The International Journal of Life Cycle Assessment (2021) 26:2085–2102 https://doi.org/10.1007/s11367-021-01971-5 SOCIETAL LCA Environmental and social life cycle assessment of growing media for urban rooftop farming Susana Toboso‑Chavero1,2 · Cristina Madrid‑López1 · Gara Villalba1,2 · Xavier Gabarrell Durany1,2 · Arne B. Hückstädt3 · Matthias Finkbeiner4 · Annekatrin Lehmann4 Received: 5 March 2021 / Accepted: 26 August 2021 / Published online: 18 October 2021 © The Author(s) 2021 Abstract Purpose New environmental strategies are emerging for cities to become more self-sufficient, such as hydroponic crop production. The implementation of such systems requires materials that usually originate in countries with low labour costs and other legal regulations. To what extent could these strategies be shifting problems across the globe? To answer this question, we performed a comprehensive environmental and social assessment of the various extended soilless systems used to grow vegetables on urban roofs. Methods Three different growing media constituents were chosen for this study: perlite, peat and coir; which are produced in three countries, Turkey, Germany and the Philippines, respectively, and are imported to Spain. By using a life cycle assess- ment, we evaluated the environmental performances of the production and transport of these growing media. Additionally, we performed a social life cycle assessment at different levels. First, we used the Social Hotspots Database to analyse the constituents in aggregated sectors. Second, we performed a social assessment at the country and sector levels, and finally, we evaluated primary company data for the social assessment of the constituents through questionnaires given to businesses. Results and discussion The coir-based growing medium exerted the lowest environmental burden in 5 out of 8 impact cat- egories because it is a by-product from coconut trees. In contrast, perlite obtained the highest environmental impacts, with impacts 44 to 99.9% higher than those of peat and coir, except in the land use. Perlite is a material extracted from open-pit mines that requires high energy consumption and a long road trip. Regarding the social assessment, peat demonstrated the best performance on all the social assessment levels. In contrast, coir showed the worst scores in the Social Hotspots Database and for the impact categories of community infrastructure and human rights, whereas perlite displayed the lowest performance in health and safety. Nevertheless, coir and perlite evidenced much better scores than peat in the impact subcategory of the contribution to economic development. Conclusions This study contributes to a first comparison of three imported growing media constituents for urban rooftop farming from environmental and social perspectives to choose the most suitable option. Peat appears to be the best alternative from a social perspective. However, from an environmental standpoint, peat represents a growing medium whose availability is aiming to disappear in Germany to preserve peatlands. Therefore, we identify a new market niche for the development of local growing media for future rooftop farming in cities. Keywords Life cycle assessment · Soilless systems · Open-air farming · Rooftop greenhouses · Green cities · Urban agriculture 1 Introduction Cities are primordial human settlements of prosperity in our society, generating approximately 80% of the global Communicated by Marzia Traverso gross domestic product (GDP) (Floater et al. 2014), and they provide economic and cultural wealth and dynamic * Susana Toboso‑Chavero Susana.Toboso@uab.cat territories. Nonetheless, the accumulation of populations, activities and resource demands triggers high pressures Extended author information available on the last page of the article 13 Vol.:(0123456789) 2086 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 regarding pollution, resource use, and land/space competi- countries than in the developed countries (Hammami et al. tion (Legner and Lilja 2010). Organisations, governments 2008), is also inherent in obtaining the necessary products for and academia have focused their attention on cities as high the implementation of FEW systems on rooftops. The main emitters but also because they offer potentials for multi- elements are extracted and produced overseas, such as the purpose and easily replicable solutions for sustainability growing media for agriculture, often coir or perlite, which actions (Grimm et al. 2008; Rosenzweig et al. 2010). are manufactured in Asian countries, and Turkey, Greece Many strategies for redressing the ecological problems and different African countries (Bennett 2018; U.S. Geologi- associated with urban areas have emerged over the years. cal Survey 2019), or the production of photovoltaic panels, These initiatives can be grouped into different topics, such mainly dominated by China, which yielded 43% of the global as waste management, energy efficiency, water demand, production in 2018 (Solar Power Europe 2019). This separa- buildings, and renewable energy (Lamb et al. 2019). One tion between the points of production and consumption causes initiative has stood out for its remarkable exploitation environmental and social impacts that should be screened potential: the use of urban roofs for different purposes, as and included in any new strategy we propose to enhance the roofs can comprise up to 32% of the horizontal surface of sustainability of cities. Notwithstanding, this global delocali- build-up areas and are mostly underutilised spaces (Frazer sation has also brought prosperity, in some cases, to these 2005). Roofs can be used for implementing energy pro- countries that have become factories for developed countries duction (Madessa 2015; Kyriaki et al. 2017; Bazán et al. (Panagariya 2019). Some of these positive consequences 2018), green roofs (Fioretti et al. 2010; El Bachawati et al. include job creation, GDP increase and improvement of infra- 2016; Brudermann and Sangkakool 2017), rooftop farm- structure (World Trade Organization 2017, 2018). ing (Montero et al. 2017; Nadal et al. 2017, 2018a, b), Intended for calculating environmental impacts of the the harvesting of rainwater (Farreny et al. 2011; Angrill production of such systems, the life cycle assessment (LCA) et al. 2012, 2016) or a combination of these applications (International Organization for Standardization 2006) is the (Benis et al. 2018; Corcelli et al. 2019; Toboso-Chavero leading and most extensive methodology (European Com- et al. 2019, 2021). mission 2003). The environmental burdens of some elements To deploy these new systems, not only the environmental, of these systems described herein have been extensively social and economic benefits should be analysed but also assessed, such as the manufacturing of PV panels in