**2.1. Waste waters characteristics and treatments**

The waste waters constitute the liquid fraction of the olive mill byproducts and are composed by the olives water content and by the waters used in the milling (olives and equipments washing waters and the waters of dilution process in the three phases centrifugal systems). As reported in Table 1, the different extraction systems produce, from 100 kg of processed olives, around 10 liters of waste waters for the two phases system, around 55 liters for the pressure crushers, and more than 100 litres for the continuous three phases system, that they reduce to only 35 litres in case of recycle of water.


**Table 1.** Mass balance in the olive oil extraction

The main characteristic of WW is the presence of organic compounds such as organic acids, lipids, alcohols and polyphenols that turn it into phytotoxic materials, that might have unfavourable impact on plants (Capasso et al., 1992; Kavdir & Killi, 2008). It also represents a great environmental hazard if not properly managed. However, WW contain valuable resources, such as a high organic matter concentration and some nutrients, especially potassium, that could be usefully used to improve the physic-chemical and biological properties and then soil fertility and productivity; representing a valid option to close the residue-resource cycle (Roig et al., 2006). In Table 2 are reported the averages of main chemical WW characteristics, given by several Authors (Aktas et al., 2001; Filidei et al., 2003; Moreno et al., 1987; Paredes et al., 1999; Piperidou et al., 2000; Saviozzi et al., 1991; Vlyssides et al., 1996; Vlyssides et al., 2004 – as cited in Roig et al., 2006).


**Table 2.** Average composition of olive mill waste waters.

About the microbiological characterization, the results of different analyses performed on different kind of WW, have individualized 130 species of lipolytic microorganisms (56 Fungi, 22 Yeasts, and 52 Bacteria), cellulolytic Bacteria and pectinolytic Fungi, while not are resulting the nitrificants nor the actinomycetes (Pacifico, 1989; Ramos-Cormenzana, 1986).

For the waste waters treatment have been proposed both physic-chemical and biological processes (Amirante & Di Rienzo, 1993; McNamara et al., 2008; Rozzi & Malpei, 1996; Vigo et al., 1990; Vitolo et al., 1999).

Among the first ones, finalized to the volumes reduction, and to the mineralization of organic compounds, they are:


174 Olive Germplasm – The Olive Cultivation, Table Olive and Olive Oil Industry in Italy

with solvents of the residual oil from virgin pomace.

**2.1. Waste waters characteristics and treatments** 

a sustainable crops production.

**2. Olive mill wastes** 

Milling technology H2O

**Table 1.** Mass balance in the olive oil extraction

3 phase with water

recycle

Althought in literature can be found numerous findings on the influence of raw and composted organic materials on soil fertility and crops growth, only few published studies are focused on influences of waste waters and pomace compost on the soil-plant system, for

In this chapter on report the state of the art of the by-products composting, and results of some application of raw and composted olive industry by-products on soil and crops.

The olive mill byproducts are classified, according to the different systems of olive oil extraction, as: Olive mill Waste Waters (WW); Virgin Olive Pomace (OP), by pressure mills (OPP), with around 30% moisture; by centrifugal "three phases" mills (OP3), with around 50% moisture; or by centrifugal "two phases" mills (OP2), with moisture more than 60%. The Solid Defatted Pomace (SDP), is the byproduct of the pomace industry, after the extraction

The waste waters constitute the liquid fraction of the olive mill byproducts and are composed by the olives water content and by the waters used in the milling (olives and equipments washing waters and the waters of dilution process in the three phases centrifugal systems). As reported in Table 1, the different extraction systems produce, from 100 kg of processed olives, around 10 liters of waste waters for the two phases system, around 55 liters for the pressure crushers, and more than 100 litres for the continuous three

phases system, that they reduce to only 35 litres in case of recycle of water.

Pomace

3 phase continuous 50 55-57 48-54 80-110 Pressure 0-10 30-35 25-30 56-58

2 phase 0-10 75-80 60-70 10

(kg/100 kg olive)

The main characteristic of WW is the presence of organic compounds such as organic acids, lipids, alcohols and polyphenols that turn it into phytotoxic materials, that might have unfavourable impact on plants (Capasso et al., 1992; Kavdir & Killi, 2008). It also represents a great environmental hazard if not properly managed. However, WW contain valuable resources, such as a high organic matter concentration and some nutrients, especially potassium, that could be usefully used to improve the physic-chemical and biological properties and then soil fertility and productivity; representing a valid option to close the

0-20 56-60 50-52 33-35

Pomace moisture (%) Waste waters (kg/100 kg olive)

added (%)

	- adoption of two phases mills, and management of the fluid pomaces.

