The New Smell of Natural Gas

How Gas Leaks Stop Fuel Cells and What To Do
by Christine Lepisto, Berlin on 07. 5.09

Is Your Gas Leaking?

What does natural gas smell like? If you said, "rotten eggs," think again. Natural gas is completely odorless. The stink that alerts you to a leaky stove or bad connection on the barbecue grill is an additive. The sulfur-based additive is put in natural gas on purpose, to avoid the countless deaths and destruction that undetected gas leaks would otherwise cause. But the sulfur additive is poison to fuel cells. Currently, fuel cell manufacturers have to use a filter to remove the sulfur compound.

Removal is inefficient: why add a thing just to take it out again? And it raises the question about consumer protection in case leaks develop downstream from the filter. Researchers in Germany are hard at work on a solution to the dilemma. And now the first German gas customers are experiencing the scent of success. What a stinky scent it is!

Why Sulfur Additives Stink (Figuratively)
Early in 2009, the EU reduced the minimum levels of sulfur additives required in natural gas. As the fuel increases in popularity for tanking up cars as well as other alternative fuel uses, the pollution by-product (sulfur dioxide) of burning the sulfur additive created cause for concern. Furthermore, the sulfur is damaging to drivetrains. The need for a substitute without the side effects of sulfur was clear.

The gas suppliers turned for answers to researchers at the Karlsruhe Engler Bunte Institute and at the flavor and fragrance manufacturer Symrise in Holzminden. And a new stink was developed for gas. It is a mixture of two acrylates and a pyrazine.

The New Smell of Natural Gas
The new odor is hard to describe. Even its inventors can hardly say what it smells like. Some say it reminds them of garlic, others that it smells sweetish. But all agree that the new additive is even stinkier than the old rotten eggs smell. In the meantime, many communities in northern Germany have started using the additive instead of the sulfur compound.

So far, the biggest issue to arise is the lack of recognition by consumers: awareness of the new smell is needed to trigger the appropriate safety reaction. But the development promises to solve sulfur related problems in fuel cell technology. Since natural gas may be a necessary pathway to fuel cells, given the complexity and hazards of storing pure hydrogen, this additive is worth watching.

A practical consideration I had not thought about before. IF we are headed toward natural gas vehicles, it makes sense to know when there is a leak.