Energy Analysis and Current Value Stream Map Applied to a Typical Triple Concentrate Tomato Paste Production Plant with an Average Production Capacity of 500 ton/day

Pila j3

Economic Development, Italy

Introduction

According to Eurostat, in Europe, in 2015, concentrated tomato puree and paste (PRODCOM Code 10391721) represented more than 8.5 billion Euros of production value (in particular 72.5 million Euros in Italy, 49.8 in Spain, 45 in Portugal, 12.3 in France and 8.3 in Greece). Cooperatives and enterprises involved in the transformation of tomatoes show a relevant energy consumption that depends on the specific final product.

On average, for preserved tomatoes, thermal energy consumption is 1,200-1,500 kJ/kg (0.333-0.417 kWh/kg) and the one of electricity is 0.009-0.0012 kWh/kg; for tomato concentrates, thermal energy consumption is 8,500-12,000 kJ/kg (2.361-3.333 kWh/kg) and the one of electricity is 0,050-0,085 kWh/kg (data from ENEA, ENEL, ENI, IASM, December 1985). The significant variation in the electrical energy consumption among different tomato plants is mainly due to the production capacity. A typical medium, medium-large plant producing some hundreds tons of fresh tomato paste per day requires a constant and continuous supply of fresh tomato fruits (raw materials), that can be achieved only through a careful management of fruit harvesting and delivering. In this way, the right amount of tomatoes may reach the plant at the right moment. The installation of cement tanks in the processing plant is very common and facilitates the immersed in water quick storage of the raw material waiting to enter and the replenish constantly the processing chain. It is of fundamental importance that the tomato processing line is continuously operative at the maximum capacity, avoiding working at very low capacity or intermittently. In fact, every time the tomato line process is switched off, machines must be accurately cleaned, thus loosing several working hours, consuming a great amount of water, and wasting either fresh tomatoes waiting in trucks outside the plant or tomatoes in the facility in various stage of processing, particularly in the evaporator. As for the majority of fruit and vegetable, being perishable products, fresh and ripe tomatoes cannot wait more than 24-48 hours to be processed outside the plant, particularly during the hot sunny season, where the temperature may be over 30 °C, because this would determine a less quality final product with a lower Brix. Thus, definitely, the best solution is to produce paste all day, every day. Tomatoes contain on average 95% water and only 5% solids and sugars, and in fact production of tomato paste requires very large fruit amounts. The term “tomato paste”, which includes different degrees of concentration, is related to canned tomatoes prepared by eliminating a part of the water from the pulpy juice obtained by homogenising fresh tomatoes and sieving the resulting chopped product. To prepare tomato paste, tomatoes must be riche in colour, flavour and aroma, with the right acidity level and high sugar content. For definition, tomato paste contains more than 18% solid material (18°Brix); double concentrate tomato paste contains more than 28% solid material (28°Brix) and it is obtained by Hot Break (HB) technology. In HB, immediately after chopping, fresh tomatoes are heated to 85-100°C. Then, triple concentrate tomato paste contains more than 36% solid material (36°Brix) and it is obtained by Cold Break (CB) technology. In CB, after chopping, tomatoes are heated to 65-75°C. In general, production of tomato paste is performed during the prime time of the tomato season, when fresh tomatoes offer their best quality. Tomato is considered a tender warm season crop. Most cultivated tomatoes require around 75 days from transplanting to first harvest and can be harvested for several weeks before production declines. Production of concentrate tomato products can be carried out at different scales, from small scale (kilograms per hour) to large industrial scale (up to 200- 300 tons per hour), in which the energy consumption per unit of production is greatly reduced. In medium and medium-large industries, the capacity of the whole tomato paste processing line in cold-break (but also in hot-break) system may be from 0,5 to 80 tons/hour, meaning from 0,5 up to 80 tons of tomato fresh fruits (input capacity) may be processed per hour. Higher capacity of tomato processing are recommended. This study has been conducted for the Project “SCOoPE”, “Saving Cooperative Energy”, funded by the H2020 Programme of the European Union (Project ID: 695985; www.scoope.eu).

Conclusion

The industry of tomato concentrates meets important energy expenses, first of all due to the thermal treatments which require high amounts of natural gas, fossil oil or coal. Also electrical costs are very high in tomato paste processing plants and there are two main wastes that need to be valorized and re-used, as the water required for fruit washing and as fruit flow driver through the processing line before the first encountered thermal treatment (cold break or hot break), and also the tomato wastes, including tomato pomace, skins and seeds. For example, the tomato skin is well known as a rich source of lycopene, an antioxidant carotenoid. Tomato wastage is often dried and used to feed dairy cattle, for pet food or it is sent to landfill. In this case, there is also the potential for this waste to feed decentralised combined heat and power plants (CHPs) to generate energy locally [7]. Nowadays tomatoes for industries are also produced during all year under greenhouse conditons. Energy is one of the highest expenses in greenhouse production and sometimes supplemental lighting may not be economically feasible. There are several innovations that allow certain energy savings, such as the installation of a LED lighting system, which allows shorter ignition times and a lower thermal energy emission [8, 9]. Even more interesting is the chance of designing different plant specific light spectra based on their particular metabolic system with the aim of maximizing energy radiation by the lamps. Thus, in the near future it will be possible to use the light spectrum that best fits the photosynthetic pathway of some plant fruits increasing both quantity and quality of the harvest. Growing times will be also accelerated by acting on stimulation of germination and/or flowering time. Another technology that allows a sustainable acclimatization, particularly adapted to Mediterranean areas and linked to the energy efficiency, is the the solar cooling technology. In fact, this technology allows to maintain the internal greenhouse ait temperature in winter season by heating and in summer season by cooling [10].

Acknowledgements

SCOoPE Project is funded by the H2020 Programme of the European Union. The authors of the manuscript wish to acknowledge also other partners of the Project that gave inputs to this study, in particular Cooperativas Agro- alimentarias (Juan Sagarna, Irene Cerezo, Susana Rivera), CIRCE (Inmaculada Fraj), and D.R.E.A.m. (Enrico Pietrantonio and Chiara Chiostrini), in addition to other colleagues of ENEA (Alberto Mastrilli) and UPM (José Luis García).