Producing hydrogen without greenhouse gas emissions is hard and expensive, right? Wrong!

All you need to do is to take several coke cans, shred them into metal scrap and put them into a bucket of water. Out comes hydrogen.

But the problem is, the amount of gas that gets produced by this method is so small that it’s hardly worth the effort. This is because the oxygen in the water quickly reacts with the surface aluminium to form a film of oxide, which prevents further reaction. The answer is to find a chemical (a catalyst) that will scrub off the oxide layer. Some researchers have used gallium for that purpose. Others have shown that if you use a fine dust of silicon-doped aluminium, the hydrogen yield is pretty high.

However, aluminium is costly. Indeed, you can use aluminium scrap, but scrap is never pure metal; it comes alloyed with other materials, which hampers hydrogen production.

‘Production of hydrogen using metal scrap’ is a subject matter of intense research today.

A group of scientists headed by Professors RB Harikrishna, Hemagni Deka, T Sundararajan and G Ranga Rao, of the Department of Chemical Engineering, IIT Madras, have demonstrated that discarded metal wastes can be used as feed-materials for thermochemical production of green hydrogen. The gas is produced by splitting water using industrial waste-metal scrap at high temperatures. This process requires significant energy input in the initial stage to attain the desirable temperature. Subsequently, the energy input can be reduced due to the exothermic nature of the process, the researchers note in a recent publication in The International Journal of Hydrogen Energy. They studied the reaction between metal scrap and steam for hydrogen production. Their method produced 500 mL of green H2 per gram of scrap material at 1150°C, with a conversion efficiency of about 94 per cent. “This is a potential method to utilise scrap metals for large scale production of green hydrogen without carbon emissions,” they say. Through this process, a ton of metal waste can produce approximately 5,00,000 litres of hydrogen. The byproduct produced is primarily magnetite, which is a potential additive for magneto-rheological fluids. This is an environmentally friendly process and can be developed as a cost-effective method for green hydrogen production. There are many other types of scrap metal materials which can also be employed to generate hydrogen by this process.

Monolithic gain

Meanwhile, US-based company in Nebraska called Monolith has claimed to have developed a technology for producing cheap green hydrogen using methane pyrolysis. It still uses natural gas, but says the emissions are just 0.45 kg of CO2, per kg of hydrogen produced compared with 11.3 kg of the conventional, ‘steam methane reforming’ process. If the feedstock is from biogenic or recycled sources, CO2 emissions will be negative, says Monolith.

The company is backed by investors such as Decarbonization Partners, Mitsubishi Heavy Industries, Warburg Pincus and TPR Rise Climate.

The process is simple—use electricity to super-heat methane. The process needs one-seventh of the electricity that an electrolyser would (about 55 kWhr per kg of Hydrogen). The heat breaks the bonds between the hydrogen and carbon atoms on the CO2 molecule. Hydrogen and carbon atoms emerge out of the contrivance separately, so you end up with two useful products—hydrogen and carbon black.