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Environmental impact of Agaricus bisporus cultivation process
Europ. J. Agronomy 71 (2015) 141–148
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European Journal of Agronomy journal homepage: www.elsevier.com/locate/eja
Environmental impact of Agaricus bisporus cultivation process F.J. Leiva a , J.C. Saenz-Díez b , E. Martínez a , E. Jiménez b , J. Blanco a,∗ a b
Department of Mechanical Engineering, University of la Rioja, Edificio Departamental—C/Luis de Ulloa, 20, 26004 Logro˜ no, La Rioja, Spain Department of Electrical Engineering, University of la Rioja, Edificio Departamental—C/Luis de Ulloa, 20, 26004 Logro˜ no, La Rioja, Spain
a r t i c l e
i n f o
Article history: Received 5 June 2015 Received in revised form 15 September 2015 Accepted 22 September 2015 Available online 1 October 2015 Keywords: Environmental impact Life cycle assessment Mushroom growing Agaricus bisporus
a b s t r a c t This paper analyses the environmental impact of the process of cultivating Agaricus bisporus. Cultivation is the final phase of the mushroom production process. We seek to quantify the environmental impact of this process by means of a life-cycle analysis (LCA). This paper presents a cradle-to-gate LCA of the process of farming Agaricus bisporus mushrooms, based on actual data from a production plant gathered over the course of a year so as to provide accurate information on the environmental impact of the various activities that make up the production process. An overall analysis of the main phases of the production process reveals that the activity with the greatest impact in almost all categories is the climate control of the growing chambers, because of the considerable amount of energy required to power the system, which is running continuously. The only impact categories in which climate control is not the number one phase are global warming in the growing phase and ozone layer depletion and eutrophication in the covering soil preparation phase. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Agaricus bisporus is a basidiomycete mushroom belonging to the Agaricaceae family which is cultivated in over 70 countries (Ma et al., 2014; Saravanan et al., 2013), and has for decades been the most widely grown of all mushrooms (Foulongne-Oriol et al., 2014; Tautorus and Townsley, 1984). It is used mostly in cooking, where it has been an important component of the human diet for over 200 years (Morin et al., 2012), but is also widely used in medicine since it has anti-microbial, anti-tumoral, anti-carcinogenic and anti-oxidant properties (Özc¸elik and Peks¸en, 2007). It provides substantial amounts of high-quality proteins, amino acids, polysaccharides and vitamins (Moon and Lo, 2013; Wani et al., 2010), low energy levels and certain important elements such as potassium and phosphorus, and is acknowledged as being of gastronomic value (Vetter, 2007). The fruiting bodies of this mushroom have been used for centuries as foods and food flavourings (Ma et al., 2014). It is farmed under ambient conditions designed to suit its growth, but can be found in all highly humid regions between spring and autumn (Akinyele et al., 2012).
It grows mainly on substrates that must be partly decomposed so that they are free of soluble sugars conducive to the growth of mould and bacteria (Donini et al., 2006). This paper sets out to analyse the environmental impact of the process of cultivating Agaricus bisporus. Cultivation is the final phase of the mushroom production process. Scientific studies have been conducted on other varieties of mushrooms (Tongpool and Pongpat, 2013; Ueawiwatsakul et al., 2014), but there is little scientific literature on the environmental implications of the production process of Agaricus bisporus. We seek to quantify the environmental impact of this process by means of a life-cycle analysis (LCA). By identifying and analysing the inputs and outputs of the various activities involved we have been able to draw up a cradle-to-gate LCA for the process. This LCA is based on data from production plants in the La Rioja region of Spain. La Rioja is Spain’s number one producer of Agaricus bisporus, with a total of 215 ha given over to its cultivation (43.3% of the total for Spain). The region produces 52% of Spain’s national output (Ministry of Agriculture, 2014) and 4.25% of that of Europe (Sonnenberg et al., 2011). 1.1. Mushroom growing
∗ Corresponding author. E-mail addresses: [email protected] (F.J. Leiva), [email protected] (J.C. Saenz-Díez), [email protected] (E. Martínez), [email protected] (E. Jiménez), [email protected] (J. Blanco). http://dx.doi.org/10.1016/j.eja.2015.09.013 1161-0301/© 2015 Elsevier B.V. All rights reserved.
Mushrooms were originally grown in caves, but the process has gradually shifted to climate-controlled chambers where growing conditions can be controlled. This entails energy consumption and requires cooling systems (Foulongne-Oriol et al., 2014).
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The development of a new colony of Agaricus bisporus begins with the germination of spores. Their hyphae grow and form a large mycelium network. Various factors then induce the mycelium to produce fruiting bodies under controlled climate conditions (LeivaLázaro et al., 2015; Umar and Van Griensven, 1997). The fruiting bodies of Agaricus bisporus begin to develop and grow as soon as the primordia appear. They ripen, produce spores, then finally go into senescence, the period between full maturity and the death of the organism. The post-harvesting period of the fruiting bodies is of the utmost importance for marketing purposes, as they must maintain their characteristic colour and aroma (Umar and Van Griensven, 1997). A quality substrate is a prime requirement for growing mushrooms successfully: they absorb all their nutrients from the substrate, which is also an important source of lignocellulose for the development of the fruiting body (Tripathy et al., 2009). The substrate comprises mainly compost with a covering layer of soil on which the fruiting bodies form (Berendsen et al., 2012). The compost substrate is generally made up of manure, mostly chicken manure at present because it is in abundant supply (Castle, 1993). The job of the covering layer is to keep the crop properly hydrated at all times and protect it from aggressive microflora (Gillmann et al., 1994). The covering layer is generally composed of neutralised peat with chalk or limestone (Castle, 1993). Peat is used as a covering material (Gülser and Peks¸en, 2003; Noble et al., 2003). The physical and chemical properties required of peat (and any other substrate) include high porosity and water retention capacity, a pH of between 7.2 and 8.2, an active lime concentration of between 2.5 and 3.5% and a total nitrogen concentration of between 0.7 and 0.8%. The material must also have low inorganic and organic nutrient contents and be free from contaminations and pests (Gülser and Peks¸en, 2003). The mycelia of different species grow differently, depending on the type of medium used and the pH, though growth is also influenced by genetic make-up, by the substrate, by the temperature (De Andrade et al., 2010) and by the ageing of the mycelium (Mata and Savoie, 2013). During incubation and coverage, the temperature must be kept below 28 ◦ C. The ambient temperature needs to be brought down to stimulate sporophore production. Temperatures of 16–19 ◦ C are recommended during the fruiting period (Foulongne-Oriol et al., 2014) and 21–25 ◦ C during the growth phase (Largeteau et al., 2011). Studies have demonstrated that Agaricus bisporus can withstand temperature increases and has adapted to temperatures as high as 25 ◦ C during the fruiting phase (Largeteau et al., 2011).
