Dams spring hope for carbon farming potential

An undervalued part of the Australian farm could be used to reduce carbon emissions.

Scientist Jackie Webb surveyed 38 dams in the NSW Riverina to test for greenhouse gas emissions. Photo: Rachael Lenehan

Agricultural dams could become the next realm of carbon farming after new research found some types of water storages produce fewer emissions.

The study was the first detailed assessment of the carbon footprint of irrigation dams and showed ­existing models were significantly over-estimating their methane emissions.

It also found that some farm dams were acting as carbon sinks, revealing the possibility to improve dam management to reduce or offset on-farm emissions.

Lead researcher Jackie Webb, a freshwater and agricultural scientist from Deakin University’s Centre for Regional and Rural Futures, said it showed farm dams could be an option for carbon farming.

Commissioned by federal statutory corporation AgriFutures, the testing of 38 irrigation dams in the Murrumbidgee Valley in NSW showed that dams without high nutrient run-off produced less methane and nitrous oxide.

Earlier studies looked at the emissions of dams on livestock farms that emitted higher levels of greenhouse gases, particularly methane, because of the higher presence of nutrients in the water and its effect on algal growth and decaying organic ­matter.

Dr Webb said emissions could be reduced by deepening dams, ensuring they remained flooded and establishing floating vegetation. “Excessive ­nutrients can lead to low oxygen conditions, which activates the anaerobic microbes that produce methane,” she said.

“So, if you can reduce nitrogen run-off going into a dam that would most certainly help.”

AgriFutures manager Michael Beer said the report showed how important infield research was to understanding emissions and setting the scope of the challenge for the industry to reduce its carbon footprint.

“Over the past 30 years or so the agriculture sector has been pretty good at bringing down its greenhouse gas emission numbers,” Mr Beer said. “It’s really important that we get the method for how we calculate gas emissions pretty right.

“That work is incredibly significant, because if we’re talking about real data, science-based information, saying that we’re been over-estimating all this time, that gives us a sense of comfort that that research has brought those expectations back a little bit to reality and that takes measurement in the field.”

The report was one of 15 ­research projects commissioned by AgriFutures in 2021 as part of its Carbon Initiative Program to fill gaps in knowledge and deliver innovative approaches to problems facing farmers as countries and organisations move towards net-zero carbon emissions.

“We were looking to validate a number of theories and in some cases we were really able to come up with confirmation of things that could work strongly,” Mr Beer said.