Study of the environmental impact of the cultivation of tomato in greenhouse multitunnel

The setting for the study was the coast of Almería, Spain. They chose a multitunnel unheated greenhouse, a passive system requiring little energy, and whose most important inputs are fertilizers and water. The infrastructure of the Conservatory consists of a frame of steel, with a curved roof, and a plastic cover. This study was conducted using the methodology of life cycle analysis (LCA). Defined the limits of the system, from the extraction of raw materials to the obtaining of the harvest, including the management of waste generated and excluding marketing. The studied system was modelled by considering the following subsystems: structure, ancillary equipment, climate control system, fertilizers, pesticides and waste management.

The results of the environmental assessment showed that the main environmental burdens were structure, the auxiliary equipment and fertilizer. The structure was the major environmental burden due to the large amount of steel in the frame. The great contribution of ancillary equipment was due to the manufacture of the substrate (perlite) and the electricity consumption for the operation of the system of irrigation. The use of fertilizers led to major environmental impacts as a result both the processes of manufacture of fertilizers and emissions from its use. The main recommendations proposed based on the results are aimed at reducing these impacts. Increase productivity and extend the useful life of the greenhouse could directly reduce environmental burdens per unit of product. Reduce the volume of substrate for plant and recycle the used substrate are additional proposals. Finally, given that the analyzed system was a cultivation without soil with open irrigation system, will optimize the contribution of fertilizer and water.

The expansion of horticulture in the Mediterranean area has meant a significant economic progress, especially in marginal areas. The warm climate allows the production of crops in the greenhouse with low energy requirements. However, with the increase in protected cultivation and the awareness by consumers on the environmental aspects, it is important to analyse the environmental damage that occur throughout the process of cultivation. This study was developed to detect environmental weaknesses in the production of tomato in greenhouse multitunnel in a Mediterranean climate. This work is part of the project Euphoros (Euphoros, 2008-2012), which aims to develop a sustainable global warming, make efficient use of resources, with a reduction of the external inputs while maintaining high productivity. The studied system spanned throughout the life cycle of the crop, from the extraction of raw materials to the production of tomatoes and the Elimination of waste materials. The methodology of the analysis of of life cycle (LCA), a useful tool, adopted internationally to study the environmental aspects and potential impacts throughout the entire lifecycle of a product or activity was used to assess the environmental impact, including the stages of acquisition of raw materials, production, use and disposal of waste.

Similar conditions of temperate winter studies have been conducted in Catalonia (Anton et al., 2005), the Canary Islands (Torrellas et al., 2008) and Granada (Romero-Gámez et to the., 2009). However, this is the first which focuses in Almería. Crops in the Mediterranean basin occupy approximately 170,000 has and Spain has the largest area of crops protected in Europe with 50.365 hectares of greenhouses. The largest greenhouses in Spain areas are located on the coast of Almería, Murcia and Granada, in the southeast of the Iberian Peninsula, and the Canary Islands in the Atlantic Ocean. Almería has almost 60% of the surface of greenhouses in Spain. The cultivation of tomato is one of the most important (EFSA-PPR, 2009).

The objective of this study was to assess the environmental impacts of the current production of tomato in greenhouse multitunnel in a Mediterranean climate, and detect the main damage which could be reduced through the implementation of the new technological advances which will take place in the course of the project Euphoros. The tool of the life cycle assessment (LCA) was used for the assessment of impacts. This technique evaluates the potential environmental impacts throughout the entire lifecycle of a product, service or process, "the cradle to the grave". This means that the study included (Figure 1), as well as the manufacture of the product itself, the production of raw materials, their use and maintenance, and management of the waste once over its useful life (Puig et to the.)(, 2005). As defined by the standard ISO 14040 (ISO-14040, 2006) the LCA is a "compilation and assessment of the inputs, outputs, and the environmental potential impacts of a product throughout its life cycle system".

The first LCA studies were conducted to analyse industrial processes. The concerted action "Harmonization of environmental ACL for Agriculture" (Audsley, 1997) can be considered as the first attempt to adapt the methodology to agriculture. The first applications of LCA in agriculture were carried out from the extensive farming and livestock products. In these works generally compare conventional and organic production methods. Posteriormete, the LCA was extended to processed products: milk, butter, bread, etc. (Anton, 2008).

According to the methodology proposed by the norm ISO 14040, LCA project is divided into four phases: objectives and scope of the study, inventory analysis, analysis of the impact and interpretation (Figure 2). These four phases are iterative and this allows to go to increase the level of detail of the study.

The phase the objective and scope of the study defines the subject of study and includes the reasons that lead to do it. It is also the phase in which the functional unit (UF) is defined. The functional unit reflects the main function of the system and serves as a reference to quantify the inputs and outputs of the system. Given that the main function of a greenhouse is producing, in this study was taken as a functional unit production of tomatoes. Selected UF was 1 tonne of tomatoes.

