As it is well known to persons skilled in the art, for"oil residues"it is meant the residue of olive oil pressing, formed by dregs of skin, pulp and pit.

For their disposal, nowadays oil residues are spread directly on the fields, optionally along with other refuses of oil mills such as the so-called vegetation waters.

Such an on-field spreading of the oil residues entails significant organizational drawbacks for the olive oil millers, who have to manage refuses with a high content of moistness and therefore easily susceptible of evil-smelling anaerobic fermentations. Moreover, on-field spreading entails technical drawbacks linked to the percolation of the masses and to need for a suitable machine for their uniform distribution, above all in the case of the wet oil residues from the so-called two-phase extraction systems. In addition, the spreading of oil residues that have been subjected, even briefly, to a stocking under absence of oxygen causes also the freeing in the atmosphere of smells unpleasant for people living nearby the oil mills and in the rural areas concerned by the spreading.

Lastly, to these drawbacks it should be added the fact that oil mill activity, and therefore the oil residues disposal needs, coincide with a period of the year in which soils are often saturated with water or icy, conditions that make a spreading impossible (Italian Law 576/96) or that anyhow increase the risk of polluting the superficial water bodies (drainage canals, channels, rivers, phreatic surfaces, and so on) due to the potential washing away of the most soluble organic fractions present in the refuses, notoriously characterized by high values of BOD5 and COD.

Another known method of use of the oil residues-carried out in the so-called'oil residues mills'-consists in their treatment with a solvent and their subsequent pressing, yielding the so-called oil residues oil. However, the latter is generally considered an inferior product; moreover, the production of said oil yields a nearly nonexistent economical advantage, both for the producer and the oil miller. In particular, oil residues mills run into problems in the extraction of oil with solvents, above all in the case of the so-called"wet oil residues"obtained in two-phase oil mills. In addition, as it is known, oil residues mills have a negative environmental impact owing to the emissions produced.

Hence, the technical problem underlying the present invention is to provide a method and an apparatus for the disposal of oil residues allowing overcoming the drawbacks mentioned hereto with reference to the known art.

Such a problem is solved by a method according to claim 1 and by a corresponding apparatus according to claim 21.

According to the same inventive concept, the present invention further provides a product according to claim 36.

Preferred features of the present invention are provided in the dependent claims thereof.

The present invention provides several relevant advantages.

First of all, the proposed method of disposal fully exploits the oil residues for agronomical purposes, without the drawbacks associated with their immediate and direct on-field spreading and avoiding the treatment in oil residues mills and therefore the production of oil residues oil. Hence, the problem of the disposal of refuses of oil mills is solved at the root, and all the drawbacks associated with the anaerobic fermentations of the oil residues and to the entailed emission of unpleasant smells are eliminated.

The recovery for agronomical purposes of the by-products of oil mill processing ensures a real and immediate advantage for the oil miller, witnessing a refuse to be disposed of turn into an asset.

The product obtained with the method and the apparatus of the invention can find wide use as a farming substrate in nurseries and for soilless cultures as a substitute for peat or other organic-mineral substrate (peat + perlite) and for the fertilization of soils as a substitute for synthetic chemical fertilizers, optionally by the same olive grower.

Hence, the invention makes the entire olive-oil industry eco-efficient in coincidence with the production of extra-virgin and virgin olive oil and safeguards and recovers soil fertility.

Concerning the oil mill, by virtue of the invention it can also do without means for stocking the refuses, as the processing of its by-products is made viable directly on site, online with the mill, automatically and continuously.

Moreover, the method and the apparatus of the invention entail a high flexibility of application, being adaptable to the various typologies of oil mills available on the market, and in particular to that referred to as two-phase.

Other advantages, features and the operation modes of the present invention will be

made apparent in the following detailed description of some embodiments thereof, given by way of a non-limiting example. Reference will be made to Figure 1 of the annexed drawing, showing a block diagram of an embodiment of the apparatus according to the present invention.

First of all, it will be described an embodiment of the method of treatment of oil residues according to the invention.

