ENVIRONMENT METHANE
System in-line to cut methane Adapting systems used to provide clean drinking water almost eliminates methane from dairy effluent. Anne Lee reports.
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areful science and a pinch of good fortune have resulted in one of the biggest breakthroughs to date for New Zealand dairy farmers searching for ways to cut methane emissions. Lincoln University scientists, working with Ravensdown on effluent technology which clarifies effluent, have found the same drinking water treatment additive it uses almost eliminates methane emissions from effluent ponds. It’s resulted in a new system that allows the additive to be mixed “in-line” as the effluent flows to the effluent pond. Methane emissions from effluent ponds make up about 4-5% of a dairy farm’s total methane emissions. The ability to cut that out almost altogether is significant given most other practical, ready to go options result in a drop in milk production. It’s also significant in terms of helping farmers get to the looming target set by the Government of cutting biogenic methane emissions by 10% from 2017 levels by 2030. Lincoln University emeritus professor Keith Cameron and Lincoln University professor Hong Di had been carrying out further studies into the ClearTech effluent system they helped develop when they made the methane reduction discovery. That system uses an additive, iron sulphate, commonly used in treating drinking water to improve water quality. The scientists were checking for any unintended consequences of using the additive, looking for any negative outcomes. Instead, they found a major positive and have been working to understand the 64
After the discovery that methane emissions dropped by about 95% and some further testing, the decision was made to scale up the experimental design. Lincoln University emeritus professor Keith Cameron and Lincoln University professor Hong Di.
greenhouse gas (GHG) benefits and what’s behind them further. A peer-reviewed paper was published in the Journal of Soils and Sediments earlier this year. It detailed the experiments carried out at Lincoln University and the results that showed methane emissions could be reduced by 99.9% when iron sulphate was mixed with the effluent. Initially the studies collecting gases from treated effluent were carried out in small experimental-sized columns. After the discovery that methane emissions dropped by about 95% and some further testing, the decision was made to scale up the experimental design. That meant the installation of 100,000 litre tanks at the Lincoln University Dairy Research Farm (LURDF). Keith says there was some nervousness given scaling up biological system experiments can see a drop in efficacy.
“It’s often called going into the ‘valley of death’,” Di says. But in this case the reverse happened and the reductions were even greater at up to 99.9% less methane emitted. They also found the effect on methane reductions continued for two months after the last dose of iron sulphate, boding well for New Zealand dairy farming systems where seasonal dry-off means no effluent is added to the pond over winter months. Based on their research and in conjunction with the scientists, Ravensdown has developed a new system, EcoPond which enables the iron sulphate additive to be mixed with effluent “in-line” as it flows from the farm dairy and yard to the effluent pond. The EcoPond system differs from ClearTech in that it doesn’t include a clarification tank where the effluent is mixed with the additive to allow the
Dairy Exporter | www.nzfarmlife.co.nz | November 2021