LCA provides a quantitative basis for assessing potential improvements in the environmental performance of a system throughout its life-cycle, and is therefore an increasingly important tool for decision-making in the field of environmental management (Azapagic and Clift, 1999; Siracusa et al., 2014), under standard ISO 14040 (Martínez et al., 2009). It helps to decide which is the best possible option (Guinee et al., 1993; Jiménez et al., 2014; Stevenson et al., 2014) and provides a basis for assessing potential improvements in the environmental performance of a system or product (Azapagic and Clift, 1999; Khoshnevisan et al., 2013; Ulloa et al., 2011). It was developed to analyse environmental impacts such as global warming, soil use and water use, depletion of the ozone layer, acidification, human toxicity, eco-toxicity, depletion of natural resources, energy consumption and eutrophication (Jiménez et al., 2014). It can also be used as a tool for identifying critical points in production processes with a view to identifying potential improvements (Belussi et al., 2015), and as a tool for examining all environment-related aspects and potential impacts of products or services, since it considers all aspects and phases of each product or process (Jiménez et al., 2014). The LCA model used here was drawn up using the Simapro 7.3 software package and the CML 2000 Leiden calculation method. One of the first requirements is to properly define the goals and limits of the system. This is essential for the assessment of the final results, because it is necessary to know not only the extent of the impact assessed but also the extent of the study and the different process phases taken into account. The main goal is to obtain a comprehensive environmental view of the process, by identification and analysis of the inputs and outputs of materials and energy associated with the different ways in which each activity involved in the process of growing Agaricus bisporus takes place. 2. Materials and methods 2.1. Goals and scope A cradle-to-gate analysis is conducted, examining the production processes and identifying in each case the materials used, the energy resources and the process flows involved up to the production of the final functional unit. Also included are the flow of products from the entry of raw materials (including transport from the source firm to the producer) and the harvesting of the end product. The phases of the life-cycle taken into account therefore range from material inputs to the storage of the end product, in order to identify the critical activities within the process.
1.2. Life-cycle assessment (LCA) LCA is an appropriate way of assessing and analysing the environmental impact and other environment-related issues of services, materials and products throughout their life cycles (Azapagic and Clift, 1999; Baumann and Tillman, 2004; Leiva-Lázaro et al., 2014). It can be defined as a compilation and assessment of the inputs, outputs and potential environmental impacts of a product system throughout its life-cycle (Nicolae and George-Vlad, 2015). LCA is conducted with two main goals: • to quantify and assess the environmental performance of a product, process or activity over its whole life-cycle (Pieragostini et al., 2014); • to provide a basis for assessing potential improvements in the environmental performance of a product system (Azapagic and Clift, 1999).
2.2. Functional unit The functional unit used for this study is a 1 kg of Agaricus bisporus mushrooms. 2.3. System boundaries Limits are set on actions in order to focus the study. The limits in regard to the LCA cover overall production of the product, i.e. the growing of 1 kg of mushrooms (defined as the functional unit) and their distribution (see Fig. 1). The activities included within the system boundaries are the following: • Materials input, including transport from point of origin. • Fuel consumed by forklift trucks and dozers.
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Fig. 1. System boundaries.
• Electricity consumed by process production equipment. • Movement of materials and products from the entrance points used within the production plant. • CO2 emissions during growing. • Loading and transporting of end product. • Distribution of end product to consumers. • Waste management.
The following are excluded from the system boundaries:
• All the activities and consumption inherent in the production, acquisition and maintenance of capital goods. These items are excluded because of their scant impact on the functional unit and because of a lack of data. • Setting up and dismantling of the growing plant. This exclusion is based on the scant impact of this item on the functional unit and on a lack of data. • Transportation and treatment of organic waste produced at the plant. • Treatment of waste from the end product at the consumption stage.
2.4. Assumptions • There is no stocking of the end product, i.e., all output is distributed. • The ventilation in the growing chambers is considered to be constant throughout the process. • The functional unit considered is 1 kg of mushrooms. • The capacity of the growing chambers is 1656 seed packages. • Daily output is considered to be the same for each working day, with the growing chambers kept at maximum capacity as regards seed packages. • CO2 concentrations during the growing process are measured on site with a calibrated measuring device. • A seed packages is a mixture of compost and mycelium seeds (Leiva-Lázaro et al., 2015) with an average weight of 19 kg. 2.5. Inventory For this study a cradle-to-gate LCA of the full process of growing Agaricus bisporus mushrooms has been carried out. Raw material consumption and the distances covered by suppliers have been taken into account. The study also includes all the sources of energy used in the process.
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Table 1 Inventory data for climate controlled chambers.
Table 4 Inventory data for preparation of the growing chambers.
Materials
Quantity per kg of product
Materials
Quantity per kg of product
Electricity usage Biomass Disinfectant
2.04E − 01 kWh 1.68E + 02 kcal 1.24E − 04 L
Disinfectant Water Diesel Seed packages
2.51E − 04 L 7.20E − 05 m3 2.68E − 03 L 1.78E − 01 packages
The inventory is drawn up in line with the data provided and collected over the course of a year, beginning and ending in August. To facilitate analysis and assessment, the process is divided into various phases (see Fig. 1):
Once the covering soil is prepared the mixture is placed in a container ready for its subsequent use during the covering phase.
• Climate controlled chambers: temperature control of the facility. • Ventilated chambers: temperature control of the facility. • Preparation of the covering soil: preparation of the soil used to cover the seed packages with mycelium for the growing process. • Preparation of the growing chambers: placement of trays and utensils required for the growing process. • Growing process: divided in various phases, such as, mycelium activation, homogenisation and end product harvesting. • Waste management: management of the waste produced during the growing phase up to the harvesting of the end product for subsequent processing.
2.5.4. Preparation of the growing chambers The next phase of the process is the preparation of the growing chambers so that the seed packages can be placed in them. The materials and resources used in this phase are listed in Table 4. The process begins with the disinfection of the growing chambers to prevent the appearance of contaminations during the growing process (see Fig. 2, Disinfecting GC activity). Once disinfection is completed, the chambers are prepared by setting out the cages where the seed packages are to be placed (see Fig. 2, Preparing GC activity). The seed packages are then placed on the cages so that the growing process can begin (see Fig. 2, Placing seed packages activity).
