Geothermal: Possible downside

I came across this article today based on some observations made at the Hellisheidi geothermal power plant in Iceland.

Geothermal Is Not So Clean

Not long after the station started producing electricity, Reykjavik residents became aware that they had to clean silverware every three to four days instead of three to four months because it was always covered with black soot.

Truck drivers who drove daily to sand mines in the western part of Hellisheidi found that the rubber in the suspension and steering systems of their vehicles became hard and prone to breakage after only a year, whereas normally it would take three to five years for this to happen.

People suspected that the Hellisheidi plant was responsible for the damage, but at first this was never discussed openly.

Then in September 2008, people saw that the moss vegetation adjacent to the Hellisheidi plant was severely damaged.

Those are the symptoms. What is the problem?

Although no definite conclusions could be made because the effect of hydrogen sulphide (H2S) on moss has not been researched, there are strong indications that sulphur, derived from H2S, is the cause of the damage at Hellisheidi and nearby Nesjavellir.

The damage stems from the steam produced at the plant. Most of this is water, but 0.4 percent of the steam contains gases of various kinds - 83 percent is carbon dioxide (CO2), 16 percent hydrogen sulphide (H2S), and the remainder other gases. Trace elements in the steam include sulphur, mercury, boron, arsenic and aluminium.

The solution?

Johannsson says it is technically possible to reduce H2S levels from geothermal plants, but this is costly. "Various methods are known which are used all over the world," he says. "The disadvantages of these methods are that pure sulphur, sulphuric acid or gypsum are left behind and there is an over-supply of all these products on the world market. However, Reykjavik Energy are trying out an experimental project of pumping the H2S back into the geothermal system."