'Big Dry' cranks out C02

Greenhouse gas emissions are soaring as coal and gas-fired generators run flat out, day and night, to compensate for fast-emptying hydro storage lakes.

Estimated carbon dioxide equivalent emissions from the thermal generators have risen to around 230,000 tonnes a week, 50% higher than this time last year, according to energy market consultancy Energy Link.

In mid-December carbon emissions were about 60,000 tonnes a week.

The main culprits are the four coal-fired generators at Genesis Energy's Huntly power station, which Energy Link estimates are emitting around 150,000 tonnes of greenhouse gases each week.

Genesis Energy spokesman Richard Gordon said it was not his company's wish to run the dirty Huntly generators so hard and for so long.

"But with the hydro lakes under pressure, Huntly has become the default reserve generator to provide security of supply to the electricity system," he said.

Gordon said any increase in emissions from thermal generators was "part of the cost" the country was paying for the current power shortage.

And that cost could continue through to 2012, when New Zealand has to account to the Kyoto Protocol.

The four main Huntly generators produce 1000MW of electricity, about 15% of the country's total power needs.

While they can run on less environmentally harmful natural  gas, or a mixture of coal and gas, they are now burning virtually 100% coal, which is cheaper than natural gas.

Although Genesis Energy keeps records of weekly emissions from its thermal generators, it would not provide latest figures.

However, Energy Link has estimated weekly carbon dioxide emissions from thermal generators based on generation output, the kind of fuel being used, and an assumption on each plant's thermal efficiency.

Energy Link director Paul Baker said his company's records could not show if current greenhouse gas emission rates from electricity generation had ever been as high.

Latest Ministry of Economic Development (MED) figures paint a far rosier picture of emissions from electricity generation.

In the December quarter, 63% of emissions associated with electricity generation were from burning gas, and 30% from coal. But it is not difficult to see those numbers turned around when 2008 figures are released.

Soaring greenhouse gas emissions from electricity generation couldn't have come at a more embarrassing time for New Zealand's Kyoto obligations.

The first Kyoto commitment period began on January 1 and runs to December 31, 2012. Emissions above 1990 levels during those five years must be offset either by forest plantings, or by purchase of Kyoto-certified carbon credits.

In March the government's provision for Kyoto liabilities was $1.009 billion, up from $704 million last June.

Electricity generation accounts for 11% of New Zealand's greenhhouse gas emissions, but since 1990 it has been the fastest-growing contributor up 138%.

More dry winters could see the electricity generation emission levels, fired by fossil fuel generators providing base load and default reserve provision, adding to our Kyoto bill, not subtracting from it.

Controlled lake storage levels fell below 50% of average late last week. Excluding Wakatipu and Wanaka lakes, whose waters cannot be stored, the levels for other storage lakes were at 47% on average on Thursday. Storage levels have been continuously falling since May 11, and have fallen from 64% of average one month ago (May 5). A national power savings campaign is expected to be launched this week.