Economic analysis and energy valorization of by-products of the olive oil process: “Valdemone DOP” extra virgin olive oil

Economic analysis and energy valorization of by-products of the olive oil process: “Valdemone DOP” extra virgin olive oil

Renewable and Sustainable Energy Reviews 57 (2016) 1227–1236 Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews jour...

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Renewable and Sustainable Energy Reviews 57 (2016) 1227–1236

Contents lists available at ScienceDirect

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Economic analysis and energy valorization of by-products of the olive oil process: “Valdemone DOP” extra virgin olive oil Maurizio Lanfranchi n, Carlo Giannetto, Angelina De Pascale Department of Economics, University of Messina, Via dei Verdi, 75 98122 Messina, Italy

art ic l e i nf o

a b s t r a c t

Article history: Received 15 February 2015 Received in revised form 13 October 2015 Accepted 17 December 2015 Available online 8 January 2016

The paper analyzes the biomass resulting from the processing of olive oil, in order to evaluate, in terms of economic sustainability, its importance in energy processes and the use of alternative paths other than the normal disposal process of the residues of the oil industry productive chain. Attention has been focused on the manufacturer of “Valdemone DOP” extra virgin olive oil, located in Sicily (Italy), in order to evaluate the possible energy recovery, directly by the farmer, of by-products of the production chain of olive oil, in order to make the whole process more efficient, using the scraps from the mill directly on site. The economic analysis aims at identifying measures for energy recovery from by-products; in order to reduce the incidence of the cost of waste disposal on the cost of the production of the oil; to energy conservation through the use of by-products as renewable fuel. & 2015 Elsevier Ltd. All rights reserved.

Keywords: Biomass Productive chain of the oil industry Energy conservation Use of waste Olive oil Farm

Contents 1. 2.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objective of the research and delimitation of the territory covered by the survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Literature review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. Methodology proposal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. The case analyzed: a local farm producing “Valdemone DOP” olive oil and floriculture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. Estimated costs of the production of Valdemone DOP oil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Obtainable results. Enhancement of by-products for energy purposes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Environmental analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. Discussions and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction It is estimated that in Italy there are more than 500 varieties of olives (cultivar), of which almost 90% are registered in the register of Italian olive cultivation. These cultivars are able to realize numerous productions of excellence; examples are: leccino, casaliva, pisciottana, coratina, moraiolo biancolilla, frantoio, taggiasca, n

Corresponding author. E-mail addresses: [email protected] (M. Lanfranchi), [email protected] (C. Giannetto), [email protected] (A. De Pascale). 1364-0321/& 2015 Elsevier Ltd. All rights reserved.

1227 1228 1229 1229 1231 1231 1232 1233 1234 1235 1235

moresca, carolea, etc. Each of which has different peculiarities, which vary from region to region. Italy has historically been one of the leading countries in the world for the production and exporting of olive oil. According to estimates by the United Nations Conference on Trade and Development Site, in fact, Italy is in second place in the category, on a global scale in the production of this product, preceded only by Spain. This report provides a clear fact, which is that more than 71% of world production comes from EU countries. The top three producers in the world are able to achieve a production of approximately 69.47% of the total global olive oil.


M. Lanfranchi et al. / Renewable and Sustainable Energy Reviews 57 (2016) 1227–1236

Olive cultivation covers an area of about 12 million hectares with nearly a billion olive trees, mainly for the production of olive oil. The Italian olive growing is widespread, especially in the southern and island regions, where there is the concentration of about 80% of the total production. The Italian region that has the greatest extent of land dedicated to the cultivation of olives is Puglia with its 377,550 ha, followed by Calabria (194,887 ha) and Sicily (161,967 ha). However, this activity is totally absent, only in the Valle d'Aosta in Piemonte and Friuli Venezia Giulia in Veneto. The total production area reaches an area of around 1,169,833 ha. 32% of the production area is concentrated in Puglia, and the first three Italian regions in this activity (Puglia, Calabria and Sicily) have more than 50% of the production area. The Italian olive growing is characterized greatly by fragmentation, this is due, in part, to the topography of the country (67% in the hills and 11% in the mountains), and in part to the low mobility of EC assistance. Analyzing, in detail, the type of production harvested, the result in that most of the production is destined for olive oil, and little to table olives. The olive is a classic example, which essentially represents the principle of multi-functionality of agriculture; in fact, it is able to achieve four functions at the same time these being production, environmental development, rural development and food security. In this context, the olive oil sector plays an important role in many Italian regions. From the point of view of production, the Gross Saleable Production of the sector represents 5.7% of the national Gross Saleable Production, and the UAA devoted to olive trees, amounts to 1,169,833 ha, and is, therefore, 8.2% of the total UAA. In addition to the production function, the role of the olive tree is also considered effective from the environmental point of view, since, in many regions, its use has improved the rural landscape and helped to mitigate and prevent erosion and landslides, and has contributed to reduce the problem of desertification [1]. The olive groves, in fact, represent shelter and food for wildlife, as well as plant and animal biodiversity. From the environmental point of view, as can be seen in the next section, the olive cultivation can also play a vital role in the exploitation and utilization of production waste for energy purposes [2]. From the point of view of rural function, the olive promotes rural employment, especially seasonal employment, and interacts with a number of complementary activities to agriculture. Examples are the setting up of farm-tourism activities, catering and sales on the farm of typical products, the creation of food, wine and museum tours, the organization of particular activities on the farm, the recovery of corporate structures no longer in use, such as old mills, which can also be re-used for productive purposes and not just to be admired. It is also a way of improving the quality of life of residents and visitors and creates location opportunities for offfarm enterprises. From the point of view of the safety function, carried out by the food production of oil, its beneficial characteristics on the quality and health of the product are indisputable, not to mention the importance it has in the Mediterranean diet. The

new guidelines on rural development of the Common Agricultural Policy are looking for sustainable farming activities capable of achieving the development of areas where human presence is strong, and in the more marginal areas where there is a risk of land abandonment [3]. In relation to these focuses, the olive sector plays an important role in Italy, taking on not only an economic function, but also an environmental, social, food and culture function with the rediscovery of the historical memory of the olive growing areas [4]. That is why we must ensure and encourage productive activities that last in time in accordance with the bond of protection in the areas concerned, maintaining the promises made to the potential users of the areas [5].

