Market of Olive Residues for Energy


Published on

Market of Olive Residues for Energy

Published in: Design, Business, Technology
1 Like
  • Be the first to comment

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Market of Olive Residues for Energy

  1. 1. Market of Olive Residues for Energy Regional Energy Agency of Central Macedonia 1
  2. 2. Work Package 3: Analysis of Local Situations + SWOT analyses + Possible Trends One joint report for the 5 Regional “state of the art” reports from eachDeliverable 3.1: involved area describing the current olive-milling residues market (with a focus on energy uses. Regional Energy Agency of Central Macedonia (REACM) -Leader of WP3: ANATOLIKI S.A.Partners Involved: ARE Liguria-Italy, UC Liguria-Italy, AGENER-Spain, IPTPO-Croatia, UP ZRS- SloveniaDate: July 2008 2
  3. 3. 1. Olive Oil Extraction Process and By-Products (solid olive oil residues)................................... 52. Pomace Oil Extraction Process and By-Products (pomace oil solid residues).......................... 93. Olive oil and solid residues production in Spain, Italy, Greece, Slovenia & Croatia ................ 184. Energy Exploitation Methods .............................................................................................. 236. The current supply chains and the end-uses of solid residues in each region. ....................... 297. National and Regional policy aspects .................................................................................. 428. Technological Equipment & Costs ....................................................................................... 489. Annex ................................................................................................................................ 6410. References ....................................................................................................................... 65 3
  4. 4. With more than 4.5 million hectares under cultivation, it is the second-most important agro-food sector in Europe. The production residues of olive and olive oil production are utilised as solid biomass fuel. The estimated amount of residues is about 1.5 million tons, including stones/pits and exhausted olive pomace. The raw material is the so-called olive pomace. The olive pomace is a by- product of the olive oil production process and constitutes a mixture of olive pits, olive pulp and the water added in the olive mills. The moisture content is approximately 40-70-% depending on the olive oil extraction process. The amount of raw material depends on climate conditions, which determine the annual production period (8 to 9 months/year).The production of olive oil begins with the picking of olives, continues with their transport and endsup with their processing in olive mills. After harvesting, any remaining leaves are removed; the olivesare washed, and are ground into a pulp using a revolving mill, usually constructed with stainless steelor granite. The entire olive, including the pit, is pressed until it becomes a paste, which is thenwhipped, adding water. Next comes the phase to separate solid from liquid, either by the traditionalprocess, or by a continuous system (centrifuge): 3-phase process or 2-phase process.Olive mill technology generates a variety of wastes both solid and liquid. Solid wastes are generatedalso in the olive groves during pruning of olive trees. In this category of wastes are also included:leaves and small branches, the olives pits and the remained pomace resultant from olive oilextraction. Leaves can be used as animal feed, as fertilizer or in the production of compost, whilesmall branches, pits and dried olive pomace also can be used for energy production. Liquid wastesare known as Olive Mill Waste Water (OMWW) and are used in some cases as additives for themanufacture of cosmetics and also for biogas, since substantial amounts of unrecoverable oil andfine residues of pomace remain in the particles of OMWW.Figure 1:Olive pomace (virgin) Figure 2: Olive PitsThe scope of this report is to study the energy exploitation potential of solid wastes producedduring olive oil extraction, as well as to analyse the regional situation in the five regions below: 1. The region of Liguria in Italy. 2. The region of Jaen in Spain. 3. The region of Chania in the island of Crete, Greece. 4. The region of Istria in Croatia. 5. The region of Istria in Slovenia. 4
  5. 5. 1. Olive Oil Extraction Process and By-Products (solid olive oil residues). Four to ten kilos of olives are needed to produce just 1 litre of olive oil. The olive tree begins to produce olives between the ages of 5 to 10 years, reaching maturity at about 20 years. After 100 to 150 years, its production begins to decline. The age of the tree influences only the quantity produced, not the quality. Theharvesting can be done by hand hitting the tree with a flexible pole so that the olives fall into canvascovers placed on the ground or by means of mechanical vibrations.Some olive varieties may be picked in October when they are still green, while other varieties may beleft until February when they are at the peak of ripeness and bursting with oil. Olives are usuallypressed within 24 hours if the weather is hot. If the weather is cooler, the pressing may occur within72 hours of harvesting.Until about 30 years ago, almost all olive oil was obtained through pressing. In the 70s, the millsgradually abandoned the traditional olive pressing process for economical reasons. Nowadays thetraditional method is only used for processing small quantities of ecological olive oil. The alternativemethod is the continuous system works by means of the centrifugation of the beaten olive paste,producing three products: oil, pomace and residual water, just like the pressing system. During the90s, there was a major change in the raw material arriving at the olive pomace oil extractors. Thiswas due to the fact that a large number of Spanish mills changed the olive oil continuous extractionequipment, converting from the three phase to the two phase system in order to optimize extractioncosts and prevent the production of a highly polluting residual wastewater.At present, three types of olive pomace can be considered, depending on the extraction system usedon the olives (shown in Figure 3):Figure 3: Flow scheme of the 3 different olive oil production processes, a) traditional process, b) 3-phasedecanter process, c) 2-phase decanter process.Source: TDC OLIVE “By product Reusing” 5
  6. 6. • The Traditional process”, also known as traditional method. The ground paste is placed between pressing mats and is subject to pressure, to expel the oil mix (mixture of oil and water). The mixture is then poured into a vat or holding tank. This is allowed to rest so that gravity and different densities come into play, separating the oil from the water. • The “3-phase process”. The process based on a 3-phase decanter: 1 litre of water is added per kilo of paste; it is then added to a horizontal centrifugal machine, where the solid is separated from the oil must. The must is then passed on to a vertical centrifugal machine, where the oil is separated from the vegetable water. • The “2-phase process”. The process based on a 2-phase decanter: Same process as above, but instead of adding water for the horizontal centrifugation, the vegetable water is recycled.The main differences between the extracted raw materials are due to water content. Two-phasepomace has moisture approximately 50-70% and contains a certain amount of sugars as a result ofthe presence of vegetation water, while traditional pomace has a moisture content of between 25-30% in the pressing system, and 45-60% in 3-phase centrifugal systems.Figure 4: Example of an olive oil processing lineIn Spain the most widely used process is the “2-phase”. In Italy both “3-phase” and traditionalmethods are used, while in Greece “3-phase” is more common. In Slovenia the only method not usedis the “3-phase” and finally in Croatia all methods are used.Comparing the three processes: • The main disadvantage of the “3-phase process” is the huge amount of water needed and consequently the production of vegetable water. • The stream of the milled olives in “2-phase process” is separated in a 2-phase decanter. This system enables reduced fresh water consumption and the elimination of wastewater streams. Unfortunately, pomace which is produced comprises both, solids and water (OMWW) from the olives and poses again difficulties for disposal, as it is very difficult to handle, dries out very slowly and it is again very polluting. 6
  7. 7. • As a method of pressing, the traditional process entails high labour costs and has certain disadvantages due to the fact that the pressing devices used cannot prevent small pieces of paste from one batch remaining in the press to the next batch, thus contributing to an increase in acidity.More specifically three-phase centrifugation has the following advantages: • It enhances the subsequent drying process, since at least 25% of the residual water contained in the “2-phase process” is removed from the paste. This moisture decrease allows for the use of lower drying temperatures, which is favourable for obtaining an oil of better quality in the further chemical extraction. • Major energy and financial savings are derived because the evaporation of the residual water in the evaporators/concentrators of the power plants takes place with zero net energy consumption. In fact, the process uses the residual energy of the exhaust steam from the turbine. • It enables a residual water concentrate to be obtained, which is rich in mineral salts, sugars and polyphenols. This concentrate is of high commercial value due to its use as animal feed and organic-mineral fertilizer. • The resulting residual water is the departure point for obtaining compounds of high added value because they are beneficial to human healthThe main olive solid residues which are generated during the olive oil production are the following: Pits: The olive stones. Pomace or virgin pomace or olive pomace or crude olive cake: The residual paste after the olive oil extraction. It is constituted from a mixture of olive pit/stone, olive pulp & skin, as well as pomace olive oil plus the water added in the olive mills. The moisture content is about 35-70% depending on the olive oil production process.Table 1: Solid olive oil by-products glossary English pits or stones Spanish huesco Italian nocciolino Greek κουκούτσι Croatian koštice maslina Slovenian koščice English pomace or virgin pomace or olive pomace or crude olive cake (The residual paste after the olive oil extraction) Spanish orujo Italian sansa vergine Greek ελαιοπυρήνας Croatian komina maslina Slovenian oljčne tropine (Ostanek oljčne drozge po ekstrakciji oljčnega olja) 7