The biological treatments of purification include both aerobic and anaerobic processes. The aerobic biological treatments are based on the microbic degradative activity that transform the decomposable organic matter in not pollutants mineral elements and humus-like substances.

Olive Mill By-Products Management 177

as well as the crop yield (Alianiello et al., 1998; Andrich et al., 1992; A.R.S.S.A., 2001; Ben Rouina et al., 1999; Bonari et al., 1993; Catalano et al., 1985; Di Giovacchino & Seghetti, 1990; Di Giovacchino et al., 2001; Levi-Minzi et al., 1992; Montemurro et al., 2007, 2011; Saviozzi et

Another option concerns WW composting through biological processes of aerobic stabilization, on supporting matrixes with adequate physical and mechanical properties (porosity, structure, texture), to allow the reactions of bio-oxidation in the solid phase. In this way it is possible to obtain a not phytotoxic organic material, humus-like partially transformed, that could be used in fertilization plans to restore or maintain soil fertility on partial or total substitution of mineral fertilizers (Benitez et al., 1997; Filippi et al., 2002; Galli

The WW contain appreciable amount of mineral elements and organic substances, and can be considered as liquid amendments by vegetal origin. WW application to the soil could realize the double purpose to allow a natural chemical and biological degradation and to enrich the soil in organic matter and in mineral elements. This means that the agronomical use of these waters represents one of the most effective systems to decrease their BOD5. For this reason, the elevated values of WW BOD5 and COD that make extremely risky WW disposal in surface or ground water bodies, would come to lose importance in the case of soil distribution. The WW poliphenols, held substances of elevated polluting power in the case of disposal in the surface and ground water bodies, do not represent a pollution factor for the soil, being instead precursory in the synthesis of humic substances that represent the most active fractions of soil organic matter with important role in soil organic fertility and

protection from synthetic organic contaminating, as pesticides and heavy metals.

when distributed in dates and doses selected through rigorous agronomical criteria.

50 and 80 m3 ha-1 yr-1, for the pressure and continuous milling systems, respectively.

For this, the most effective option appears to be the use of WW as liquid organic amendment or fertigant, and the WW recycle in soil could be a valid alternative to other depurative treatments. In fact, WW affect positively crop performances, of olive, grapevine and cereals,

On the contrary, an incorrect WW management, may cause temporary immobilisation of soil mineral nitrogen and, consequently, crop yield reduction, due to the deficiency of N uptake by the plants; also increasing environmental pollution risks. To avoid these effects, the maximum amount of waste water that can be applied is restricted by the Italian law to

Phytotoxic effects can also be avoided applying simple and few expensive WW pretreatment before the application to the soil, using biological or mineral catalysts, or submitting them to suitable composting processes, mixed with other organic by-products.

The stabilization of WW through composting on effect with repeated saturation of supporting materials with suitable physical-mechanics characteristics (porosity, structure, texture) as straws, leaves, sawdust, rapiers, or pomace, to maintain a moisture level useful

al., 1991; Tamburino et al., 1999; Tomati & Galli, 1992).

*2.1.1. Waste Waters agronomical value* 

et al., 1997; Paredes et al., 2002; Tomati et al., 1995; Vallini et al., 2001).

The anaerobic processes are characterized by microbial pools that works in absence of oxygen, converting the organic polluting substances in biogas (methane) and carbon dioxide or in hydrogenated volatile substances (fatty acids and alcohols), (Filidei et al., 2003). Three main physiological groups of microorganisms are involved: fermenting bacteria, organic acid oxidizing bacteria, and methanogenic archaea. Microorganisms degrade organic matter with a sequence of biochemical conversions to methane and carbon dioxide. Syntrophic relationships between hydrogen producers (acetogens) and hydrogen scavengers (homoacetogens, hydrogenotrophic methanogens, etc.) are critical to the process. A wide variety of process applications for biomethanation of wastewaters, slurries, and solid waste have been developed. They vary from the simple WW open-air storage to the treatment in Completely Stirred Tank Reactor (CSTR) through co-digestion with others organic matrixes, up to treatments in special digesters, as UASB reactors (Up-flow Anaerobic Sludge Blanket) and with different process conditions (retention times, loading rates, temperatures, etc.) to maximize the biogas production (Angelidaki et al., 2011).

Even if these treatments are able to demolish the WW polluting power, in the practice they are often not economically sustainable. The seasonality of WW production and the characteristics of biological toxicity, make difficult the management of their treatment in the purification installations of the urban waters. Conversely, the relative low quantity produced by single milling plants do not make economic WW purification in specific installations.