2. Objective of the research and delimitation of the territory covered by the survey The cultivation of olives is considered an environmental friendly activity. The use of large quantities of chemicals and fertilizers is nowhere near to other cultivation and the use of energy is limited to tractors, gasoline instruments and electrical items [6]. In any case, the use of energy in respect to the production of olives is not really considered important [7]. On the basis of these considerations, the production of olive oil can surely be considered a low impact environmental process. However, the olive cultivation and the work in the mills are generating a large amount of solid and semi-solid waste, which is becoming an important issue in most transformation plants. The elimination of this waste is becoming one of the more pressing environmental problems that the Europe has to deal with. As well as the characteristics and the type of waste produced during the production of oil, the situation is worsened by the type of mills and characteristics of the olive cultivated [6]. In the area dealt with, but really in all the Mediterranean, most of the mills are family run with limited finances, rather small, scattered in the territory or situated within the cultivar. All the above leads to economic, technical and organizing limitations, which makes it very difficult to organize a central handling of the waste thus making the elimination of waste very costly [8]. With this in mind, this work, conscious of the need to find new ways to manage and recycle all the waste from the processing of olives, fixes the following targets: – measures able to maximize energy production from waste processing; – reducing the burden of the cost of waste elimination on the cost of the finished product; – energy saving through the use of production waste as fuel.

Table 1 Data at the provincial level of the regional total. Source: Based on region Sicily data. Area (hectares) and production (tons): olive, table olives, olives for oil, oil pressure. Year 2013 Olives Total area Messina Sicily Percentage value of regional total n

Production area

35,150 35,150 136,630 134,895 25.7% 26.1%

Total production

Harvested production


351,500 2853.960 12.3%

281.200 2734,784 10.3%

r t

r¼ measured value; s ¼the estimated value; t ¼total.

Olive virgin pomace (quintals/ year)

Olive exhausted pomace (quintals/year)

Olive vegetation water (m3/year)

126,540 1,230,653 10.3%

69,597 676,859 10.3%

168,720 1,640,870 10.3%

Olive pits


(quintals/ year) 25,308 246,131 10.3%

s s

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For the purpose of this study, the area of production of "Valdemone DOP" extra virgin olive oil includes the territories of the municipalities in the province of Messina except for Floresta, Moio Alcantara and Malvagna. To this end, Table 1 shows, the amount of olives produced, the estimated quantity of virgin olive pomace (45% harvested production/weight olives) and the relative potential quantity of exhausted olive pomace (55% weight olive virgin pomace) [9,10], available at the provincial and regional level and then for each municipality which fall within the area analyzed. The total potential amount, at the provincial level, is about 281,200 quintals/year. The production of vegetable water is linked to the system of oil extraction, therefore to avoid overestimates; a precautionary average coefficient of 0.6 l/kg of processed olives was used [5]. 2.1. Literature review On the subject of olive oil extraction systems, the main byproducts are vegetable water and virgin pomace. Virgin pomace is a semi-solid mixture which contains oil residues, water and solid parts of drupes (pulp and woody fragments of the pits) which are left after crushing. The process can be broken down into various moments of processing, with various degrees of difficulty: firstly with the olive paste before oil extraction, then the virgin pomace immediately after mechanical extraction of the oil, followed by the exhausted pomace after the extraction, with solvents, of the remaining oil [11]. The quantity of virgin olive pomace and olive pits is largely dependent on the type of system used to extract the olive oil [12]. The retrieving of the olive pits depends on the amount of virgin pomace used. Due to this variable, very few studies have concentrated on the economic potential of retrieving olive pits for energy purpose [13]. On the contrary, a number of research groups have gone into the study of alternative uses of all the other organic residues mainly in retrieving precious substances e.g. active carbon [14–18]; or as fodder for animals [19]. In many cases, the exhausted olive pomace, due to its high calorific value, is used as fuel in the mills for the production of energy through combustion [20]. However, the overall amount of energy retrieved is very low, seeing that most of the energy produced is used in the process of drying [6]. Other less known uses of olive pomace include its use as an absorbent in treating water contaminated by heavy metals [21], and its application to land as a pesticides enhancer [22]. The review of Rodríguez et al. has highlighted how the olive oil industry produces a precious wood cellulose biomass, the olive pits, which can be used as biofuel [23]. Due to its interesting characteristics, a number of studies have proposed methods of using the wood cellulose material to produce thermal or electric energy, has been presented by Gonzàlez et al. and Duràn [24,25]. According to Cordero et al., Gonzàlez et al. and Vitolo et al., olive pits have a low ash content and a very low sulphur content, features that indicate that it can be considered a good quality fuel and also as a source of renewable energy [26,24,27]. Furthermore, on the basis of its yield of combustion, olive pits represent a valid alternative to traditional pellets (biomass fuel which is having a rapid diffusion in markets) [28]. On this subject, this work describes and evaluates the possible conditions of realization of a production plant of boilers fuelled by pits, obtained from local enterprise, capable of substituting traditional fuels (mainly diesel fuel or natural gas). According to García-Maravera et al. who conducted an “analysis of olive plantation residual biomass potential for electric and thermal energy generation” [29], and as demonstrated by Tous et al. conversion of that residue into energy can increase the value of waste and reduce the environmental impact of waste elimination [30]. Furthermore, it can be


considered as one of the main sources of energy, especially in rural areas, where often it is the only source of accessible and convenient energy [31]. A more detailed study on the use of olive pits for thermal energy has been done by Arvanitoyannis et al. and by Caputo et al. [32,33]. However, there are not enough detailed studies on the comparison between the uses of methane or olive pits to fuel a boiler on situ. The numerous combinations possible of biomass sources (such as wood and its waste, agricultural crops and their by-products, the residues of agroindustrial and food processes), the different approaches available for the conversion (food chain/heat generation or fuel for means of transport), makes it difficult to make the best decision when taking into account the economic and energy cost [34]. Having this in mind, this work, presents an analysis to evaluate the economic viability of the use of biomass (such as olive pits) for the direct production of energy (heat) through the process of combustion. To this end, a study conducted by Daskalakis and Iyer has been considered [35]. They present an analysis of the costs to replace three old boilers in the Arnot Ogden Medical Centre, a non-profit medical structure, of about 433,000 sqft in Elmira, NY. The analysis showed how a biomass-fuelled boiler represented a higher economic investment in respect to a boiler fuelled by methane. Thermal processes fuelled by pits have been chosen for this analysis, because even if they are mature enough in a technological sense, they still have not reached their full diffusion potential. Finally, in the case of anaerobic treatment of the processing residues (after having extracted the pits) dei residui di lavorazione (dopo aver estratto il nocciolino) it is possible to produce biogas, which in turn consents the production of electricity. On this, as Arvanitoyannis et al. explain, the production of biogas would seem to be another effective and promising way of producing energy from waste [36].