2.5.1. Climate controlled chambers This study covers two types of chamber: climate-controlled and ventilated. The growing process in climate-controlled chambers includes constant temperature control and a heating system powered by biomass. The materials and resources used in this phase are listed in Table 1. 2.5.2. Ventilated chambers The growing process in ventilated chambers features only a ventilation system to keep clean air constantly recirculating through the interior of the chambers. The materials and resources used in this phase are listed in Table 2. 2.5.3. Preparation of the covering soil The first phase of the growing process is to prepare the soil used to cover the seed packages. The materials and resources used in this phase are listed in Table 3. The process begins with the disinfection of the area where the covering soil is to be prepared, so as to prevent the appearance of contaminations during the growing process (see Fig. 2, Disinfecting CS activity). Peat is received in big-bags, which are deposited in the disinfected area. This peat does not contain sufficient moisture, so water is added to bring the moisture content up to the level required for covering soil. In this phase fungicides are also added to prevent pests and/or contaminations during the growing process (see Fig. 2, Mixing activity). Table 2 Inventory data for ventilated chambers. Electricity usage Materials
2.48E − 02 kWh Quantity per kg of product
2.5.5. Growing process The next phase is the growing process itself, which culminates with the harvesting of the end product. The materials and resources used in this phase are listed in Table 5. This process begins once all the seed packages have been placed on the cages in the chambers with the covering soil prepared earlier and water has been added to start the growing phase (see Fig. 2, Covering seed packages activity). Continual fumigation by adding fungicides and insecticides is required to prevent the appearance of pests during the growing process (see Fig. 2, Fumigation activity). During the growing process homogenisation (activation of the mycelium) and fruiting (development of the fruiting bodies) begin (see Fig. 2, Homogenisation activity and Fruition activity). When the fruiting process is completed the fruiting bodies are harvested in three different collections in each chamber (see Fig. 2, Harvesting activity). During harvesting, the product is manually cut and placed in boxes for its subsequent distribution (see Fig. 2, Distribution activity). 2.5.6. Waste management The final phase is the management of the waste produced during the process. The materials and resources used in this phase are listed in Table 6. Table 5 Inventory data for growing process. Materials
Quantity per kg of product
Water Fungicide Insecticide Box Labels
1.04E − 03 m3 8.36E − 02 L 1.71E − 04 L 8.36E − 02 units 8.36E − 02 units
Table 3 Inventory data for preparation of the covering soil. Materials
Quantity per kg of product
Peat Fungicide Disinfectant Water
5.18E − 03 t 7.81E − 02 L 2.79E − 05 L 2.01E − 01 m3
Table 6 Inventory data for waste management. Materials
Quantity per kg of product
Diesel Transport
8.92E − 04 L 1.24E − 01 kg/km
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Fig. 2. Flow chart of the Mushroom cultivation process.
The waste produced when mushrooms are cut is deposited in a container for subsequent collection and treatment. Packages and spent soil at the end of the growing process are placed in a separate container for collection and treatment at a specific plant (see Fig. 2, Removing packages and Soil activity). 3. Results This paper presents an LCA carried out to identify the main environmental impacts in the process of growing Agaricus bisporus mushrooms, based on a cradle-to-gate approach. It is conducted with SimaPro® software, using the CML Leiden 2000 method to calculate environmental impact. The functional unit set for the LCA is 1 kg of product. The environmental impact results obtained from the LCA are presented below. The overall environmental impact of the product in all the impact categories analysed is presented first, and then the results for each of the three phases are presented separately.
3.1. Overall environmental impact analysis Table 7 presents the overall environmental impact results for the product studied, covering all the impact categories considered. The weight of each phase of production considered in this LCA (i.e., preparation of covering soil, preparation of growing chambers, growing process and waste management) is also shown. An analysis of the main phases of the overall production process reveals that the preparation of growing chambers is the process with the greatest impact in almost all categories. This is because it consumes a great deal of energy. The environmental impact of this phase varies depending on the impact category considered, from 48.39% for seawater eco-toxicity to 74.12% for eutrophication (see Table 7). In the growing process the greatest impact is that of global warming, at 99.28%, and in the climate control of the chambers it is soil eco-toxicity, at 87.88 % (see Table 7). This is because the carbon sink effect of the organic matter in the compost and in the covering
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Table 7 Global environmental impact, CML .ethodology. Impact category
Unit
Total
Preparation of the covering soil
Preparation of the growing chambers
Growing process
Waste management
Ventilation
Climate control
Abiotic depletion (AD) Global warming (GWP100) Ozone layer depletion (OLD) Human toxicity (HT) Fresh water aquatic ecotox (FWAE) Marine aquatic ecotoxicity (MAE) Terrestrial ecotoxicity (TE) Photochemical oxidation (PO) Acidification (AC) Eutrophication (EU)
kg Sb eq kg CO2 eq kg CFC-11 eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg C2 H4 kg SO2 eq kg PO4 – -eq
6.78E − 03 4.42E + 00 9.07E − 08 4.32E − 01 5.47E − 02 4.36E + 02 −1.01E − 02 2.58E − 04 7.95E − 03 2.41E − 03
1.96E − 03 −1.37E + 00 3.54E − 08 8.07E − 02 6.27E − 03 4.68E + 01 −9.60E − 03 5.43E − 05 1.60E − 03 5.34E − 04
3.76E − 03 −1.45E + 00 4.98E − 08 2.88E − 01 3.46E − 02 2.11E + 02 −2.89E − 03 1.27E − 04 4.29E − 03 1.79E − 03
5.44E − 05 7.10E + 00 6.38E − 10 1.64E − 03 3.35E − 04 1.64E + 00 3.73E − 05 1.10E − 06 2.15E − 05 2.17E − 06
1.79E − 05 3.92E − 04 3.47E − 10 2.68E − 04 2.83E − 05 2.42E − 01 1.62E − 06 2.63E − 07 4.69E − 06 4.72E − 07
1.06E − 04 1.51E − 02 4.55E − 10 5.62E − 03 1.41E − 03 1.90E + 01 2.52E − 04 8.02E − 06 2.14E − 04 7.34E − 06
8.87E − 04 1.33E − 01 4.05E − 09 5.57E − 02 1.21E − 02 1.57E + 02 2.11E − 03 6.74E − 05 1.83E − 03 7.94E − 05
Table 8 Detail of the environmental impact by activities, CML methodology. Preparation of the covering soil
Preparation of the growing chambers
Category
Unit
Mixing
Disinfecting CS
Placing seed packages
Disinfecting GC
Preparing GC
AD GWP100 OLD HT FWAE MAE TE PO AC EU
kg Sb eq kg CO2 eq kg CFC-11 eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg C2H4 kg SO2 eq kg PO4 eq
1.96E − 03 −1.37E + 00 3.54E − 08 8.06E − 02 6.25E − 03 4.67E + 01 −9.61E − 03 5.43E − 05 1.59E − 03 5.34E − 04
2.51E − 06 2.05E − 04 3.58E − 11 1.09E − 04 1.70E − 05 1.20E − 01 3.48E − 06 6.05E − 08 1.36E − 06 8.25E − 08
3.72E − 03 −1.45E + 00 4.91E − 08 2.86E − 01 3.44E − 02 2.10E + 02 −2.92E − 03 1.26E − 04 4.27E − 03 1.78E − 03
2.26E − 05 1.84E − 03 3.22E − 10 9.83E − 04 1.53E − 04 1.08E + 00 3.14E − 05 5.45E − 07 1.22E − 05 7.42E − 07
1.78E − 05 3.72E − 04 3.44E − 10 2.63E − 04 2.74E − 05 2.39E − 01 1.58E − 06 2.59E − 07 4.57E − 06 4.48E − 07
Growing process Category
Unit
Covering
Fumigation
Homogenisation
Fruition
Harvesting
Distribution
AD GWP100 OLD HT FWAE MAE TE PO AC EU
kg Sb eq kg CO2 eq kg CFC-11 eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg C2 H4 kg SO2 eq kg PO4 eq
3.43E − 05 2.60E + 00 3.35E − 10 8.29E − 04 1.70E − 04 7.69E − 01 1.71E − 05 5.49E − 07 8.64E − 06 7.16E − 07
8.60E − 06 9.49E − 01 1.22E − 10 3.75E − 04 5.96E − 05 4.14E − 01 1.19E − 05 2.10E − 07 4.68E − 06 2.84E − 07
1.34E − 06 2.78E − 01 1.91E − 11 5.83E − 05 9.04E − 06 6.37E − 02 1.86E − 06 3.23E − 08 7.25E − 07 4.40E − 08
1.34E − 06 7.45E − 01 1.91E − 11 5.83E − 05 9.04E − 06 6.37E − 02 1.86E − 06 3.23E − 08 7.25E − 07 4.40E − 08
2.74E − 06 2.53E + 00 2.66E − 11 1.32E − 04 5.13E − 05 2.13E − 01 2.95E − 06 1.14E − 07 1.86E − 06 1.24E − 07
3.43E − 05 2.60E + 00 3.35E − 10 8.29E − 04 1.70E − 04 7.69E − 01 1.71E − 05 5.49E − 07 8.64E − 06 7.16E − 07
soil used in preparation for covering and in the preparation of the growing chambers has a positive impact in the said categories. By contrast, the phase with the least impact is that of waste treatment, because of its low energy demand and demand for materials. The figures for impacts are much lower than the other phases, and in fact vary from 0.002% in the global warming category to 0.38% in the ozone layer depletion category (see Table 7).
