Thursday, July 7, 2022

New tool for environment impact

AgResearch scientists have been poring over data recording water usage on farms in the Waikato and Canterbury regions for the first study of the dairy industry’s water footprint, which reports potential environmental impacts related to water use across a product’s life cycle. Dr Marlies Zonderland-Thomassen, senior scientist environmental footprinting and life cycle assessment at AgResearch and the study’s co-author, said the footprints can help to identify strategically important ways to improve environmental performance. There’s also increasing interest in their use for environmental reporting and product labelling. The study looked at Waikato (non-irrigated moderate rainfall) and Canterbury (irrigated low rainfall) dairying in 2004/05 to illustrate differences in water footprint methods and evaluate different methods of measuring them.

Average dairy farm systems for the regions were used, based on a representative group of farms from a benchmarking study: 130 farms for Waikato and 37 farms for Canterbury. The data collected showed similarities between different water footprint methods, but total estimates differed due, for example, to the inclusion of how land conversion from native vegetation to agriculture affected freshwater availability.

In both cases, degradative water use made the greatest contribution to the water footprint, indicating improved nutrient management was the priority to reduce water footprints in these systems.

This sort of work is gaining traction internationally with application of water footprinting to businesses and products supported through the development of a new international standard (ISO 14046). Sector guidelines for dairying are being prepared by the International Dairy Federation (IDF).

The results of the study were published last year in Agricultural Systems, an international scientific journal. Zonderland-Thomassen’s co-author was Dr Stewart Ledgard, the principal scientist at AgResearch who encouraged her to leave the Netherlands in 2010 to join AgResearch’s land and environment group.

Findings were also presented by Brad Ridoutt from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) animal, food and health sciences, to the Australasian Dairy Science Symposium four months ago as he set out the case for application of a new calculation process to meet the requirements of the emerging ISO standard.

Zonderland-Thomassen was hired by Ledgard especially to work on the environmental footprints of farming systems in this country as he had recognised that water footprinting was an emerging sphere of study internationally along with eco-labelling. Droughts were increasing the focus of scientists and policy-makers on water use efficiency.

“So when I came to work for AgResearch, my focus was to become an expert in this area,” she said.

She had been doing similar work in the Netherlands, mostly with dairying but also with pork and poultry. She first studied animal sciences at Wageningen University, then worked there as a junior lecturer on sustainable food security and organic farming systems. Her PhD study was on life cycle assessment of Dutch dairy cattle production systems with her thesis incorporating the water quality impacts of dairy farming with regard to nitrate leaching and phosphorus run-off.

Her first visit to New Zealand was for an internship with AgResearch at Invermay, then she returned for four weeks in 2005 to help with calving at a friend’s farm in Edendale, Southland.

In 2009 she visited the life cycle assessment team at AgResearch’s Ruakura Research Centre in Hamilton and a year later became a member of the team.

Covering the country

Since the publication of the Waikato-Canterbury comparative study last year, her team has been exploring new indicators, although the work is geared to the same base studies that underpinned the earlier study. A paper is being considered to expand on the presentation made to the dairy science symposium in Australia.

More significantly the scientists aim to expand their work to develop a New Zealand-weighted average of the dairy farming water footprint, with data from all regions.

“It’s the same approach as we use in carbon footprinting,” she said. “We compute water footprint data from all the regions in NZ, use a weighting factor based on how much milksolids (MS) each region contributes to the country’s total production, and then compute a NZ-weighted average.

“We are still in the middle of those analyses.”

Measuring the water footprint requires the scientists to estimate how much water is used at the farm level, including drinking water for cows and cleaning water in the dairy. Then they estimate how much of the water is actually lost.

From the water footprinting point of view, the interest is not the actual amount of water the cow consumed but respiratory losses and evaporation from water troughs.
The scientists use a model within Overseer to compute the evaporation when irrigation is applied.

Using DairyBase they estimate how much electricity is used, how much fertiliser, is applied and how much palm kernel or other feed is used as part of their life-cycle approach.

They collaborate with other researchers, with information from a Plant and Food PhD student, Indika Herath, who has estimated the water footprinting of hydro-electricity, incorporated in the study.

Zonderland-Thomassen said various tools were available for farmers and a harmonised approach was needed. Several approaches were taken in the two case-study farms to enable comparisons with overseas studies.

In Waikato, it became clear that the main contributors to the water footprint using the stress-weighted water footprint approach were fertiliser and electricity. This approach accounts for local water stress. The knowledge gained can help Waikato farmers to focus on how much fertiliser they apply or how to become more energy-efficient.

In Canterbury the biggest evaporative losses occurred through irrigation so efficient use of irrigation should be the major area of focus.

Quality and quantity

She said NZ seemed to have a comparative advantage over overseas products if only water consumption was looked at because it is a country with relatively low water stress levels. But if water quality aspects were included “then it could be that our clean and green image looks a little bit different”.

NZ’s water quality advantage, or loss of it, depended on farm inputs as well as production efficiency.

In the Netherlands milk production/cow might be higher but water impacts are higher too because of the heavy use of feed supplements and concentrates.

The study also shows that, compared to the limited studies available overseas, the water footprint of milk produced in Waikato is lower than that for Dutch milk from an intensive irrigated dairy farm, but for Canterbury it’s higher.

Compared with a Water Footprint Network study in which a world-weighted average water footprint of milk was computed, the water footprint of Waikato is 10% lower while that for Canterbury is 3% greater. Compared with data from a study in South Gippsland, in the Australian state of Victoria, the water footprint in Waikato was 10 times lower while that in Canterbury was 6.5 times higher.

“So there is definitely something to gain in the Canterbury region especially,” Zonderland-Thomassen said.

She is now talking with a German scientist and believes it’s likely in the future NZ footprinting will be compared with German results.

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