The WW open-air storage is the simplest and economic system of storage and treatment. During the open-air storage by the action of aerobes and anaerobes microorganisms, it will be partially purified and stabilized. However, the WW open-air storage require ample surfaces away from inhabited centers, for the stink development, and exposes to risks of soil and subsoil water contamination, if the basins are not correctly waterproofed (Catalano et al., 1985).

In fact, these wastes can constitute a "secondary raw materials", to be consider as a resource, being of a vegetable origin, which have not undergone chemical manipulations nor received additives, and therefore without pathogenic microorganisms and viruses, as well as pollutants or toxic products. The optimal operative option results therefore to be the agronomic utilization of the WW that, when correctly managed, allows to exploit its fertilizing characteristics with low costs of management, reducing the risks of environmental pollution.

Many studies have been conducted on soil application both on olive orchard and herbaceous crops, studying differing time and doses of WW application. The results showed both the agronomic benefits and the limitations of raw WW disposal. When correctly managed, the WW application on soil generally results increasing the organic matter, phosphorus and potassium content; improving both physical and hydraulic soil properties as well as the crop yield (Alianiello et al., 1998; Andrich et al., 1992; A.R.S.S.A., 2001; Ben Rouina et al., 1999; Bonari et al., 1993; Catalano et al., 1985; Di Giovacchino & Seghetti, 1990; Di Giovacchino et al., 2001; Levi-Minzi et al., 1992; Montemurro et al., 2007, 2011; Saviozzi et al., 1991; Tamburino et al., 1999; Tomati & Galli, 1992).

Another option concerns WW composting through biological processes of aerobic stabilization, on supporting matrixes with adequate physical and mechanical properties (porosity, structure, texture), to allow the reactions of bio-oxidation in the solid phase. In this way it is possible to obtain a not phytotoxic organic material, humus-like partially transformed, that could be used in fertilization plans to restore or maintain soil fertility on partial or total substitution of mineral fertilizers (Benitez et al., 1997; Filippi et al., 2002; Galli et al., 1997; Paredes et al., 2002; Tomati et al., 1995; Vallini et al., 2001).

### *2.1.1. Waste Waters agronomical value*

176 Olive Germplasm – The Olive Cultivation, Table Olive and Olive Oil Industry in Italy

maximize the biogas production (Angelidaki et al., 2011).

al., 1985).


The biological treatments of purification include both aerobic and anaerobic processes. The aerobic biological treatments are based on the microbic degradative activity that transform the decomposable organic matter in not pollutants mineral elements and humus-like substances.

The anaerobic processes are characterized by microbial pools that works in absence of oxygen, converting the organic polluting substances in biogas (methane) and carbon dioxide or in hydrogenated volatile substances (fatty acids and alcohols), (Filidei et al., 2003). Three main physiological groups of microorganisms are involved: fermenting bacteria, organic acid oxidizing bacteria, and methanogenic archaea. Microorganisms degrade organic matter with a sequence of biochemical conversions to methane and carbon dioxide. Syntrophic relationships between hydrogen producers (acetogens) and hydrogen scavengers (homoacetogens, hydrogenotrophic methanogens, etc.) are critical to the process. A wide variety of process applications for biomethanation of wastewaters, slurries, and solid waste have been developed. They vary from the simple WW open-air storage to the treatment in Completely Stirred Tank Reactor (CSTR) through co-digestion with others organic matrixes, up to treatments in special digesters, as UASB reactors (Up-flow Anaerobic Sludge Blanket) and with different process conditions (retention times, loading rates, temperatures, etc.) to

Even if these treatments are able to demolish the WW polluting power, in the practice they are often not economically sustainable. The seasonality of WW production and the characteristics of biological toxicity, make difficult the management of their treatment in the purification installations of the urban waters. Conversely, the relative low quantity produced by single

The WW open-air storage is the simplest and economic system of storage and treatment. During the open-air storage by the action of aerobes and anaerobes microorganisms, it will be partially purified and stabilized. However, the WW open-air storage require ample surfaces away from inhabited centers, for the stink development, and exposes to risks of soil and subsoil water contamination, if the basins are not correctly waterproofed (Catalano et

In fact, these wastes can constitute a "secondary raw materials", to be consider as a resource, being of a vegetable origin, which have not undergone chemical manipulations nor received additives, and therefore without pathogenic microorganisms and viruses, as well as pollutants or toxic products. The optimal operative option results therefore to be the agronomic utilization of the WW that, when correctly managed, allows to exploit its fertilizing characteristics with low costs of management, reducing the risks of environmental pollution.

Many studies have been conducted on soil application both on olive orchard and herbaceous crops, studying differing time and doses of WW application. The results showed both the agronomic benefits and the limitations of raw WW disposal. When correctly managed, the WW application on soil generally results increasing the organic matter, phosphorus and potassium content; improving both physical and hydraulic soil properties

milling plants do not make economic WW purification in specific installations.