3. Methodology proposal The methodology used in achieving the goal of the analysis consisted in analyzing the region with three levels in mind. (1) First level: identification of olive farms based on the agricultural area utilized (Table 2). (2) Second level: definition of the area analysed and identification of the type of enterprise. (3) Third level: main activity. According to the first criterion, namely according to UAA, three classes of farms were identified: from 0 ha to 5 ha, from 5 ha to 20 ha, more than 20 ha. To target the object of the analysis attention was focused on farms with a class UAA of up to five hectares, in the light that this class represents 93.57% of the sector. Table 2 Classification of oil farms for UAA for the entire province of Messina. Source: ISTAT data. Farms by class of utilized agricultural area (UAA), in hectares. Classes of agricultural area in use Surface do not specified Municipality Messina




% of total % of total % of total Total 93.57 5.42 1.01 100


Table 3 Valdemone DOP oil production and related products and by-products resulting from the processing of olives. Source: Based on ISTAT data. Land use

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28



Total area

Harvested production

Olive virgin pomace

Olive exhausted pomace

Olive vegetation water

Olive pits

(quintals/ year)



(quintals/ year)


n. olive farms


Utilized agricultural area (UAA)

UAA olive trees for the production of table olives and oil

























342 150 177

342 150 176

308 122 101

r r r

4263.10 1688.60 1398.00

1918.40 759.9 629.1

1055.10 417.9 346

2557.90 1013.20 838.8

383.7 152 125.8

s s s

307 122 100

r r r

247 484 136

247 484 136

196 473 120

r r r

2712.90 6546.90 1661.00

1220.80 2946.10 747.4

671.4 1620.40 411.1

1627.70 3928.20 996.6

244.2 589.2 149.5

s s s

195 472 120

r r r

1276 320 284

1276 320 284

1056 120 196

r r r

14,616.40 1661.00 2712.90

6577.40 747.4 1220.80

3617.60 411.1 671.4

8769.90 996.6 1627.70

1315.50 149.5 244.2

s s s

1.051 112 196

r r r

158 28 215 513 54 154

158 28 215 513 54 154

150 22 200 476 40 108

r r r r r r

2076.20 304.5 2768.30 6588.50 553.7 1494.90

934.3 137 1245.70 2.964.80 249.1 672.7

513.9 75.4 685.1 1630.60 137 370

1245.70 182.7 1661.00 3953.10 332.2 896.9

186.9 27.4 249.1 593 49.8 134.5

s s s s s s

148 22 200 476 40 108

r r r r r r

386 199 171

386 198 171

319 176 142

r r r

4415.40 2436.10 1965.50

1986.90 1096.20 884.5

1092.80 602.9 486.5

2649.20 1461.60 1179.30

397.4 219.2 176.9

s s s

319 175 142

r r r

342 466

342 466

251 411

r r

3474.20 5688.80

1563.40 2559.90

859.9 1408.00

2084.50 3413.30

312.7 512

s s

251 408

r r

155 138 370 73 30 37 33

155 138 370 73 30 37 33

136 134 190 42 26 34 32

r r r r r r r

1882.40 1854.70 2629.80 581.3 359.9 470.6 442.9

847.1 834.6 1183.40 261.6 161.9 211.8 199.3

465.9 459 650.9 143.9 89.1 116.5 109.6

1129.50 1112.80 1577.90 348.8 215.9 282.4 265.8

169.4 166.9 236.7 52.3 32.4 42.4 39.9

s s s s s s s

136 134 188 42 25 34 31

r r r r r r r

r¼ measured value; s ¼the estimated value; t ¼total.

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Region Area object of Analysis Barcellona Pozzo di Gotto Castroreale Falcone FondachelliFantina Furnari Gioiosa Marea Gualtieri Sicaminò Messina Milazzo Monforte San Giorgio Montagnareale Oliveri Pace del Mela Patti Roccavaldina Roccella Valdemone Rodì Milici Rometta San Filippo del Mela San Pier Niceto Santa Lucia del Mela Saponara Spadafora Terme Vigliatore Torregrotta Valdina Venetico Villafranca Tirrena

Total area

M. Lanfranchi et al. / Renewable and Sustainable Energy Reviews 57 (2016) 1227–1236

The second level chosen as a criterion in the analysis conducted consisted in the definition of the area under study and the identification of the type of enterprise [37]. The towns investigated are located on the Tyrrhenian coast of Sicily in an area ranging from Messina to Patti, these are predominantly coastal or hilly areas, involving a total of 28 municipalities. On the basis of the available evidence, we proceeded to obtain and clarify the data relating to the waste from the production of Valdemone DOP oil (Table 3), and the relative number of farms involved, in various capacities, in the oil industry. We have taken into account farms without a crusher, farms with a crusher, farms with mills that differentiate their prevalent activity of production, agricultural cooperatives and buyers of the distribution. Analysis of the data showed that, in the territory, farms are:


35% are individual producers; 30% are social cooperate oil mills; 25% are bottling and distribution enterprises; 10% are oil mills.

The type of farm selected is the one referred to as "mills". We have chosen this type of farm because the study focused primarily on the waste generated by the transformation process of the olives and the use of on-site waste resulting from the extraction process [38]. We first dealt with a sample comprising 620 mills. The sample was further divided by size UAA (emerged from the first criterion), the reference class is the one with a utilized agricultural area between 2 and 5 ha, the number was thus reduced to 60 mills, which is about 1% of the sector analyzed. The third criterion is that of the prevalent activity, of the area considered. The seasonal nature of production and the corresponding yield have led many local producers to diversify their production activities to ensure adequate margins to remunerate the production factors. On the basis of these considerations, emphasis was placed on the particular oil producing system of the territory analysed, the breakdown of the various operations of supply and processing are: (1) Direct production/transformation: own mill with the alternative of self-consumption or sale of produce (15% of the entire sector). (2) Processing for third parties: the mill provides for the pressing of the olives supplied by third parties who subsequently take the oil produced after paying a fee (25% of the entire sector). (3) Purchase: the mill buys the olives, processes them and then sells the oil on the spot wholesale or sells it retail (0,5% of the entire sector). (4) Olive oil businesses that do the grinding, cultivating, processing/transformation of olives from their own property, as well as the grinding for third parties (which in fact represents the greater part of the system, set at 55% of the whole sector). Table 4 Products and by-products resulting from the processing of 605 quintals of olives. Production processed




Olive Olive exhauspomace ted pomace (quintals/ (quintals/year) year)

Olive vegetation water (m3/year)

Olive pits (quintals/ year)

Olive oil (quintals/ year)







The analysis of the data has shown that most of the mills in the area covered by system 4, devote their activity to processing their own olives and for third parties [39]. Due to the seasonal nature of the work of transformation, this system allows, in fact, farms to work on larger quantities of raw material and recoup most of the costs associated with processing, which often is not possible in limited territorial extensions [6]. As noted earlier, given the seasonal nature of the product, most of the enterprises set aside a part of the land for other agricultural activities, breeding stock or activities related to the processing, taking advantage in some cases of greenhouses, or areas dedicated to them. The agricultural area in this case is distributed as follows: approximately 82% for the cultivation of olive trees, 18% to other crops or activities.