The method of this embodiment is integrated in the processing cycle of an oil mill, by providing the continuous treatment of the oil residues directly received from the separation of the oil from the olive paste. The method provides an additioned oil residues apt to act as soil improver and/or fertilizer. As it is well-known to a person skilled in the art, for"soil improver"it is meant a material that, added to a soil or substrate, improves its biological (microbial activity), physical (structure and hydric properties) and/or mechanical (workability) features.

The method comprises first of all a step of separating the ligneous portion of the oil residues deriving from a breaking of the endocarp, a portion commonly called'pit'.

For simplicity's sake, hereinafter said step will be referred to as stoning step.

In the present embodiment, the stoning step provides the treatment of the oil residues by a centrifuging operation that separates the pit from the oil residues.

It will be appreciated that the separation of the pit at a preliminary step of the treatment allows profitable industrial uses thereof, like, e. g. , the combustion for heat production, the use for the sand-blasting of monuments and airplane fuselages, the use as substrate for hydroponic cultures, the production of insulating material or of activated carbon, other uses for energy production, and so on.

Therefore, the scored oil residues obtained with the stoning step consists of the pulp and skin of the olives and of the vegetation water, and it typically has a moisture rate ranging from about 74 to 76%, therefore being rather fluid. Apart from its water content, such a pitted oil residues has a complex composition, and the main content will be provided by the organic substance (e. g. residual fats, pectins, sugars, hemicellulose, cellulose, proteins, phenolic compounds, volatile substances, and so on) assessed at about 94% of the dry substance, and by the ashes (in general mostly Potassium, Calcium and microelements).

Preferably, the method further comprises a step of collecting the stoned oil residues, e. g. in a tank, and the additioning thereto of elements fostering the maturation of the product, like, e. g. , microbial starters active on the oil refuses.

The method then comprises a mixing step, preferably carried out in a tank, during which additives are added to the stoned oil residues. The additives added to the stoned oil residues are apt to: (a) reduce the moistness of the stoned virgin oil residues to make the end product non-percolating; (b) allow an adequate air circulation in the end product; and (c) decrease the Carbon/Nitrogen ratio of the starting oil residues, in order to cause a more rapid degradation thereof and, above all, to reduce to a minimum the competition of the soil toward the culture for the Nitrogen present in the circulating solution.

The specific kind and quantity of additives to be added to the stoned oil residues depend on the specific processing needs, e. g. on the kind of oil residues, the oil mill and the kind of end product to be obtained.

Concerning additives with properties (a), preferably there are added additives of organic origin having a high water absorption capacity, like, e. g. , shavings and sawdust from natural wood, Gramineae straw, raw wool waste, and so on.

Concerning additives with properties (b), these may be in the form of relatively coarse material. Preferred suchlike additives are straw, pruning residues and olive tree leaves and twigs, the latter, e. g. , residues of olive cleaning upstream of the oil extraction process in an oil mill.

Concerning additives with properties (c), these preferably are materials per se rich in organic or mineral Nitrogen, apt just to produce enrichment in Nitrogen of the mixture.

The use of additives with properties (c) ensures the end mixture, once intended for the ground, to degrade without causing competition for Nitrogen between the telluric microflora and the root systems of the cultivated vegetables. In fact, such a phenomenon occurs when organic matrices with a high (>30) C/N ratio are contributed to the ground, causing a temporary immobilization of the mineral Nitrogen present in the liquid phase of the soil by the microorganisms called to mineralize the organic matrix, thereby bringing about an undesirable phenomenon that depresses the growth of cultivated vegetables.

Preferred additives with properties (c) are, e. g. , raw wool waste or raw wool tel quel, typically having a Nitrogen content ranging from about 6 to 4.5% and exhibiting a high hygroscopicity for low moisture (typically ranging from 12 to 14%). Moreover, raw wool waste and raw wool tel quel have an organic substance content equal to about the 76% on the fresh weight and about the 9% of ashes on the fresh weight

(mainly consisting of Calcium and Potassium, whereas among microelements Iron stands out). In this case, the end mixture can be assimilated to an organic fertilizer.

