A biogas plant. Photo: 123RF
A major international energy report has found biogases have the potential to cover a quarter of the world's current demand for fossil fuel gas.
Biogas is typically produced using a process called anaerobic digestion - where organic matter is broken down with an absence of oxygen inside a sealed structure.
New Zealand's first biogas facility to pump into the national gas pipeline opened in Reporoa in 2022 and can meet the demand for gas from about 7000 homes.
Proponents of biogas say it has the potential to help fill the shortfall from declining gas fields in this country.
But its current rate of uptake means the country is well behind that as a possibility. The government canned a proposal to mandate food scrap collection for all councils, which critics have said has stymied investment in biogas generation.
The head of the World Biogas Association, Charlotte Morton, is in New Zealand as a keynote speaker at the Biogas Forum. She told RNZ's Nine to Noon biogas made up about 5 percent of the world's gas use at present.
Raising that to 25 percent, or more, could be done without impacting the world's food supply, Morton said.
"It's every type of organic waste, plus crops that can be grown as part of regenerative farming that actually ensure that more food - plus energy - is produced in a sustainable way.
"And so if we are not recycling all the organic waste that we humans are generating every year, and globally that we're talking about 105 billion tonnes of organic wastes, that's human sewage, food waste, agri-waste, manures and slurries, et cetera, we are creating a problem for our rivers and oceans, for the environment. We're emitting horrendous levels of methane emissions, so it's actually quite imperative that we recycle those organic wastes."
She said recycling organic waste would also reduce methane emissions significantly.
"We would be able to deliver half of the global methane pledge… almost 160 countries have committed to reducing their methane emissions by 30 percent against 2020 levels by 2030."
Doing so would require plants of "a variety of sizes from quite small on-farm AD (anaerobic digestion) plants to quite large scale civic AD plants", Morton said.
"They'll be taking… the solid fraction of wastewater treatment and recycling it and capturing the energy… The municipal plants will be taking food waste and other food and drink processing wastes and recycling that.
"One of the things that is really important is to prevent more food waste going to landfills, because whilst it's really good that covered landfills are, ensuring that the methane is being released and burnt - so turning methane into carbon dioxide, which is 86 times less harmful than methane, that's really important."
While carbon dioxide does not contribute to warming as much as methane in the short-term, it lasts in the atmosphere much, much longer.
"But landfills, you can never capture all of the methane that's coming from them, so they are leaking about 25 percent of the methane they're generating," Morton said.
While countries like Italy, Germany, France and the UK are leading the way, for New Zealand to join them will take the government to "put in place the right regulatory framework that would allow developers to put together projects that are able to attract finance".
"As a circular economy technology, or process, it's really important that you have that right regulatory framework because it needs to cover the collection of all the feedstocks we just talked about. The industry calls them feedstocks rather than waste, because they are a resource in the wrong place.
"Then you need to be able to have the right regulatory framework to support the development of a biogas industry itself. You've also then got to have the grid connections, at the other end, and of course one of the byproducts is digestate, which is a biofertiliser - so you need to ensure you've got the right standards in place to ensure that that biofertiliser can be then go back to land and restore soils."
Morton said biogas was "molecularly identical" to fossil methane, which meant it would be a "drop-in fuel for existing households or commercial infrastructure" already using gas.
"That's one of the huge benefits to it."
The Climate Commission expects gas to be a part of the energy mix until 2050, in declining quantities.
Experts have said gas prices were likely to go up for household consumers as fewer people used it.
Multiple reports have concluded electrification is cheaper for new homes than installing gas and increasingly cheaper for many existing homes also looking to replace their appliances.
Sign up for Ngā Pitopito Kōrero, a daily newsletter curated by our editors and delivered straight to your inbox every weekday.