coun- the potential drawbacks and externalities1 of the production tries such as China, Germany and Spain (Sumper et al. 2011; of these products to attain a holistic and forward-looking Gerbinet et al. 2014; Yue et al. 2014; Fu et al. 2015; Hong overview of the corresponding strategy (Ramaswami et al. et al. 2016; Xu et al. 2018; Lamnatou et al. 2019). Nonethe- 2016). Materialising these food-energy-water (FEW) systems less, few studies have focused their interests only on the requires the manufacturing of new materials/products such as growing media used for soilless culture systems (Verhagen photovoltaic panels, rainwater tanks, greenhouses and grow- and Boon 2008; Warwick HRI 2009; Quantis 2012; Stucki ing media. Such externalities generated by the production of et al. 2019; Vinci and Rapa 2019) because they are usually new materials are usually related to the maelstrom of global not assessed stand-alone and without relating them to plant trade; thus, the production, and also the supply chain, have management practices (e.g. fertigation) (Barrett et al. 2016). become longer and more complex (Pichler et al. 2017). The Additionally, little attention has been given to the social locations of consumption and production are separated by impacts, either positive or negative, that these complex sup- several miles, and developed countries are mainly favoured ply chains have (Traverso et al. 2012a). Social impacts affect by cheap products with high environmental and social the local communities, workers, and society in general in impacts (Hoekstra and Wiedmann 2014) while developing these centres of production. One of the widespread frame- countries bear the brunt of these externalities (Riisgaard et al. works used to account for social impacts is the social life 2010). The differences in the living and working conditions, cycle assessment (S-LCA) (UNEP/SETAC 2009), which the low labour costs or lenient environmental and labour is also used and recommended by the European Commis- regulations make these developing countries appealing to sion (Mancini et al. 2018). The S-LCA has already been companies (Hoekstra and Wiedmann 2014). applied in the renewable energies sector (Traverso et al. This globalised delocalisation, i.e. the relocation of produc- 2012a; Corona et al. 2017; Takeda et al. 2019), but to our tion activities from developed to developing countries, which knowledge, it has not yet been applied in the growing media mainly occurs because of lower labour costs in the developing sector. This methodology does not have an ISO standard but has a guideline that was updated in December 2020 (UNEP et al. 2020). The S-LCA still has various limitations due 1 to the complexity of social aspects and because of the lack An externality is a consequence of an economic activity that affects other parties and is not reflected in the final cost of a product or ser- of data and tools used as sector-specific social indicators vice. or general standardised indicators for social performance 13 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 2087 (Traverso et al. 2012b; Zamagni et al. 2015; UNEP et al. is sourced from tropical countries with large crops of coco- 2020); only two databases are in operation, the Social Hot- nut trees mainly from Indonesia, the Philippines, India and spots Database (SHDB) (New Earth 2019) and the PSILCA Sri Lanka. The perlite consumed in Europe usually comes (Ciroth and Eisfeldt 2016). For a general and first screening from Greece and Turkey because China, the largest producer of aggregated sectors, these databases are suitable; however, of perlite, mainly consumes all its produced perlite inter- for specific products/sectors, in-depth and specific screen- nally (U.S. Geological Survey 2019). The highest projected ings are recommended. increase by 2050 is assigned to coir and then perlite, the pro- Therefore, to gain insight into this gap in knowledge duction of which is expected to increase by approximately regarding suitable growing media for implementation on 700% of its current production (Growing Media Europe urban roofs, we targeted our study toward the most exten- 2019). Coir, from coir fibres and the coir pith, is the only sively used growing media constituents in the sector to ana- growing medium that is used exclusively for horticulture, lyse their environmental and social impacts. We selected while peat is also used for producing energy and perlite has the most commonly used growing media worldwide: perlite, more diversified uses. (Table 1) peat and coir (Growing Media Europe 2019). Hence, our research has a twofold goal: to assess the environmental and social impacts, including the positive and negative impacts, 2 Materials and methods of the extraction and production of three constituents to be used in urban rooftop farming (URF), i.e. in open-air The system under study involves the growing media used to farming (OAF) and in rooftop greenhouses (RTG) to grow grow vegetables on rooftops. The growing media are mainly vegetables. This is the first attempt to dive into the growing imported from other countries to Spain, which is the top pro- media sector suitable for urban rooftops, procuring compre- ducer of vegetables and fruits in the European Union (EU) hensive environmental and social life cycle assessment of (Messe Berlin 2020). We selected the three most extensively three different growing media constituents. used growing media constituents: perlite, peat and coir (Growing Media Europe 2019). The methodology consists 1.1 Case study description of two parts: the environmental LCA (E-LCA) (Sect. 2.1.1) and the social LCA (S-LCA) (Sect. 2.1.2) of these growing Various constituents are used as components of the soilless media constituents. growing media sector. In this case, three different constitu- ents were chosen. The data used to characterise the grow- 2.1 Life cycle assessment ing media were defined based on the literature (Maher et al. 2008; Barrett et al. 2016) and based on their relevancy to The E-LCA was performed following the ISO 14,040–44 this research. Consequently, five different categories were (International Organization for Standardization 2006) and proposed: physical characterisation, including the main fea- the S-LCA was performed using the established guidelines tures; the market price; the world’s leading producers; the for S-LCA (UNEP/SETAC 2009). Details are provided for total production (current and forecasted); and the applica- the different sections of the LCA, including the goal and tions of each growing medium. Data were retrieved from the scope, inventory and life cycle impact assessment. The literature, mainly from scientific papers, books and different S-LCA was conducted in three steps: (a) a social risk hotspot reports. assessment, (b) country- and sector-specific assessment and Perlite is an inorganic