Of course, Nitrogen enrichment may be attained by alternative additives, e. g. not of an organic but of a mineral kind. In this latter case, preferably there are used nitrogenous fertilizers, e. g. , in the form of nitrate, and even more preferably Calcium nitrate or Potassium nitrate, typically more stable with respect to other nitrogenous mineral fertilizers. In this case, the end mixture takes on the aspect of an organic- mineral fertilizer.

Of course, the quantity of the additives with the property (c) at issue may be adjusted depending on the end Nitrogen titer that is to be attained.

Preferably, the mixing step provides a mixing operation that moves the stoned oil residues, also in order to prevent the separation of its two phases consisting of pulps and skins (solid phase) and of vegetation water (liquid phase).

The mixing step may further provide a grinding operation suitable for chopping twigs and leaves, recovered from a washing of the olives prior to the pressing, and ligno- cellulosic organic material (straw, shavings, etc. ) added to the oil residues to absorb<BR> their excess moisture, i. e. , basically additives with property (b).

Preferably, the grinding operation is apt to yield a coarse chopping (3-4 cm minimum) so that the resulting mass exhibits an internal macroporosity apt to cause aerobic fermentation to the biomass.

Lastly, the method of the present embodiment comprises a step of packaging, which in the present embodiment provides the automatic packaging of the end substrate in closed net bags that, once filled with product, exhibit a weight preferably ranging from 20 to 30 kg.

It will presently be appreciated that, at the end of the treatment, the additioned oil residues is a product partially stabilized, non-percolating, not evil-smelling, exhibiting chemico-physical features assimilable to those of a soil improver, of an organic or organic-mineral fertilizer and of easy stocking, even nearby the oil mill, transport and agronomical use.

Moreover, it should be noted that, also by virtue of the specific packaging modes illustrated above, the stocking of the packaged product (prior to and/or after its transport) allows the obtained mixture to undergo a further aerobic maturation that may help to improve its chemico-physical features, on the other hand making a subsequent agronomical use thereof as soil improver and/or organic fertilizer easier and more profitable. Moreover, during stocking, the moisture content in the biomass is reduced, making the agronomical use of the refuse easier (less handling of masses) and more effective.

The keeping of the mixture in an oil mill or in a firm, when carried out under adequate conditions, may be prolonged without inconveniences (production of bad smells), waiting for the best time for its sale or use.

It will be appreciated that the obtained product is a relevant source of biodegradable organic substance for soils, useful to preserve and improve their fertility. In fact, such an organic substance determines a series of actions beneficial to the ground, among which there may be mentioned: an increase of the macroporosity, allowing a higher oxygenation of the surface contour of the ground (free from cultivation) concerned by the root growth and the microbial activity; an increase of aggregate stability, important to prevent phenomena of erosion as well as of formation of surface crusts owing to the beating action of rain; an improved water retention of the ground, due to the increase of the microporosity thereof ; and a greater bio-availability of microelements for plant nutrition. The latter action can be ascribed to the well-known chelating and/or complexing capacity of the organic fraction of the soil, which, just by virtue of its chemical features, tends to prevent chemical insolubilization processes at the expense of said microelements-processes generally occurring in calcareous soils that are extremely common in Italy. Lastly, by the contributions of organic material, it is attained the aim of opposing the phenomenon of soil desertification, which is concerning ever-wider areas in the Mediterranean environment, where, on the other hand, olive-growing is widespread and therefore oil mill activity is more concentrated.

It will presently be better understood that in the case of the mixture enriched by Nitrogen-rich materials of organic origin, the invention reduces the need to resort to synthetic chemical fertilizers.

Moreover, given the certain nature of the components inletted during the mixing step, the product could easily be certified by controlling bodies for a use thereof in the so- called organic farming, thereby foreshadowing the birth of a market for said by- product ; the latter would substitute manure, scarcely available on the market, or other organic fertilizers required from organic farming firms and rather expensive.

With reference to Fig. 1, it will now be described a preferred embodiment of the apparatus for the treatment of oil residues according to the invention, generally indicated by 1 in said figure. Of said apparatus 1 there will be discussed only those aspects not already illustrated with reference to the method of the invention.

