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Lignite and the future of hydrogen

Lignite and the future of hydrogen

This week Dr Jan Wright, Parlimentary Commissioner for the Environment, released a report - subsequently backed by academics - condemning moves by Solid Energy and the L&M Group to exploit low-grade lignite coal reserves beneath Southland. Plans include the conversion of lignite to diesel fuel, as well as the production of fertiliser and coal briquettes for export.

As Dr Wright points out in her report, this is not a new issue. Lignite has been considered for its potential to free New Zealand from dependence on imported transport fuel since the oil price shocks of the 1970s. The technology for converting lignite to diesel has existed since the 1920s, and is heavily relied upon by South Africa.

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However, the poor quality of lignite means that burning it or converting it to other fuels releases large quantities of greenhouse gases. Lignite, or "brown coal", falls along the spectrum between peat and coal, and has a high moisture content, which substantially reduces its efficiency.

According to the report: "In greenhouse gas terms, [lignite-converted] diesel is almost twice as bad as the diesel we use now"

Many plans for future coal exploitation rely heavily on the prospect of carbon capture and storage (CCS), envisaging technologies that will efficiently lock away excess carbon dioxide from the conversion process deep underground in geological formations. However, the technologies that underpin CCS have not yet been developed for use on a commercial scale, and are likely to be a long way off. (See this earlier Science Media Centre alert)

Interestingly, a major strand of clean energy research in New Zealand is geared towards the production of hydrogen from coal and lignite. The FRST project 'Hydrogen Energy for the Future of New Zealand' provided for creation of a coal gasifier and further research into high purity hydrogen production for fuel cells from lignite.

Underpinning the investment is an idea that still seems to hold sway decades after it was first proposed: "Given that the country has significant coal reserves, but dwindling gas supplies and insufficient economically viable renewable resources to meet likely future demand, there will be several decades during which hydrogen production from coal will play a major role."

ENDS

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