3.2. Environmental impact phase by phase Each phase is analysed separately below, identifying each activity considered in each case and its weight in the environmental impact of the various categories.
3.2.1. Preparation of the covering soil In this phase the activity with the greatest impact in all categories is the mixing of the covering soil, because it consumes more energy and material resources than the disinfection phase. The environmental impact of this phase ranges from 99.72% in the water eco-toxicity category to 99.98 % for eutrophication (see Table 8). The impact of the disinfection and cleaning of the covering soil preparation area is much lower than that of the soil mixing, ranging from 0.09% in the acidification category to 0.27% in fresh-water eco-toxicity (see Table 8).
It is worth noting that there are positive impacts during the covering soil mixing phase in the categories of global warming and soil eco-toxicity due to the absorption of CO2 by the organic matter in the peat. That is why there is only a negative impact in the disinfection phase in the mixing area. 3.2.2. Preparation of the growing chambers In the preparation of the growing chambers the phase of placing the packages in the chambers is the activity with the greatest impact in almost all categories, because the machinery used consumes more energy. In figures this environmental impact ranges from 99.72% in the freshwater eco-toxicity category to 99.98% for eutrophication. The biggest impacts in the categories of global warming and soil eco-toxicity can be found in the disinfection of the growing chambers, at 83.22% and 95.02%, respectively, due to the fact that there are positive impacts from the incorporation of compost and the mycelium seeds in the chamber preparation phase, so the biggest negative impacts are found in the growing chamber disinfection phase. By contrast, the growing chambers preparation phase has low impacts in almost all categories because most of the demand for energy and use of materials take place in other activities. Its impact ranges from 0.03% in the eutrophication category to 16.78% in the global warming categories, with the exception of ozone layer deple-
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tion, where the lowest impact can be found in the disinfection of the growing chambers, with 0.65% (see Table 8).
3.2.3. Growing process In the growing phase the activity with the greatest impact in almost all categories is the covering of the seed packages with compost, because of the energy consumed in this process. The extent of the impact varies from one impact category to another, with a figure of 36.58% in the global warming category and as much as 63.16% in abiotic depletion. In the harvesting phase there is a significant impact of 35.62% in the global warming category. The only impact category in which the growing phase does not have the greatest impact is eutrophication, where the end product distribution process accounts for 44.25% of the total impact (see Table 8). By contrast, the processes with the lowest impacts in almost all categories are homogenisation and fruiting, with figures that range from 2.02% in the eutrophication category to 4.98% in soil eco-toxicity. An exception is the global warming category, where the lowest impact is that of the distribution phase, with 0.012 % (see Table 8).
4. Discussions and conclusions This paper presents a cradle-to-gate LCA of the process of farming Agaricus bisporus mushrooms, based on actual data from a production plant gathered over the course of a year so as to provide accurate information on the environmental impact of the various activities that make up the production process. An overall analysis of the main phases of the production process reveals that the activity with the greatest impact in almost all categories is the climate control of the growing chambers, because of the considerable amount of energy required to power the system, which is running continuously. The only impact categories in which climate control is not the number one phase are global warming in the growing phase and ozone layer depletion and eutrophication in the covering soil preparation phase. The result obtained in the category of global warming is 4.42 kg CO2 eq. Comparing with other cultures, such as strawberry (4.4 kg CO2 eq.) or lettuce (5.5 kg CO2 eq.) (Gunady et al., 2012), the result is similar, and it is within a range of acceptable emissions for edible cultures. Therefore, the CO2 emissions associated to the production of Agaricus bisporus suppose a less relevant impact than the initially estimated. Besides, this value represents a reference for the implementation and control of measures to reduce the environmental impact of mushroom production plants. Analyzing in detail the production process, in the preparation of covering soil the activity with the greatest impact in all categories is the mixing of the soil, because of how much energy it requires. In the preparation of the growing chambers phase the disinfection of the chambers is the activity with the greatest impact in many phases, because of the large amount of energy required and the use of chemical disinfectants. Exceptions are abiotic depletion, ozone layer depletion, photo-chemical oxidation and eutrophication, in which the greatest impact can be found in the process of placing the seed packages in the growing chambers. In the growing process phase the activity with the greatest impact in almost all categories is the covering of the packages with compost, because of the amount of energy consumed by the cooling system for final storage. The exception is eutrophication, where the biggest impact is found in the end product distribution phase.