The apparatus 1 of the present embodiment is integrated in the processing cycle of an oil mill, directly and continuously receiving the oil residues deriving from olive

pressing, and it is apt to outlet additioned oil residues apt to act as soil improver and/or fertilizer for grounds or for other uses.

First of all, the apparatus 1 comprises a unit for the separation of the pit. For simplicity's sake, hereinafter said unit 2 will be referred to as stoning unit.

In the present embodiment, the stoning unit 2 is connected to or incorporating the inlet of the oil residues to be treated, and it preferably comprises a centrifuge separating just the pit from the oil residues. Then, the separated pit is directed, by suitable means, to a suitable outlet, and it could be intended for industrial uses, as already illustrated above.

The composition of the stoned oil residues obtained downstream of the unit 2 has already been discussed with reference to the method of the invention.

The apparatus 1 further comprises a tank 3 for collecting the stoned oil residues, located downstream of the stoning unit 2, receiving just the product outletted from the unit 2 and in which it is possible to add to the stoned oil residues mass said elements fostering the maturation of the product, like, e. g. , microbial starters active on oil refuses.

The apparatus 1 further comprises a mixing unit 4, allowing the addition to the stoned oil residues of the additives hereto-illustrated with reference to the method of the invention. The unit 4 comprises a tank 5, whose capacity is of course dimensioned on the basis of the quantities of material to be treated, in connection with the production of refuses of the oil mill into which the apparatus 1 is integrated.

Inside the tank 5 there operates mixing means 6, e. g. , in the form of rotating augers, moving the substance contained in the tank 5 in order, as mentioned above, to prevent the separation of its phases.

The mixing unit 4 further comprises adding means 7, apt to feed the additives with said properties (a), (b) and (c) into the tank 5.

The mixing unit 4 could further comprise grinding means 8 for chopping twigs and leaves recovered from a washing of the olives prior to the pressing and said ligno- cellulosic organic material. Such means could e. g. comprise cutting elements incorporated into said rotating augers.

Preferably, and as hereto-mentioned with reference to the method described above, the grinding means is apt to yield a coarse chopping (3-4 cm minimum), so that the mass outletted from the mixing unit 4 exhibits an internal macroporosity apt to cause aerobic fermentation to the biomass.

The mixing unit 4 further comprises timing means 9, apt to allow to program a treatment period adequate to the specific processing needs mentioned above, and

metering means 10, just apt to allow an adjusting of the quantity and/or kind of additives added into the tank 5 depending on said needs.

Lastly, the apparatus 1 of the present embodiment comprises a packaging unit 11, which in the present embodiment is a bagger consisting of a module capable of rapidly and automatically receiving the product from the mixing-grinding cycle and of foreseeing just to the packaging of said product. Preferably, net bags are used that, once filled with product, exhibit a weight preferably ranging from about 20 to 30 kg.

The advantages associated with the treatment obtained with the apparatus of the invention, and with its specific embodiment described hereto, have already been described with reference to the method of the invention, and therefore will be omitted.

* * * An experimental example of application of the method (and of the apparatus) of the invention in a preferred embodiment thereof is illustrated hereinafter.

Different mixtures of stoned virgin oil residues and of the above-indicated hygroscopic organic additives were tested. The most significant responses were attained with the mixtures made as reported in the following Table 1.

TABLE 1 Mixture Pitted virgin oil Ligno-cellulosic Raw wool waste residues material (% b/w) (% b/w) (% b/w) I 72 22. 5 5. 5 II 72 17 11 MI72280 Each of the specific mixtures I, II, III indicated in Table 1 exhibits different chemical composition features, above all with regard to the Nitrogen content. In particular, mixtures I and III can mainly be deemed excellent soil improvers, whereas mixture II, given the higher Nitrogen content, can be assimilated to the category of organic fertilizers.

In the following Table 2 there are reported the analytical values related to the three mixtures, detected at the attainment thereof and at subsequent times, on aerobically stocked samples.