  8. 8. English “traditional system” pomace (contains:pomace oil, pulp, pits, approx.25 % humidity)Spanish orujoItalian sansa vergineGreek ελαιοπυρήνας παραδοσιακού συστήματοςCroatian sirova komina maslinaSlovenian oljčne tropine tradicionalne predelave (vsebnost: ostanek olja v oljčnih tropinah, meso ali pulpa (mezokarp), koščice (endokarp), približno 25 % vlage)English “2-phase” pomace (contains:pomace oil, pulp, pits, approx.60 % humidity)Spanish alperujoItalian sansa vergineGreek Διφασικός ελαιοπυρήναςCroatian komina maslina – produkt 2-faznog centrifugalnog sustavaSlovenian oljčne torpine 2-faznega sistema (vsebnost: ostanek olja v oljčnih tropinah, meso ali pulpa (mezokarp), koščice (endokarp), približno 55 % vlage)English “3-phase” pomace (contains:pomace oil, pulp, pits, approx.50 % humidity)Spanish orujoItalian sansa vergineGreek Τριφασικός ελαιοπυρήναςCroatian komina maslina – produkt 3-faznog centrifugalnog sustavaSlovenian oljčne torpine 3-faznega sistema (vsebnost: ostanek olja v oljčnih tropinah, meso ali pulpa (mezokarp), koščice (endokarp), približno 48 % vlage 8
  9. 9. 2. Pomace Oil Extraction Process and By-Products (pomace oil solid residues).Olive pomace is the solid by-product obtained from the extraction of olive oil. It is made up of skin,pulp and stone (pit, kernel). Olive pomace after the extraction of olive oil still contains some oil,called pomace oil, which can be subtracted with further procedures from the olive pomace. Thestone can be separated from the olive pomace in order to be sold as a biofuel, but the extractionmay become complicated. Only a minimum quantity of stone is separated to allow drying andextraction in optimal conditions.The pomace oil can be separated in two ways: i) using solvents (traditional method), and ii) throughphysical extraction or centrifugation (second centrifugation). The first process is based on a solid-liquid extraction where the fats are separated (extracted) with a solvent (hexane). Once thisoperation has been carried out, the oil from the mixture with hexane is separated throughdistillation.According to the traditional method, pomace oil is extracted from the dried pomace (8% moistureapproximately) with solvent (hexane). Then the hexane, which is dangerous for the public health, isseparated from the pomace oil. The product obtained is called crude pomace oil or pomace oil.The extraction of the pomace oil begins with the delivery of fatty olive pomace from oil mills. Thetrucks from the oil mills unload the raw material in a storage yard. The two components of the olivepomace (the pulp and the stone) are separated. This is because the pulp contains a major part of oilwhile the stone, which presents an important percentage of the solid, contains so little oil that itsrecovery is not interesting.The system used for the drying process is a rotating cylinder ,as shown in figure 5, heated internallyby hot gases fed from a combustor or burner situated in the front part of the cylinder. Thetemperature inside the dryer, which is usually made from steel, may exceed 427oC. The rotary dryerhas a slight inclination (about two degrees) and except from drying the pomace, acts as a conveyingdevice and stirrer. The flow of the air inside has the same direction with the dried material. Tofacilitate fast drying, metallic fins are used inside the rotating cylinder so as to blend the pomace. Theoutgoing dry pomace is carried from the dryer for additional processing. The goal of the dryingprocess is to reduce the moisture of pomace to approximately 8%. Values of final moisture above10% are highly associated with hexane retention (and the associated potential health effects) in thefinal product. On the other hand, low (below 8%) moisture levels increase the chance of fire insidethe rotary dryer.Furthermore, if the fresh or stored two-phase pomace is subjected to a second centrifugation, it ispossible to extract between 40-60% of the retained residual oil. The process is carried out usinghorizontal centrifugal machines or decanters. The oil obtained is known as “second centrifugationoil” and is commercially classified for its properties as “crude pomace oil”.The pomace enters the rotor through an immobile input pipe and is driven ahead by an inner rotor.The centrifugal forces cause the solids to sediment on the rotor walls. The worm screw turns in thesame direction as the rotor, but at a different speed, making the solids move towards the conical endof the rotor. Separation takes place along the cylindrical part of the rotor, and the oil leaves the rotorthrough adjustable plates on the casing. The extraction of this residual oil by centrifugation can be 9
  10. 10. carried out in two or three phase systems depending on the capacity of the extractors for eliminatingthe residual water produced in three-phase centrifugation.Figure 5: Material and air flow in the structural parts of a rotary dryerSource: Rotary Drying of Olive Stones: Fuzzy Modeling and Control, N. C. TSOURVELOUDIS, L. KIRALAKIS,Department of Production Engineering and Management, Technical University of Crete, University Campus,Chania, GREECEPomace from the traditional extraction system and those from the three phase extraction requiredifferent preconditioning procedures than those coming from two phase pomace prior to theirextraction with solvent. Figure 6 shows the block diagram of the treatment for pressed pomace orpomace from the three-phase process, where the pneumatically removal of the stone is done justafter drying. The stone is separated, in the majority of cases, using separating machines where theair which flows against the pomace current pulls off the lighter pulp particles, leaving behind theheavier and larger stone pieces. To separate the pulp from the air flow which carries it, cyclones areused, which enable the air to be cleaned and emitted into the atmosphere. The pressed pomace andpomace from the three-phase process must be directly subjected to a drying process immediatelyafter leaving the mills in order to prevent the rapid deterioration of the oil, particularly free acidity.Figure 6: Block diagram of the oil production from pressed pomace or 3-phase pomaceSource: Production of pomace olive oil, By Pedro Sánchez Moral and M Victoria Ruiz MéndezThe other main difference between 3- phase pomace and pomace from the two-phase process lies inthe method of removing the stone. Figure 7 shows the block diagram corresponding to the 10
  11. 11. treatment of two-phase pomace in order to obtain oil from this residue by using solvents. Stoneremoval, as can be seen, is prior to drying and is carried out using mills with filters withapproximately 3mm spaces, which allow solids smaller than this size to pass through, expelling thelarger stone directly to the drying phase. This provides greater yield in the physical extraction,reduced waste due to the metal parts which rub directly against the paste to be extracted and betterexploitation of the resulting by-products.Figure 7: Block diagram of the oil production from 2-phase pomaceFigure 8: 2-phase production chain of olives to produce olive oil and fuel.Source: Andalusian Energy Agency/VTT, EUBIONET2 IEE Project 11
  12. 12. This phase is compulsory for the process of extraction of pomace oil with hexane process. This stageconsumes a great amount of energy and is under continuous research with the objective ofminimizing storage, residence times, energy costs, and to improving the quality of the obtained oil.Normally, drying takes place in rotary heat dryers in which both the product (pomace) to be driedand the hot drying gases are introduced at high temperatures (400 to 800°C). When the pomaceleaves the “trommel”, it should have the appropriate moisture content of approximately 8%.The hot drying gases may come from a number of sources: a) From the combustion of the residual exhausted olive pomace which is obtained after the extraction with solvents of the dry fatty pomace. This is a more widely-used fuel, but it is also the most polluting due to the emission of fine particles produced in the combustion. These fine particles are swept away by the drying gases. b) From the combustion of stones. This material may come either from the pomace paste itself after the drying phase, or from the previous centrifugation before the physical extraction phase. Due to the low ash content of these stones and the type of combustion, this material is very efficient, in terms of heat, cost and environmental impact. These pieces of stones have found important markets outside, with their exportation being very active. This demand has increased its price, which is nowadays rather high. It should be noted that the olive stones have several important advantages as a fuel: • It is an annually renewable fuel with zero net contribution to the greenhouse effect. • It is not subjected to