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Acknowledgments This paper has been supported by the project of the Government of La Rioja (ADER 2011-I-IDD-00043) “Producción sostenible del ˜ champinón de La Rioja y mejora de la protección ambiental, a través de la investigación de Ecoindicadores del Análisis de Ciclo de Vida (ACV)”. References Akinyele, J.B., Fakoya, S., Adetuyi, C.F., 2012. Anti-growth factors associated with Pleurotus ostreatus in a submerged liquid fermentation. Malays. J. Microbiol. 8, 135–140. Azapagic, A., Clift, R., 1999. Life cycle assessment and multiobjective optimisation. J. Clean Prod. 7, 135–143. Baumann, H., Tillman, A.M., 2004. The Hitch Hiker’s Guide to LCA: An Orientation in Life Cycle Assessment Methodology and Applications Studentlitteratur AB. Lund, Sweden. Belussi, L., Mariotto, M., Meroni, I., Zevi, C., Svaldi, S.D., 2015. LCA study and testing of a photovoltaic ceramic tile prototype. Renew. Energy 74, 263–270. 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European Journal of Agronomy journal homepage: www.elsevier.com/locate/eja
Environmental impact of Agaricus bisporus cultivation process F.J. Leiva a , J.C. Saenz-Díez b , E. Martínez a , E. Jiménez b , J. Blanco a,∗ a b
Department of Mechanical Engineering, University of la Rioja, Edificio Departamental—C/Luis de Ulloa, 20, 26004 Logro˜ no, La Rioja, Spain Department of Electrical Engineering, University of la Rioja, Edificio Departamental—C/Luis de Ulloa, 20, 26004 Logro˜ no, La Rioja, Spain
a r t i c l e
i n f o
Article history: Received 5 June 2015 Received in revised form 15 September 2015 Accepted 22 September 2015 Available online 1 October 2015 Keywords: Environmental impact Life cycle assessment Mushroom growing Agaricus bisporus
a b s t r a c t This paper analyses the environmental impact of the process of cultivating Agaricus bisporus. Cultivation is the final phase of the mushroom production process. We seek to quantify the environmental impact of this process by means of a life-cycle analysis (LCA). This paper presents a cradle-to-gate LCA of the process of farming Agaricus bisporus mushrooms, based on actual data from a production plant gathered over the course of a year so as to provide accurate information on the environmental impact of the various activities that make up the production process. An overall analysis of the main phases of the production process reveals that the activity with the greatest impact in almost all categories is the climate control of the growing chambers, because of the considerable amount of energy required to power the system, which is running continuously. The only impact categories in which climate control is not the number one phase are global warming in the growing phase and ozone layer depletion and eutrophication in the covering soil preparation phase. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Agaricus bisporus is a basidiomycete mushroom belonging to the Agaricaceae family which is cultivated in over 70 countries (Ma et al., 2014; Saravanan et al., 2013), and has for decades been the most widely grown of all mushrooms (Foulongne-Oriol et al., 2014; Tautorus and Townsley, 1984). It is used mostly in cooking, where it has been an important component of the human diet for over 200 years (Morin et al., 2012), but is also widely used in medicine since it has anti-microbial, anti-tumoral, anti-carcinogenic and anti-oxidant properties (Özc¸elik and Peks¸en, 2007). It provides substantial amounts of high-quality proteins, amino acids, polysaccharides and vitamins (Moon and Lo, 2013; Wani et al., 2010), low energy levels and certain important elements such as potassium and phosphorus, and is acknowledged as being of gastronomic value (Vetter, 2007). The fruiting bodies of this mushroom have been used for centuries as foods and food flavourings (Ma et al., 2014). It is farmed under ambient conditions designed to suit its growth, but can be found in all highly humid regions between spring and autumn (Akinyele et al., 2012).
It grows mainly on substrates that must be partly decomposed so that they are free of soluble sugars conducive to the growth of mould and bacteria (Donini et al., 2006). This paper sets out to analyse the environmental impact of the process of cultivating Agaricus bisporus. Cultivation is the final phase of the mushroom production process. Scientific studies have been conducted on other varieties of mushrooms (Tongpool and Pongpat, 2013; Ueawiwatsakul et al., 2014), but there is little scientific literature on the environmental implications of the production process of Agaricus bisporus. We seek to quantify the environmental impact of this process by means of a life-cycle analysis (LCA). By identifying and analysing the inputs and outputs of the various activities involved we have been able to draw up a cradle-to-gate LCA for the process. This LCA is based on data from production plants in the La Rioja region of Spain. La Rioja is Spain’s number one producer of Agaricus bisporus, with a total of 215 ha given over to its cultivation (43.3% of the total for Spain). The region produces 52% of Spain’s national output (Ministry of Agriculture, 2014) and 4.25% of that of Europe (Sonnenberg et al., 2011). 1.1. Mushroom growing
∗ Corresponding author. E-mail addresses: [email protected] (F.J. Leiva), [email protected] (J.C. Saenz-Díez), [email protected] (E. Martínez), [email protected] (E. Jiménez), [email protected] (J. Blanco). http://dx.doi.org/10.1016/j.eja.2015.09.013 1161-0301/© 2015 Elsevier B.V. All rights reserved.
Mushrooms were originally grown in caves, but the process has gradually shifted to climate-controlled chambers where growing conditions can be controlled. This entails energy consumption and requires cooling systems (Foulongne-Oriol et al., 2014).
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The development of a new colony of Agaricus bisporus begins with the germination of spores. Their hyphae grow and form a large mycelium network. Various factors then induce the mycelium to produce fruiting bodies under controlled climate conditions (LeivaLázaro et al., 2015; Umar and Van Griensven, 1997). The fruiting bodies of Agaricus bisporus begin to develop and grow as soon as the primordia appear. They ripen, produce spores, then finally go into senescence, the period between full maturity and the death of the organism. The post-harvesting period of the fruiting bodies is of the utmost importance for marketing purposes, as they must maintain their characteristic colour and aroma (Umar and Van Griensven, 1997). A quality substrate is a prime requirement for growing mushrooms successfully: they absorb all their nutrients from the substrate, which is also an important source of lignocellulose for the development of the fruiting body (Tripathy et al., 2009). The substrate comprises mainly compost with a covering layer of soil on which the fruiting bodies form (Berendsen et al., 2012). The compost substrate is generally made up of manure, mostly chicken manure at present because it is in abundant supply (Castle, 1993). The job of the covering layer is to keep the crop properly hydrated at all times and protect it from aggressive microflora (Gillmann et al., 1994). The covering layer is generally composed of neutralised peat with chalk or limestone (Castle, 1993). Peat is used as a covering material (Gülser and Peks¸en, 2003; Noble et al., 2003). The physical and chemical properties required of peat (and any other substrate) include high porosity and water retention capacity, a pH of between 7.2 and 8.2, an active lime concentration of between 2.5 and 3.5% and a total nitrogen concentration of between 0.7 and 0.8%. The material must also have low inorganic and organic nutrient contents and be free from contaminations and pests (Gülser and Peks¸en, 2003). The mycelia of different species grow differently, depending on the type of medium used and the pH, though growth is also influenced by genetic make-up, by the substrate, by the temperature (De Andrade et al., 2010) and by the ageing of the mycelium (Mata and Savoie, 2013). During incubation and coverage, the temperature must be kept below 28 ◦ C. The ambient temperature needs to be brought down to stimulate sporophore production. Temperatures of 16–19 ◦ C are recommended during the fruiting period (Foulongne-Oriol et al., 2014) and 21–25 ◦ C during the growth phase (Largeteau et al., 2011). Studies have demonstrated that Agaricus bisporus can withstand temperature increases and has adapted to temperatures as high as 25 ◦ C during the fruiting phase (Largeteau et al., 2011).
