Shares in NZX Limited have taken a hit on the company’s own exchange today after it slashed $19.9 million from the expected sale proceeds of its carbon trading business.

At 3pm NZX shares were down 13c at $2.05, a fall of 6%, on mild volume.

Late on Friday, after the market closed, NZX announced it would write down the carrying value of remaining sale proceeds of its TZ1 Registry, which it sold to UK firm Markit Group last year.

The nascent market for Emissions Trading Scheme (ETS) carbon credits has moved up another step, with the first NZU carbon credits now up for public auction.

Auction site Trade Me is currently the only local public platform for trading carbon credits, other than buying directly from a forest owner or broker, although the NZX has 180 customers on its TZ1 carbon trading registry that it expects to be trading by the end of the year – after the government reports back on the ETS around September or October.

Analysts have upped their valuations for stock exchange operator NZX as it finalises a lucrative sale of its TZ1 carbon credit registry but warn that the deal will expose NZX’s balance sheet to a higher risk of currency fluctuation.

NZX is set to receive US$35.6 million worth of shares in private UK financial services company Markit in exchange for TZ1 Registry.

Credit Suisse analyst Greg Main points out that this will see a large proportion of the NZX balance sheet held in US dollars, as it cannot sell the Markit shares until the end of 2011.

Exchange operator NZX is in advanced discussions to sell the registry division of its TZ1 carbon market business.

UK-based Markit, a financial information services company, is offering $66.55 million worth of Markit shares for the company. The deal should be complete by the first quarter of this year, subject to due diligence on both sides.

The deal will also give NZX an equal share in any TZ1 Registry profits for the next three years, while Markit will carry any losses.

NZX's carbon market subsidiary TZ1 has picked up another role in the world's emerging environmental markets.

TZ1, which describes itself as an environmental markets infrastructure provider, announced today it had been appointed as a global registry for the Malua Wildlife Habitat Conservation Bank (biobank).

The biobank, which is raising money for rainforest conservation in Malua, Malaysia, says it is a new business model for rainforest conservation.