growing medium sourced from (c) a company-specific assessment. open-pit mining in different countries, whereas peat (extracted from peatlands) and coir are organic grow- 2.1.1 Environmental life cycle assessment (E‑LCA) ing media, albeit coir is a by-product from coconut trees (Table 1). In general, the three constituents do not contain Goal and scope The goal of this study was to analyse the enough nutrients for plants; therefore, they need additional environmental and social impacts of the extraction, produc- fertilisers. They have similar air-filled porosities and high tion and transportation of three different growing media con- water retentions. Furthermore, peat and coir have lower stituents imported to Spain that are suitable for URF. The bulk densities than perlite. Regarding the market prices, the function of these growing media is to serve as the medium most economical constituent is peat, then, coir, as it is a by- with which to grow vegetables, and the functional unit is 1 product obtained from coconut husks, while perlite costs ­m3 of a growing medium for URF, so the reference flow is 1 twice as much as the other two constituents. The producers ­m3 of each growing media. The system boundaries include of peat are mainly located in Europe. Therefore, the cost of the extraction and production of the constituents (perlite, peat transport and the related environmental impacts are pre- peat and coir) and their transportation to Spain from Tur- sumably lower than those of the other growing media. Coir key, Germany and the Philippines, respectively (see system 13 2088 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 Table 1  Characterisation of the growing media. kt, kilotons. 1 (Grillas Geological Survey 2020); 4 (Growing Media Europe 2019); "a" only et al. 2001; Maher et al. 2008; Papadopoulos et al. 2008; Barrett et al. for Europe; "b" Coconut production 2016); 2 (Soil and Substrate Preparers Association 2020); 3, 5 (U.S. boundary diagrams in the supplementary information). The be included, and the end-of-life phase is also not included. use phase is not included because other elements, such as Consequently, we focused the analysis on the stand-alone fertilisers, water and auxiliary equipment, would have to constituents. 13 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 2089 Life cycle inventory (LCI) The life cycle inventory can be the WC impact category at the country level to relate to the seen in the supplementary information (Table 1), which potential local impacts of water consumption in the studied includes the constituents and their transportation based countries. on the functional unit. We used Simapro 9.0 software by PRé Consultants, Ecoinvent 3.5 database (Swiss Centre For 2.1.1.1 Interpretation A sensitivity analysis was per- Life Cycle Inventories 2018) and GaBi ts software 9.1.0.53 formed to evaluate the significant parameters and how they by Sphera. We used the cutoff system model, therefore, influenced the outcomes. Three different parameters related in the case of the coir, as a by-product enters the system to energy and transport were used for the sensitivity analysis burden-free. because these growing media constituents are energy inten- sive. We proposed an improved scenario using more eco- Life cycle impact assessment (LCIA) For the LCIA, we used friendly road (euro 5 to euro 6) and ship transports and more the ReCiPe 2016 (Huijbregts et al. 2017) midpoints (hier- decarbonized energy in the production of perlite, which archical) V1.03. According to previous literature (Boneta requires a high amount of heat to expand it. The parameters et al. 2019; Rufí-Salís et al. 2020), we selected the following can be seen in the supplementary information. impact categories: global warming (GW; kg ­CO2 eq), terres- trial acidification (TA; kg ­SO2 eq), freshwater eutrophication 2.1.2 Social life cycle assessment (S‑LCA) (FE; kg P eq), marine eutrophication (ME; kg N eq), ecotox- icity (ET; kg 1,4-DCB) (which sums all three impact catego- A first social analysis was performed to obtain a general ries, including marine, terrestrial and freshwater ecotoxicity), overview of the growing media and to identify higher social land use (LO; m ­ 2a crop eq), fossil resource scarcity (FRS; kg risks using the SHDB. Subsequently, the second and third oil eq) and water consumption (WC; ­m3) (Goedkoop et al. assessments were conducted to narrow down the social anal- 2013). We applied the WAVE + factor (Water Accounting ysis of these growing media in their countries of origin at and Vulnerability Evaluation Model) (Berger et al. 2018) to the sector and company levels. Fig. 1  Workflow used in this study, from a general analysis to a specific analysis. GTAP, Global Trade Analysis Project; SHDB, Social Hotspots Database 13 2090 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 Goal and scope The goal of the S-LCA was the same as statistics (DataComex) (The Ministry of Industry Trade and that in the E-LCA but reduced in scope and focused only Tourism). We selected the countries that imported the largest on the extraction and production of the three constituents, percentage of each growing medium (higher than 3%) (see excluding transportation. We used the same functional unit Fig. 3). Hence, the first outcomes came from the SHDB per- as that in the E-LCA, i.e. 1 ­m3 of growing medium for URF. formance in the aggregated mineral and plant-based sectors. Three different scales were taken into account to comprehen- Site-specific data for perlite, peat and coir sively analyse constituents’ production, i.e. country-specific, We performed more specific analyses because the social sector-specific and company-specific indicators, following assessment with the SHDB was performed for aggregated the UNEP/SETAC S-LCA guidelines (UNEP/SETAC 2009). sectors. Consequently, we collected data in two ways: Figure 1 illustrates the steps taken to obtain the different social indicators at different scales. – Country- and sector-specific data retrieved from official Two systems can be implemented on URF: OAF and statistics, institutions and experts, and RTGs. Such systems require different elements to grow – Company-specific data (primary data) obtained through vegetables. Among these components, a growing medium questionnaires is essential for the proper operation of URF, and it is the component with the most volume used. In this context, an We performed a comprehensive social analysis related array of growing media can be used for vegetable cultiva- to the Sustainable Development Goals (SDGs) and in rea- tion. These substances have to share features such as light- sonable time consuming. Therefore, we selected the same ness, porosity and water retention capacity (Maher et al. impact categories proposed by the SHDB except for govern- 2008; Papadopoulos et al. 2008). In