LCA provides a quantitative basis for assessing potential improvements in the environmental performance of a system throughout its life-cycle, and is therefore an increasingly important tool for decision-making in the field of environmental management (Azapagic and Clift, 1999; Siracusa et al., 2014), under standard ISO 14040 (Martínez et al., 2009). It helps to decide which is the best possible option (Guinee et al., 1993; Jiménez et al., 2014; Stevenson et al., 2014) and provides a basis for assessing potential improvements in the environmental performance of a system or product (Azapagic and Clift, 1999; Khoshnevisan et al., 2013; Ulloa et al., 2011). It was developed to analyse environmental impacts such as global warming, soil use and water use, depletion of the ozone layer, acidification, human toxicity, eco-toxicity, depletion of natural resources, energy consumption and eutrophication (Jiménez et al., 2014). It can also be used as a tool for identifying critical points in production processes with a view to identifying potential improvements (Belussi et al., 2015), and as a tool for examining all environment-related aspects and potential impacts of products or services, since it considers all aspects and phases of each product or process (Jiménez et al., 2014). The LCA model used here was drawn up using the Simapro 7.3 software package and the CML 2000 Leiden calculation method. One of the first requirements is to properly define the goals and limits of the system. This is essential for the assessment of the final results, because it is necessary to know not only the extent of the impact assessed but also the extent of the study and the different process phases taken into account. The main goal is to obtain a comprehensive environmental view of the process, by identification and analysis of the inputs and outputs of materials and energy associated with the different ways in which each activity involved in the process of growing Agaricus bisporus takes place. 2. Materials and methods 2.1. Goals and scope A cradle-to-gate analysis is conducted, examining the production processes and identifying in each case the materials used, the energy resources and the process flows involved up to the production of the final functional unit. Also included are the flow of products from the entry of raw materials (including transport from the source firm to the producer) and the harvesting of the end product. The phases of the life-cycle taken into account therefore range from material inputs to the storage of the end product, in order to identify the critical activities within the process.
1.2. Life-cycle assessment (LCA) LCA is an appropriate way of assessing and analysing the environmental impact and other environment-related issues of services, materials and products throughout their life cycles (Azapagic and Clift, 1999; Baumann and Tillman, 2004; Leiva-Lázaro et al., 2014). It can be defined as a compilation and assessment of the inputs, outputs and potential environmental impacts of a product system throughout its life-cycle (Nicolae and George-Vlad, 2015). LCA is conducted with two main goals: • to quantify and assess the environmental performance of a product, process or activity over its whole life-cycle (Pieragostini et al., 2014); • to provide a basis for assessing potential improvements in the environmental performance of a product system (Azapagic and Clift, 1999).
2.2. Functional unit The functional unit used for this study is a 1 kg of Agaricus bisporus mushrooms. 2.3. System boundaries Limits are set on actions in order to focus the study. The limits in regard to the LCA cover overall production of the product, i.e. the growing of 1 kg of mushrooms (defined as the functional unit) and their distribution (see Fig. 1). The activities included within the system boundaries are the following: • Materials input, including transport from point of origin. • Fuel consumed by forklift trucks and dozers.
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Fig. 1. System boundaries.
• Electricity consumed by process production equipment. • Movement of materials and products from the entrance points used within the production plant. • CO2 emissions during growing. • Loading and transporting of end product. • Distribution of end product to consumers. • Waste management.
The following are excluded from the system boundaries:
• All the activities and consumption inherent in the production, acquisition and maintenance of capital goods. These items are excluded because of their scant impact on the functional unit and because of a lack of data. • Setting up and dismantling of the growing plant. This exclusion is based on the scant impact of this item on the functional unit and on a lack of data. • Transportation and treatment of organic waste produced at the plant. • Treatment of waste from the end product at the consumption stage.
2.4. Assumptions • There is no stocking of the end product, i.e., all output is distributed. • The ventilation in the growing chambers is considered to be constant throughout the process. • The functional unit considered is 1 kg of mushrooms. • The capacity of the growing chambers is 1656 seed packages. • Daily output is considered to be the same for each working day, with the growing chambers kept at maximum capacity as regards seed packages. • CO2 concentrations during the growing process are measured on site with a calibrated measuring device. • A seed packages is a mixture of compost and mycelium seeds (Leiva-Lázaro et al., 2015) with an average weight of 19 kg. 2.5. Inventory For this study a cradle-to-gate LCA of the full process of growing Agaricus bisporus mushrooms has been carried out. Raw material consumption and the distances covered by suppliers have been taken into account. The study also includes all the sources of energy used in the process.
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Table 1 Inventory data for climate controlled chambers.
Table 4 Inventory data for preparation of the growing chambers.
Materials
Quantity per kg of product
Materials
Quantity per kg of product
Electricity usage Biomass Disinfectant
2.04E − 01 kWh 1.68E + 02 kcal 1.24E − 04 L
Disinfectant Water Diesel Seed packages
2.51E − 04 L 7.20E − 05 m3 2.68E − 03 L 1.78E − 01 packages
The inventory is drawn up in line with the data provided and collected over the course of a year, beginning and ending in August. To facilitate analysis and assessment, the process is divided into various phases (see Fig. 1):
Once the covering soil is prepared the mixture is placed in a container ready for its subsequent use during the covering phase.
• Climate controlled chambers: temperature control of the facility. • Ventilated chambers: temperature control of the facility. • Preparation of the covering soil: preparation of the soil used to cover the seed packages with mycelium for the growing process. • Preparation of the growing chambers: placement of trays and utensils required for the growing process. • Growing process: divided in various phases, such as, mycelium activation, homogenisation and end product harvesting. • Waste management: management of the waste produced during the growing phase up to the harvesting of the end product for subsequent processing.
2.5.4. Preparation of the growing chambers The next phase of the process is the preparation of the growing chambers so that the seed packages can be placed in them. The materials and resources used in this phase are listed in Table 4. The process begins with the disinfection of the growing chambers to prevent the appearance of contaminations during the growing process (see Fig. 2, Disinfecting GC activity). Once disinfection is completed, the chambers are prepared by setting out the cages where the seed packages are to be placed (see Fig. 2, Preparing GC activity). The seed packages are then placed on the cages so that the growing process can begin (see Fig. 2, Placing seed packages activity).
