7 Jul 2021

Report finds biogas a viable alternative for New Zealand

7:36 pm on 7 July 2021

New Zealand has the potential to produce enough renewable gas to supply three quarters of all commercial users.

Vegetable steamer on a gas hob.

File image. Photo: 123RF

A part-government funded report from the country's biggest gas distributor, First Gas, engineering firm Beca, and Fonterra, found that 4 percent of the country's energy related emissions could be avoided by low-emitting, renewable alternatives.

One avenue being pursued is anaerobic digestion, whereby organic waste from kitchens and the farm is broken down and turned into biogas, which is then cleaned and upgraded into biomethane.

This gas could then be easily transported within the current gas pipeline network, without the need for changes to the infrastructure.

Beca's industrial sustainability lead, Eleanor Grant, said widespread use of biomethane would have significant environmental benefits.

"Our estimates indicate that implementation of wide-scale anaerobic digestion in New Zealand could produce enough renewable gas to supply all residential users and three quarters of commercial gas users with carbon free fuel, equivalent to taking 415,000 petrol cars off our roads."

The production process also captures the methane from the organic waste that would otherwise be released as it naturally degrades, she said.

Anaerobic digestion also produces a beneficial by-product, digestate, which is a combination of organic liquids and solids, that can be used as a nutrient rich fertiliser or a base for bio-plastics.

Sheep and beef farm in Manawatu

Organic waste from kitchens and farms can be used to make biogas. Photo: RNZ/Sally Round

First Gas general manager of commercial and regulation Ben Gerritsen said the small scale of development we have seen to date is down to two factors.

"Firstly, the fact is we have had relatively cheap natural gas in New Zealand to date."

This has had a lot of benefits to commercial industries, he said, but it meant the costs associated with biomethane production was unable to be competitive.

"The second reason is that we have actually had relatively low-cost waste disposal options available as well, which really has meant that we haven't put the focus on how we can dispose of our organic waste that these biogas technologies require."

A third challenge highlighted in the report is that New Zealand lacks a scheme to certify green energy or the digestate that is produced in anaerobic digestion, so it can be sold as a fertiliser.

Distributing biomethane in Canterbury would also run into problems, as the region does not have a gas reticulation network.

Overcoming the barriers

The report said research found in countries that have seen fast uptakes of biogas productions benefited from support various support from the government.

This included taxes on organic waste dispiosal, green investment schemes, guaranteeing biomethane producers above market prices for what they deliver to the grid, and facilitating cross-industry collaboration.

Grant said the promotion of more circular economies for all kinds of waste in New Zealand would also create a more sustainable approach to waste management and allow a more regenerative economy to develop.

"Strategies like this help make alternative biofuels more attractive and more cost-comparative with incumbent fossil fuels in the early stages of investment," she said.

Gerritsen said the carbon price forecasts in the Climate Change Commission's advice to the government meant it was likely that higher tariffs would be applied to the price of natural gas in the future.

He was also encouraged by the government's wase minimisation levy which was set to increase year on year, as it would create an incentive to find sustainable ways to dispose of organic waste.

"Anaerobic digestion is clearly an effective disposal option," he said.

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