this case study, three ance, and 14 indicators within these impact categories were constituents were analysed: perlite, peat and coir. selected to analyse the social impacts at the country and sector scales considered under the scope of this research (see Life cycle inventory (LCI) For this research, we collected two Table 1). The indicators were chosen following the UNEP/ different types of data: general data and site-specific data. SETAC S-LCA guidelines (Benoît-Norris et al. 2013) and General data belong to the potential social risks at the coun- for being the most extended and accessible indicators in try and sector scales in aggregated sectors applied in the the growing media sector. The stakeholders relevant to SHDB, and site-specific data relate to social impacts at the this project were the local community, society and work- country, sector and company scales in the specific sectors ers, and the countries selected were Turkey, Germany and of perlite, peat and coir. the Philippines, which export the largest amount of each For this research, we collected two different types of data: growing medium to Spain. Table 2 summarises the different general data and site-specific data. General data belong to impact categories, subcategories, indicators and stakehold- the potential social risks at the country and sector scales in ers selected in this research; moreover, the last column indi- aggregated sectors applied in the SHDB, and site-specific cates our own classification of how these social indicators data relate to social impacts at the country, sector and com- are related to SDGs. pany scales in the specific sectors of perlite, peat and coir. The company-specific data of the growing media con- Data from the social hotspots database (SHDB) stituents were gathered through a questionnaire. The ques- Social performance was analysed by means of the SHDB. tionnaire was sent via email to 22 companies of the growing The SHDB is based on an input–output model, the Global media sector, but only three companies answered it. The Trade Analysis Project (GTAP), and includes country-spe- questionnaire was divided into a first part including basic cific indicators for 57 aggregated sectors in 140 countries. information about the company/organisation, then some gen- We used the SHDB 2019 version (New Earth 2019) based eral questions related to social reports; the last part dealt on the GTAP global equilibrium model version 9. First, with more specific questions about three major themes: there are five impact categories in the SHDB: community health and safety, human rights, and labour rights and decent infrastructure, governance, health and safety, human rights, work in the company. The design protocol can be checked in and labour rights and decent work. Second, the stakehold- the supplementary information (page 2). (Table 2) ers we chose to examine were local community, value chain actors, consumers, workers and society; third, we deter- Social life cycle impact assessment (LCIA) This research fol- mined the country of origin. In our case study, perlite and lows the use of an ordinal scale to analyse the social perfor- peat belonged to the aggregated mineral nec (not elsewhere mance of the three types of growing media by comparing the classified) sector, and coir belonged to the plant-based three options (known as the type I approach). The resulting fibre sector of the GTAP model. We retrieved the import indicators are scored depending on their relative relevance data (2018) of these growing media to Spain from official among the three options (UNEP/SETAC 2009). 13 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 2091 Table 2  Summary of the impact categories and subcategories, social indicators, and stakeholders and these related to SDGs, proposed for this research. NA, not available Social Hotspots Database (SHDB) inventory inputs for the SHDB were the aggregated sector of We used the SHDB to assess generic social hotspots. This each growing medium: the mineral nec sector for perlite and method measures the risk hours of the social impact: “risk peat and the plant-based fibre sector for coir. The countries hours represent the weighted cumulative labour hours where of perlite production were Turkey, South Africa, Greece, workers in the supply chain may be at risk for each specific the UK, Germany, Uganda, Brazil and Mozambique; those social issue” (Takeda et al. 2019). It, therefore, assesses for peat were Germany, Latvia, the Netherlands, Estonia, the indicators by assigning a risk level, proposing different Lithuania, Ireland and Finland; and those for coir were the classes of risks, from very high to high, medium and low, Philippines, India, Mozambique, Tanzania, Madagascar, based on the data distribution, expert judgement and litera- Kenia, Ecuador and Colombia. ture. It is based on labour intensity and divides the GTAP Site-specific assessment data into wage payments by country and sector by the aver- In the case of each site-specific assessment, we scored age country and sector wage; this method offers estimates of the indicators in reference to the direct comparison of the worker hours for each sector in each country. The data used alternatives. The indicators were divided into three different for the SHDB come from public institutions, country statis- scales: the country scale, sector scale and company scale. tics, NGO reports, trade unions and academic papers. The Country scale 13 2092 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 The outcomes obtained from the country-specific data 3 Results and discussion were presented numerically on a scale from high (most posi- tive) to medium to low (least positive) performance by a This section presents the results of the E-LCA (Sect. 3.1) comparison among the alternatives, and a colour scale was and the S-LCA (Sect. 3.2) and a comprehensive assess- applied. ment of all the outcomes (Sect. 3.3). Sector scale For the sector scale, we quantified all the indicators and 3.1 Environmental life cycle assessment provided a comparative scale among the options: high, medium or low performance. Additionally, a colour scale The environmental assessment is represented by each con- was applied. stituent in its country of origin. The outcomes illustrate Company scale that in 7 out of 8 impact categories, perlite, along with The primary data from companies were assessed follow- its transport from Turkey, had the highest environmental ing the same method as that used for the sector scale. When burdens, accounting for 44 to 99.9% higher impacts than possible, a score was given to each indicator (high, medium those of peat and 65 to 99.7% higher impacts than those or low performance), and a colour scale was applied. of coir (Fig. 2). In particular, perlite had higher impacts in Subsequently, the different outcomes of the different