4. The case analyzed: a local farm producing “Valdemone DOP” olive oil and floriculture In order to achieve the objectives of the analysis, we proceeded with the sample resulting from the application of the above criteria. We performed a microeconomic analysis of a local farm, with a territorial extension of 3.5 ha with its own mill producing Valdemone DOP oil, where processing was done both for its own purpose and for third parties [40]. The farm as well as producing oil, works in the floricultural industry with cultivations in greenhouses located on the same surface area. The land area is distributed as follows: 3 ha for intensive olive plantation and 0.2 ha for a greenhouse of 500 m2. The intensive olive plantation consists of approximately 831 plants. The average productivity of olives is 135 quintals; from which 21.6 kg of Valdemone DOP oil (about 16%) is obtained. The mill also grinds for third parties, round about 470 quintals of olives per year, for a total (own olives and conferred by third party) of 605 quintals of olives per year (Table 4). The enterprise also owns a greenhouse of 500 m2 for nursery activities, used for floriculture, with a height of 4 m and arcades of 8.40 m, the greenhouse is heated by 70 kW diesel system. 4.1. Estimated costs of the production of Valdemone DOP oil. The specification of Valdemone DOP oil production emphasizes that "The harvest takes place between October and January, manually or with the aid of mechanical devices, provided they do not damage the olive." With that in mind, we shall proceed to calculate the cost of labour in the olive harvest, assuming that the collection is performed using four devices i.e. facilitated mechanical picking, in which compressed air and electrical devices are used by the operators, thus making it possible to double the daily productivity [41]. Mechanical picking through the use of mechanical instruments enables for the picking of nearly all the produce of the plant, nearly 98%, with a net reduction of the picking costs to 27% of GSP (Gross Saleable Production) [42]. The tools used are basically instruments (e.g., hydrolic combs, portable shakers, etc.) which shake the branches reducing picking time. These devices can be carried by the pickers, working from the ground, or as is the case these days, working from mobile platform being hooked up to a compressor carried by a tractor or even attached to a mobile compressor, in some cases the compressor can have a small engine which runs on liquid fuel [43]. The mechanization of agricultural operations, in particular in picking, can effectively be a solution to reduce the production costs and even solve some of the numerous problems linked to the labour necessary for such operations. However, it is still necessary to verify some fundamental factors:


M. Lanfranchi et al. / Renewable and Sustainable Energy Reviews 57 (2016) 1227–1236

– The morphology of the olive plantation, which constitutes a parameter to the size and type of machinery to be introduced. – The climatic characteristics of the area, which impose very important decisions in the organization of the operations. – The characteristics of the olives to be picked.

The production cost (Table 8) considering all factors of production is therefore: The farm has also costs for the disposal of production residues (pomaceþ oil vegetation water) which include the transport cost to nearest plant, which are:

As a result, the productivity of the picking system depends on the geographical placement, or better still, on the not interfering with the characteristics of the territory. This type of harvesting is very apt in mountainous areas and in small olive plantations. Our analysis studies, an intensive plantation located in low hills with 277 plants per hectare with an average productivity of 45 quintals/ha of olives and a production of oil of 72 quintals/ha. The surface area used allows a healthy growth of the tree and requires the use of mechanical combs. Mechanical harvesting requires the organization of a squad made up of workers equipped with harvesting devices, a compressor, large sheets and personnel for the laying of nets and the picking of the fruits. The quantifying of the cost of the various work squads, for the harvesting of the olives, allows us to define the various technological choices on which to decide in relation to the size of the plantation and to the production. In this study, we have two teams of labourers, both of 2 workers equipped with harvesting devices and 2 workers for the laying of nets to collect the drupes. Thus acknowledging the efficiency of mechanical harvesting (Table 5) as proposed by Polidori [41]. Furthermore, in order to compare the efficiency of the 2 methods of harvesting which are most suitable to the case study (manual and mechanical or facilitated) as well as the labour costs, the cost of labour is estimated by averaging the Italian National Collective Bargaining Agreement (CCNL) of farm workers resulting in €13/h and assuming, on the basis of the prevailing literature, that a worker collects an average of 100 kg of olives every 7 h [41,44,45]. In addition, we considered the estimated fuel costs (average) at €5 per day per device (Table 6), on the basis of a consumption of 5/ 6 l (20/24 total litres) of fuel needed to harvest 15/18 ql of olives per day, calculating that the price of agricultural fuel varies from €0.98 to €1.040 per litre (based on the Chamber of Commerce price list for the province for 2014). For the estimate of the cost of fuel, we consulted “The fuel statistics in agricultural cultivation and processing” and subsequent listing made by the National Body for Agricultural Mechanization, as completion to the Decree of the Ministry for Agriculture and Forestry of 26 February 2002 [46]. On the basis of the above source, it is estimated that for the Region of Sicily, the consumption of discounted gasoline for agriculture was at 67 l per hectare. Therefore, seeing that the estimated yield per hectare is 49 ql, 56/67 l per hectare are needed, thus confirming what was previously stated. Obviously, it is evident that it is not possible to generalize when speaking of productivity of labour and collection sites, but cases are to be discussed case by case. It is assumed that the land is owned, therefore we do not consider the cost of depreciation of the olive plants, while the costs of pruning and other costs of upkeep of the olive plant are noted under "other expenses" (Table 7) [47].

 Average cost of residue disposal: €3.5 per quintal and a trans

port cost of €10 per quintal, assuming a radius distance of 50 km from the mill, which gives a yearly cost of €1225.13. Average cost of the disposal of OVW (Olive Vegetation Water): approx. €3.33 per quintal, which gives an annual cost of €1208.79.

Total disposal cost: €2433.92 Adding the cost of disposal to the total cost of production, we will have the new cost of production (Table 9): The price per litre comes to approximately €7.56. However, it should be pointed out, that the price quoted refers to bulk, i.e. without including the cost of bottling, distribution and marketing of the product (generally not less than €2.50 a bottle). In addition, for the purposes of our analysis, in the study of waste we must take into account the opportunity cost of olive pits or income foregone resulting from allocating the olive pits for disposal and not to more productive uses (Table 10).

