What is the water footprint of chocolate? The answer is not at all simple!

Today, no one is surprised anymore that different products have different water footprints. It is well known that animal production needs much more water than plant production, and beef is more water-intensive than poultry. At environmental picnics and science festivals there are contests to guess the water footprint of various products, and I have to admit that the kids who participate are usually surprisingly aware of the ranking of products in terms of the water intensity of their production. This is gratifying.

But before we start revolutionizing our plates, as well as our technologies and supply chains, it’s worth checking that we know what the water footprint of the products we choose actually is. Because, as usual, the devil is in the details, and it all depends on what is counted, how it is counted, and what data is included in the model.

Necessary change in approach to water consumption

Modern food production and transportation require huge water resources. An assessment of the environmental impact of consumption in the EU indicates that food systems are one of the main factors of negative impacts on this resource, such as its depletion and decline in quality. The need for radical changes in food production to reduce water consumption and improve water efficiency has been widely advocated.

This proposal is reflected in a number of policy initiatives, including the UN’s 2030 Agenda for Sustainable Development, particularly Sustainable Development Goals 2, 6 and 12, as well as the Green Deal regulations and the farm-to-table strategy. However, in order to implement such a change, it is necessary to identify and quantify the effects of food production and consumption on water consumption. And for this purpose, tools have been developed to determine the so-called “water footprint. water footprint.

The water footprint can be counted in several ways

The concept of a “water footprint“(WF) was proposed in 2002. by a Dutch scientist from the University of Twente, Professor Arjen Y. Hoekstra [1]. In general terms, it is an indicator of the consumption of freshwater by a consumer or producer at different stages of a product’s life.

Several methods are available for calculating the waterfootprint, such as the WFA(Water Footprint Assessment) method [2], the Available WAter REmaining(AWARE) model [3], WAVE and WAVE+(Water Depletion under the Water Accounting and Vulnerability Model) [4, 5], Water Deprivation [6] or Water Stress Index [7]. These methods present slightly different approaches, take into account different aspects and elements of WF, and therefore also produce different results and may lead to quite different conclusions. Therefore, it is important to be aware of what counts and what counts.

A good example of the different approaches to calculating WF are two popular models: the volumetric WFA and the impact-based AWARE. WFA calculates the volume of water needed to produce specific commodities, while AWARE quantifies the environmental impact of water use, measured as the volume of water used relative to the available water remaining in a given area after human and ecosystem demands are met.

The main difference between the models is that the former is limited mainly to the production stages ( cradle to farm gate), while the latter covers the entire supply chain, up to the end of a product’s life. In this way, AWARE shows greater alignment with policy ambitions expecting the entire product supply chain to be taken into account, and is recommended by the UN and the European Commission as a reference method for measuring the environmental footprint. At the same time, WFA can still be successfully used to manage targets at the manufacturer level.

Different stages of production, different colors of water footprint

Analyzing the different stages of a product’s life, such as primary production, transportation, consumption and disposal, involves considering different types of water footprints. Thus, the concept of Hoekstra and co-authors [2] distinguishes between green water footprints (the amount of rainwater required to produce a product), blue water footprints (the amount of surface water and groundwater required to produce a product) and gray water footprints (the amount of freshwater required to dilute wastewater produced in the manufacturing process to maintain compliant water quality). By not considering all stages of a product’s life, some of these footprints, while important, may be overlooked in the final assessment of a product’s PE.

Different calculation methods, different water footprint of products

It is clear that since different models take into account different approaches and the range of resources consumed, they will give different results. Experts at the EC-JRC in Italy looked at the problem, comparing the water footprint of 45 representative food products, calculated using the WFA and AWARE methods. The results are not surprising, but they give food for thought.

If we consider only the primary production of food (a comparable stage in both models), the overall pressure on water resources according to WFA is between 39 and 71^m3 eq/year per EU inhabitant, while according to AWARE it is dozens of times higher, ranging from 2.8 thousand to 4.2 thousand^m3 eq/year/inhabitant. What’s more, if in the AWARE method we consider the entire supply chain, and not just the production stage, the impact is even greater (by an average of 30%) and ranges from just over 4 thousand to 5.6 thousand^m3 eq/year/inhabitant. That is, the differences are fundamental!

In ranking the water-intensity of products, both methods show that at the primary production stage, almonds and cashews are in the lead (among those analyzed), for which crop irrigation plays an important role. But coffee, for example, already ranks 3rd. Rank in the WFA ranking, but as high as 7th. in AWARE. Comparing bread and rice, for example, the latter ranks high because of the water needed to irrigate crop fields, while bread’s low position is due to wheat’s much lower needs in this regard. The products with the greatest distance between positions in the rankings are chocolate and tea, ranking relatively low in WFA. WF concordance for the two calculation methods tested was found for 53 percent. of products with distances less than or equal to 5 positions.

Different stages of the cycle use different amounts of water

The situation changes when we consider all stages of a product’s life throughout the supply chain in the PE assessment. Overall, about 70 percent. of the total impact of food production and consumption in the EU is associated with the primary stage of its production, and 30 percent. with the remaining stages of the supply chain, but this is a large generalization. As many as 25 of the 45 products assessed have higher water consumption later than in primary production.

Considering the entire life cycle of a product, according to the AWARE model, tea, almonds, cashews, chocolate and wine have the highest water consumption. In contrast, bread, potatoes and sugar have the smallest impact on water resources. Tea’s water footprint is generated by primary production by only 17 percent, and the largest share of its WF is associated with the final stages, where tap water is used for sanitary purposes (wastewater treatment).