lev- freshwater eutrophication (FE) (2.4E-01 kg P eq) and eco- els were compared (Tables 4 and 5), and the overall per- toxicity (ET) (5.9E + 03 kg 1,4-DCB eq) compared to the formances of the three growing media constituents were those of other two constituents (peat and coir). There was determined (Fig. 4). only one category where the highest environmental impact Fig. 2  Relative impacts of the extraction and production of 1 m ­ 3 of ication (FE; kg P eq), marine eutrophication (ME; kg N eq), ecotox- each growing media constituent and its transport. Relative impacts icity (ET; kg 1,4-DCB), land use (LO; ­m2a crop eq), fossil resource are shown with respect to the highest values in the graph and table scarcity (FRS; kg oil eq) and water consumption (WC; m ­ 3). See all with absolute values. The impacts include global warming (GW; kg the absolute values in the supplementary information ­CO2 eq), terrestrial acidification (TA; kg ­SO2 eq), freshwater eutroph- 13 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 2093 was attributed to peat; this impact was the land use (LO) impact, which gave comparable results of 250 kg C ­ O2 eq/ impact category (3.1E + 01 ­m2a crop eq) due to the extrac- m3 and 41–85 kg ­CO2 eq/m3, respectively. tion of peat. On the other hand, coir obtained the highest impact in water consumption before the WAVE + factor 3.1.1 Consistency and completeness analysis was applied; however, after applying this factor, the water consumption of the perlite growing medium rose consid- We used the most updated datasets for the modelling of the erably due to the scarcity of this resource in its country three growing media constituents. For electricity, water and of origin, Turkey. Coir only obtained significant impacts heating, we used specific processes from each country. For compared to perlite in marine eutrophication (ME) and transportation, we used a European dataset for Germany, a water consumption (WC) because of its transport by sea, “rest of the world” (ROW) dataset for Turkey and a global representing 56 and 42%, respectively, of the impacts of dataset (GLO) for the Philippines. We did not use any alloca- perlite. tion in the case of coir by-product as other studies did (Quantis The extraction and production of perlite dominated 2012); therefore, we considered the coir burden-free. Further- the environmental impacts; perlite had the highest con- more, as stated in the methods section, we did not model the tribution in most of the categories (5 out of 8 midpoints), use phase or end-of-life phase because other materials and pro- whereas its transport by road caused the highest environ- cesses are necessary in those phases, e.g. fertigation; therefore, mental burden in ecotoxicity (92%) and land use (60%). we analysed the stand-alone constituents. Considering these results, the best performance was observed for coir, despite the long route it must take by ship. Because coir is a by-product that is transformed into 3.1.2 Sensitivity analysis a product and almost does not have environmental impacts, most of its impact comes from its transportation by ship. The sensitivity analysis further supported the importance of Peat also had low environmental burdens except for those energy (electricity, heating and fuel) in these growing media. of global warming, land occupation and fossil resource We consider transportation, which relies on distance from scarcity. Consequently, perlite is the least favourable the country of origin and the weight/volume of the grow- option from an environmental perspective since it implies ing media constituents, in the sensitivity analysis due to the the extraction of a mineral, the use of new resources, the relevance of the results depending on these parameters and consumption of energy for expanding the perlite, and a how the country of origin where the constituents come from long trip by lorry from Turkey. can affect the environmental performance. We have found two studies which are comparable to The analysis indicated that with changes such as the use our study in terms of system boundaries and assumptions, of an electricity mix that is less reliant on fossil fuels and albeit they use different impact assessment methods than more recent vehicles (euro 5 to euro 6) and ships, most of the one we applied (ReCiPe). Quantis (2012) performed the outcomes improved considerably (Table 3). We found an LCA of various substrates and applied the Impact reductions in the impacts from 100 to 0.1%. Perlite would 2002 + method (Jolliet et al. 2003), obtaining similar global reduce its impact on all midpoints by changing the energy warming impacts as we found for the three growing media that perlite requires for its manufacturing and by changing constituents except for perlite, ours is expanded perlite and the mode of transportation from lorry euro 5 to euro 6. For the global warming impact is much higher (620 kg C ­ O2 eq/ peat and coir, only changing the transportation mode would m3). They ranked from highest to lowest as follows: black decrease their impacts in most of the categories except peat (150 kg C­ O2 eq/m3), perlite (100 kg C ­ O2 eq/m3), white marine eutrophication and land use for peat and terrestrial peat (90 kg ­CO2 eq/m3) and coir (70 kg kg ­CO2 eq/m3). acidification and ecotoxicity for coir. (Table 3) Another study by Eymann et al. (2015) assessed peat and Accordingly, changing the processes that require relevant coir using the IPCC 2013 method for the global warming amounts of energy to other processes based on renewable Table 3  Sensitivity analysis based on more environmentally friendly alternatives for the energy source of perlite production and the transport of the three constituents. See the absolute values in the supplementary information (Table 4) 13 2094 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 PERLITE PEAT COIR Fig. 3  Social risks obtained from the SHDB regarding the aggregated sectors and the imports of the three growing media to Spain. h, hours energies or cleaner technologies can aid in enhancing the and labour rights and decent work (27 h), and this country environmental performances of these growing media. exports the third part of total perlite imported to Spain. Regarding peat, Latvia, Lithuania and Estonia exhibited 3.2 Social life cycle assessment the highest risk, particularly in the health and safety cat- egory. The rest of the countries performed properly, meaning 3.2.1 Outcomes from the social hotspots database (SHDB) that the risk hours ranged only from 22 to 53 h. Germany is the country that performed best, with only 22 h, and its high- These outcomes are related to the growing media constit- est score was in health and safety. Moreover, the import of uents in the aggregated sector of each country, retrieved peat to Spain was predominantly concentrated in this coun- from the SHDB (Fig. 3). The figures on the top are the total try (42%). risk hours per country and their imports to Spain in 2018, In general, concerning the coir-based growing media, all and the bottom figures are related to the five social impact of the countries had very high numbers of risk hours, from categories. Ecuador, with 198 risk hours, to the highest, India, with The SHDB offers a general overview of the different 319 h; in India, governance, human rights, and labour rights aggregated sectors. For the mineral aggregated sector to and decent work had the highest scores. The Philippines is which perlite belongs, the highest-risk hours fall into two the third best-performing among these countries and exports African countries: Uganda (243 h (h)) and Mozambique the most coir to Spain, comprising 28% of the total exports. (294 h), which mainly have risks in community infrastruc- In general, the Philippines has high risks in all the impact ture and governance, though they represented only 6% and categories. 