5. Obtainable results. Enhancement of by-products for energy purposes In our study, the use of olive pits is considered, extracted from the pomace produced by a continuous biphasic process with a special machine to remove olive pits, to power a generator of heat in the greenhouse belonging to the farm and used in the production of flowers. The greenhouse has an area of 500 m2, the generator has an output of 70 kW for a daily operating time of 4 h, coinciding with the night hours, because given the docile nature of the climate of the area in question it is not necessary to operate during daylight hours, and only for a total of 4 months a year. The generator is currently on diesel fuel with an annual consumption of 1500 Euros, which is a burden on the operating costs of the farm. The study proposes to replace the fuel with the fuel resulting from the processing of the olives, so as to reduce costs, thus recovering the opportunity cost of the disposal of residue, and also reduce the amount of waste to be disposed of, consequently reducing pollutant emissions due to the use of the biomass to near-zero emission [48–50]. In the calculation of cost-effectiveness, two alternatives are taken into account; replace the existing power supply with natural gas or fuel oil from the olive pits. The olive pits, compared to methane, appears to be a fuel of regular size, dry, and low in oil content (compared to the much richer pomace oils, even if dried). The calorie value varies from 4500 to 6700 kcal/h per kg.

Table 5 Efficiency of mechanical harvesting compared to manual harvesting. Type of site

Volume of the plant (m3)

Plants/Average per day

Manual 35/50 8 (10) Mechanical 35/50 16 (20) Source: Adapted from Polidori and Omodei Zorini In the case examined Manual 35/50 8 (10) Mechanical 35/50 16 (20)



Ql day worker

Ql day site

1 1

1 1

1 2

1 2

8 8

2 2

1 2

8 16

Total time (h)

Total labour cost

– –

117.6 59.5

12,230.4 6188.0

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Table 6 Cost of labour – harvesting with the aid of mechanical devices. Workers

Mechanical devices

Harvested quintals/day

Days worked

Total harvested quintals

Cost of labour euro

Fuel cost euro

Total cost euro









Table 7 Other expenses.

Table 11 Investment cost-comparison between methane and olive pits.

Other expenses

estimated amount in €

Other charges (pruning, fertilization, soil tillage, maintenance, biological defence (partially subsidized), etc.). Overheads Pressing (was estimated at €10 per quintal) Total þLabour cost Total gross (labour cost for collection þother outgoings) – Subsidized revenue – Community contribution revenue (CAP 2007–2013) €1000 per hectare (for 2014) Net total

approx. 7890

approx. 2800 approx. 1360 approx. 12,040 6358.00 18,398  3.000 15.398

1 2 3 4 5 6 7 8 9 10 11 12

Boiler of 70 kW

Olive pits

Methane gas

Total investment (price boiler) (€) Installation costs for heating type baseline (€) Cost of capital (€/year) (10/years) Unit of measure PCI (kcal/u.m.) Fuel cost (€/u.m.) Combustion efficiency Fuel cost (€/year) Maintenance costs (€/year) Variable annual costs (€/year) (8 þ9) Total annual costs (€/year) (10 þ3) Opportunity cost olive pits Total net annual costs (€/year) (117 12)

6400 25,000 3100 kg 5600 0 0.8 0 250 250 3350  817.00 2533

4800 25,000 2980 m3 8500 0.848 0.9 407.04 125 532.04 3512.04 þ817.00 4329.04

Table 12 Comparison of theoretical emissions of the two fuels. Source: Adapted from Pattara et al. [11].

Table 8 The production cost. Max cost of total production


Olive oil per kg Olive oil per litre

€7.13 €6.53

Table 9 The new cost of production. €15,398 €2433.92 €17,831.92 €8.26 €7.56

Production cost þ Waste disposal cost Tot. Olive oil per kg Olive oil per litre

Table 10 The opportunity cost. Opportunity cost olive pits (in terms of loss of income)

Average price per quintal in € 12/18

Loss of income in €

Average price



The comparison between the two fuels will allow us to carry out a cost-benefit analysis related to the use of biomass (Table 11). From the analysis, the olive pits present higher investment costs for the purchase of the generator and for maintenance costs, while the boiler fuelled by methane has a lower cost both as an investment and for maintenance. However, even if the two investments differ substantially in a different ratio for each item cost, the costs of the facility adjustment, which represent the highest item cost, is the same for both types of installation. The investment for the generator fuelled by methane has higher overall costs. The plant fuelled by biomass would allow a considerable saving linked to the near zero cost due to the recovery of the fuel [50,51].



Olive pits

Methane gas

Ashes Carbon dioxide (max) Sulphur dioxide (SO2) Azote (N2) Theoretical fumes Theoretical air

% weight % weight mg/N m3 % weight kg/kg combustible kg/kg combustible

0.5–1.5 14.44 0 71.14 11.12 10.87

0 8.87 1.671 74.22 31.11 30.11

6. Environmental analysis On the basis of the bibliography [52,53], we proceeded to make a comparison between the two fuels in order to identify the relevant emission. As can be seen from the data shown in the table (Table 12), the analysis leans in favour of biomass. Therefore, we proceeded with the chemical analysis of the olive pits (Table 13, adapted from Pattara et al. and Salem et al.) [11,49]. Finally, we can summarize and analyze (Table 14), the calculation relevant to the installation of a olive pit powered generator considering the price, consumption, the amount of olive pits necessary for its function and savings in terms of cost per annum of methane. Not considering the recovery of the opportunity cost of the olive pits which was estimated in €817.00 per year, the annual cost of the boiler is approximately €2942.96, against the €3512.04, which is net of the opportunity cost of the olive pits for the planned investment and the purchase of a facility, with the same characteristics, but fuelled by methane. The residue of the depleted olive pomace (pulp, without pits, approx. 10% humidity), can be used for the purpose of biogas production [54], as reported in Table 15. Anaerobic digestion is appropriate for high humidity biomass treatment [55]. The fuel used will be the one, which can be digested, depending on the fatty material, humidity, etc. Degasified pomace can be energy used in a biomass direct combustion thermoelectric power station [56,57]. Biogas can be used to generate heat and/or power, as well as treated as a transport fuel. The digested residual, on the other


M. Lanfranchi et al. / Renewable and Sustainable Energy Reviews 57 (2016) 1227–1236

hand, can be applied to the land, instead of inorganic fertilizers to improve soil fertility. The reduction of costs for the disposal of residual materials facilitates a reduction of the production costs of the product, thereby increasing the profit margin of the farmer or a reduction in the sale price [58,59].

