Environmental analysis along the supply chain of dark, milk and white chocolate: a life cycle comparison

The present study aims at detecting the potential environmental impacts due to the life cycle of three chocolate types: dark, milk and white ones. Two different approaches are followed: firstly, 1 kg of chocolate is assumed as functional unit according to the guidelines of the PCR Basic Module for food products (IES 2019); then, 1 kcal is defined as functional unit for a further comparison of the analyzed products. The study considers the life cycle “from cradle to grave”, dividing it into raw material production (i.e. cocoa, milk powder, sugar and final product packaging), cocoa transport, chocolate manufacturing and packaging waste management (Fig. 1). The packaging material for cocoa bean transport, usually jute sacks, is excluded. The retail and storage steps are neglected since they equally apply to three chocolate types and do not affect the comparison.

The study is performed using the simulation software SimaPro 9 and the database Ecoinventv.3.5 (Wernet et al. 2016).

According to the PCR Basic Module for food products (IES 2019), the following indicators for environmental impacts and for resource use are considered: Acidification potential (AP) according to CML 2001 non-baseline—January 2016 (University of Leiden 2016); eutrophication potential (EP), global warming potential (GWP), abiotic depletion – elements (ADP, el), abiotic depletion – fossil fuels (ADP, ff) according to CML 2001 baseline—January 2016 (University of Leiden 2016); photochemical oxidant creation potential (POCP) according to ReCiPe 2008 (Goedkoop et al. 2009); net water use and cumulative energy demand (CED).

In the inventory analysis, data about dark, milk and white chocolate supply chain are collected by secondary and tertiary sources: in particular, numerical data for cocoa co-products and milk powder production and for chocolate manufacturing are referred to existing recent literature, whereas data for the production of sugar and other auxiliary materials (e.g. fertilizers, pesticides) are retrieved from specific processes available in Ecoinvent v. 3.5 (Wernet et al. 2016). Then, all phases involved in the supply chain are modelled through SimaPro 9 software. The percentage of different ingredients is defined according to All. I, d.lgs. n. 178/2003 (European Directive 2000/36/CE) (ADICONSUM 2003). The lecithin, used as an emulsifier, is neglected due to low present amount. Table 1 reports proposed chocolate composition, with the reference ranges in European legislation.

In the following paragraphs, inventory data of the main steps of chocolate supply chain are presented in more details.

Cocoa farm is characterized by a relevantly high emission impact, in relation to other permanent fruit cultivars: low yield per hectare is the main reason in this regard. Indeed, the usable product is limited considering the elimination of husks, the weight lost during fermentation and sun-drying. Moreover, the increased demand in the last period has forced the production optimization through an intensive use of chemical substances. For every analyzed case, synthesis and usage of fertilizers are the main sources of environmental impacts. As Fig. 2 shows, Indonesia monoculture case represents the worst condition. The emission of NO into air and those of nitrate and phosphate into water, both due to N- and P-based component application, respectively contribute to more than 85% of AP (88.1%) and EP (88.5%). The direct and indirect emissions of N₂O also cause 34.3% of the total GWP, whereas the fertilizer production adds another 38.9% to GWP and consumes 62.2% of the total energy (CED) requested by the cultivation phase. In the Ecuador case study, pesticides have a higher contribution: for instance, 23.3% of AP, 14.1% of EP and 35.9% of GWP in comparison with 2.5% of AP, 3% of EP and 12.3% of GWP in Indonesia monoculture system. Except for water consumption, Ghana shows the best performance in all the impact categories owing to the application of N-free fertilizers and the absence of diesel consumption in agricultural machinery. A possible optimization is the substitution of the agrochemicals with organic products. Since the cocoa production stage creates a large amount of solid waste due to husks (about the 67% of the fresh pod weight), these may become organic fertilizers. Moreover, cocoa residue could be also used for bioenergy production (Kamp and Østergård 2016).

As Fig. 2 shows, pollution due to the transport step is influenced by travelled distances, so Ghana scenario results to be the best solution. Among all the case studies, GWP, POCP and CED are the categories mainly affected by the transportation phase: from 10.8% for Indonesia monoculture system to 22.3% for Ecuador in the case of GWP; from 36.7% for Ghana to 52.3% for Indonesia agroforestry system in the case of POCP; and from 12.9% in Ghana to 24.1% in Indonesia agroforestry system in the case of CED.

As far as Abiotic Depletion is concerned, pesticide production results the most impacting process (above 75%) in terms of ADP, el, whereas fertilizer production contributes between 40.2% (Ghana) and 62.3% (Indonesia monoculture system) to ADP, ff.

The environmental impacts caused by the production of 1 kg of chocolate are assessed and compared for dark, milk and white cases. The study evaluates the effects due to the production of ingredients (milk powder, sugar, cocoa liquor, powder and butter), energy and water consumption for final product refining. As in previous literature LCA studies (Konstantas et al. 2018; Vesce et al. 2016), Figs. 3, 4, 5, 6, 7, 8, 9 and 10 show that cocoa derivatives and milk powder provide the major contributions. The first ones are widely influenced by the producer countries. Indeed farming requests an intensive use of agrochemicals and the bean transforming phase needs a high energetic consumption (Ntiamoah and Afrane 2008). The milk powder manufacturing also has an intensive energetic usage because of evaporation and drying steps (Finnegan et al. 2017). For instance, in Ecuador case study, AP impacts are mainly due to cocoa derivatives (96%) in dark chocolate, cocoa derivatives (19%) and milk powder (63%) in milk chocolate and cocoa butter (27.6%) and milk powder (65.1%) in white chocolate. Similar percentages are obtained for EP: analyzing Ghana as farmer country cocoa derivatives contributes for 91% in dark chocolate, while 76.3% is due to milk powder in white one. In accordance with literature (Büsser and Jungbluth 2009), the milk and white chocolates have the most relevant GWP impact: considering an average value between proposed situations, about 4 kg CO₂ eq. are obtained in comparison with 2 kg CO₂ eq. due to dark chocolate production. POCP and ADP, ff have quite similar results, as the milk powder present in milk and white chocolate compensates for the major amount of cocoa co-products in dark chocolate. On the contrary, ADP, el impacts result higher for dark chocolate since the contribution (per mass unit) of milk powder is lower, due to the relevant impact of pesticides applied during cocoa cultivation. Except for Ghana case study where a considerable amount of water is used by cocoa farming, the milk powder production requests about 70% of net water consumption in chocolate supply chain (Fig. 9), whereas the water use for property chocolate refining step is very low (Vesce et al. 2016). Similar considerations are valid for needed energy: indeed, only the milk powder manufacturing spends 46 MJ (around 66%) as Fig. 10 shows.

