Editor’s note: This is Part Four in a series on the research and development work of a team of scientists led by Dr. James Tour of Rice University. This episode looks at a valuable by-product of using the Flash Joule Heating process to produce the wonder material graphene. That by-product is hydrogen, which is the fuel used in fuel cells and a key element of other products such as fertilizers and fuel oils. Costs of producing hydrogen by this method are exceedingly low and the environmental benefits are significant. 

We recommend you read the four parts of this series in order. The first three parts are here (Part One), here (Part Two), and here (Part Three). 

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In addition to Flash Joule Heating (FJH) making graphene, a valuable secondary product is also harvested during the FJH process: green hydrogen. 

Hydrogen is a valuable fuel. Hydrogen made by a so-called “green” production method is even more valuable. This is the type of hydrogen produced during the Flash Joule process.

Let’s dive into the details of hydrogen production as a by-product of the Flash Joule Heating process, a method that can turn any carbon-based material into flash graphene. To do that, we need to explore the environmental benefits, the chemistry and the economics of the process. 

Environmental benefits

The environmental benefits of the Flash Joule process are enormous. FJH can cleanly recycle low-value, problematic waste materials such as waste plastics, coal waste (fly ash), discarded electronics and most any carbon-rich material into two highly valuable products: turbostratic or flash graphene and hydrogen. It’s that simple.

The chemistry of flash joule heating

The chemistry of the FJH process is straightforward. However, to get a complete picture of its potential, some background information and an illustrated example need to be explored.

The Flash Joule process converts in a four-second, ultra-high temperature flash low-value carbon-based feedstocks into graphene and hydrogen. 

So far in this series, we’ve focused on how flash graphene is made, as well as extraordinary material’s applications and benefits. Now let’s examine hydrogen. 

The value of hydrogen

First, why is hydrogen valuable? As noted in part one of this series, hydrogen is one of only three elements in the periodic table that can be the building blocks of fuel. Carbon and plutonium are the other two. Carbon is the base element in fossil fuels and plutonium is the same for nuclear fuels. 

Today, hydrogen is commonly used in the making of agricultural fertilizer. 

“When the Heber-Bosch process came in—when we learned how to make fertilizer from nitrogen and hydrogen—there was a huge uptick in human population,” Dr. Tour noted in a recent YouTube presentation.

 This population increase was largely due to increased food production worldwide by the application of chemical fertilizers. (Heber-Bosch is a procedure used to synthesize ammonia from nitrogen and hydrogen gases.) 

Hydrogen is also used to hydrogenate fuel oils, which purifies and puts more thermal content into the fuel oils. 

Hydrogen’s most recent application is in fuel cells. Fuel cells are known as clean fuel sources because when used, their only by-products are electricity, water, and heat. Fuel cells work by converting the chemical energy of hydrogen and an oxidant into electricity through an electrochemical process. 

A side effect of making hydrogen for fuel cells 

However, there is another part of the hydrogen story relative to fuel cells.

At present, the most popular method of making hydrogen for fuel cells, as well as other applications such as fertilizer, is to mix methane with steam and a nickel catalyst. 

“It’s called steam methane reforming, and you get hydrogen (H2) out plus carbon dioxide (CO2),” Tour explained. “The problem is that you make 11 to 12 kilograms of carbon dioxide for every kilogram of hydrogen you make. So when you run on a fuel cell with hydrogen, that hydrogen has already come at a cost of a lot of CO2 being produced. That’s the problem with hydrogen today.

“Twenty years ago, hydrogen came from oil. Now the dominant method is steam methane reforming from natural gas,” but that still produces CO2 at an 11-1 ratio, Tour added. Other sources report 8 kilograms of CO2 emitted into the atmosphere for every kilogram of hydrogen produced by this method. 

• Note that the projected future spike in “Other” hydrogen production includes fuel cells. 
• MMT = million metric tons.

The costs of making hydrogen: “grey” steam methane reforming vs. “green” electrolysis vs. FJH

At present, hydrogen production from natural gas through the steam methane reforming method runs around $1.50 per kilogram of hydrogen, at current natural gas prices. This is known as grey hydrogen.

The grey hydrogen process is by far the most economical method of producing hydrogen today. However, it is not the cleanest.

Though it is beyond the scope of this article to discuss the environmental effects of emitting CO2 into the atmosphere, it is safe to say that large-scale industrial release of CO2 is viewed negatively. So, as far as that point of view relates to the manufacture of hydrogen, the less CO2 created in the process the better. 

This brings us to the making of “green hydrogen.”

What is green hydrogen?