market fluctuations because the material is produced in the same plants where it is consumed. Thus, its price does not depend on the international market for fossil fuels. • Its combustion produces hot gases in a stable range of temperatures, which may reach up to 800°C. • With careful control of the combustion, the drying gases broadly comply with European Legislation for gaseous pollutants. c) The drying gases can also come from the exhausted gases from a turbine or gas engine in a cogeneration process of electricity using natural gas. Obviously, this installation must be close to the drying installation. In recent years, in order to increase profitability, some of such cogeneration plants have made agreements with drying plants for selling them the exhausted gases from their turbines or engines. Alternatively, they have created joint enterprises for this business. From an environmental point of view, the use of these gases is the cleanest system for drying pomace. However, they have two main disadvantages: • Natural gas is a non-renewable fossil fuel, which is subject to huge market fluctuations. Unexpected high prices for the gas can seriously affect the economic viability of the plants. • The hot gases produced never exceed 500°C. This circumstance makes the enlargement of the drying facilities necessary. On the other hand, the low temperature of the hot gases produces better quality chemically extracted oil.The most important element of the drying process is the drying drum, a “trommel”, which consists ofa rotary cylinder supported on rolling strips. A toothed sprocket and two rollers control its rotation.The rotation speed depends on the size of the cylinder. The cylinder may be a single or a doublepassage drier. In the double passage driers, there are two concentric cylinders where the exteriorcylinder is supported by the interior one which, in turn, is supported on the rolling strips. There are aseries of blades in the interior of the inner cylinder which ensure that the pomace comes into contactwith the hot gas flow. They also impulse the pomace to move forward. Inside the drum, the hot 12
  13. 13. gasses transfer their heat to the water contained in the olive pomace, which is evaporated. Thegasses and the steam are then put in contact with fresh material until them al cooled to below 100°C.The gasses are evacuated from the drum, together with the produced steam, through cyclones, by aninduced draught fan. In addition, this device produces a light vacuum in the drum. Before beingemitted to the atmosphere these gases are passed through highly efficient cyclonic decanters whichremove the fine particle in suspension and make them suitable for emission.The oil reflects the thermal aggression to which it is submitted by developing brown colours, due tothe alteration of the double bonds of the hydrocarbonate chains, and the formation of triglyceridedimers and polymers. Drying also produces an increase in the concentration of oxidized compounds,significantly higher K232 values, and oxidized triglycerides, which increase by 35%.The strong drying process which was applied after the first appearance of the of two-phase pomacecaused the formation of an unusually high quantity of Polycyclic Aromatic Hydrocarbons (PAHs),possibly due to the polymerization of the sugars at temperatures above 400°C and the direct effectof combustion fumes on the material to be dried.Depending on the degree of humidity at the entrance to the dryer, different drying processes can bechosen. At present there are basically three types of drying:Single stage direct drying.This type of single stage dryer is ideal for pomace cake, 3-phase pomace and two-phase pomacewhen this has previously passed through the dehydrated physical extraction stage in three phases.This drying system can also be used for 2- phase pomace which does not need to be totally dried, asrequired for chemical extraction, but will be used as fuel in cogeneration plants with biomass forproducing electricity.Two stage direct drying.This system is ideal for pomace from the three phase process which is to be dried at lowtemperatures in order to improve the quality of the oils obtained in the chemical extraction step. It isalso highly suited to drying 2-phase olive pomace where the first drying stage reduces the humidityto below 50% and the second further reduces it to around 10%, as required for a good chemicalextraction.Direct drying in one stage with recirculation of dried pomace and prior mixing.This system is highly advisable for two-phase pomace, when humidity, after stone removal andphysical extraction, is above 70%. The advantage of the procedure lies in the recirculation of part ofthe dried pomace which leaves the dryer. This material is then mixed with damp olive pomace. Themixture is, therefore assimilated to a pomace from the three-phase process with moisture content 13
  14. 14. below 50% at the entrance to the dryer. The mixture then follows a similar process to that of pomacecoming from the 3-phase process, permitting an increase in dryer yield and production.Chemical extraction with solvents is achieved in three phases: preparation of the fatty pulp,extraction with hexane, desolventization of the extracted pulp and distillation of the fatty miscella.However, after the drying process, the pomace requires certain preparation in order to maximize theextraction efficiency. This is due to the fact that the dried pulp is not appropriate for directextraction. The main problem is related to the extremely low percolation. Therefore, the treatmentshave the objective of preparing the pulp so that an increase in solvent penetration into the solidlayer could be obtained. This preparation will, therefore, facilitate oil extraction and the subsequentdesolventization and extractors’ unloading.This preparation is made by granulating the pulp with machinery which is used, among other uses, inthe granulation of compound animal feeding stuffs. However, the fatty "pulp" is not easily granulateddue to its high oil content. To improve the conditions of the process, a suitably -sized mesh, (6 x 60m/m) should be selected, and steam should be used in small quantities as compacting agent.However, the use of large quantities of steam is detrimental because, then, the humidity content ofthe granule will increase, and this will negatively affect the subsequent extraction.In the former discontinuous extractors stones are still used to increase percolation. In general, if the“granulated pulp” fractions and the stone fragments are going to be remixed for extraction, thedegree of compaction is less important than when only the granulated pulp fraction is extracted. Inthis case, a certain level of compromise is required, enabling good percolation, desolventization anddischarging together with good drainage.The advantage of submitting only the correctly granulated pulp to extraction is that the materialsubmitted to extraction is richer in fat. This, in turn, leads to solvent and energy savings as well as anincrease in distillation and extraction capacity because the granulated pulp contains, at least, 15%less inert material than if it also contained stones. To achieve this, the pulp must be correctlyseparated from the stone fragments, which should be sufficiently clean to ensure that the oil contentin stones is below 2 %.The extraction with solvent (chemical extraction) process may be achieved in three different types ofextractors:DiscontinuousThese are extractors with simple contact equipment, where both the extraction and the distillationof the resultant miscella are carried out in a discontinuous or batch format. They are no longer usedfor economic, technical or safety reasons.Semi-continuousThis is the most generalized system in the pomace oil sector. In this case, extraction is made throughthe gradual enrichment of the miscella, using a system of multiple contacts with fixed layers. In otherwords,, the fresh solvent is introduced into the tank where the solid is most drained in fat, flowingthrough the different tanks and leaving the system through the most recently filled tank. This takesplace in discontinuous extractors but the distillation process is continuous. The system is made up ofa series of cylindrical extractors consisting of loading and discharging nozzles, hexane or miscellainputs and steam input for the desolventization. There is also an air output. The extractor itself 14