The WW contain appreciable amount of mineral elements and organic substances, and can be considered as liquid amendments by vegetal origin. WW application to the soil could realize the double purpose to allow a natural chemical and biological degradation and to enrich the soil in organic matter and in mineral elements. This means that the agronomical use of these waters represents one of the most effective systems to decrease their BOD5. For this reason, the elevated values of WW BOD5 and COD that make extremely risky WW disposal in surface or ground water bodies, would come to lose importance in the case of soil distribution. The WW poliphenols, held substances of elevated polluting power in the case of disposal in the surface and ground water bodies, do not represent a pollution factor for the soil, being instead precursory in the synthesis of humic substances that represent the most active fractions of soil organic matter with important role in soil organic fertility and protection from synthetic organic contaminating, as pesticides and heavy metals.

For this, the most effective option appears to be the use of WW as liquid organic amendment or fertigant, and the WW recycle in soil could be a valid alternative to other depurative treatments. In fact, WW affect positively crop performances, of olive, grapevine and cereals, when distributed in dates and doses selected through rigorous agronomical criteria.

On the contrary, an incorrect WW management, may cause temporary immobilisation of soil mineral nitrogen and, consequently, crop yield reduction, due to the deficiency of N uptake by the plants; also increasing environmental pollution risks. To avoid these effects, the maximum amount of waste water that can be applied is restricted by the Italian law to 50 and 80 m3 ha-1 yr-1, for the pressure and continuous milling systems, respectively.

Phytotoxic effects can also be avoided applying simple and few expensive WW pretreatment before the application to the soil, using biological or mineral catalysts, or submitting them to suitable composting processes, mixed with other organic by-products.

The stabilization of WW through composting on effect with repeated saturation of supporting materials with suitable physical-mechanics characteristics (porosity, structure, texture) as straws, leaves, sawdust, rapiers, or pomace, to maintain a moisture level useful

to the bioxidative reactions (Benitez et al., 1997; Garcia-Gomez et al., 2003; Paredes et al., 2000; Tomati et al., 1995; Vallini et al., 2001).

Olive Mill By-Products Management 179

improvement of soil fertility. Moreover, the findings of different researches indicate the increase in organic matter and nutrient contents, an improvement in the aggregate stability

In order to the possible ground water pollution, other results have shown that also up to 500 m3 ha-1 of WW application do not represent a pollution danger of the surface water in the clay soils. (Andrich et al., 1992; Ben Rouina et al., 1999; Briccoli-Bati & Lombardo, 1990;

The olive pomace is composed of fruit matter (olive skins, flesh, seeds and stone fragments), and of different amount of vegetation and process water which contains the water-soluble

The OPP and OP3 are usually destined to the pomace industry, for the extraction of residual oil by solvents; and then used as fuel, also in cogenerative processes (Molinari & Bonfà, 2005). These by-products could also be used as animal food, or in biodegradative processes to produce ethanol (Ballesteros et al., 2002), or compost for agricultural utilization. Nevertheless the olive pomace, being constituted by vegetable not fermented organic matter, does not contain heavy metals, toxic pollutants or pathogens, and can be considered as a vegetable amendment (Table 3), (Alburquerque, et al. 2004). Therefore, it can be used in the agricultural

soils without any treatment, as allowed by the current normative (Law 574/1996).

**Parameters Range**  Humidity % 55 - 75 pH (H2O) 4.8 – 6.5 EC (dS m-1) 0.9 – 4.7 Ash (g kg-1) 24 - 151 TOC (g kg-1) 495 - 539 C/N ratio 28 - 73 Total N (g kg-1) 7 - 18 P(g kg-1) 0.7 – 2.2 K(g kg-1) 7.7 – 29.7 Ca(g kg-1) 1.7 – 9.2 Mg(g kg-1) 0.7 – 3.8 Na(g kg-1) 0.5 – 1.6 Fe (mg kg-1) 78 - 1462 Cu(mg kg-1) 12 - 29 Mn(mg kg-1) 5 - 39 Zn(mg kg-1) 10 - 37

and, as a consequence, a better physical soil properties.

Lombardo et al., 1995; Palliotti & Proietti, 1992).

**2.2. Pomace characteristics and treatments** 

constituents of the fruits, in order to the extraction system used.

**Table 3.** Main characteristics of the olive pomace (dry weight)

In this way, on allow on the WW the bioxidative reactions in solid phase, handling to a final product, without phytotoxic effects, useful in the agricultural soils as organic amendment.