A greenhouse multitunnel on the coast of Almeria (Spain) was the setting for the study. This type of greenhouse consists of a steel structure, of arched roof, and a plastic cover. Due to its global nature, a complete LCA can be voluminous. That is why perfectly identified limits should be established. The limits of the system determine the processes that are included in the production system. In the present study these boundaries were defined from the extraction of raw materials to the exit of the greenhouse, including the management of waste generated. The later stages of packaging and marketing were not taken into account. The processes included in the environmental assessment were: the extraction of raw materials, the manufacturing of the components of the greenhouse, the transport of materials, waste disposal, and energy consumption, water, fertilizers and pesticides.

The phase of the analysis of inventory (ICV) includes both data collection and calculation procedures to identify and quantify all the adverse environmental effects associated with the functional unit. In a generic way, we will call these environmental effects such as "environmental load". Environmental burden is considered the exit or entry of matter or energy of a system that causes a negative environmental impact. In order to facilitate the analysis of inventory and the interpretation of the results, the production system has been structured in the following subsystems: the structure of the greenhouse, the auxiliary equipment, climate control system, fertilizers, pesticides, and the management of waste (Figure 3).

The details of the farming operations, such as the dose of fertiliser or water consumption, were picked up by the Experimental Station of the Cajamar Foundation (EEFC) (Fundación_Cajamar, 2008), El Ejido, Almeria. The structure of the greenhouse was modelled from a set of data that characterize the typical structure of a greenhouse multitunnel. Used for database Ecoinvent (ecoinvent, v2.2, 2010) and LCAFoods (Nielsen et al., 2003) to obtain the data relating to the processes of manufacture of the materials involved in the greenhouse, substrates, fertilizers and pesticides, the production of electricity, transport of materials and waste treatment processes. The software tool used for the environmental assessment was the programme SimaPro version 7.2 (PRéConsultants, 2010).

In an LCA study, it is necessary to select indicators and the categories of impact (see table 1). A category indicator is a quantitative representation of a category of impact. A category of impact is a class which represents aspects of environmental interest and which are assigned the results of the analysis of inventory. The categories of impact selected for the evaluaciónambiental were:

-Demand of accumulated energy, CED (MJ eq) (Frischknecht et al., 2005), as the indicator of energy flow, and five categories of impact defined by the CML2001 method v. 2.05 (Guinée et al., 2002.)

-Depletion of nonrenewable resources AD, (kg Sb eq)

-Acidification of air, AA (SO₂eq kg)

-Eutrophication us (kg PO₄^-3 eq)

-Global warming, GW (kg CO₂ eq) and

-Formation of photochemical oxidants, PO(kg_C__{_2_}_H__{_4_} _eq).

The useful life of the greenhouse was estimated at 15 years, in accordance with the guidelines of the European Committee for Standardisation (CEN, 2001). The analysis of inventory was prepared according to Audsley (1997), Anton (2004) and ISO (ISO-14040, 2006) standards. We considered the manufacturing processes of the elements of steel and plastic. It was estimated that steel had made from steel waste recycling. The process of galvanizing of the surface was also included.

The main features of the defined subsystems were:

- Structure: including steel elements were pillars, reinforcements of the frame, gutters, spreaders, profiles, arches and Windows. The system of training was of wire, and the cover and padded floor of low density polyethylene. Both front and side walls were made of sheet of polycarbonate and mesh insecticide from the Windows of polyethylene. The pilasters and main hallway were concrete (table 2).

- Auxiliary equipment: This included the irrigation system, the facilities of drainage and collection of rainwater, the consumption of electricity by the system of irrigation and the substrate. A system of irrigation was used drip without recirculation of drainage water.The sidewalk, protector of benches, pipes, drippers, pegs, microtubos and fertilizer tanks were plastic, and the injectors and pumps of steel. The used substrate was perlite ready in polyethylene bags, with three plants in each one of them. The density of cultivation was 1.2 plantas•m^-2, with 2 stems per plant. The period of cultivation was from September 2007 to June 2008, giving a performance of 16.5 kg•m^{- 2}. The total amount of water consumed was 4.748 m³•you^-1, of which 25% was a Leach. Therefore, the water consumption was 28.8 l•kg tomato^-1.

- Climate control system: as in most of Mediterranean greenhouses, there is a heating system and only a natural ventilation is carried out. This subsystem only considered the consumption of electricity for the operation of the enhanced Windows.

- Fertilizers: the total quantities of N, P and K applied to the crop were: 798.4 kg•ha N, 220.8^-1 kg•ha^-1 P, 1.296,3 kg• has K^{- 1} . We calculated the emissions to air of NH_{3 -}N, n-N₂or and NOx-N and the emission to water of NO₃- N (Audsley, 1997;) Brentrup et al., 2000.), also included emissions during the manufacturing process.