  15. 15. operates as an extractor and desolventizer. The extractors are loaded with fatty pomace in pelletform from an upper hopper. The exhausted olive cake is discharged under pressure afterdesolventization. As there are several extractors in the system, the unit is similar to a continuousextractor in that, while one is filling up, others are at the washing with hexane or enriched miscellastage and another is at the desolventization and discharge stage. There are a number ofmanufacturers of semi continuous extractors differing only in size, in the number of extractorsinstalled and the continuous or semi-continuous distillation system installed. Other differences areinsignificant.ContinuousIn this system, the basic operation of solid-liquid extraction is carried out through multiple contactsin counter current. The input and the solvent enter the extraction stage system at opposite ends.With the system of multiple contacts against the flow, the solid is gradually impoverished in fats fromthe first to the final stage, while the hexane miscella is gradually enriched from the last to the firststage. The separation efficiency in this type of operation is greater than in the other forms of contact.Most frequently used in the industry are continuous moving solid layer and percolation extractors.The most notable differences between the different suppliers are in the system unit or the extractionunit, which is made up of three basic sections: a) Extraction of oil, and b) Desolventization of pulp –cooling, and, c) Distillation and recovery of solvent.The efficiency of the best-known extractors (DE SMET, ROTOCEL, LURGI, CROWN, EX – TECHNIK) issimilar. The differences lie in other aspects, such as: construction quality, knowledge of the rawmaterial, technical service, operating and safety system facilities. The authorized solvent for theextraction of fats is n-hexane. Its main advantages are selectivity, extraction power, almost zeroinfluence on the oil quality, physical properties, (latent heat of vaporization, boiling temperature(60°C), steam tension) and chemical properties (low corrosive action).Certainly, the extraction stages that have suffered major evolution and have been subjected to moreconceptual changes with respect to their basic design in recent years have been desolventization andcooling. The reasons behind this pressure for new developments are demands for a decrease inenergy and hexane consumption, in addition to questions of safety in storage and transportation.To remove the hexane retained in the solid, a desolventizer is used: it consists of a vertical columnmade up of various cylindrical trays, each of which has a double base heated by steam. The solventsimply evaporates in the heat into a dry atmosphere in the upper trays. A direct jet of steam is usedon the lower trays to remove the majority of the residual solvent from the exhausted olive cake. Theexhausted olive cake is usually dried and cooled on additional trays located below those used in thedesolventization process.Distillation is the process which separates the components of the dissolution, exploiting the differentboiling points of the micelle components through the addition of sufficient heat for the componentwith the lowest boiling point to distil.Moreover, the addition of heat is combined with the action of a vacuum unit, allowing thetemperatures reached to be lower than would be necessary under atmospheric conditions, thus atthe same time managing to increase the energy performance of the process and its efficiency.The purpose of the distillation of the miscella is to separate, by evaporation, the solvent from the oilwhich remains liquid throughout the operation. The following points should be observed during theprocess: a) the hexane should be recovered in order to reincorporate it into the process. b) The oilshould be free of hexane in order to prevent risk in the subsequent processing (storage and refining). 15
  16. 16. The oil should be in the distillation unit for as short a time as possible, only as long as necessary forthe finished product to be lower than 150 ppm of hexane in oil.Finally, hexane leaks should be avoided, not only for safety reasons due to the formation of explosiveatmospheres, but also because the concentration of hexane saturation in the air is high and increaseswith temperature. Taking into consideration the fact that in Andalusia there is a large extractionindustry, every possible effort is made to ensure that measures are taken to reduce levels of OrganicSolvent consumption which currently stand at 6000 t/year compared to 1500 t/year under theNational Plan for the Reduction of Annual Emissions of VOCs.The exploitation of pomace from an environmental point of view may be approached in a number ofways, such as composting gasification, steam explosion treatment for obtaining hydroxytyrosol (orthe extraction of oils as presented above. The by-products generated are the stone, the fat-free solid(or exhausted olive cake) and the residual wastewater.The stone has very good properties as a fuel for heating, even for domestic installations. In additionto the use as fuel, with the properties discussed above, stones are also used as abrasive material forcleaning walls, for example, in the manufacturing of furfural, and for the manufacturing of activecarbon for the treatment of gases, water or other special applications.The traditional use of exhausted olive pomace is as fuel in drying ovens or steam boilers because ofits thermal capacity. As mentioned above, the pomace oil extraction industry is a high energyconsumer, particularly at the pomace drying stage and during extraction with solvent. This fact,together with the imbalance currently existing in Spain between the generation of and increasingdemand for electrical energy has led the sector to propose electrical cogeneration projects, suchthat, by exploiting the calorific potential of the exhausted olive cake or the pomace (biomass), it ispossible to generate electrical energy and exploit the residual thermal energy for the stages of dryingand extraction with solvent. Similarly, the ashes produced in combustion are used to manufacturemanures, given their high soluble potassium content.And finally, what is perhaps the newest use of olive mill wastewater, complex agro industries areintegrally exploiting the pomace with evaporators/concentrators capable of removing the olive millwastewater and exploiting the residual energy of the exhaust steam from electricity generatingturbines. The liquid generated in this process is used as cooling water in the capacitors and theresulting concentrate is excellent for use in the manufacturing of manures and fertilizers, and for itsuse as animal feed.Table 2: Solid pomace oil by-products glossary English pomace oil or olive kernel oil or olive pomace oil or crude pomace oil Spanish orujo Italian Olio di sansa 16
  17. 17. Greek πυρηνέλαιο Croatian ulje komine maslina Slovenian ostanek olja v oljčnih tropinah dried pomace English (contains:pomace oil, pulp, pits, approx.10% humidity) Spanish orujo deshidrato Italian Sansa essiccata Greek ξηρή ελαιοπυρήνα Croatian suha komina maslina Slovenian suhe oljčne tropine (vsebnost: ostanek olja v oljčnih tropinah, meso ali pulpa (mezokarp), koščice (endokarp), približno 8 % vlage) exhausted pomace or depleted olive pomace or extracted olive English pomace or exhausted (deoiled) olive cake (contains: pulp, with or without pits, approx.10 % humidity) Spanish orujillo Italian Sansa esausta Greek πυρηνόξυλο Croatian iscrpljena komina masline Slovenian Suhe tropine brez ostankov olja (vsebnost: meso ali pulpa (mezokarp) z koščicami ali brez, približno 8 % vlage)Harvesting of olive tree prunings takes place twice a year, once after harvesting of olives and asecond time at the end of spring. It is 100% manual operation and there is not any specific field trialfor cost estimation. Most of the amount of that type of biomass is burned at the roadside afterharvesting. Only high diameter branches are collected and used by inhabitants for domestic heating.A little percentage of these quantities is provided to the wood market, but there is no specificinventory in the area. Proximate analysis and energy content are shown in the following table. Theconversion of olive pellets for subsequent heating is being recently considered.Table 3: Proximate analysis and energy content 17
  18. 18. 3. Olive oil and solid residues production in Spain, Italy, Greece, Slovenia & CroatiaMost countries along the Mediterranean Sea produce olive oil in varying quantities. Spain, Italy, andGreece represent more than three-fourths of the total olive oil output in the world. The largestproducer, Spain, supplies about one-third of the olive oil globally. The olive oil produced in Spain isexported to nearly 100 countries. Italy is the second largest producer, with one-fourth of the worldstotal production. Greece is the third largest producer, representing about one-fifth of the global totalproduction. With a consumption of about 20 quarts (19 litres) per person per year, Greeks are thelargest consumers of olive oil per capita in the world.Figure 9: Olive figures by producing countrySource: TDC-Olive networkSpain has 2.5 million hectares of olive tress under cultivation, where the Andalusia region (No 1 inthe graph below) occupies the southern third of the peninsula and represents the most importantregion, with about 1,158,959 ha area under production, it produces approximately 75% of the totalolive oil produced in Spain. The Andalusia Community is composed of eight provinces, from east towest: Almería, Granada, Jaén, Córdoba, Málaga, Seville, Cádiz, and Huelva. The production of olive oilis extended throughout the region, although it is concentrated primarily in the provinces of Jaén andCórdoba. The province of Jaén, with approximately a quarter of the Spanish olive growing surfacearea, represents about 40-45% of the Spanish olive oil production and nearly 15-20% of the worldproduction. It is interesting to note that the province of Jaén produces more olive oil than all ofGreece.A high number of olive mills exist in Spain. The majority of the olive mills uses two-phase extractionsystems. Moreover, there are about 50 pomace oil extracting industries, only 20% of which areCooperative Societies. They are characterised by the absence of public undertakings and foreign 18
  19. 19. capital. These companies frequently work as extractors of pomace oil, thus prolonging the plants’utilization period.Figure 10: Spanish and Andalusia regions for olive growingThe Italian olive production covers approximately an area of 1.2 million ha, 80% of which is locatedin southern Italy, where Puglia represents the most important region, with about 370.000 ha,followed by Calabria (about 186.000 ha) and Sicily (about 60.000 ha). These three regions account formore than 60 percent of Italian olive production. In the centre-north of Italy, the most importantregions for olive-tree production are Tuscany (about 108.000 ha), Lazio (about 87.000 ha), Campania(about 81.000 ha), and Abruzzo (about 44.000 ha). The other Italian regions, except Piedmont andValle d’Aosta which have lesser olive production, cover a relatively small area: Sardinia (about 39.000ha), Basilicata (about 31.000 ha), Umbria (about 28.000 ha), and Liguria (about 14.000 ha).Figure 11: Distribution of olive cultivation areas in Italy with reference to climateThe main extraction systems in Italy are classic press, continuous centrifugation (two-phase andthree-phase options) and various mixed systems plus the percolation system, which is statistically 19
