As well as extensive involvement in hydrocarbon exploration and production in the Taranaki region, Todd Energy through its Nova Energy brand also pioneered the use of landfill gas in New Zealand.

Landfill gas is produced as part of the landfill decomposition process.  Landfill gas is a mixture of methane gas (about 55%), carbon dioxide (about 40%), and nitrogen.

Landfill gas collection has been tried and tested around the world and "conventional" wisdom is that it is burnt onsite to generate electricity. In addition to investigating electricity generation, Todd Energy has looked past the traditional use to assess the most efficient use of this valuable energy source.

What is unique about the Todd Energy approach to landfill gas is the treatment of the gas to supply customers directly. The treatment process removes impurities and excess carbon dioxide using a "scrubbing" process.

The resulting methane is then odorised and pumped under pressure through underground pipes directly to our commercial customers. To further improve reliability and supply additional customers landfill gas can mixed with pipeline gas to ensure a consistent, uniform energy supply.

How does the landfill gas process work?

We have a number of collection system options, which can be tailored to suit the landfill.

The landfill may be covered with an impermeable plastic membrane. Bores are drilled and linked to a network of pipes beneath the membrane and extraction systems installed across the landfill.

Once collected, landfill derived methane can be used in two ways:

• The gas is used as a replacement for other fossil fuels; or
• The gas is flared off into the atmosphere as carbon dioxide and water (far less harmful to the environment than directly releasing methane).

Todd Energy has the expertise and capabilities to handle both options but primarily focus on industrial and commercial use of landfill derived methane. Landfill gas collection facilities currently operate at Porirua and Happy Valley landfills and the option and feasibility of adding new generation capacity to utilise this resource are currently being investigated.