What defines green hydrogen? As Dr. Tour explains, “If you use renewable energy to electrolyze water, to turn water into H2 and oxygen, you can do that.” The process makes less than four kilograms of CO2 for every kilogram of hydrogen, “so it’s considered a clean source of H2.”

However, there is a fundamental problem with making hydrogen this way. It’s expensive. 

In contrast to the cost of producing hydrogen from natural gas using steam methane reforming, the current cost of making hydrogen through electrolysis using renewable sources runs in the $5 per kilogram range. There are ongoing efforts to bring those costs down, but that discussion is a long one and also is beyond the scope of this story. 

The economics of making hydrogen by the flash joule process 

In contrast to the high cost of making green hydrogen from renewables, the economics of the Flash Joule process to do the same are impressive. Let’s walk through them. 

Using plastic wastes as sample feedstocks, the FJH process manufactures graphene for an electricity cost of less than $40 per ton. And costs are in that ballpark for most any type of carbon-based feedstock.

Other costs to the process include the costs of the feedstocks, the capital expenses related to scaling the process into an actual graphene manufacturing facility, complete with the ability to transport in and handle quantities of feedstock materials, as well as a method to efficiency capture the hydrogen produced as a by-product of the process. These are some of the issues that need to be dealt with to scale up the FJH process successfully.

Tour compares the production costs of hydrogen made by the FJH method versus hydrogen made from renewable energy sources, as described above. Both are low enough in CO2 emissions to be considered green. 

However, the big difference is money, Tour notes, as green hydrogen production using only renewable sources costs almost $5 per kilogram. “That cannot work” because “grey hydrogen [made by steam methane reforming] is $1.50 per kilogram. You’ve got to be able to compete with this.”

The FJH process of producing hydrogen alongside graphene does this in spades, he asserts.

“We are at -$4.50 per kilogram [for H2] when we sell our graphene,” he says, noting that he has heard it argued that the negative dollar price point is only “because you’re selling your graphene for $60,000 a ton.” He emphatically disagrees: 

“No. I took $60,000 a ton, divided that by 20, or $3,000 a ton, projecting to where it would be if it were a bulk plastic. At $3k per ton of graphene, we’d still be making $4.50 a kilogram to make hydrogen. 

The chart below shows the negative production cost of Flash Joule-produced hydrogen from polyethelyne (FJH PE H2), the relatively low production cost of grey hydrogen (Grey H2), and the high production cost of green hydrogen (Green H2).

As a side note, the amount of hydrogen produced by Flash Joule Heating is roughly proportional to the percentage of hydrogen in the feedstock used. Polyethylene contains by weight 14 percent H2. Other plastics contain similar percentages of hydrogen.

Chart showing how much H2 & flash graphene is produced by FJH from plastic waste

A glance at the chart below illustrates a few key points regarding flashing plastic waste materials into hydrogen and graphene. 

Chart Key

H2 – hydrogen, the most abundant chemical substance in the universe; C2Hx – various hydrocarbons such as ethylene, ethane or acetylene; CO2 – carbon dioxide; CH4 – methane, a primary component of natural gas; C3-C5 – generally refers to hydrocarbons such as propane, butane and pentane

PE – polyethylene, the most common plastic; PP – polypropylene; PS – polystyrene; ABS – a common polymer used in consumer goods such as LEGOs; polycarbonate – used in eyeglasses; PVC – used in plastic piping, credit cards and bottles; PET – polyethylene terephthalate – used in plastic containers

Flash Joule Heating for Clean H2 Production

First, note that the chart shows the production of various elements and compounds from eight different types of plastic waste, which are shown by their acronyms across the bottom of the chart. 

You can refer to the chart key to see what the various acronyms stand for, both for the types of plastics and the elements and compounds (at the top right of the chart) that are produced by the Flash Joule Heating process. 

The first key point to note is that H2 is by far the most abundant by-product of the process. 

Note that the horizontal black and blue, dot-connected lines represent the percentage amounts of H2 and flash graphene (FG) produced by the Flash Joule Heating process. 

In addition, note that the combined output of hydrogen and flash graphene add up to more than 90 percent of what is produced overall by the process. In other words, this is a very efficient process. It also is a clean process, as it leaves no toxic residue in its wake.

Note also that CO2 production from the process is quite low. This fact qualifies hydrogen made from the FJH process as “green hydrogen.”

“This is a way to take carbon-based waste, plastic waste, household waste if it’s not glass or metal it’s carbon, take the hydrogen off as H2, turn the carbon into graphene, put [the graphene] into building materials [and] it never enters the CO2 cycle again,” Tour says. 

“It is a great show for humanity,” he concludes.