” hydrogen currently accounts for about 95% of hydrogen production today. So, what about the other 5% of hydrogen? What’s the difference between blue and green; and are either of them a viable, carbon-free solution? Here’s what we know.
Blue and Green Hydrogen, Explained
The overwhelming majority of hydrogen plants that produce the hydrogen used by refineries and other manufacturers is now called “grey” hydrogen. This is most frequently made from reforming natural gas or other hydrocarbons. The production of grey hydrogen is energy efficient but is a significant emitter of carbon dioxide.
“Blue” hydrogen production is made in substantially the same way as grey hydrogen but employs carbon capture to varying degrees in the process. The captured carbon dioxide is either stored underground, underwater, or utilized for enhanced oil recovery.
Blue hydrogen processes are likely to be the most prevalent near-term means of reducing carbon emissions in the production of hydrogen. Carbon capture may be retrofitted to the large fleet of existing reformers, many of which already are capable of sequestering a portion of the carbon dioxide emitted. The only roadblock to such retrofits is securing the capital to cover the expense, which may be justified by incentives, credits, or by finding buyers for the carbon dioxide which may include enhanced oil recovery users.
Unlike blue and grey hydrogen, “green” hydrogen is not produced from hydrocarbons at all. In the most frequently mentioned green hydrogen processes, water is separated into hydrogen and oxygen in a process called electrolysis. To be truly green, the production process must be carbon-free; so the significant amount of required electricity for electrolysis would be derived from green energy, such as solar plants or windmills.
Most electrolysis processes require precious metals like platinum and iridium which are rare and expensive. The demand for these metals, combined with a lack of supply, drives the cost of electrolysis to a point that inhibits scale in today’s energy grid. (1)
In addition, while electrolysis is attractive from a carbon emissions point of view, it is an energy-intensive means to make hydrogen with current technology. According to the U.S. Office of Energy Efficiency & Renewable Energy, today's grid electricity is not the ideal source of "green" electricity for electrolysis because most of the electricity is generated using technologies that rely on fossil fuels. Electricity generation using renewable or nuclear energy technologies, either separate from the grid, or as a growing portion of the grid mix, is a possible option to overcome these limitations for hydrogen production via electrolysis. (2)
In the short term, the development of more efficient fossil-fuel-based electricity production with carbon capture, utilization, and storage (2) has become a more pragmatic near-term goal.
The Practical Hurdles of Decarbonization
The potential role green and blue hydrogen could play in decarbonizing the world’s energy supply is undeniable, but there are significant obstacles to its widespread use. It is substantially more expensive than conventional hydrogen production, and thus its value is completely tied to its “green-ness”. About 20% of the world’s energy supply is created with wind or solar energy. This is a significant problem for green hydrogen; if the process uses electricity generated by natural gas, coal or other fossil fuels, it loses much of its value and purpose.
Also, wind and solar energy are non-dispatchable. This means that it cannot be willingly turned on or off. When there is not enough wind or sun to generate electricity, backup power sources must be used. This is a big drawback for hydrogen production as many of its uses demand high reliability.
Other Paths to Eco-Friendly Hydrogen
Other less-publicized methods of hydrogen production are emerging in response to calls for decarbonized hydrogen production. Some of these have been developed from the push for renewable fuels production, which often require large amounts of hydrogen. Others have resulted from the ability to realize enhanced value for “greener” hydrogen.
One of our clients, Omni Conversion Technologies, is pioneering a technology that uses municipal solid waste to produce a promising type of green hydrogen. Using waste materials to produce hydrogen, which otherwise would release greenhouse gases when landfilled, has a net-negative carbon footprint. The “net-zero” hydrogen made by this means has enhanced value to fuel producers of all types in that it enables them to receive credits for lower carbon-intensity fuels. Projects based on this technology are progressing.
For renewable fuels production based on hydro-processing, at least three driving forces are in place to produce green hydrogen. First, these type processes require large amounts of hydrogen. Second, the lower the carbon footprint of the hydrogen used for this purpose, the higher value the resulting renewable fuel has due to incentives for low carbon intensity in production. And third, such processes generate by-product fuels that may be used for hydrogen production. These by-products of renewable fuels production are of course produced from renewable vegetable or animal sources. This type of design results in a closed-loop integration for renewable fuels production without introducing fossil fuels into the equation and includes an economical and energy efficient means of hydrogen production.
Choosing a Cleaner Future
The energy industry isn’t simple. There are many factors to consider when it comes to switching energy sources and creating a decarbonized planet. At KP Engineering, we understand that today’s renewable energy needs require technical expertise, innovative engineering, and top-tier project execution. For over fifteen years, we have designed cost-effective projects in a timely manner, and we are committed to helping our clients create a more sustainable future.
Evaluating hydrogen for your project? Leverage our process engineering experience.