  20. 20. insignificant. Mixed systems can be defined as a whole group of possible combinations between thefirst two types. For example, a roller crusher, typical of a traditional extraction, can substitute a disccrusher or a hammer crusher in a continuous processing line. On the contrary, a disc crusher can beplaced before a press, normally after the mixer. Mixed systems can be sometimes a solution tospecific problems and should represent about 9% of all extraction systems, though they are oftenidentified with the continuous group. On national basis, the press and the continuous systemsseemed to equal each other (44.8% the first and 45.6% the second) until the end of the ’90 but todaythings have changed and the centrifugal technology prevails on the traditional. Giving a close look tothe different regions, the continuous prevails remarkably in the south while the press system stillplays a major role in the centre-north of the country. No data are available on the percentageincidence of two-phase and three-phase options within the continuous centrifugation category.Greece devotes 60% of its cultivated land to olive growing. Greece holds the third place in worldolive production with more than 132 million trees, 3000 mills and 220 bottling companies whichproduce approximately 350,000 tons of olive oil annually, out of which 82% is extra-virgin. About30% per cent of Greek oil is produced in island Crete, 26% in Peloponissos (southern peninsula), 10%in the Aegean island of Lesvos, 10% in the Ionian Islands (Adriatic Sea) and the remaining 24% isscattered around the rest of the country. Olive groves represent 20.5% of total farmland and olive oilproduction 14% of total plant production. In total approximately 1,200,000 hectares of land grow,over 140,000,000 trees. Only one sixth of those trees are intended for table olive production.Consumption of olive oil in Greece is the highest in the world, 23 kilos per capita, compared to theE.U. average of 4.65 kilos, Spain’s 13.68 and Italy’s 12.41 (Source: International Olive Oil Council).Figure 12: Distribution of olive cultivation in GreeceFigure 13: Olive Oil production in Greece 20
  21. 21. There are about 2,700 registered olive mills in Greece. The vast majority of the producers are smallscale land owners with 3.2-4.8 ha or less. The percentage of the olive mills depending on theextraction method used is: 80% olive mills using the three-phase method, 18% use the classicalextraction method and a very small percentage use the two-phase or “ecological” two-phasemethod. These percentages are not related to the production volumes.There are near 520,000 olive growers, 50.5% of which are professional farmers. The large number ofolive growers in relation to the cultivated land reveals that there is no large scale industrialised olivefarming. This means that olive cultivation although systematic and much improved by the applicationof recent technological developments and scientific progress still remains a “family” affair.20% of themills are cooperative ones while the rest belong to the private sector. Private mills are usually smallfamily operations. The average mill employs specialized personnel (1-2) and some 3-4 non specializedlabourers.There are 35 olive pomace extraction plants in Greece with the largest number concentrated in Crete(11) and the Peloponnese oil (10). Crude Olive Pomace Oil production comes to an average of 40,000tons per year.The average production of olive groves is particularly high, 360 kilos/ hectare when thecorresponding world average is 160Kg/ hectare. In certain areas such as Crete average production iseven higher going up to 500Kg/ hectare.Table 4: Type of Olive solid residues Type of solid residues Number OliveCountry Data virgin dried of olive- cultivation leaves pruning pits pomace pomace mills area (in ha) National × × × × × 1722 2.509.677 Spain Regional × × × × × 327 n.a -Jaen- National × × × × × 6000 1.200.000 Italy Regional × × × × 180 13.500 -Liguria National × × × × × 2500 1.125.000 Greece Regional × × × × × 124 41.759 -Crete- National × × × × 125 30.000 Croatia Regional × × × × 18 3.600 -Istria - National × × × 12 1470Slovenia Regional × × × 11 1420 -Istrian - 21
  22. 22. Table 5 Type of Olive oil production methods Production methods used Country Data 2 phase 3 phase Traditional centrifugal centrifugal Other system system National 100% Spain -Jaen- 100% National 37.5% 0.7% 47.5% Mixed (2.5) - 9,6 %. Other- 4,2 % Italy -Liguria- 52% 0,005% 30% Mixed (2.5) - 13 %. Other- 0,02% National 5% 7% 88% Greece -Crete- 1% 5% 94% National 43% 57% (2-phase and 3-phase) Croatia -Istria - 6% 63% 31% National 33,3% 33,3% 33,3% Slovenia -Istrian - 36% 27% 36%Table 6: Olive by-products Quantity of (tn/year) Country Data dry produced virgin pit/stone pomace olive oil pomace (with pits) National 1.230.000 4.920.000 4.222.000 2.500.000 Spain -Jaen- 544.555 2.058.221 1.770.378 1.050.000 National 721.418 n.a n.a n.a Italy Not 3.240 potentially -Liguria- 5.500 12.000 existing (27% of virgin pomace) National 352.000 598.000 53.800-161.500 Greece -Crete- 33.300 n.a 56.500 5.100-15.400 National 5.000 18.200 n.a 3.640 Croatia -Istria - 810 3.509 n.a 710 National 275 1100 n.a 281 Slovenia -Istrian - 255 1000 n.a 258 22
  23. 23. 4. Energy Exploitation MethodsThermochemical processes are quite flexible in their current application and it can be stated that noinstallation is similar to another. On the other hand, it is also true that installations are less bulky,simpler and smaller compared to biochemical ones, whereas they have to use heat and/or gasimmediately. A customised exhaust filtering system must be used in order to avoid environmentallyharmful gases.These thermochemical processes are: combustion, gasification, pyrolysis. These processes are thesimplest to apply and they are based upon the thermal transformation of the biomass whensubjected to high temperatures (300-1500 oC).Figure 14: Overview of thermochemical processes.Source: CRES – Centre for Renewable Energy SourcesThe simplest way to exploit olive solid residues for energy production is by direct combustion. Thiscan take place however, only after olive pomace is dried. Combustion type of boilers gives off theirheat to radiators in exactly the same way as e.g. an oil-fired one. These boilers are mainly automatic;since they are equipped with a silo containing olive dried pomace or exhausted pomace. A screwfeeder feeds the fuel simultaneously with the output demand of the dwelling. A typical example ofdried or exhausted pomace boilers is shown in figure 15Advantageous features of these kinds of boilers are the high thermal efficiency, the low operationcost and the need of non frequent cleaning. Despite an often simple construction, most of theautomatically fired boilers can achieve an efficiency of 80-90% and a CO emission of approximately100 ppm. For some boilers, the figures are 92% and 20 ppm, respectively. An important condition forachieving these good results is that the boiler efficiency during day-to-day operation is close to full 23
  24. 24. load. For automatic boilers, it is of great importance that the boiler nominal output (at full load) doesnot exceed the maximum output demand in winter periods.Figure 15: Mile Boiler P, Samaras, GreeceFigure 16:Energía de la Loma, S.A, Spain.In terms of large scale plants utilizing olive husk, fluidized bed combustors proved to be a reliablesolution. In a fluidized-bed boiler, the fuel is fed into a solid bed, which has been fluidized, i.e., liftedoff a distribution plate by blowing air or gas through the plate. The amount of bed material is verylarge in comparison to that of the fuel. Fluidized bed combustors have a variety of advantages,including their simplicity of construction, their flexibility in accepting solid, liquid or gaseous fuels (incombination and with variable characteristics), and their high combustion efficiency at a remarkably 24
  25. 25. low temperature 750-950 °C which minimizes thermal NOx generation and enhance the efficiency ofSO2 absorption from the products of combustion. Fluidized bed units are eminently suitable forintermittent operation. The fluidized bed (FB) boilers provide good possibility to burn severaldifferent fuels in the same boiler: coal, peat together with biomass, waste, recycled/recovered fuel(REF) or refuse derived fuel (RDF). The combustion may take place under atmospheric or highpressure either in bubbling (BFB) or circulating fluidized bed (CFB) boiler. FB boilers are wellcontrollable because of the fluid like bed and are reliable in operation. Furthermore, the ashesproduced after combustion can be used as additives in manufacture.The gasification process can be broken down into three phases. The first phase is a process ofpyrolysis during which the biomass is converted by heat into char and volatile matter, such as steam,methanol, acetic acids and tars. The second phase is an exothermic reaction in which part of thecarbon is oxidized to carbon dioxide. In the third phase, part of the carbon dioxide, the volatilecompounds and the steam are reduced to carbon monoxide, hydrogen and methane. This mixture ofgases diluted with nitrogen from the air and unreduced carbon dioxide is known as producer gas. Ifthe original feedstock is charcoal, then the gasification process becomes two-phased, and theamount of tar produced is cut down. A composition of olive kernel gasification with air mixture isshown in table 7.Syngas (from “synthesis gas”) is the name given to a gas mixture that contains varying amounts ofcarbon monoxide and hydrogen generated by the gasification of a carbon containing fuel to agaseous product with a heating value. Syngas consists primarily of carbon monoxide, carbon dioxideand hydrogen and has less than half the energy density of natural gas. Syngas is combustible andoften used as a fuel source or as an intermediate for the production of other chemicals. Syngas foruse as a fuel is most often produced by gasification of coal or municipal waste. Four types of gasifierare currently available for commercial use: countercurrent fixed bed, co-current fixed bed, fluidizedbed and entrained flow. Concerning olive dried pomace the fluidized bed reactors have already beentested in terms of gasification.Table 7: Gas mixture from olive kernel gasification with air Component % vv CO 8.6 CO2 21.7 H2 5.4 CH 4 3 C2H4 1.6 C2H6 0.3 N2 59.46Tar production in this case seems to be the major problem which this procedure faces, since it isformed at a temperature of ≈800°C and disturbs the fluidization. Another problem to solve duringthis process is the gas cleaning from tar and other suspended solids that come from fluidized bed orchars. Ash-related problems including sintering, agglomeration, deposition, erosion and corrosion,due to the low melting point ash of agroresidues consist a main obstacle for economical and viableapplication of this conversion method for energy exploitation of the specific residues 25
  26. 26. Pyrolysis is the transformation of a compound or material into one or more substances by heat alone(without oxidation); in other words thermal decomposition. Pyrolysis is somewhat similar tovaporization, however, it is a relatively slow chemical process compared to the vaporization. Thetemperature at which pyrolysis occurs depends on the fuel type and the heating rate. Coal forexample pyrolises at about 420oC. This temperature is below the spontaneous ignition temperatureof coal. Pyrolysis products consist of volatile gases, liquids (tar), and char generally. Products rangefrom lighter volatiles to heavier tars. The composition of the volatile matter (gases), products ofpyrolisis, depends also on the fuel. Pyrolysis of biomass is the thermal degradation of the material inthe absence of reacting gases, and occurs prior to or simultaneously with gasification reactions in agasifier. The liquid fraction of pyrolisised biomass consists of an insoluble viscous tar, andpyroligneous acids (acetic acid, methanol, acetone, esters, aldehydes, and furfural). The distributionof pyrolysis products varies depending on the feedstock composition, heating rate, temperature, andpressure.BIOCHEMICAL PROCESSESThis biochemical process consists in the treatment of the biomass introduced in a digester withoutoxygen. After the biomass is introduced in the digester, a bacterial culture which is responsible forthe biogas production is added.The anaerobic digestion is not the only option in the biological treatment of vegetable water, but isthe most widespread application of waste management for energy exploitation.In this process, and after having homogenised the biomass that is going to be used, a mixture ofgases is obtained; the most important one is methane.This process depends on the operation temperature. This operation parameter is fundamental inorder to obtain a good yield during the process. Dependence of this process on temperature is due tothe bacteria charged for the digestion, which acts at certain temperatures. The biogas produced isresponsible for the biomass agitation that takes place in the digester.The obtained biogas in anaerobic digestion is obtained at the rate of 300 l/kg of dry material, with anapproximate calorific value of 5,500 Kcal/m3. The biogas composition is variable, but it ispredominantly formed of methane (55-65%) and carbon dioxide (35-45%) and in less proportion,nitrogen (0-3%), hydrogen (0-1%), oxygen (0-1%) and hydrogen sulphide (tracks).Anaerobic digestion is appropriate for high humidity biomass treatment, since a watery mean helpsthe process. The fuel used will be the one which could be digested, depending on the fat material,humidity, etc. Degasified two-phase pomace or “alperujo” can be energy used in a biomass directcombustion thermoelectric power station.Biogas can be used to generate heat and/or power, as well as treated as a transport fuel. Thedigested residual, on the other hand, can be applied to the land-farm, instead of inorganic fertilizersto improve soil fertility. 26
  27. 27. Hundreds of biogas applications have been established during the last two decades in Europe. Thebiogas schemes applied include several technological solutions characterised by different digesterdesign, mixing process, filtering and various end uses.Recent studies report the use of fermentation processes, as a way to obtain some interestingindustrial bio products (bio alcohols). During many years of applied research, attention has been paidto the use of acid and enzymatic hydrolysis processes, in order to convert the lingo-cellulosicresidues into fermentable sugars to obtain ethanol, unicellular protein and several chemicalproducts.Generally, most of the ligno-cellulosic residues, before being submitted to fermentation, have to besubmitted to a series of treatments, in order to optimise conditions. The complete sequence wouldbe: • Pre-treatment by mechanical, physical or biological ways. • Chemical or enzymatic hydrolysis. • Hydrolysed conditioning. • Fermentative processes: in co-culture and in a sequential way, throughout a sacharification and simultaneous fermentation, by direct microbial conversion.Currently many technologies are been developed in order to obtain liquid bio fuels (ethanol) fromlingo-cellulosic materials. Two main lingo-cellulosic materials sources exist in the olive oil sector: thetwo-phase or “alperujo”, the three-phase pomace, and the olive grove pruning.Research in three-phase pomace (which could be also extended to two-phase pomace or “alperujo”),is done by separating the extracted pulp from the pit fragments, using temperatures between 190-236 ºC and time periods between 120-240 seconds, has achieved a selective solvolysis of their maincompounds (lignin, hemi cellulose and cellulose). After a fast auto hydrolysis process (steamexplosion) the result is one soluble and another insoluble fragment.The average heating value of dry pomace (with stones, low moisture content) is 3500-4000 kcal/kgwhile for pits is 4000-4500 kcal/kg.Table 8: Comparison of Heating Values of Olive by-products Kcal/kg Spain Italy Greece Slovenia CroatiaAverage heating value of dry pomace 3.500 – 3800 n.a. 4.216 n.a.(with stones, low moisture) 4.000Average heating value of virgin pomace 4.604 – 1800 1.800 n.a. 4219( with pomace oil & pits, high moisture) 4.974Average Heating value of pit/stone 4100 4.750 4.500 4.805 4.500 27
  28. 28. As we can see from the table 8 dry pomace and pits have a little less heating value as compared tocoal and a little more than wood. The energy potential than can be produced in each country isdepicted in table 9 below.Table 9: Energy Potential from Olive by-products Regional data Spain Italy Greece Slovenia CroatiaMWh/year ~Jaen~ ~Liguria~ ~Crete~ ~Istria~ ~Istrian~Energy potential of dry 231.700-pomace(with stones, low 3.183.064 n.a. n.a. n.a. 267.400moisture)Energy potential of virginpomace ( with pomace oil & 4.307.906 25.000 4.587 17.206pits, high moisture)Energy potential of 26.780- 5.005.814 17.898,57 1.570 4.930pit/stone 80.330Table 10: Heating value of fossil fuels. Fuel kcal/kg 1 Propane 11060 2 Butane 10940 3 LPG Mixture 10960 4 Diesel 10200 5 Fuel Oil 9600 6 Town Gas 9100 7 Coal 4498 8 Wood 3890 9 Natural Gas 8300 – 9700 kcal/m3 28
  29. 29. 6. The current supply chains and the end-uses of solid residues in each region.Province of JaenJaén is the region with the main production of olive oil in Spain. Therefore the elimination of thewaste is very important in this process. To eliminate the residues, the olive-mills use a 2-phaseprocess: Olive pomace results from the extraction of olive oil through physical processes. With avariable composition, it is mainly used as a raw material to extract the residual oil that remains in thesolid cake, prior to drying. A by-product designated as virgin pomace is obtained (humidity 62-70%)that goes through a pitted machine, while the pit is mainly used as fuel to produce heat for thermaluse. Afterward, the virgin pomace goes through a process of drying and extraction and new by-product results, designated dry pomace (humidity 10%). This by-product is mainly used as fuel toproduce electricity.Figure 17: Supply chain chartBoth of the following two types of energetic applications of the olive grove solid residues are used inSpain:1. Thermal application: The biomass (olive solid residues) is used for the domestic sector, for heating and sanitary hot water (SHW); also at industrial level for steam process that comes from reused residues.2. Electrical application: The technology used for obtaining electricity is the Rankine vapour cycle, with generation or co-generation (heat + electricity) electrical plants (steam conventional cycles). Another alternative is the electricity generation through gasification processes.The optimal electrical energy plant size is between 10 to 25 MW, the normal size is 25 MW so that itis the most profitable.Since some years ago, the Spanish Government began to promote thermal installations, but at thebeginning problems or barriers in energy exploitation were existed. In Spain the development of thesector (of biomass installation) depended on two factors: Logistics & Distribution. Nowadays, a lot of 29