TABLE 2 MIXTURE I To 32 dd stocking 80 dd stocking Moisture (% t. q. ) 68.00 50. 71 20.86 pH 5. 36 6.93 7.00 Specific EC (dS/m 25 °C) 2.07 2.03 2.87 Ashes (% t. q. ) 3.29 4.93 8.08 Total C (% t. q.) 14. 38 22. 17 35.64 Total N (% t. q. ) 0.46 0.78 1.38 C/N (da SV) 31.26 28.42 25.83 Calcium (% t. q. ) 0.25 0.37 0.40 Magnesium (% t. q. ) 0. 06 0. 13 0. 12 Potassium (% t. q. ) 0. 87 1. 49 1. 88 Manganese (mg/kg t. q. ) 19. 91 32.22 50.48 Iron (mg/kg t. q. ) 783 1351 1599 MIXTURE 11 Moisture (% t. q. ) 64.30 50.80 27.92 pH 5. 39 6.74 6.70 Specific EC (dS/m 25 °C) 1.87 1. 89 2.74 Ashes (% t. q. ) 3.59 4.84 7.21 Total C (% t. q. ) 16.06 22.21 32.63 N tot. (% t. q. ) 0.78 1.23 1.61 C/N (da SV) 20.60 18.06 20.27 Calcium (% t. q.) 0. 10 0. 35 0. 45 Magnesium (% t. q. ) 0. 05 0. 09 0. 14 Potassium (% t. q. ) 0. 68 1. 14 1. 45 Manganese (mg/kg t. q. ) 11. 44 25.82 40.18 Iron (mg/kg t. q.) 435 1248 1280 MIXTURE III Moisture (% t. q. ) 68.30 46.65 22.12 pH 5. 25 6.43 6.40 Specific EC (dS/m 25 °C) 1.92 2.22 3.42 Ashes (% t. q. ) 3.13 4.65 7.08 Total C (% t. q.) 14. 31 24.41 35.52 Total N (% t. q. ) 0.30 0. 67 1. 03 C/N (da SV) 47.69 36.44 34.49 Calcium (% t. q. ) 0. 15 0. 28 0. 26 Magnesium (% t. q.) 0. 05 0. 06 0. 07 Potassium (% t. q. ) 0. 97 1. 56 2. 05 Manganese (mg/kg t. q. ) 17. 71 20.28 32.25 Iron (mg/kg t. q. ) 489 1057 998

The three prepared mixtures I, II and III, which right from their obtainment and during stocking prove non-percolating and not evil-smelling, were experimentally investigated in open field, in repeated annual fertilizing tests in olive groves under comparison with ordinary mineral fertilizing systems, finding no difference in terms of plant growth and production. In nursery tests concerning potted cultivation of olive plantlets the behaviour of the same mixture was quite different. In this case, mixture II, used in the 15 to 30 % b/w ratio when making the culture substrate, was the one yielding optimal growth responses. The same mixture II is currently being tested also for the cultivation of strawberries in soilless cultures; initial data, collected over a two-year testing period, show that mixture II, used in a ratio of 25-50% b/w of the culture substrate (blond peat + agriperlite) causes a vegeto-productive behaviour of the culture comparable to that of the reference standard substrate.

* * * It will be understood that the present invention is susceptible of several embodiments alternative to those described hereto For example, the method of treatment could essentially comprise only the step of mixing the oil residues with an additive apt to decrease the Carbon/Nitrogen ratio thereof, and likewise the apparatus could essentially provide only the mixing unit.

Moreover, variant embodiments could provide the adding of yeasts or bacteria accelerating the fermentation process.

Again, the apparatus of the invention could incorporate, at the level of the above- described mixing unit, one or more moisture sensors controlling the adding means, so that the contribution of additives is determined by the initial properties of the treated oil residues.

Lastly, it will be appreciated that the proposed method of treatment is also susceptible to be used for the treatment of other organic waste material apt to be recycled for agronomical purposes, e. g. vegetable residues, fruit, various ligno- cellulosic biomasses, and so on.

The present invention has hereto been described with reference to preferred embodiments thereof. It is understood that there could be other embodiments afferent to the same inventive kernel, all falling within the protective scope of the claims set forth hereinafter.