By Alan Hewett
As we move, albeit tardily, towards a clean energy future, hydrogen has been hailed as a major solution to reducing global emissions, halting climate change and creating employment.
What is hydrogen exactly? Well, it is an invisible, colourless and odourless gas that burns cleanly and is the most abundant element in the universe. However, on earth it doesn’t appear pure in nature and needs energy to release it from either water or fossil fuels There are colour codes to identify hydrogen, and these refer to the processes used to make it.
Brown hydrogen is produced from coal and the emissions released into the atmosphere. Grey hydrogen comes from natural gas and the emissions are also released into the air. Blue hydrogen is produced by natural gas, but the emissions are subject to carbon capture and storage. Then there is green hydrogen that is produced by renewable energy.
So to achieve net zero emissions by 2050 should we wholeheartedly embrace green hydrogen production? Well, the process is extremely energy intensive. Renewable power has increased dramatically and combined with batteries is making a significant contribution to our energy requirements. However, after production green hydrogen has to be compressed for transport and use, either by high pressure or very low temperature, which adds to costs significantly
So there has to be massive investment in renewable energy and the infrastructure required to create manufacturing plants. There is no doubt that green hydrogen can help high polluting sectors such as steel, cement, aluminium, shipping and aviation but is there an environmental cost?
Could hydrogen worsen global warming? In the atmosphere ozone and water vapour reacts with sunlight to produce hydroxyl radicals. These oxidants help remove emissions from fossil fuel burning. It’s possible that hydrogen will react with these oxidants and reduce their effectiveness. Measurements taken at Cape Grim in Tasmania have revealed hydrogen concentration in the atmosphere has increased by 4% in recent years. A problem arises with leakage from production and storage. Hydrogen has its dangers on earth too, it ignites easily.
Certainly, there are questions concerning hydrogen, but consider this, researchers have estimated that replacing fossil fuels with hydrogen with a leakage rate of 1% the climate impact would be 0.6% of the fossil fuel system. Worth it?