Parliamentary Commissioner for the Environment Simon Upton, scientists, advisers and public feedback during consultation on the Zero Carbon Bill increasingly favour splitting the treatment of short and long-lived gases, reducing net carbon dioxide emissions to zero by 2050 but stabilising levels of short-lived gases such as methane.
Net zero means emissions generated are no greater the amount removed from the atmosphere through sinks such as forestry.
Carbon dioxide accounts for 45% of New Zealand’s emissions, methane 43% and nitrous oxide 11%.
Emissions of long-lived gases such as carbon dioxide and nitrous oxide steadily accumulate in the atmosphere and can remain intact for 1000 years.
But short-lived gas like methane, which comes from livestock but also coal mines, natural gas fields and pipelines, breaj down over 12 or so years though some molecules become carbon dioxide.
The Government is consulting on the Zero Carbon Bill and whether to replace the 2050 target of a reduction in greenhouse gases to 50% below 1990 levels with one of three options: Net zero carbon dioxide by reducing net carbon dioxide emissions to zero by 2050, net zero long-lived gases and stabilised short-lived gases by reducing emissions of long-lived gases to net zero by 2050 while stabilising emissions of short-lived gases or net zero emissions of all greenhouse gases.
Professor Ralph Sims, a director at the Centre for Energy Research at Massey University, said treating methane differently would take some pressure off the farming sector given research to date has identified solutions that provide only small reductions in emissions.
But treating methane differently is not exactly straightforward.
“As methane molecules break down in the atmosphere over a decade or two they produce CO2.
“If the methane is bio-based it can be argued that the resulting CO2 is recycled back through the growing pasture or rice plants.
“However, if it is fossil-based methane then the resulting CO2 is no different from that released from fossil fuel combustion.
“Therefore, any mitigation policy that is less stringent on agricultural methane emissions has to consider its impact on fossil methane emissions that cause greater warming.”
Professor Robert McLachlan of the applied mathematics department at Massey University said it is in NZ’s interest to separate the treatment of methane from long-lived gas.
But he warns methane accounts for a quarter of global warming and reducing emissions would provide an immediate decrease in temperature, whereas cutting carbon dioxide would not.
Associate Professor Ivan Diaz-Rainey, the co-director of the Otago Energy Research Centre at Otago University supports a policy that encourages a reduction in methane but puts a greater emphasis on reducing carbon dioxide.
“This is probably the right answer and it will require major changes to the Emissions Trading Scheme, so more policy uncertainty.”
“But, overall, it feels like we are still standing at the starting line asking where and how far we should run to shed some kilos while many others have been running and some running hard for quite some time.
“Could we not at least jog, have policies that start to reduce CO2 such as strong incentives for electric vehicles and domestic energy efficiency while we continue to figure out exactly what we are going to do with agriculture?”
In a report last March Upton, advocated different treatment for short and long-lived gases.
“While it (the Climate Commission) should be able to chart a path to net zero carbon dioxide emissions the appropriate long-run treatment of its agricultural gases requires urgent attention.
“This could mean different targets for different gases. It could also mean restricting the way in which actions in respect of one gas or sink can be used to offset another gas.”
Meanwhile, agriculture companies are well represented among the 60 NZ businesses from a variety of sectors that have formed the Climate Leaders Coalition and committed to measuring and publicly reporting their greenhouse gas emissions.
Cumulatively the 60 firms contribute nearly half of NZ’s carbon emissions but will work to reduce greenhouse gas emissions with the aim of keeping global warming to within 2C as specified in the Paris Agreement.
The primary sector members are Ngai Tahu Holdings, Fonterra, Ravensdown, Silver Fern Farms and Synlait.
The Farming Leaders Group has also committed to zero carbon emissions by 2050.
