EcoPond: A Possible Breakthrough in Reducing Greenhouse Gas Emissions on New Zealand Dairy Farms

 

Introduction

Did you know that effluent and its storage systems account for 10% of methane greenhouse gas emissions on an average New Zealand dairy farm? This makes effluent the second  largest contributor to methane greenhouse gas emissions on a dairy farm, so exploring potential ways to reduce emissions in this area is crucial for the country’s agricultural sector to meet climate change reduction targets. One of the promising solutions is the EcoPondTM, a technology being commercialised by Ravensdown following trials completed by Lincoln University in collaboration with MPI. This post will explore how EcoPondTM is able to reduce emissions.

How the EcoPondTM Works

The EcoPondTM is designed to treat effluent ponds with iron (ferric) sulphate, a common treatment in wastewater plants used to reduce the smell caused by emissions of hydrogen sulphide gas. It was not known if iron sulphate would have any effect on methane emissions until the Lincoln University research team discovered this in 2021. Methane is produced in anaerobic conditions due to the breakdown of organic matter in the effluent. Treatment with ferric sulphate and sulphuric acid has been shown to reduce methane emissions by over 90%, with an average reduction of 96% (Cameron & Di., 2021). This significant decrease is attributed to four key mechanisms:

1. Increased Microbial Competition for Organic Matter:

The addition of the iron (ferric) and sulphate during treatment boosts the growth of naturally occurring  ‘sulphate reducing bacteria’ and ‘ferric reducing bacteria’ in the effluent. These bacteria outcompete the methanogens (methane producing bacteria) for the organic matter (food) in the effluent and this significantly reduces methane production.

2. Direct Inhibition:

The products created by sulphate-reducing bacteria during sulfate reduction are toxic to the methanogens and this also reduces the production of methane.

3. Anaerobic Oxidation of Methane (AOM):

Anaerobic oxidation of methane is primarily catalysed by methanotrophic archaea and sulfate-reducing bacteria which consumes a significant amount of any methane that may still get produced. Iron has been shown to increase the rate of AOM in various environments which reduce methane emissions.

4. Increase in oxidation state of the effluent pond:

Treating dairy effluent with ferric sulphate and sulphuric acid raises the ‘oxidation’ state of the effluent pond. This de-activates the methanogens because they can only produce methane under low oxygen (i.e. anaerobic) conditions.

Additional Benefits of the EcoPondTM

While the primary purpose of the EcoPondTM technology is to reduce methane greenhouse gas emissions, it also shows potential in reducing phosphorus leaching losses from effluent application areas. The treatment with ferric iron takes dissolved phosphate out of solution by forming slow-release iron-phosphate compounds which are less mobile and therefore less likely to leach into waterways. Additionally, the EcoPondTM treatment has also been shown to significantly reduce carbon dioxide emissions by 52 % and can reduce sulphide gas (H2S) by forming insoluble ferrous sulphide. Another notable benefit is the reduction of E. coli in treated effluent due to the bacteria becoming encapsulated during treatment and being deactivated by the iron sulphate and sulphuric acid.

The Kavanagh Farm: A Pilot Net Zero Dairy Farm

Located just outside of Hawera, the Kavanagh farm is one of four Dairy Trust Taranaki farms. The current trial on the Kavanagh farm is a demonstration of a journey towards a profitable net zero carbon emission dairy farm. The trial is run by Dairy Trust Taranaki in collaboration with Nestle and Fonterra over a ten-year trial period with the practices implemented being economically viable and practical for farmer adoption. The pilot farm is set to test various farm system changes, carbon sequestration methods and new technologies, including the EcoPondTM.

The EcoPondTM trial was set up during the dry season of the 2024/2025 season. The trial consists of eight 2 m deep columns of effluent, four are left untreated and four are treated with EcoPondTM (these are re-treated every six to eight weeks).  Each week our science technicians take gas measurements of each of the columns after a lid has been applied to see how much methane is being emitted at various time points. These samples along with pH and redox readings are sent to Lincoln University where they are analysed. Following calving, an additional step is completed each week. After the measurements have been taken a 14 L effluent exchange is completed by removing the effluent from the column and replacing it with fresh effluent. This is to mimic the input of fresh effluent into the system and to see how the treatment effects the methane emissions between treatments.

The Kavanagh Farm trial results show that the EcoPondTM treatment has reduced methane emissions by 93% over 140 days, with only two treatments added (see figure below).

 

Conclusion

The EcoPondTM technology represents a significant step towards achieving reduced methane greenhouse gas emissions in the dairy industry. By effectively reducing methane and carbon dioxide emissions and offering additional environmental benefits, EcoPondTM provides a practical and promising solution for sustainable dairy farming. It will be exciting to see the broader impact of this technology on New Zealand’s agricultural sector and its contribution to global climate change efforts.

 

 

 

  • Taylah is one of the science technicians at Dairy Trust Taranaki who started in March 2024. The science technicians work across all four of our research farms to collect data including botanical compositions, weekly ecopond measurements, herd tests, plot trials and much more. Prior to starting at Dairy Trust Taranaki and moving back home to the region, Taylah completed a Master of Science majoring in biological science at Massey University where she focused on plant microbiology.