In contrast, products such as almonds, cashews and chocolate have the largest share of water footprint at the primary production stage – more than 90 percent. – due to the irrigation of their crops. The role of primary production was most significant (more than half of the share) in 20 of the 45 products analyzed, and this is a key difference that is not accounted for by WF calculations performed using the WFA model. Comparing the status in the list when evaluating primary production and the entire supply chain, tofu, canned tuna, canola oil and beer had the greatest distance between the rankings.

For products with low water content (e.g., noodles, quinoa) that require additional consumption of this resource during preparation (e.g., cooking), the consumption stage proved to be a significant element. Other products, such as carrots, beer, soybean oil and tofu, have the largest water footprint in the wastewater treatment and ancillary processes due to human excretion.

For as many as 14 products evaluated, the main stage was wastewater treatment, and in the case of mineral water and soy beverages, this phase consumed most of the total water used (more than 90 percent). This means that the consumption at the primary production stage and other stages of the supply chain is lower for them than the amount needed for consumption and excretion. Therefore, wastewater is a sensitive stage of the supply chain that should be taken into account when assessing the water footprint.

Coffee or tea?

It is interesting to compare the PE of tea and coffee. These are two of the world’s most popular beverages with a similar preparation method, which involves brewing ground beans or leaves. However, it turns out that water consumption at different stages of their production and consumption is different. Tea requires a large amount of water for hydration (about 29^m3 eq/kg), while coffee needs almost 30 percent. less (20^m3 eq/kg).

Analyzing the total supply chain, this distance becomes even greater – in the case of coffee, water consumption for primary production accounts for about 1 percent of the total impact, for preparation about 12 percent, and for economic and wastewater needs about 78 percent. In the case of tea, primary production accounts for 29 percent, preparation 5 percent, and as much as 65 percent is associated with wastewater. The main differences are therefore due to water consumption during primary production and that needed for preparation per kilogram of product.

Chicken or beef?

When analyzing rankings commonly available on websites, let’s be vigilant. According to a study by Gerbens-Leenes and co-authors [8], beef has a higher total WF than pork, which in turn has a higher WF than poultry. But the global average blue and gray water footprints for the three meat products are already similar. When grazing systems are taken into account, the blue and gray water footprints of poultry and pork are larger than those of beef. So again – the environmental burden depends on how and what you count. And keep in mind that water footprint is only one of the environmental footprints and the total burden of a given product is also made up of other components (e.g. carbon footprint), but that’s a topic for a separate story.

Chocolate or potatoes?

It is worth noting that, according to the cited studies, the most water-intensive products are those that, in principle, can be considered luxuries, rather unnecessary for our survival. For the sake of the planet, they can be quietly dispensed with. At the other end of the scale are those that form the basis of our food security. This is somewhat comforting, because even if we’ve completely shriveled up, like that frog in Brzechwa’s poem, we can probably live without almonds, cashews, and even coffee or chocolate (sic!). Without bread and potatoes it would be more difficult.

Of course, for those who do not feel like giving up water-intensive products, as long as they are legal and available, no one can forbid their acquisition. However, it is worth realizing that in the near future, with the deepening water crisis, the rising costs of their production and transportation may cause them to disappear from our market on their own or make their prices absurdly high. Fortunately, then we will be left with good, native and nutritious cereals and potatoes. And the Polish market will perhaps open up again to chocolate-like products and acorn coffee. There is a niche to be developed!

Photo. main: American Heritage Chocolate/unsplash

In the article, I used, among others. z:

[1] Hoekstra A.Y.. (ed.) (2003) Virtual water trade: Proceedings of the International Expert Meeting on Virtual Water Trade, Delft, The Netherlands, December 12-13, 2002, Value of Water Research Report Series No.12, UNESCO-IHE, Delft, The Netherlands, www.waterfootprint.org/Reports/Report12.pdf.

[2] Hoekstra A.Y., Chapagain A.K., Aldaya M.M., Mekonnen M.M. (2011). The Water Footprint Assessment Manual. Setting the Global Standard. EARTHSCAN. https:// doi.org/10.1080/0969160x.2011.593864

[3] Boulay A.M., Bare J., Benini L., et al., (2018). The WULCA consensus characterization model for water scarcity footprints: assessing impacts of water consumption based on available water remaining (AWARE). Int. J. Life Cycle Assess. 23, 368-378. https://doi.org/ 10.1007/s11367-017-1333-8

[4] Berger M., Van Der Ent R., Eisner S., et al., (2014). Water accounting and vulnerability evaluation (WAVE): considering atmospheric evaporation recycling and the risk of freshwater depletion in water footprinting. Environ. Sci. Technol. 48, 4521-4528. https://doi.org/10.1021/es404994t

[5] Berger M., Eisner S., Van Der Ent R., et al., (2018). Enhancing the water accounting and vulnerability evaluation model: WAVE+. Environ. Sci. Technol. 52 (18), 10757-10766

[6] Loubet P., Roux P., Núñez M., et al., (2013). Assessing water deprivation at the sub-river basin scale in LCA integrating downstream cascade effects. Environ. Sci. Technol. 47 (24), 14242-14249

[7] Pfister S., Koehler A., Hellweg S., (2009). Assessing the environmental impacts of freshwater consumption in LCA. Environ. Sci. Technol. 43, 4098-4104. https://doi. org/10.1021/es802423e

[8] Gerbens-Leenes P.W., Mekonnen M.M., Hoekstra A.Y., (2013). The water footprint of poultry, pork and beef: A comparative study in different countries and production systems, Water Resources and Industry, 1-2, 25-36, https://doi.org/10.1016/j.wri.2013.03.001.