3% of the total imports to Spain, respectively. The follow- Taking into consideration these outcomes, the best scores ing countries that perform worst are South Africa, Turkey were obtained for peat in Germany, followed by perlite in and Brazil. The highest risks among the impact categories Turkey, and the highest risk was assigned for coir in the in Turkey are health and safety (65 h), human rights (28 h) Philippines. 13 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 2095 3.2.2 Social assessment at the sector and country scales performance because 8 out of 14 indicators (57%) performed more positively than the other two options. In contrast, coir The following assessment was focused on the specific sec- obtained the worst performance, with 7 out of 14 indicators tors of perlite, peat and coir from the countries that export (50%) displaying the lowest values, and perlite had most the most of each growing medium to Spain (Table 4). These of the intermediate values (50%) among the three options. outcomes provide specific data about the types of growing (Table 4) media in three different countries that are relevant import- In three out of four impact categories, i.e. community ers in this sector. Peat from Germany depicts the best infrastructure, human rights, and labour rights and decent Table 4  Social assessment of the three constituents at the country and Classification of Social Institutions and Gender Index (SIGI category sector levels. The sources of the data can be checked in the supple- (very low, low, medium, high, very high) (OECD 2020) mentary information (Table 5). Gender inequality is sourced from the 13 2096 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 Table 5  Social assessment at company scale of the three constituents. The complete questionnaire and answers can be checked in the supplementary information (Table 6) 13 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 2097 work, peat in Germany had the best achievement indicators, 3.2.3 Social assessment at the company scale followed by perlite in Turkey and coir in the Philippines. These achievements mainly occurred due to the better work- The following assessment at the company level was retrieved ing conditions and better infrastructure in a highly devel- from the questionnaire sent to 22 companies. After a long oped country such as Germany. In contrast, in the subcat- period, we received answers from three companies in each egory of the contribution to economic development, perlite sector and country (Table 5). In general, the peat and coir showed the best behaviour, followed by coir and then peat. companies shared slightly more information than did the The reason for this result is that the perlite sector and the perlite company. Regarding community infrastructure, both coir sector (coconut production) in the studied countries are companies (peat and coir) have ongoing social or community more prominent, creating more jobs and contributing more developments, such as the promotion of nature, research and to the corresponding GDP than the peat sector, which is a education or the provision of different projects in schools. In small, family sector with fewer than 20 permanent workers all three companies, most workers are locals (perlite: 100% in the companies that is shrinking in recent years due to the local; peat: 80% local and 20% migrants; coir: 100% local). Climate Action Plan 2050 proposed by the German gov- In the same context, the peat and coir companies fol- ernment to preserve peatlands (Federal Ministry for Envi- low different certifications: the Social Accountability 8000 ronment Nature Conservation and Nuclear Safety 2016). (SA8000) certification, which involves recognised stand- By the same token, in the health and safety category, the ards of decent work, and the ISO 9000 production, which is best performance is observed for coir, then for peat, and the related to quality management systems; however, the perlite worst performance is observed for perlite. The cause of this company answered positively about the code of conduct in result is the high incidence of fatal and non-fatal injuries in the company but did not mention any specifics. All the com- mining, which is the mode of production of perlite, an inor- panies agreed that they control parameters such as noise, ganic mineral coming from open-pit mines. Perlite mining dust and fatal and non-fatal injuries, but none of them pro- is usually associated with a range of respiratory problems vided any data related to these statistics. (Sampatakakis et al. 2013; Maxim et al. 2016). Nevertheless, Regarding gender inequality, the coir company received in most countries, perlite is classified as a “nuisance dust” the best score because 50% of employees in management (Maxim et al. 2016). positions are women; however, the company was unbal- Concerning the analysis of various stakeholders, the rank- anced in the workforce because 70% of workforce employ- ings for the local community and society follow the general ees are women. In contrast, in the peat company, the major- trend, i.e. peat, perlite then coir, due to better conditions in ity of employees in management positions are men, and of Germany and Turkey than in the Philippines. Nevertheless, for the total labour force, only 33% are women. Concerning the worker group, the worst performance is assigned to perlite child labour, all of the companies concurred that it is not in Turkey because of the worst values of the fatal and non- an issue in this sector. Regarding fair salary and excessive fatal injuries and excessive working hours indicators, whereas work hours, the companies claimed these were internal coir exhibits the best scores in general in this group but the information or that they follow national sector-specific worst values for the child labour and