The water footprint of food waste: case study of fresh mango in Australia

Abstract

In many parts of the world, freshwater is already a scarce and overexploited natural resource, raising concerns about global food security and damage to freshwater ecosystems. This situation is expected to intensify with the FAO estimating that world food production must double by 2050. Food chains must therefore become much more efficient in terms of consumptive water use. For the small and geographically well-defined Australian mango industry, having an average annual production of 44,692 t of marketable fresh fruit, the average virtual water content (sum of green, blue and gray water) at orchard gate was 2298 l kg⁻¹. However, due to wastage in the distribution and consumption stages of the product life cycle, the average virtual water content of 1 kg of Australian-grown fresh mango consumed by an Australian household was 5218 l. This latter figure compares to an Australian-equivalent water footprint of 217 l kg⁻¹, which is the volume of direct water use in Australia having an equivalent potential to contribute to water scarcity. Nationally, distribution and consumption waste in the food chain of Australian-grown fresh mango to Australian households represented an annual waste of 26.7 Gl of green water and 16.6 Gl of blue water. These findings suggest that interventions to reduce food chain waste will likely have as great or even greater impact on freshwater resource availability as other water use efficiency measures in agriculture and food production.

Introduction

The world faces a food security challenge of massive proportion. Currently, there are an estimated 1.02 billion undernourished people in the world, representing about 15% of the total population (FAO, 2009). Yet demand for food is also forecast to double by 2050 based on projected population and socio-economic growth (FAO, 2008). While agricultural yields have shown impressive increases over the twentieth century, largely due to genetic improvements, irrigation, fertilization and the use of pesticides, environmental sustainability in many locations has been compromised (Nellemann et al., 2009). One of the greatest constraints on current and future food production is the availability of freshwater, which is now a scarce and overexploited resource in many parts of the world (Bartram, 2008, Falkenmark, 2008). The Aral Sea tributaries, Chao Phraya, Colorado, Ganges, Huai, Indus, Jordan, Lake Chad tributaries, Murray, Nile, Rio Grande and Yellow are among a growing list of rivers where consumptive water use by agriculture has reduced flows severely, in some cases causing flows to become intermittent in the lower reaches (Falkenmark and Lannerstad, 2005). The Punjab province of Pakistan, the Gujarat and Rajasthan states of India, and the North China Plain are but a few of the major food producing regions where groundwater is being extracted at unsustainable rates (Falkenmark and Lannerstad, 2005).

Consumptive water use refers to the removal of water from a local hydrological system, thereby rendering it unavailable for further use (Falkenmark and Lannerstad, 2005, Liu et al., 2009). That is, there is no verifiable return flow to the local source of origin. Present consumptive water use for global food production has been estimated at between 16,950 and 18,600 km³ yr⁻¹ (Rockström et al., 2007, Rockström et al., 2009) consisting of around 35% green water consumption by rainfed croplands, 10% blue water consumption by irrigated croplands and 55% green water consumption by pastures. Blue water is derived from surface and groundwater sources whereas green water is derived directly from natural rainfall over agricultural lands. These figures highlight the dominance of green water in current global food production, even though irrigation accounts for around 70% of all freshwater withdrawals (UNESCO-WWAP, 2006). However, what is alarming from both a food security and environmental sustainability perspective is that at current rates of agricultural water use efficiency, an estimated additional 5700 km³ yr⁻¹ of freshwater will be needed to meet the demand for food in 2050 (Rockström et al., 2009). Since the availability of additional blue water resources is limited, a range of strategies have been proposed for achieving future food security. These include the continued conversion of natural ecosystems to new agricultural lands to access greater volumes of green water, water productivity improvements in agriculture (i.e. so-called crop per drop improvements), shifting diets to minimise the consumption of products which have high consumptive water requirements, water saving through increasing trade in agricultural commodities, and reducing food chain losses (Nellemann et al., 2009, Rockström et al., 2007, Rockström et al., 2009, Rockström, 2003, Chapagain et al., 2006, Yang et al., 2006, Lundqvist et al., 2007, Rockström and Barron, 2007, Yang and Zehnder, 2007, Liu and Savenije, 2008, Liu et al., 2008).

Regarding food chain losses, it is commonly believed that these are in the order of 30–50% between farm and fork (Henningsson et al., 2004, Kader, 2005, Bloom, 2007, Lundqvist et al., 2008, Meeusen and Hagelaar, 2008), although detailed characterisation is lacking in Australia (Morgan, 2009) and elsewhere. Substantial variation from one food chain to another is likely. Broadly speaking, a contrast exists between developing countries where losses tend to be high toward the beginning of the food chain due to poor harvesting, storage and transport, and developed countries where losses in wholesaling, retailing and consumption often predominate (Lundqvist et al., 2008). This is due to the expectation by consumers in developed countries for produce in perfect condition and a tiny blemish or deviation from optimal ripeness can exclude a product from consumer consideration. In describing food waste, a distinction must also be made between avoidable food waste, representing food that could have been eaten, and unavoidable food waste, representing bones, peel, pips and stones and the like which are generally inedible, but nonetheless may have other beneficial uses.

Supply chain waste, from farm to consumer, naturally represents a cost to the firms involved in terms of unrealised sales, excessive raw material usage and disposal costs (Henningsson et al., 2004, Pagan and Prasad, 2007). However, the effort and expense associated with reducing waste do not always justify the necessary investments when viewed from a purely financial perspective. One of the reasons why firms are not more active in reducing waste is that many of the environmental costs are externalised. Recently, however, there has been a growing interest in making transparent the environmental impacts of the production and consumption of goods and services (Lebel and Lorek, 2008). Many businesses are seeking to demonstrate good corporate citizenship by measuring, reporting and addressing negative social and environmental impacts arising from their operations and product life cycles (Chapagain and Orr, 2009). The recent popularisation of carbon footprinting, disclosure and labelling is evidence of this. In addition, product environmental labelling initiatives in many jurisdictions are enabling consumers to become more aware of the impacts of their purchasing decisions and thereby take greater responsibility for their consumption patterns. Such developments are creating new incentives for reducing food waste. As one example, US food service provider Bon Appetit has announced a plan to cut food waste by 20% with the intention of cutting greenhouse gas emissions by more than 2000 t CO₂-eq yr⁻¹ (Environmental Leader, 2009). Another example, driven by public policy, is the Love Food Hate Waste campaign in the UK (www.lovefoodhatewaste.com).

Food that is not consumed or used in some other beneficial ways represents a waste of all of the resources that were used in its production and distribution, such as water. As already mentioned, water availability is a critical concern to future food security and environmental sustainability. Our research concerns the mapping of food waste through the distribution and consumption stages of the product life cycle and the use of water footprinting to assess the impact on water resources. This case study focuses on the small and geographically well-defined Australian mango industry. To our knowledge, this is the first application of water footprinting to assess the impact of food waste on water resources.