  30. 30. companies related to this sector create new distribution companies that supply biomass to all thethermal installations.Figure 18: Energy Production Potential from Biomass in Andalusia, SpainThe biomass industry remains underdeveloped in most industrialized countries. It supplies just threeper cent of Spain’s total electricity consumption, while in most industrialized countries the figure isonly one per cent. This is mainly due to lack of government support. Spanish biomass electricityproducers receive a premium on top of the normal price for electricity; however this premium is nothigh enough to make biomass attractive to most investors so it is necessary to increase thepremiums for the biomass sector.The implementation of the biomass electricity installations mainly depends on government policy. Inthe years 2004-2007, the price of which was established by government, were not profitable forimplementation of olive-pomace installations. Finally in May 2007 the prices changed andinvestments in the biomass sector helped to develop old projects and start new ones.Potential facilitating factors, opportunities or barriers concerning the energy exploitation of oliveresidues:Biomass energy is increasingly popular as an alternative energy source for a variety of reasons: • It is widely available in the region (Jaen). • It can provide solutions to the climate change issue. The use of biomass does not increase atmospheric levels of carbon dioxide, a primary greenhouse gas, because of the life-cycles of plants and trees. The use of biomass can also decrease the amount of methane, another greenhouse gas, which is emitted from decaying organic matter. Biomass is a renewable, CO2 –neutral, fuel making it a valuable technology in efforts to reduce CO2 emissions in order to curb global warning and climate change.Spain’s olive-mills use a process of two phases to eliminate olive grove residues. This process is themost appropriate for the extraction of olive oil: Olive residues can be composted, burned, use forheating, for animal feed supplement or returned to the olive trees as mulch. The biomass or wastesrepresent a cheap and technically feasible option to contribute to the reduction of the CO2emissions. 30
  31. 31. • When utilizing the 2-phase system the fresh water consumption is reduced and also the wastewater streams are eliminated. • When the refined oil is extracted, the leftover fibrous material is primary lignin and cellulose. This residue has still a high calorific value, and it can be composted, burned, use for heating, for animal feed supplement or returned to the olive trees as mulch. • The remaining leaves and stone can be pyrolysed under non-oxidative atmosphere or gasification can take place with energy or alternative fuel production. It can be a solution to the environmental problems that their land filling or combustion could create.Liguria RegionLigurian millers are craftsmen who work third party’s olives (imported olives) or their own’s (localolives). The quantity of residues therefore depends on imports but it is not easily figured. Mostmillers (over 60%) deliver pomace to pomace refineries: there are 2 small refineries in Liguria, butmost pomace is sent to Tuscany or Latium (where there are big refineries) that pays very little money(more or less as much as the transport cost). Therefore, in Liguria there is only virgin pomacepotentially available. The other millers use pomace for agronomic use (10%) and the rest dispose of itin another way. Liguria has a few pilot projects for alternative disposal of pomace (calcium addictionto 2-phase pomace and then delivery to a biomass plant located in another region) but there areenvironmental, procedural, legal or technical difficulties.Olive pit separation from virgin pomace (pit recovery range amounts to 18-30%) seems to have thehighest potential in terms of heating value and price. At the moment pits are not purchasable inshops, only some mills sell them directly. There is a small district heating system in Arnasco fuelledwith pit.The following energy applications can use olive solid residues.Anaerobic digestion: widely applied 40-50% of organic material is transformed into biogas which canbe used to generate electricity or thermal energy. The main drawback is the production of smallquantities of mud.Gasification or combustion: to produce thermal energy or for cogeneration. Gasification allows usingvirgin pomace which is transformed into syngas made of CO and H. In Italy syngas is used to generateelectricity in Calabria in a plant owned by Guascor. It produces 23MWt and 4.2 MWe. This kind ofplants has the advantages that pomace does not need to be dried and high performances, but theyneed big quantities of pomace. The small quantities of pomace available in Liguria make it noteconomically viable the use for this kind of plant application.Direct combustion is motivated by the high heating value of the pomace which is 4.65 kWh/kg (thepit has a heating value of 5.4 kWh/Kg and can be used as it is or to produce pellets). Unfortunatelyfor direct combustion it is needed to have dry pomace (according to law) but in Liguria there is onlyvirgin pomace. In Italy there exist biomass plants burning dry pomace together with wood chips andother biomass. • In Liguria there are cases of pit separation and consequent use it as domestic fuel. It is also sold for the same aim. 31
  32. 32. • There is a case of use of calcium for pomace drying (UNIECO) at Lucchi & Guastalli mill with subsequent use as fuel in biomass boilers (in Tuscany and Lombardy) • There is a small (70 kW – 64 mt length) district heating plant running with olive nut in the municipality of Arnasco. It heats up the church and the annexed building.Figure 19: Pomace production in the region of Liguria divided in province areas belowPotential facilitating factors, opportunities or barriers concerning the energy exploitation of oliveresidues: • Green certificates for electrical energy • Possibility to use heat for the many greenhouses in Liguria (flowers and farming) • Funding opportunities for <1MW plants, coming from the Rural Development Plan 2007- 2013 • Mills have a low energy demand (for electricity in the range 16-70 kW and for heat around 40.000 kcal) therefore there is a need for different potential users. • Presence of virgin pomace only and absence of regional pomace refineries therefore, need to find a way to dry pomace in order to increase its heating value. Pelletising could be a solution? • Presence of many scattered small mills, therefore the transport factor becomes crucial in the feasibility study. And transport in Liguria is particularly difficult due to orography • Presence of different milling systems, which generate different kinds of pomace. • Seasonality of residues. • Different crop yield each year. 32
  33. 33. Chania RegionIn Greece oil refineries buy virgin pomace from olive millers, extract pomace oil from virgin pomaceand they use the exhausted pomace either for their own energy needs or they sell it to the millers asa heating fuel.Dried or exhausted pomace is mainly used for heating purposes today on Crete for: a) Houses b) Greenhouses c) Various small-sized industriesToday, exhausted pomace is used extensively in Crete for heat production; in the future, it has verygood prospects in power generation and/or heat and power cogeneration. Since a large proportionof power in Crete is generated today from wind energy, it is likely that, in the future, biomass willalso contribute to the generation of green electricityFigure 20: Supply chain chartIts heating value is 3500-4000 Kcal/ kg (with a moisture content of 12%) and its price isapproximately 0,05 Euros/ kg; thus, it is a very attractive option as a fuel in comparison to oil. Driedor exhausted pomace, however, has not yet found applications in power generation or cogenerationof heat and power in Greece. Because it can be easily burnt and the combustion technology is wellknown widely, it can be used as a solid fuel for power generation in the future. Presently, it is used inhouses and in greenhouses for space heating and hot water. Also, it is used in various industries fordrying purposes and/or for hot water heating. Greece exports small quantities to other Europeancountries each year, where dried or exhausted pomace is used as fuel. The required machinery forthe dried or exhausted pomace combustion is the boiler (including the burner), which is quite simpleto use and not expensive. These boilers are reliable and made locally.Potential facilitating factors, opportunities or barriers concerning the energy exploitation of oliveresidues: 33
  34. 34. Dried or exhausted pomace can be used for power generation or cogeneration of heat and power inCrete, since it presents many advantages, such as: • There is no need for harvesting of raw materials and transportation because it is produced in the dried or exhausted pomace processing plants. • Its moisture content is very low and its heating value is high. • Its price is rather low in comparison with its heating value. • The combustion technology is well known. Since it is granular, either fixed bed reactors or fluidized bed reactors can be used. • The generated power can be consumed either inside the plant or can be sent to the grid. • The Greek Government offers good subsidies for investments in the field of Renewable Energy Sources and, of course, in Biomass. • The use of Biomass for power generation in Crete will reduce the CO2 emissions on the island. • In the case that such a plant should be created, various other solid agricultural residues can be used together with the Olive Kernel Wood as raw materials. • The creation of such a plant will help in power generation to and from small-decentralized plants instead of larger centralized power plants that exist today in Crete. • The sulphur content of dried or exhausted pomace is minimal. • The efficiency of small-sized combustion plants is very low. The dried or exhausted pomace processing plants operate seasonally. The produced heat from dried or exhausted pomace should be used at the time that cogeneration of the heat and power is obtained (during its operational period which is from November – April), or outside the plant for nearby heat- requiring operations. • Initially, the price of the dried or exhausted pomace may rise, due to an initial local deficit of this Biomass source. • Nowadays, fewer people work in agriculture. There are no incentives or opportunities to the farmers to exploit olive residues in order to produce energy from them. • People should be informed about the environmental and energy benefits of the olive residues exploitation. • Cretan’s admitted that they would like to exploit olive residues only if they had a financial incentive. • Most millers are at a senior age and lack knowledge about new possibilities and procedures for olive residues exploitation.Table 11: Relationship between Energy production & Energy consumption in ABEA olive industry Total Energy Total Energy consumption (Biomass Energy production/ Year production (Biomass) +Electric) Energy consumption (1010 kcal) (1010 kcal) 2001 4.7 2.72 1.73 2002 7.1 4.54 1.56 2003 5.7 3.84 1.48 34