7. Discussions and conclusions In relation to the goal of the research, aimed at the need to pin point new instruments for the management and recycling of waste from the olive processing, we have tried to show how the recycling and the energy enhancement of biomass residue from the olive oil process can allow the transformation of waste materials into energy products. As abundantly demonstrated by the various studies on the subject, this would allow the production of renewable biomass energy without employing agricultural land for energy purposes. In particular, with this study, we have analyzed on olive plantation with its own mill and which differentiates its productive activity through greenhouse flower cultivation. In the light of this, the analysis conducted, has given the following results, confirming the theory of the literature on the subject dealt with:

 reduction in the manufacturing waste disposal costs, and;  use, on-site of waste for energy purposes, for fuelling a boiler to heat the floriculture greenhouse, resulting in lower energy bills. This study confirms, as theorized by Azbar et al. [6] that olive mill waste has a primary importance from an environmental point of view. Actually, this waste can be considered as both a resource to be retrieved and a waste to be treated. The literature review has shown how many authors worked on efficient and cost-effective Table 13 Chemical analysis of olive pits. Source: Adapted from Pattara et al. [11] and Salem et al. [49]. Carbon














Table 14 Calculation of the olive pits powered generator installation. Boiler of 70 kW Consumption per hour Consumption per day Consumption per year Boiler cost Cost of installation, adjustment, maintenance, installation/year (10/years) Quantity of olive pits required Cost fuel supply (€) – Annual savings in terms of avoided methane costs Total/year

approx. 60,000 kcal 10.71 kg/h 42.84 kg/d 5.141 kg/y 6400€ 3350€ approx. 51 q/a 0  407.04€ 2942.96€

treatment alternatives. To achieve this goal, several alternatives and/or their combinations have been tested including the mechanical, physical, biological, chemical and thermal methods, as illustrated for example by Stavropoulos and Zabaniotou [14], or by Carraro et al. [19], etc. In accordance with these researches, this analysis has shown that it is possible to recover significant quantities of materials at a very low cost and to reduce the pollution burden on the environment. The starting point, as argued by Belevi, is represented by the fact that an output of a process can be an input to another process in the system as an import good or product. This is called material flux. As a result of this, the processes are linked through the flow of goods [60] or products. The retrieving of economic and commercial valorization processes of olive industry by-products (virgin pomace, vegetation water and pits in particular), which up to recently were considered as a real problem for the environment, and of no economic interest, now are considered capable of activating processes or procedures capable of reducing the costs of olive plantations or mills, as highlighted by Mahmoud et al. [8]. Therefore, capable of diminishing the burden linked to the disposal of residue from the processing of olives. We stress that the term “process” has been used in accordance to the definition given by Brunner and Rechberger, therefore it “denotes the transport, transformation or storage of materials and goods” [61]. Such a process from the point of view of the territorial development, proves itself capable of even stimulating the birth of activities that are not only capable of exploiting economically and commercially the various by-products of olive processing but also determining how and in which sector to use them [62]. In the case study, the enterprise sustained costs for all the disposal of residues of the process to the amount of €2433.92, which included the transport to the nearest disposal plant. It has been shown how the retrieving and valorization of said residues contribute to the lowering of these costs, confirming the theory of García-Maravera et al. [29], and of Tous et al. [30], and what was sustained by Arvanitoyannis et al. [32], in regards to the production of biogas, assigning to special production plants the waste resulting after the extraction of the pits. The recycling, on site, of the surplus (pits) for energy purposes, to fuel a boiler to heat a flower greenhouse, has contributed to reduce the energy bill, consenting to the total retrieving of the opportunity cost of pits and a saving of €407.04, which, otherwise, would have affected the costs of the enterprise if it had opted for a methane fuel plant. The choice of deciding for a boiler fuelled by biomass, instead of one fuelled by methane, as a solution to substitute an old inefficient gasoline boiler, has confirmed what was extensively discussed by Daskalakis and Iyer [35]. In spite of a bigger investment, in respect of the alternative proposed, due to higher installation and maintenance costs, the pits fuelled boiler has proven that it offers a distinct benefit, due to an operating saving of about €4070.40, due to fuel cost (methane), and a saving on investment capital of about €17,960.40, in the course of a 10 year cycle, confirming the same results of the study. This has brought to further results:

Table 15 Average production of biogas through residue of the depleted olive pomace. Amount of biomass available in tons (approximately)

Biogas Production (m3)

Electricity production (kW h)

Thermal energy production

Biogas production cost per unit Average costa (euro/m3 biogas)a








This parameter represents the cost that must be incurred to produce the unit volume of biogas (m ) from the unit weight of biomass (t).


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 green energy production;  additional income resulting from the recovery of the opportunity cost-associated with non-use of the olive pits;

 complete recycling of by-products of the processing of the 

olives and the resulting zero environmental impact related to the disposal of olive vegetation water and virgin olive pomace; finally, oil price reduction or increase of the profit margin from the sale of the product which can reduce the "cost of disposal".

The first result was obtained by comparing two low environmental impact fuels, such as methane and pits to fuel a 70 kW boiler necessary to heat the flower greenhouse. As adequately demonstrated in Table 12, as well as the composition of the fuel itself, Table 13, the results obtained show how pits register a better performance, environmentally speaking, confirming what highlighted in the study of Cordero et al., Gonzàlez et al. and Vitolo et al. [26,24,27]. Furthermore, this consents the retrieving of the opportunity cost-related to the disposal of pits, in fact, if it were to be disposed as ordinary waste, this would mean a loss of income, for the mill, of about €817.00. The third result has been obtained through the recycling of pits as fuel, as well as by conferring the residue of the process (after the extraction of the pits) to special biogas production plants. On this last point, it is worth remembering what was said by Arvanitoyannis et al. [36] who, in his study highlighted the possibility of producing biogas from olive processing waste, as an efficient and promising method of producing energy, this study confirms that line of thought. This conclusion has been reached, in particular, by considering that possibility in relation to the process waste after having removed the pits from the pomace and having retrieved the other by-products as an added value (as shown in Table 15). This operation is useful because it faces the problem of residue disposal (e.g. pits free pomace, vegetable water), which would otherwise create further economic and environmental costs. Last, but not least, the wiping of disposal costs, which can probably lead to a reduction of the price of oil or an increased margin of profit, deriving from the sale of the product, which would come off the item “cost of disposal”. As shown, one of the items that most burdens the production of oil is the one which comes from the disposal of olive processing residue. This study wants to stress how subtracting the item “residue disposal costs” from the total cost-sustained for the production of the oil, we come to a retail price of €6.53 per litre, instead of €7.56, with consequent positive effects (diminishing) on the end price of the product. Finally, the area subject to analysis, considered 6269 olive farms, for a total agricultural area used for the cultivation of olives fixed at 20,316 ha [63], which yields an average production of 871,864 quintals of olives, which in turn gives 83,699 quintals of oil, and 78,468 quintals of olive pits per year. In terms of recovery of the opportunity cost, associated with the loss of income resulting from the disposal of the olive pits, rather than its energy enhancement, would mean a gain for the entire area of approximately €118,719.17 per year, plus a biogas production of approximately 784,600 m3. If the entire provincial production was taken into account for a total quantity of olive pits of approximately 25,308 quintals, it would be equivalent to a gain in terms of the opportunity cost of the not abandloned olive pits, of approximately €382,900.66/year. However, it is to be remembered that the operations expressed in terms of productivity and feasibility do not lead to generalization, but need to be dealt with case by case.