fair salary indicators. rules. However, the perlite company that mentioned that Fig. 4  Summary of the three growing media constituents and their performances in each assessment type 13 2098 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 the salary in this sector is higher than that in other sectors, it is a mineral extracted from mines that requires energy, which coincides with the fair salary indicator at the sector water and many other processes to be produced and due scale retrieved from official sources (Table 4). However, to its road transportation from Turkey; for example, this all of the companies failed to provide any specific figures. could be reduced if perlite comes from Greece, one of the With respect to policies related to non-discrimination and main exporters. Furthermore, the perlite company limited freedom to join trade unions, the companies asserted that their answers mainly to yes/no and did not provide suffi- they follow the standards and laws related to their countries, cient details about the social data of the company. Despite but no specific data were provided. these results, this growing medium is affordable, and many These outcomes demonstrate some main issues: (a) com- conventional greenhouses in Almeria (Spain), where the panies in this sector lack knowledge about the social life highest concentration of greenhouses in the world exists, cycle assessment; (b) it is very complex to obtain social data use this growing medium due to its easy management and from companies; 22 companies were contacted and, after competitive price (Urrestarazu 2013). Additionally, Spain is much effort, we obtained 3 responses; and (c) companies do one of the leading global producers of vegetables and fruits, not share or do not have sufficient social data, and the data producing 12.9 and 14.4 million tons (2018), respectively they do share are usually very unspecific. (Table 5) (Messe Berlin 2020). This growing medium showed accept- able performance in the SHDB and in country- and sector- 3.3 Overall performance for the analysed growing specific assessments, such as community infrastructure and media constituents. Which growing media are contribution to economic development. Nonetheless, in fatal most suitable for urban rooftop farming? and non-fatal injuries, perlite scored distinctly worse than the other growing media. Different outcomes emerged among the different assess- According to the outcomes, some issues should be high- ments (Fig. 4). Comparatively, the peat growing medium lighted as follows. obtained the highest performance in all the social assess- ments. This is due to its excellent performance in the SHDB • Peat is, according to this study, ideal for use on roof- and the impact categories of the local community, human tops in Spain because its social assessment is positive rights and labour rights. Most of its positive performance is at all scales; however, peat fails in the environmental related to peat being sourced from a European Union (EU) aspect due to the aim of preserving peatlands and the country, Germany, because of the deployment of human, reduction in their exploitation. A reasonable solution labour and social security rights and the remarkable work might be the combination of local by-products such as conditions in this country. On the other hand, the peat indus- cork granulates or sawdust with peat. In this line, the try is a small-scale sector that is decreasing in size due to the peat company proposed a combination of peat, coir, restrictive peat extraction regulation of the German govern- perlite and other constituents, and the coir company ment that aims to preserve peatlands and cease extraction in suggested a terracotta tile waste mixed with coir. Con- the future (Federal Ministry for Environment Nature Con- sequently, we identify a plausible new market of local servation and Nuclear Safety 2016). growing media that tailor best in the area where they Coir obtained the best environmental outcome since it is are applied. The transformation and reuse of waste a by-product resulting from coconut husks transformed into or by-products could be the solution for future URF a value-added product, despite the long journey from the (Stucki et al. 2019; Manríquez-Altamirano et al. 2020, Philippines. The coconut sector in tropical countries such as 2021; Parada et al. 2021). India, Sri Lanka and the Philippines is quite extended, and • Coir is suitable for local and short-distance countries a variety of products are extracted from coconut trees, such but not for long-distance countries, such as those in as coconut oil; coconut fibres, for example, for ropes and Europe. Coir is a good example of transforming waste mats; beverages; and medicines (Maher et al. 2008). There- into a value-added product. However, all the social fore, indicators such as GDP contribution or employment impacts of coir related to community infrastructure and share are very positive in this sector. Conversely, this grow- human and labour rights should be enhanced for better ing medium has low performance in the SHDB, being the social performance. constituent with the highest risk hours in all the impact cat- • Perlite has major environmental burdens that should be egories. In the same way, coir has low scores in community reduced, but because of its low cost, it is widespread in infrastructure, in human rights related to gender equality and Spanish greenhouses (Urrestarazu 2013). Some social indi- child labour—approximately 19% in the country and 2.8% cators of perlite should be improved, such as reducing fatal in the coconut sector—and in labour rights and decent work. and non-fatal injuries and controlling noise and dust, for Perlite is the least environmentally friendly of the three better management of all these aspects. Another solution growing media constituents under study, mainly because for this growing medium would be to reutilise it as many 13 The International Journal of Life Cycle Assessment (2021) 26:2085–2102 2099 times as possible to increase its lifespan, as some studies decent work compared to the other two alternatives. Subse- advocate that this can decrease its environmental footprint quently, coir displayed better scores than perlite in general (Diara et al. 2012; Acuña et al. 2013). but obtained the worst values of the three alternatives in the SHDB, in the community infrastructure impact category and Future URF should not repeat the same errors made in con- for social indicators such as gender inequality, child labour ventional food supply chains, such as externalising the social and fair salary. Perlite obtained the worst performance in the and environmental costs of delocalised production. Therefore, general assessment; however, it had positive impacts in the the growing medium is a key product that must be selected GDP contribution