2.5.1. Climate controlled chambers This study covers two types of chamber: climate-controlled and ventilated. The growing process in climate-controlled chambers includes constant temperature control and a heating system powered by biomass. The materials and resources used in this phase are listed in Table 1. 2.5.2. Ventilated chambers The growing process in ventilated chambers features only a ventilation system to keep clean air constantly recirculating through the interior of the chambers. The materials and resources used in this phase are listed in Table 2. 2.5.3. Preparation of the covering soil The first phase of the growing process is to prepare the soil used to cover the seed packages. The materials and resources used in this phase are listed in Table 3. The process begins with the disinfection of the area where the covering soil is to be prepared, so as to prevent the appearance of contaminations during the growing process (see Fig. 2, Disinfecting CS activity). Peat is received in big-bags, which are deposited in the disinfected area. This peat does not contain sufficient moisture, so water is added to bring the moisture content up to the level required for covering soil. In this phase fungicides are also added to prevent pests and/or contaminations during the growing process (see Fig. 2, Mixing activity). Table 2 Inventory data for ventilated chambers. Electricity usage Materials
2.48E − 02 kWh Quantity per kg of product
2.5.5. Growing process The next phase is the growing process itself, which culminates with the harvesting of the end product. The materials and resources used in this phase are listed in Table 5. This process begins once all the seed packages have been placed on the cages in the chambers with the covering soil prepared earlier and water has been added to start the growing phase (see Fig. 2, Covering seed packages activity). Continual fumigation by adding fungicides and insecticides is required to prevent the appearance of pests during the growing process (see Fig. 2, Fumigation activity). During the growing process homogenisation (activation of the mycelium) and fruiting (development of the fruiting bodies) begin (see Fig. 2, Homogenisation activity and Fruition activity). When the fruiting process is completed the fruiting bodies are harvested in three different collections in each chamber (see Fig. 2, Harvesting activity). During harvesting, the product is manually cut and placed in boxes for its subsequent distribution (see Fig. 2, Distribution activity). 2.5.6. Waste management The final phase is the management of the waste produced during the process. The materials and resources used in this phase are listed in Table 6. Table 5 Inventory data for growing process. Materials
Quantity per kg of product
Water Fungicide Insecticide Box Labels
1.04E − 03 m3 8.36E − 02 L 1.71E − 04 L 8.36E − 02 units 8.36E − 02 units
Table 3 Inventory data for preparation of the covering soil. Materials
Quantity per kg of product
Peat Fungicide Disinfectant Water
5.18E − 03 t 7.81E − 02 L 2.79E − 05 L 2.01E − 01 m3
Table 6 Inventory data for waste management. Materials
Quantity per kg of product
Diesel Transport
8.92E − 04 L 1.24E − 01 kg/km
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Fig. 2. Flow chart of the Mushroom cultivation process.
The waste produced when mushrooms are cut is deposited in a container for subsequent collection and treatment. Packages and spent soil at the end of the growing process are placed in a separate container for collection and treatment at a specific plant (see Fig. 2, Removing packages and Soil activity). 3. Results This paper presents an LCA carried out to identify the main environmental impacts in the process of growing Agaricus bisporus mushrooms, based on a cradle-to-gate approach. It is conducted with SimaPro® software, using the CML Leiden 2000 method to calculate environmental impact. The functional unit set for the LCA is 1 kg of product. The environmental impact results obtained from the LCA are presented below. The overall environmental impact of the product in all the impact categories analysed is presented first, and then the results for each of the three phases are presented separately.
3.1. Overall environmental impact analysis Table 7 presents the overall environmental impact results for the product studied, covering all the impact categories considered. The weight of each phase of production considered in this LCA (i.e., preparation of covering soil, preparation of growing chambers, growing process and waste management) is also shown. An analysis of the main phases of the overall production process reveals that the preparation of growing chambers is the process with the greatest impact in almost all categories. This is because it consumes a great deal of energy. The environmental impact of this phase varies depending on the impact category considered, from 48.39% for seawater eco-toxicity to 74.12% for eutrophication (see Table 7). In the growing process the greatest impact is that of global warming, at 99.28%, and in the climate control of the chambers it is soil eco-toxicity, at 87.88 % (see Table 7). This is because the carbon sink effect of the organic matter in the compost and in the covering
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Table 7 Global environmental impact, CML .ethodology. Impact category
Unit
Total
Preparation of the covering soil
Preparation of the growing chambers
Growing process
Waste management
Ventilation
Climate control
Abiotic depletion (AD) Global warming (GWP100) Ozone layer depletion (OLD) Human toxicity (HT) Fresh water aquatic ecotox (FWAE) Marine aquatic ecotoxicity (MAE) Terrestrial ecotoxicity (TE) Photochemical oxidation (PO) Acidification (AC) Eutrophication (EU)
kg Sb eq kg CO2 eq kg CFC-11 eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg C2 H4 kg SO2 eq kg PO4 – -eq
6.78E − 03 4.42E + 00 9.07E − 08 4.32E − 01 5.47E − 02 4.36E + 02 −1.01E − 02 2.58E − 04 7.95E − 03 2.41E − 03
1.96E − 03 −1.37E + 00 3.54E − 08 8.07E − 02 6.27E − 03 4.68E + 01 −9.60E − 03 5.43E − 05 1.60E − 03 5.34E − 04
3.76E − 03 −1.45E + 00 4.98E − 08 2.88E − 01 3.46E − 02 2.11E + 02 −2.89E − 03 1.27E − 04 4.29E − 03 1.79E − 03
5.44E − 05 7.10E + 00 6.38E − 10 1.64E − 03 3.35E − 04 1.64E + 00 3.73E − 05 1.10E − 06 2.15E − 05 2.17E − 06
1.79E − 05 3.92E − 04 3.47E − 10 2.68E − 04 2.83E − 05 2.42E − 01 1.62E − 06 2.63E − 07 4.69E − 06 4.72E − 07
1.06E − 04 1.51E − 02 4.55E − 10 5.62E − 03 1.41E − 03 1.90E + 01 2.52E − 04 8.02E − 06 2.14E − 04 7.34E − 06
8.87E − 04 1.33E − 01 4.05E − 09 5.57E − 02 1.21E − 02 1.57E + 02 2.11E − 03 6.74E − 05 1.83E − 03 7.94E − 05
Table 8 Detail of the environmental impact by activities, CML methodology. Preparation of the covering soil
Preparation of the growing chambers
Category
Unit
Mixing
Disinfecting CS
Placing seed packages
Disinfecting GC
Preparing GC
AD GWP100 OLD HT FWAE MAE TE PO AC EU
kg Sb eq kg CO2 eq kg CFC-11 eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg C2H4 kg SO2 eq kg PO4 eq
1.96E − 03 −1.37E + 00 3.54E − 08 8.06E − 02 6.25E − 03 4.67E + 01 −9.61E − 03 5.43E − 05 1.59E − 03 5.34E − 04
2.51E − 06 2.05E − 04 3.58E − 11 1.09E − 04 1.70E − 05 1.20E − 01 3.48E − 06 6.05E − 08 1.36E − 06 8.25E − 08
3.72E − 03 −1.45E + 00 4.91E − 08 2.86E − 01 3.44E − 02 2.10E + 02 −2.92E − 03 1.26E − 04 4.27E − 03 1.78E − 03