Acknowledgements This study is a result of the project “Pon04_00364 Smart Cities and Communities and Social Innovation Axis II-Development of models for simplification of the food chain” coordinated by Maurizio Lanfranchi. The work is the result of a full collaboration of the authors. However, Maurizio Lanfranchi, in addition to coordination and setting of the study, wrote the paragraphs 2 and 6, Carlo Giannetto paragraphs 1 and 4, and Angelina De Pascale paragraphs 5 and 7, while Lanfranchi, Giannetto and De Pascale wrote the paragraphs 2.1, 3 and 4.1. The authors acknowledge the helpful suggestions made by the editor and reviewers, the enterprise Idrotermica Imola Srl-Imola (BO) – Italy, for their support in providing technical data and the Prof. Frank Rotondo for his professional translation.

References [1] Maroofnezhad A. Economic evaluation of olive cultivation in the rural to improve the economy ofize city. Middle East J Sci Res 2013;18(3):389–95. [2] Gómez-Limón JA, Riesgo L. Sustainability assessment of olive groves in Andalusia: a methodological proposal. New Medit 2012;11(2):39–49. [3] Nunes LJR, Matias JCO, Catalão JPS. A review on torrefied biomass pellets as a sustainable alternative to coal in power generation. Renew Sustain Energy Rev 2014;40:153–60. [4] Sgroi F, Di Trapani AM, Foderà M, Testa R, Tudisca S. Economic assessment of Eucalyptus (spp.) for biomass production as alternative crop in Southern Italy. Renew Sustain Energy Rev 2015;44:614–9. [5] Testa R, Di Trapani AM, Foderà M, Sgroi F, Tudisca S. Economic evaluation of introduction of poplar as biomass crop in Italy. Renew Sustain Energy Rev 2014;38:775–80. [6] Azbar N, Bayhram A, Filibeli A, Muezzinoglu A, Sengul F, Ozer A. A review of waste management options in olive oil production. Crit Rev Environ Sci Technol 2004;34:209–47. [7] Tsagaraki E, Lazarides HN, Petrotos KB. Olive mill waste water and treatment. in: utilization of by-roducts and treatment of waste in the food industry. New York: Spinger; 2007. p. 133–58. [8] Mahmoud M, Janssen M, Haboub N, Nassour A, Lennartz B. The impact of olive mill wastewater application on flow and transport properties in soils. Soil Tillage Res 2010;107:36–41. [9] Saadi I, Laor Y, Raviv M, Medina S. Land spreading of olive mill wastewater: effects on soil microbial activity and potential phytotoxicity. Chemosphere 2007;66:75–83. [10] Saviozzi A, Levi-Minzi R, Cardelli R, Biasci A, Riffaldi R. Suitability of moist olive pomace as soil amendment. Water Air Soil Pollut 2001;128:13–22. [11] Pattara C, Cappelletti GM, Cichelli A. Recovery and use of olive stones: commodity, environmental and economic assessment. Renew Sustain Energy Rev 2010;14:1484–9. [12] Di Giovacchino L, Prezioso S. Utilization of olive mill by-products. In: Proceedings of the olivebioteq recent advances in the olive industry; 2006. p. 379–89. [13] Parenti A, Masella P, Guerrini L, Guiso A, Spugnoli P. Energetic and economic viability of olive stone recovery as a renewable energy source: a southern Italy case study. J Agric Eng Res 2014;45(2):60. [14] Stavropoulos GG, Zabaniotou AA. Production and characterization of activated carbons from olive-seed waste residue. Microporous and Mesoporous Mater 2005;82:79–85. [15] El-Sheikh A, Newman AP, Al-Daffaee HK, Phull S, Cresswell N. Characterization of activated carbon prepared from a single cultivar of Jordanian olive stone by chemical and physicochemical techniques. J Anal Appl Pyrolysis 2004;71:151– 64. [16] Molina-Sabio M, Sànchez-Montero MJ, Juarez-Galàn JM, Salvador F, Rodrìguez-Reinoso F, Salvador A. Development of porosity in a char during reaction with steam or supercritical water. J Phys Chem 2006;110:12360–4. [17] Sànchez MLD, Macìas-Garcìa A, Dìaz-Dìez MA, Cuerda-Correa EM, GananGomez J, Nadal-Gisbert A. Preparation of activated carbons previously treated with hydrogen peroxide: study of their porous texture. Appl Surf Sci 2006;252:5984–7. [18] Martìnez ML, Torres MM, Guzmàn CA, Maestri DM. Preparation and characteristics of activated carbon from olive stones and walnut shells. Ind Crop Prod 2005;23(1):23–8. [19] Carraro L, Trocino A, Xiccato G. Dietary supplementation with olive stone meal in growing rabbits. Ital J Anim Sci 2005;4(3):88–90. [20] Masghouni M, Hassairi M. Energy applications of olive-oil industry by-products: I. The exhaust foot cake. Biomass Bioenergy 2000;18:257–62. [21] Pagnanelli F, Toro L, Veglio F. Olive mill solid residues as heavy metal sorbent material: a preliminary study. Waste Manag 2002;22:901–7.