In general, as reported in Fig. 11, dark chocolate shows a better performance in the categories where impacts deriving from milk powder production are predominant (i.e. EP, GWP, POCP ADP, ff, CED), whereas it overtakes milk and white chocolate as milk powder contribution decreases. Water use represents a separate case since the comparison is strongly influenced by the water consumption for cocoa cultivation in Ghana (Fig. 2). Moreover, milk and white chocolate present similar results since they contain the same amount of milk powder and similar amounts of cocoa co-products (Table 1). Therefore, even though the comparison among different chocolate types varies according to the considered environmental impact category, still dark chocolate globally shows the best environmental performance, followed by white chocolate and then milk chocolate.

In chocolate supply chain, the main causes of pollution are the used raw materials: above all dairy and cocoa derivatives. Certainly, the careful choice of products with lower environmental impacts, resulting from a better management of their cultivation and processing, could improve system performances. An alternative is the substitution of some ingredients; for instance, the use of soy milk, instead of cow milk, could reduce the impacts up to 70–90% (Miah et al. 2018). However, this solution is not always possible because the replacement changes the characteristics of the final product, such as taste, nutrition values and physical appearance. For this reason, an easier reduction of impacts can be obtained focusing on packaging materials. Figure 12 presents the environmental impacts generated by the packaging production to wrap 1 kg of chocolate. The polypropylene (PP) layer results to be the least impacting material in all chosen impact categories. Two different combinations of an aluminium foil with a fibre-based material result more impacting than the PP case, mainly because of aluminium-based material production. Consequently, the aluminium layer plus cardboard is the most impacting solution in all categories: respectively, 0.0021 kg SO₂ eq. for AP, 0.0008 kg PO₄³⁻ eq. for EP, 0.4228 kg CO₂ eq. for GWP, 0.0012 kg NMVOC eq. for POCP, 1.70‧10⁻⁶ kg Sb eq. for ADP, el, 4.1419 MJ for ADP, ff, 0.0035 m³ for water use and 5.7136 MJ for energy consumption.

Mass allocation is usually suggested when allocation procedures cannot be avoided and no different physical relationships reflect the way in which the inputs and outputs are changed by quantitative variations in the products delivered by the system (IES 2019). Thus, mass allocation is applied in the first point to the cocoa co-products as defined in paragraph 2.2.2. Since different allocation choices could strongly affect the results and owing to the common use of chocolate as energy food, allocation rules based on the cocoa co-product energy content are proposed for the sensitivity analysis. The caloric intakes for cocoa liquor, cocoa butter and cocoa powder are respectively equal to 648.3 kcal/100 g, 899.05 kcal/100 g and 469.6 kcal/100 g (MP&F 2020). As reported in Table 9, this allocation choice leads to a higher allocation percentage for cocoa butter (56.7% instead of 43.9%) and to lower allocation percentages for cocoa liquor and cocoa powder (respectively 19.8% and 23.5% instead of 21.3% and 34.8%), proportionally affecting their environmental impacts. As shown in Figs. 13 and 14 for GWP category, the energy content allocation slightly rises the environmental impacts of both milk and white chocolate because of the increased impacts of cocoa butter. On the contrary, dark chocolate shows almost equal impacts as the presence of all three cocoa co-products balances the result variation. The change linked to cocoa butter also leads white chocolate to become more impacting than milk chocolate, since cocoa butter—the only cocoa co-product contained in white chocolate—is strongly unfavoured by the energy content allocation. Except for different percentage changes, the same behaviour occurs for all considered impact categories and indicators as shown by the results presented in the Supplementary Material.

Possible variation in the results could also be caused by different proportions among the mass of cocoa co-products obtained in chocolate manufacturing, as cocoa liquor contains both cocoa powder and cocoa butter in roughly equal proportion. Therefore, according to the existing proportion between cocoa butter and powder and maintaining the same overall mass for cocoa co-products (Table 6), different percentage variations in the output of cocoa liquor are applied to the manufacturing phase in the case of energy content allocation. However, as shown in Fig. 15 for GWP, the variation of the results is substantially negligible for all chocolate types in the case of energy content allocation, whereas no change is present in the case of mass allocation.

Finally, a comparison between two allocation methods is evaluated considering a functional unit of 1 kcal. The conversion of functional unit is computed according to average energy content for three chocolate types (Verna 2013): 4950 kcal/kg of dark chocolate, 5150 kcal/kg of milk chocolate and 5400 kcal/kg for white chocolate. Thus, looking at chocolate for its primary function of energy food, the application of an energy-based functional unit turns back to favour—in terms of GWP—white chocolate instead of milk chocolate in both the allocation rules applied (Fig. 16), as for the original case of 1 kg of product with mass allocation (Fig. 14).

However, regardless of the functional unit and the allocation rules applied, the qualitative comparison among three chocolate types remains similar.