Water footprinting green kiwifruit
MAF and Zespri International commissioned Landcare Research to assess the water footprint of green kiwifruit supplied to the UK — the environmental impact of water used, directly and indirectly, throughout all stages from growing the fruit through to the fruit reaching the consumer.
The research evaluated two emerging approaches - the Water Footprinting Network (WFN) and Life Cycle Assessment (LCA) - and also investigated a third hydrological-based perspective. Used in tandem, these different approaches provide deeper insight into the direct and indirect freshwater consumption by a product.
Water Footprint Network
At the orchard gate, green kiwifruit have an average water footprint of 417 litres per kg. Applying the volumetric WFN methodology to the orchard showed that, based on the national average, the majority of water consumed in the cultivation of green kiwifruit (85%) is taken from rainwater or soil moisture. Five per cent of water consumed was taken from irrigation and 10% is the volume of water needed to dilute orchard inputs below safe drinking standards, e.g. nitrogen fertiliser entering the environment.
Life Cycle Assessment Impact Assessment
The LCA work combined with volumetric results highlighted regional differences in potential environmental impacts from the freshwater used in cultivation - several regions made a relatively low contribution to national production yet had relatively high environmental impacts. For example, the contribution of the Auckland region to environmental impacts of freshwater consumption is given greater importance using the LCA environmental impact indicators than when using the WFN method.
Water management options
The hydrological perspective included run-off and drainage flows not taken into account in either the WFN and LCA footprint methods but usually included in water balance assessment, and was developed as part of research looking at reducing water use.
Hypothetically converting all irrigated kiwifruit orchards in all regions to rain-fed orchards had a significant impact on water footprints for only the low rainfall areas (Hawke’s Bay, Gisborne, and Nelson). However, this significantly reduced orchard gate returns for Hawke’s Bay and Nelson. In principle, this is a feasible option only for Gisborne. Several other options associated with the use of N fertilizer in the Te Puke region were examined. Neither the application of fast-release nitrogen fertiliser nor halving the amount of nitrogen fertiliser typically applied had a significant influence on the water footprint.
Water footprinting methods are developing very quickly as more company and sector case studies are published. Although the project highlighted a number of important data gaps requiring further investigation throughout the supply chain, the research has been of considerable value to Zespri.
The research is also used to support positive positioning with key global retailers, such as Walmart, Marks & Spencer, and Sainsburys, who are increasingly paying attention to the water footprints of suppliers. Alongside the information on the carbon footprinting work done by Landcare Research for the company, the water footprint study has been included in Zespri’s Sustainability Brochure.
MAF will use the results to understand the variances between the different methods advocated, and to formulate New Zealand’s responses to the development of the ISO water footprinting standard. In New Zealand there are potential opportunities to use water footprinting data domestically in water allocation discussions, for example, to identify rain-fed orchards that do not rely on an allocation of irrigation water.