M. Lanfranchi et al. / Renewable and Sustainable Energy Reviews 57 (2016) 1227–1236

[22] Cox L, Hermosyn MC, Cornejo J. Influence of organic amendments on sorption and dissipation of imidacloprid in soil. Int J Environ Anal Chem 2004;84:95– 102. [23] Rodríguez G, Lama A, Rodríguez R, Jiménez A, Guillén R, Fernández-Bolaños J. Olive stone an attractive source of bioactive and valuable compounds. Bioresour Technol 2008;99:5261–9. [24] Gonzàlez JF, Gonzàlez-Garcìa CM, Ramiro A, Gonzàlez J, Sabio E, Gañàn J, et al. Combustion optimisation of biomass residue pellets for domestic heating with a mural boiler. Biomass Bioenergy 2003;27:145–54. [25] Duràn CY. Propiedades termoquimicas del orujo de aceituna. Poder calorìfico. Grasas Aceites 1985;36:45–7. [26] Cordero T, Rodrıguez-Mirasol J, Pastrana J, Rodrıguez J. Improved solid fuels from co-pyrolysis of a high-sulphur content coal and different lignocellulosic wastes. Fuel 2004;83:1585–90. [27] Vitolo S, Petarca L, Bresci B. Treatment of olive oil industry wastes. Bioresour Technol 1999;67:129–37. [28] Miranda T, Esteban A, Rojas S, Montero I, Ruiz A. Combustion analysis of different olive residues. Int J Mol Sci 2008;9:512–25. [29] García-Maravera A, Zamorano M, Ramos-Ridao A, Díaz LF. Analysis of olive grove residual biomass potential for electric and thermal energy generation in Andalusia (Spain). Renew Sustain Energy Rev 2011;16(1):745–51. [30] Tous M, Pavlas M, Stehlík P, Popela P. Effective biomass integration into existing combustion plant. Energy 2011;36(8):4654–62. [31] Saidur R, Abdelaziz EA, Demirbas A, Hossaina MS, Mekhilef S. A review on biomass as a fuel for boilers. Renew Sustain Energy Rev 2011;15:2262–89. [32] Arvanitoyannis IS, Kassaveti A, Stefanatos S. Current and potential uses of thermally treated olive oil waste. Int J Food Sci Technol 2007;42:852–67. [33] Caputo AC, Palumbo M, Pelagagge PM, Scacchia F. Economics of biomass energy utilization in combustion and gasification plants: effects of logistic variables. Biomass Bioenergy 2005;28:35–51. [34] McKendry P. Energy production from biomass (part 2): conversion technologies. Bioresour Technol 2002;83:47–54. [35] Daskalakis M, Iyer V. Finding energy savings with a biomass boiler. Honeywell, Morristown N.J.|HPAC |N.J.|HPAC Engineering. June 1 [about 1 p.], Available from: 〈〉; 2009. [36] Arvanitoyannis IS, Kassaveti A, Stefanatos S. Olive oil waste treatment: a comparative and critical presentation of methods, advantages & disadvantages. Crit Rev Food Sci Nutr 2007;47(3):187–229. [37] Aghbashlo M, Mobli H, Rafiee S, Madadlou A. A review on exergy analysis of drying processes and systems. Renew Sustain Energy Rev 2013;22:1–22. [38] Issariyakul T, Dalai AK. Biodiesel from vegetable oils. Renew Sustain Energy Rev 2014;31:446–71. [39] Lanfranchi M, Giannetto C, De Pascale A. The role of nature-based tourism in generating multiplying effects for socio economic developmentt of rural areas. Qual – Access Success 2014;15(140):96–100. [40] Lanfranchi M. Sustainable technology as an instrument of the enviromental policy for the attainment of a level of socially acceptable pollution. World Futures: J Gen Evol 2010;66(6):449–54. [41] Polidori R, Omodei Zorini L. Impatto economico di tecniche alternative nei processi produttivi olivicoli in Toscana. Aestimum 2010;56:59–90. 〈www.〉. [42] Tombesi A, Guelfi P, Nottiani G. Ottimizzazione della raccolta delle olive e meccanizzazione. Inf Agrar 1998;46:79–84. [43] Pellizzi G. Meccanica e meccanizzazione agraria. Bologna: Edagricole; 1996. [44] Tombesi A, Guelfi P, Nottiani G, Boco M, Pilli M. Efficienza e prospettive della raccolta meccanica delle olive. L’Inf Agrar 2004;25:49–52.

[45] Tombesi A, Farinelli D, Ruffolo M, Scatolini G, Siena M. Un triennio di raccolta meccanica per promuovere l’olivicoltura in Umbria. In: Proceedings of the 1st Convegno Nazionale dell’Olivo e dell’Olio. Acta Italus Hortus; 2011, 1. p. 26–30. [46] EMANA. Prontuario dei consumi di carburante per l'impiego agevolato in agricoltura (Technical report). Rome, Italy: National Body for Agricultural Mechanization; 2005. [47] Lanfranchi M, Giannetto C, De Pascale A. Economic implications of climate change for agricultural productivity. WSEAS Trans Environ Dev 2014;10:233– 41. [48] Iakovou E, Karagiannidis A, Vlachos D, Toka A, Malamakis A. Wastebiomassto-energy supply chain management: a critical synthesis. Waste Manag 2010;30(10):1860–70. [49] Salem Z, Lebik H, Cherafa WK, Allia K. Valorisation of olive olive pits using biological denitrification. Desalination 2007;204:72–6. [50] Vamvuka D, Zografos D, Alevizos G. Control methods for mitigating biomass ash-related problems in fluidized beds. Bioresour Technol 2008;99:3534–44. [51] Sabina Alyanna B, Farooqi AA, Shivashankar K, Khan MM. Effect of fertilization methods on biomass, oil yield and economics in geranium (Pelargonium sp.) in India. J Essent Oil Res 1998;10(1):51–6. [52] Sahu SG, Chakraborty N, Sarkar P. Coal-biomass co-combustion: an overview. Renew Sustain Energy Rev 2014;39:575–86. [53] Annan NT, White M, Zvalo V, Ablett RF. Processing summer savory biomass for essential oil and further value added products. J Essent Oil Res 2013;25 (6):468–74. [54] Moragues-Faus A. How is agriculture reproduced? Unfolding farmers' interdependencies in small-scale Mediterranean olive oil production J Rural Stud 2014;34:139–51. [55] Lanfranchi M. Economic analysis on the enhancement of citrus waste for energy production. J Essent Oil Res 2012;24(6):583–91. [56] Greco Jr. G, Toscanoa G, Cioffi M, Gianfreda L, Sannino F. Dephenolisation of olive mill waste-waters by olive husk. Water Res 1999;33:3046–50. [57] Alterio S, Baiamonte V, Campione F, Milone D, Pitruzzella S. La Valorizzazione della Biomassa Attraverso il Riciclaggio dei Rifiuti della Filiera Olivicolo Olearia. In: Proceedings of the 60th Congresso Nazionale ATI; 2005. [58] Cicea C, Marinescu C, Popa I, Dobrin C. Environmental efficiency of investments in renewable energy: comparative analysis at macroeconomic level. Renew Sustain Energy Rev 2014;30:555–64. [59] Tudisca S, Di Trapani AM, Sgroi F, Testa R. The cost advantage of sicilian wine farms. Am J Appl Sci 2013;10(12):1529–36. [60] Belevi H, Material flow analysis as a strategic planning tool for regional wastewater and solid waste management. In: Proceedings of the workshop Globale Zukunft: Kreislaufwirtschaftskonzepte im kommunalen Abwasserund Fäkalienmanagement. Munich; 13–15 May 2002. [61] Brunner PH, Rechberger H. Practical handbook of material flow analysis, 336 p., $120, ISBN 1566706041 336. Boca Raton, FL: Lewis Publishers; 2005 Available from, 〈 practical_handbook-of-material-flow-analysis.pdf〉. [62] Lanfranchi M, Giannetto C, De Pascale A, Hornoiu RI. An application of qualitative risk analysis as a tool adopted by public organizations for evaluating “Green Projects”. Amfiteatru Econ 2015;17(40):872–90. [63] Lanfranchi M, Giannetto C, De Pascale A. A consideration of the factors influencing tourism development in relation to biodiversity conservation. WSEAS Trans Bus Econ 2014;11(1):508–13.