Geothermal energy is generally seen as a clean, renewable source of energy but it appears that in fact it may be neither.

In 2006, the Hellisheidi geothermal plant about 30km from Reykjavik, Iceland, came online. Since then, several problems have appeared.

Firstly, local residents found that they had to clean their silverware every couple of days as it was covered in black soot. Before the plant had come along, cleaning would be every couple of months.

Truck drivers in the area found that the rubber in their suspension and steering become hard and prone to breaking – an occurrence that would normally take a lot longer.

After two years, moss near the geothermal plant began to show signs of damage, with large chunks dead or dying.

Some strongly began to suspect that hydrogen sulphide (H2S) and sulphur, which is derived from H2S, were to blame although no research has been done into the effects of sulphur on moss. Mercury was also found in high concentrations in the areas of dead moss.

Steam produced at the plant appears to be the source of the problem. 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.

Hellisheidi is a windy, rainy area and the initial environmental reports believed that because of the local weather, most of the H2S would be turned into sulphur which in turn would be washed into the soil. However it appears that some of the H2S isn’t turning to sulphur and it blowing the H2S into Reykjavik, a worry that has caused the Environment Agency to find ways to reduce the levels of H2S.

Although low levels of H2S are not thought to be hazardous to human health, high levels are and little is known about the long-term effects of H2S. The World Health Organisation (WHO) guidelines state that exposure to H2S should not exceed 150 micrograms per cubic metre. Reykjavik has exceeded this level at least once. The Environment Agency are now working on new regulations surrounding the release of H2S.

So is it possible to reduce the levels of H2S released by geothermal energy plants? Yes, but it is an expensive process and not only that, but sulphuric acid or gypsum are the by-products of any of these cleaning processes, both of which are over-supplied on the world market already. Research is currently happening to see if the excess H2S can be repumped underground however research takes time and breakthroughs are not expected in this area in the very near future.

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