and fair salary indicators. to minimise environmental, social and economic impacts. Proposing local products, and, when possible, growing media from waste/by-products, can improve this selection. As shown 4.2 Limitations and methodological challenges in this study, new products, such as perlite, have high environ- mental and social burdens and long distances from their points From a methodological standpoint, it was very complex to of production in countries with lenient labour regulations that obtain data for the indicators/impact categories used for the rocket these impacts. Accordingly, we display the first attempt social assessment of not-very-mainstream products, and to conduct comprehensive assessments of three commercial companies were reluctant to share this information. There- growing media constituents that will aid in selecting the most fore, much effort had to be made in this regard. In the same feasible growing medium option, in this case for Spain; how- context, social data are not centralised in any institution, and ever, this could be used for other European countries. countries sometimes use different indicators with the same purpose; thus, it is necessary to harmonise social indicators and prioritise which social indicators to use. To progress in 4 Conclusions social assessments and make the assessments more dynamic to perform, we recommend further research aiming to (a) 4.1 Outcomes from the environmental and social prioritise social indicators, as S-LCA presents multiple indi- life cycle assessment cators; we advocate for centralising efforts in the most com- mon and widespread indicators, such as gender inequality, We contributed comprehensive assessments of three grow- labour rights, and health and safety, or SDGs indicators; ing medium constituents used to grow vegetables in future (b) increase the data availability of disaggregated sectors scenarios in cities where land availability is scarce and in databases such as the SHDB and PSILCA targeting to there will be a need for soilless systems. We analysed the easily perform social assessments; and (c) promote among most extensively used growing media, perlite from Turkey, companies the control of social data to generate open-source peat from Germany and coir from the Philippines, to be databases to be used for researchers and organisations. In used in urban roofs to cultivate vegetables by performing addition, this research was performed using the first S-LCA an environmental and social life cycle assessment. guidelines (2009) by the UNEP/SETAC Life Cycle Initia- The environmental assessment highlighted perlite as tive. Last December (2020), a new guideline was launched, the most harmful option compared to peat and coir. Due which means that many efforts are already being made, for to the extraction of new material from open-pit mines and example reinforcing and clarifying, with a range of exam- the quantity of energy needed for all the manufacturing ples, the methodological developments in S-LCAs or linking processes, the highest values in freshwater eutrophication the S-LCA impact subcategories with SDGs due to the fact (2.4E-01 kg P eq) and ecotoxicity (5.9E + 03 kg 1,4-DCB that fourteen of the seventeen goals concern social impacts eq) were obtained for perlite compared with the rest of the and have many connections with the S-LCA framework. growing media. Transport by road from Turkey to Spain Obtaining the social data for these growing media in the also contributed considerably to the environmental impacts studied countries was a constraint for this study. On the one of perlite, mainly in ecotoxicity (92%; 5.49E + 03 kg 1,4- hand, few social data, even those related to health and safety DCB eq) and land use (60%; 1.29E + 01 ­m 2a crop eq). and labour rights, are recorded by companies or for specific In contrast, the most environmentally friendly option was products, and these data are usually aggregated in general coir, despite its long transport route from the Philippines sectors such as agriculture and mining. On the other hand, to Spain. businesses are reluctant to respond to surveys and share Regarding the social assessment, owing to its origin in information; hence, new mechanisms must be developed to an EU country, peat was the most socially friendly growing foster advancements in this field, such as a kind of certifica- medium in the three assessments performed due to its more tion for sharing social data, another type of compensation, or favourable indicators in impact categories such as com- increasing pressure on companies from consumers and insti- munity infrastructure, human rights, and labour rights and tutions to demand transparency in value chains. 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The Research Executive Agency (REA) Urban Home Garden in a Mediterranean City. Front Plant Sci is not liable for any use that may be made of the information contained 10:341. https://​doi.​org/​10.​3389/​fpls.​2019.​00341 therein. This research has also received financial support from “María Brudermann T, Sangkakool T (2017) Green roofs in temperate climate de Maeztu” Units of Excellence (CEX2019-000940-M); the Spanish cities in Europe – An analysis of key decision factors. Urban for Ministry of Education, Culture and Sports grant FPU16/03238; the Urban Green 21:224–234. https://​doi.​org/​10.​1016/j.​ufug.​2016.​ European Commission’s ERC Consolidator grant 818002-URBAG and 12.​008 Greenhouses to Reduce ­CO2 on Roofs (GROOF) project (UE. Interreg Ciroth A, Eisfeldt F (2016) PSILCA — A Product Social Impact Life NWE 474, 2017–2021). 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J Ind Ecol 23:767–780. https://​ ables-Based Prod Methods Case Stud doi.​org/​10.​1111/​jiec.​12829 Toboso-Chavero S, Villalba G, Gabarrell Durany X, Madrid-López Publisher's Note Springer Nature remains neutral with regard to C (2021) More than the sum of the parts. System analysis of the jurisdictional claims in published maps and institutional affiliations. Authors and Affiliations Susana Toboso‑Chavero1,2 · Cristina Madrid‑López1 · Gara Villalba1,2 · Xavier Gabarrell Durany1,2 · Arne B. Hückstädt3 · Matthias Finkbeiner4 · Annekatrin Lehmann4 1 3 Sostenipra Research Group (2017 SGR 1683), Institute Industrieverband Garten (IVG) E.V, Wiesenstraße 21 a1, of Environmental Science and Technology (ICTA; “María 40549 Düsseldorf, Germany de Maeztu” Units of Excellence (CEX2019‑000940‑M), 4 Institute for Environmental Engineering, Sustainable Z Building, Universitat Autònoma de Barcelona (UAB), Engineering, Technische Universität Berlin, sec. Z 1, Straße Campus UAB, 08193 Bellaterra, Barcelona, Spain des 17. Juni 135, 10623 Berlin, Germany 2 Department of Chemical, Biological and Environmental Engineering, Universitat Autònoma de Barcelona (UAB), Campus UAB, 08193 Bellaterra, Barcelona, Spain 13