2.26E − 05 1.84E − 03 3.22E − 10 9.83E − 04 1.53E − 04 1.08E + 00 3.14E − 05 5.45E − 07 1.22E − 05 7.42E − 07
1.78E − 05 3.72E − 04 3.44E − 10 2.63E − 04 2.74E − 05 2.39E − 01 1.58E − 06 2.59E − 07 4.57E − 06 4.48E − 07
Growing process Category
Unit
Covering
Fumigation
Homogenisation
Fruition
Harvesting
Distribution
AD GWP100 OLD HT FWAE MAE TE PO AC EU
kg Sb eq kg CO2 eq kg CFC-11 eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg 1,4-DB eq kg C2 H4 kg SO2 eq kg PO4 eq
3.43E − 05 2.60E + 00 3.35E − 10 8.29E − 04 1.70E − 04 7.69E − 01 1.71E − 05 5.49E − 07 8.64E − 06 7.16E − 07
8.60E − 06 9.49E − 01 1.22E − 10 3.75E − 04 5.96E − 05 4.14E − 01 1.19E − 05 2.10E − 07 4.68E − 06 2.84E − 07
1.34E − 06 2.78E − 01 1.91E − 11 5.83E − 05 9.04E − 06 6.37E − 02 1.86E − 06 3.23E − 08 7.25E − 07 4.40E − 08
1.34E − 06 7.45E − 01 1.91E − 11 5.83E − 05 9.04E − 06 6.37E − 02 1.86E − 06 3.23E − 08 7.25E − 07 4.40E − 08
2.74E − 06 2.53E + 00 2.66E − 11 1.32E − 04 5.13E − 05 2.13E − 01 2.95E − 06 1.14E − 07 1.86E − 06 1.24E − 07
3.43E − 05 2.60E + 00 3.35E − 10 8.29E − 04 1.70E − 04 7.69E − 01 1.71E − 05 5.49E − 07 8.64E − 06 7.16E − 07
soil used in preparation for covering and in the preparation of the growing chambers has a positive impact in the said categories. By contrast, the phase with the least impact is that of waste treatment, because of its low energy demand and demand for materials. The figures for impacts are much lower than the other phases, and in fact vary from 0.002% in the global warming category to 0.38% in the ozone layer depletion category (see Table 7).
3.2. Environmental impact phase by phase Each phase is analysed separately below, identifying each activity considered in each case and its weight in the environmental impact of the various categories.
3.2.1. Preparation of the covering soil In this phase the activity with the greatest impact in all categories is the mixing of the covering soil, because it consumes more energy and material resources than the disinfection phase. The environmental impact of this phase ranges from 99.72% in the water eco-toxicity category to 99.98 % for eutrophication (see Table 8). The impact of the disinfection and cleaning of the covering soil preparation area is much lower than that of the soil mixing, ranging from 0.09% in the acidification category to 0.27% in fresh-water eco-toxicity (see Table 8).
It is worth noting that there are positive impacts during the covering soil mixing phase in the categories of global warming and soil eco-toxicity due to the absorption of CO2 by the organic matter in the peat. That is why there is only a negative impact in the disinfection phase in the mixing area. 3.2.2. Preparation of the growing chambers In the preparation of the growing chambers the phase of placing the packages in the chambers is the activity with the greatest impact in almost all categories, because the machinery used consumes more energy. In figures this environmental impact ranges from 99.72% in the freshwater eco-toxicity category to 99.98% for eutrophication. The biggest impacts in the categories of global warming and soil eco-toxicity can be found in the disinfection of the growing chambers, at 83.22% and 95.02%, respectively, due to the fact that there are positive impacts from the incorporation of compost and the mycelium seeds in the chamber preparation phase, so the biggest negative impacts are found in the growing chamber disinfection phase. By contrast, the growing chambers preparation phase has low impacts in almost all categories because most of the demand for energy and use of materials take place in other activities. Its impact ranges from 0.03% in the eutrophication category to 16.78% in the global warming categories, with the exception of ozone layer deple-
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tion, where the lowest impact can be found in the disinfection of the growing chambers, with 0.65% (see Table 8).
3.2.3. Growing process In the growing phase the activity with the greatest impact in almost all categories is the covering of the seed packages with compost, because of the energy consumed in this process. The extent of the impact varies from one impact category to another, with a figure of 36.58% in the global warming category and as much as 63.16% in abiotic depletion. In the harvesting phase there is a significant impact of 35.62% in the global warming category. The only impact category in which the growing phase does not have the greatest impact is eutrophication, where the end product distribution process accounts for 44.25% of the total impact (see Table 8). By contrast, the processes with the lowest impacts in almost all categories are homogenisation and fruiting, with figures that range from 2.02% in the eutrophication category to 4.98% in soil eco-toxicity. An exception is the global warming category, where the lowest impact is that of the distribution phase, with 0.012 % (see Table 8).
4. Discussions and conclusions This paper presents a cradle-to-gate LCA of the process of farming Agaricus bisporus mushrooms, based on actual data from a production plant gathered over the course of a year so as to provide accurate information on the environmental impact of the various activities that make up the production process. An overall analysis of the main phases of the production process reveals that the activity with the greatest impact in almost all categories is the climate control of the growing chambers, because of the considerable amount of energy required to power the system, which is running continuously. The only impact categories in which climate control is not the number one phase are global warming in the growing phase and ozone layer depletion and eutrophication in the covering soil preparation phase. The result obtained in the category of global warming is 4.42 kg CO2 eq. Comparing with other cultures, such as strawberry (4.4 kg CO2 eq.) or lettuce (5.5 kg CO2 eq.) (Gunady et al., 2012), the result is similar, and it is within a range of acceptable emissions for edible cultures. Therefore, the CO2 emissions associated to the production of Agaricus bisporus suppose a less relevant impact than the initially estimated. Besides, this value represents a reference for the implementation and control of measures to reduce the environmental impact of mushroom production plants. Analyzing in detail the production process, in the preparation of covering soil the activity with the greatest impact in all categories is the mixing of the soil, because of how much energy it requires. In the preparation of the growing chambers phase the disinfection of the chambers is the activity with the greatest impact in many phases, because of the large amount of energy required and the use of chemical disinfectants. Exceptions are abiotic depletion, ozone layer depletion, photo-chemical oxidation and eutrophication, in which the greatest impact can be found in the process of placing the seed packages in the growing chambers. In the growing process phase the activity with the greatest impact in almost all categories is the covering of the packages with compost, because of the amount of energy consumed by the cooling system for final storage. The exception is eutrophication, where the biggest impact is found in the end product distribution phase.
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