- Pesticides: considered the total amount of active ingredient to insecticides (3.8^-1kg•ha) and fungicides (28.5 kg•ha^-1). The manufacture of pesticides and machinery for its implementation were also incorporated into the inventory. The toxicity of the pesticide was not included because there is a general consensus for evaluation.

- Waste management: included various treatments for waste materials. The metal and polycarbonate were 100% recycled. 50% Of the concrete and the substrate were recycled and the remaining 50% deposited in landfill. 90% Of plastics is whose and 10% transported to the landfill. The Green biomass was treated in the composting plant taking into account 40% of the total fresh weight at the time of transport. We only considered emissions from transport to landfill and the composting plant, and emissions from the disposal in landfills. Transportation to recycling plants and recycling processes were not considered in the system. Estimated useful lives different depending on each material: 15 years for metals, PC, and concrete; 3 to 5 years for plastics, and 3 years for the substrate of Perlite.

This section includes the analysis of the impact of cycle of life (AICV) phase. The results of the environmental assessment show the potential environmental impacts of inputs and outputs in the phase of inventory of the system. Main environmental burdens identified in the life cycle of the production of tomato system were the structure, the auxiliary equipment and fertilizer.

In the production system, the structure was leading the charge for the categories of impact depletion of non-renewable resources and demand of accumulated energy, with a contribution of 45% and 46% of the total. The auxiliary equipment showed the increased contributions to the categories 'Acidification of air' and 'Formation of photochemical oxidants', with 37 per cent and 47 per cent of the total, and fertilizer for categories 'Eutrophication' and 'Global warming', with 58% and 46% respectively. The contributions of the climate control system, pesticides and waste management were less than 3% of the total (Fig. 4).

The high contribution of the structure was between 44% and 74% for categories of impact 'Acidification', 'Eutrophication', 'Global warming' (GW) and 'Formation of photochemical oxidants', due to the large amount of steel in the frame. Plastics were the main burdens for the category 'Depletion of nonrenewable resources' and 'Cumulative energy demand' (both 59%) (Fig. 5). The results are in agreement with the of Cowell (1998), who stressed the importance of the contribution of infrastructure to the overall environmental impacts in the agricultural systems, in contrast to many buildings in the industrial systems. Low power requirements for the process of cultivation and life span shorter than the greenhouse compared to the industrial buildings do highlight the impact of the structure.

The manufacture of perlite and electricity consumption were greater environmental burdens in the subsystem auxiliary equipment (Fig. 6). In the first case due to the consumption of natural gas for the expansion of perlite and the second produced consumption for pumping water.

The environmental impacts of fertilizers were due to the emissions produced during its manufacture and its application (Fig. 7). The production of fertilizers of N had contributions higher for most of the categories of impact, except for the US and GW, 52 per cent and 64 per cent. Emissions from the use of fertilizers were the highest for categories eutrophication and global warming, largely due to emissions of NO₃ to the water of the leachate to the category of eutrophication and the emissions of N₂ora major greenhouse, for the category of global warming gas. In so far as the risk of eutrophication, it should be noted that the methodologies currently used to assess the amount of fertiliser reaching the aquifers are only approximate and subject to debate. It has also shown that there is plenty of scope for reducing the doses of applied fertilizers (Munoz et al., 2008).

The conclusions from the findings in the phase of inventory and the results of the impact of life cycle assessment are aimed to reduce the environmental impacts and to improve production systems. The environmental assessment of the production in greenhouse multitunnel will be used to assess the possible reduction of environmental burdens in subsequent studies, through the implementation of potential improvements that will be developed during the project Euphoros.

One obvious way to reduce the impacts would be increasing productivity and extending the useful life of the greenhouse. He was considered a useful life of 15 years for the Conservatory, but it is a common practice that producers lengthen the service life. The burdens of the structure could be reduced by improving the design of the greenhouse, including materials recycled or reused in manufacturing processes. In the greenhouses of the Mediterranean, any technological improvement applied to a passive greenhouse will result in the reduction of environmental burden associated with the infrastructure.

We found a high consumption of energy for the manufacture of perlite and for the functioning of the system of irrigation. The use of solar energy, thermal storage, and other renewable energy could contribute to the reduction of the environmental impacts of the energy consumption in the production of tomato. In order to reduce the environmental impacts associated with the substrate, efforts should be directed to the process of reducing the volume of substrate used in the cultivation and recycling.

The reduction in the dose of fertiliser would have an effect in decreasing the risk of eutrophication on a system without ground and open. An irrigation of closed-loop system is also a good option to consider. Future research aimed at assessing the reduction of environmental impacts with the implementation of new improvements developed during the project Euphoros.

This study is part of the Euphotros research project (Efficient use of inputs in protected horticulture - FP7-KBBE-2007-1), financially funded by the European Union.

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