  35. 35. Figure 21: The island of CreteFigure 22: The region of Chania in the island of CreteTable 12: Olive residues production in Crete. Average heating Thermal Energy olive residues Production (tn) 2003 Yearly change value production (kcal/kg) (109kcal)pits 103695 +8.553 4437 460olive prunings 1550723 +57.670 3990 6187Istria Region 35
  36. 36. In Slovene Istria, olive residues are usually (95.4 % of residues) composted and returned to the olivegroves as fertilizer. The composting of olive residues is integrated in the processing cycle of each oilmill. After the 3-6 month composting period, the olive residues are spared on the surface as fertilizer,returning nutrients to the soil. Only 4.6 % of olive residues are used for energy purposes, to generateheat. This amount of residues produces enough green energy for heating two households. Until nowthere is no any supply chain in Slovene Istria region. The end users of olive residues are now mainlyolive millers which use olive residues for composting. Two of them use olive residues for their privateenergy purposes (heating). Both of them have around 60 tons of residues per year. If they would useall of residues, it would be enough energy for heating at least 5 more households. Presently they areheating only their own two households.In figure 23 we can see the current supply chain & end-uses of residues in the region of Istrian.Figure 23: Supply chain chartIn figure 24 are shown new capacities for local generation of electricity from Renewables. Planneddevelopment of electricity generation from renewables does not include the energy exploitation ofolive residue, because of their small quantities.Figure 24: RES production and planned new capacities 600 120 Small hydroelectric Small hydroelectric station 110 station 500 Wind 100 Wind 90 Landfil gass Landfil gass 400 80 New capacities (MWh) C apacities (M W h) 70 Purification plants Purification plants 60 300 Biogass Biogass 50 40 Wood 200 Wood 30 Solar Solar 20 100 10 Olive residues Olive residues 0 0 2010 2020 2006 year 36
  37. 37. In Slovenia olive residue is treated as waste and not as secondary product. They don’t use olive residue for energy most of them are thrown away or use like fertilizer in olive fields. Two best practices are identified in SLO Istria region, where olive miller uses olive residues mostly as fuel for house heating and water heating. A description of the above two mills follows: 1. The first is a 3-phase mill. After olive oil extraction, olive residues are too wet to burn immediately and therefore disposed to the field/meadow behind the mill. Olive residues are left to dry on the open space. Olive residues are mixed up/turned upside down several times to speed up the drying process. After certain time they are collected and loaded into big wooden containers and stored in the shed next to boiler room. Dried olive residues are used directly for burning/combustion in the stove. 2. The second mill is a traditional one which in past they used to dispose olive residues back at olive fields. Today they put them directly into a wooden container in order to dry them on open air (but under roof) and use them only for energy purposes; production of heat for heating private house and olive mill (ca. 250 m²). Figure 25: Slovenia Table 13: Olive mill dataŠt. Mill name Name Surname Address ZC Town Technology1 Oljarna TORKLA Beno Bajda Obrtna ulica 11 6310 Izola 22 Kocijančič Ido Kocjančič Frenkova 5 6276 Pobegi 23 Oljarna Torkla Šalara Franko Lisjak Obrtniška ulica 26a, Šalara 6000 Koper 24 Oljarna Torkla Krkavče Patricij Ternav Krkavče 97 6274 Šmarje 2,55 Oljarna Prinčič Prinčič Sv. Peter 18 6333 Sečovlje 26 Oljarna Krožera Fulvio Marzi Srgaši 40 6274 Šmarje 2,57 Oljarna Peroša Viktor Peroša Nova vas nad Dragonjo 8 6333 Sečovlje 38 Oljarna Čok Erika Čok Plavje 10 6281 Škofije traditional9 Oljarna Oljka Evelin Toškan Vanganel 40 6000 Koper traditional10 Oljarna Hrvatin Marinko Hrvatin Ul. 15 maja 10b 6000 Koper 2 37
  38. 38. Dobrovo v11 Oljarna v Brdih Zadružna cesta 9 5212 2 Brdih12 Oljarna Agapito Ivan Agapito Spodnje Škofije 15 6281 Škofije traditional Waste water Technology Olives processed (t) Olive oil production (t) Olive residues (t) (t) Traditional 305,8 61,2 122,3 183,45 2 phase 612,7 122,5 536,1 122,54 2,5 /3 phase 304,5 60,9 167,5 334,98 SUM 1223,0 244,6 825,9 640,97 Potential facilitating factors, opportunities or barriers concerning the energy exploitation of olive residues: • Based on upward trend of petrol prices on global markets and breakthrough of new technologies, which use alternative / renewable sources of energy (for instance wood biomass in Slovenia), the use of olive residues could be an alternative source of energy, in first place for heating / production of heat and later for production of electricity. • Since the quantity of olive residues in Slovenia is very small, the exploitation of these is not suitable for larger energy plants, such as large heating stations or power plants. Their use is most suitable for heating individual olive mills and private households, which are in direct proximity of olive mills. These conclusions are based on calculation of ratio between yearly energetic potential of olive residues, comparing to yearly energetic needs for energy in Slovenia, which is very low. • Usage of olive residues has very important impact on the environment. Figure 26 below shows emission comparison between extra-light heating oil and olive residues (if they would use all olive residues in Slovenia for heating). Figure 26: emission comparison between extra-light heating oil and olive residues ELKO Olive residues 2.500 2.000 1.500 kg 1.000 500 0 CO2 * 1000 SO2 NOx CxHy CO * 100 dust In calculation of emissions, CO2 is not considered as the result of burning olive residues. Although biomass releases carbon dioxide (CO2) into the atmosphere when combusted, the amount of CO2 released is equal to or less than the amount that the crop absorbs while growing (net emissions of CO2 are zero). 38
  39. 39. Istrian region The Istrian region (Croatia) has a long olive growing and oil producing tradition. According to the latest official statistical data, a total of 600,000 olive trees are cultivated in Istria. Lately, traditional extensive olive cultivation methods were replaced with intensive modern growing technology, and olive growing has become attractive trend in agriculture. Moreover, the olive oil is one of the most important typical food products in Istria. The olive oil market has recently improved especially since the consumers pay more attention to both health and nutritional aspects of food. Olive sector in Istrian Region (Croatia) is organized as follows: Olive producers use services of 18 olive mills, mostly SME’s (Table 14, Figure 28). Olive mills produce olive oil and they are responsible for olive mill waste management. The treatment of olive milling residues in the region encompasses different treatments. Table 14: Olive mill dataŠt. Mill name Name Surname Address Zip code Town Technology 1 Agro Millo Valter Smilović Baredine 16 52460 Buje 2 2 Agrofin Boris Vekić Zambratija bb 52475 Savudrija 3 3 Al Torcio Tranquilio Beletić Ulica Torci 18 52466 Novigrad 2 4 Baiocco Andrej Đurić Galižana 8a 52216 Galižana 3 5 Brist d.o.o. Silvano Puhar Ušićevi dvori bb 52203 Medulin - 6 Kraljević – CUI Danijel Kraljević Farnežine 52470 Umag 2 7 Olea d’ oro Germano Kraicer Partizanski put bb 52100 Pula 3 8 Pastorvicchio Antonio Pastorvicchio Istarska 28 52215 Vodnjan 2 9 Pavlović Alojzije Pavlović Crveni vrh bb 52475 Savudrija - Pilar – Stella10 Maris Pilar family Stella Maris 52470 Umag 211 Torač Franko Vladišković Žbandaj bb 52440 Poreč 212 Babić Ante Babić Stancija Vineri bb 52466 Novigrad 313 Bronzi Sergio Černeka Bronzi 51 52420 Buzet 214 Brtonigla Šišot family Ronko bb 52474 Brtonigla Traditional15 Pašutići Miljenko Prodan Pašutići bb 52420 Buzet 2 Agrolaguna16 Agrolaguna d.o.o. M. Vlašića 34 52440 Poreč 217 Rovinjsko selo Miro Pokrajac Rovinjsko selo 50 52210 Rovinj 2 Agroprodukt Agroprodukt18 d.o.o. d.o.o. Trgovačka 135 52215 Vodnjan 3 Olive mill owners manage waste waters mostly using physical treatment processes in their own organization or by means of waste management companies. There are also some cases of OMWW releasing in the environment. In Croatia, olive residues are treated as a waste and not as secondary products. But, there are some cases of crude pomace treating as an organic fertilizer, usually placed back to the olive fields (with or without composting). Some mills deposit pomace in the mill vicinity 39