Water footprint of wheat and derived wheat products in South Africa

Abstract

The main objective of this study was to assess the water footprint of wheat in South Africa, an important input in the wheat-bread value chain. The water footprint of flour, and that of bread, was calculated to determine the total water footprint of bread along the wheat-bread value chain in South Africa. Water productivities at each stage of production within the wheat-bread value chain were also determined. The study was conducted as a case study of the Vaalharts region. Farm-level data were obtained from Van Rensburg et al. (2012). A commercial processor with both a mill and bakery was used for collecting data at the processing level of the value chain. Water footprint assessment (WFA) is emerging as an important sustainability indicator in the agricultural sector. The water footprint concept takes a consumptive perspective to freshwater use that links production to final consumption by consumers. This study employed the Global Water Footprint Network Standard approach (GWFNS) to calculating the volumetric blue and green water footprint along the wheat-bread value chain. The GWFS considers three different types of water: blue water, which is all the surface and groundwater consumed along the value chain; green water, which is rainwater that does not become runoff; and grey water, which is the volume of freshwater required to assimilate pollutants to ambient levels. The results indicate that the water footprint indicator for wheat production at Vaalharts was 991.12 m3.tonne-1; of this 788.01 m3.tonne-1 originates from surface water and groundwater (blue water footprint) and 203.12 m3.tonne-1 from effective rainfall (green water footprint). The water footprint of flour and bread was 0.073 m3.tonne-1 and 0.459 m3.tonne-1 respectively. The total water footprint of the processing stage was 0.532 m3.tonne-1. The total water footprint of bread along the wheat-bread value chain was 991.84 m3.tonne-1, which is a combination of farm-level (wheat) and processing (mill and bakery) data. The water productivity assessment followed the water footprint assessment, where the value added to water was quantified along the wheat-bread value chain. This was achieved by calculating the economic water productivity (EWP) of wheat, flour, and bread, followed by the value added by the water footprint of wheat, flour, and bread along the wheat-bread value chain. The EWP of wheat, flour, and bread was 4.18ZAR.m3, 0.079ZAR.m3, and 0.038ZAR.m3 respectively. Value added by the water footprint of this value chain was 11.52ZAR.m3, which consisted of 4.0ZAR.m3 value added from the farm level and 7.49ZAR.m3 from the processing level. The total water footprint of wheat in Vaalharts is 61% lower than the global average. Approximately 79% of the water footprint of wheat was from absorbed surface and groundwater (irrigated water), which indicates a high dependency on surface and groundwater for wheat production in the Vaalharts region. Effective rainfall contributed only 21% of the total water footprint, which leaves room for possible increased usage. At the processing stage, 86% of the total water footprint in the processing stage of bread along the wheat-bread value chain was from the bakery and only 14% from the milling process. It is concluded that the amount of water used at farm level is the largest contributor to the total water footprint of bread along the wheat-bread value chain (99.95%), while processing is only accountable for 0.056%. For economic productivities, more income is generated per cubic metre of water used from wheat than any other product along the wheat-bread value chain. Due to the high contribution of wheat in this value chain, it is a conclusion that is easily understood. Value added to water encompasses the value added to the product throughout its value chain (in monetary terms) multiplied with the water footprint of the product at different nodes of production throughout the product’s value chain. Total value added to water from the water footprint assessment of the wheat-bread value chain is ZAR11.43 per kilogram. About 65% of this value is from the processing level and only 35% from farm level. This means higher income is received per cubic metre of water used in the processing level of the wheat-bread value chain than from the farm level. The result is similar to the value added per cubic metre of the water footprint of bread along the wheat-bread value chain. Despite the fact that the water footprint of wheat along the wheat-bread value chain contributes 99.95% of the overall footprint in this value chain, the income received per cubic metre of water footprint used for wheat along this value chain is only 35% (4.0ZAR.m3) of value added to the value chain.