Olive pomace

HR_Olive pomace (1)

Pomace, also known as olive cake, is an organic waste material commonly found in rural areas of coastal regions such as Dalmatia and Istria. Pomace is a by-product of the olive oil production process. During processing, olives are initially pressed to extract the oil, resulting in a mixture of fruit skin, pulp, and pit residues. It has various applications, including its use as fertilizer and a source of energy. Historically, pomace was created by pressing olives in traditional presses or crushing them with feet, and it was used along with wood for household fireplaces. Today, dried pomace continues to be used for energy production, representing an environmentally friendly way to utilize waste material from olive oil production.

Name of Material in the local and Latin language
Komina
Type of Material
Organic
Commonly Found Locations
Olive pomace is used in Dalmatia, Istria, as well as on the islands of Brač, Hvar, Korčula, and other Adriatic islands. It can also be found in the inland areas of Croatia where there are smaller olive groves, for example, in continental Istria, Primorje, and some areas of Lika and Dalmatinska Zagora.
Major Industrial Producers or Suppliers
Ponikve Krk (Dejan Kosić), uljara Nadin (Željko Vrsaljko)

Colour
Olive pomace can vary in color depending on the degree of processing and the composition of the olives used. Typically, pomace is of a darker color, such as brown or even black, due to the presence of the skin of the fruit and other organic materials. The color can range, depending on various factors such as processing time, olive variety, and production technique.
Density
The density of olive pomace varies depending on several factors, including the amount of water in the pomace, the proportion of solids (such as cellulose and pits), and different oil extraction methods.
Hardness
Pomace is quite solid due to the presence of olive skin, pulp, and pits. The hardness of pomace can vary depending on the oil extraction process and any additional processing. For example, pomace obtained by pressing may be firmer than that obtained by centrifugation.
Solubility
Most substances present in pomace are poorly soluble in water.
Structure
A solid mass consisting of olive skin, pulp, and parts of the olive pit.
Chemical Composition
The chemical constituents include cellulose, proteins, water, polyphenols, and oil. Variations and deviations may occur because the chemical composition of pomace depends on the type, condition, and origin of the olives, as well as the processing method. The parameter that can vary the most is the oil content, as it is most dependent on the variety, growing conditions, climate, and similar factors.

Industrial and Crafts Applications
It is estimated that approximately 6.8 million tons of waste is produced annually from olive oil production in the EU, while Croatia produces around 30,000 tons of olives annually, resulting in approximately 12,000 tons of fresh pomace. Pomace has diverse applications in the industry. Apart from being used as fertilizer, it has proven to be an effective natural herbicide that suppresses weed and grass growth. Extracted olive pomaces are often used as fuel for steam engines, and recent research suggests that they will become a key source of energy in EU countries in the future. Additionally, pomace can be utilized in the cosmetics industry, polymer production, and for generating thermal energy.
Historical or Cultural Uses
Olive pomaces, separated during the oil extraction process, have traditionally served as fuel for household hearths, thus representing a deeply ingrained practice originating from the term 'kamin', which translates to fireplace in both Latin and Greek. The so-called 'cake' used in household hearths was formed by pressing in traditional presses or by stomping with feet. Pomace has also been utilized as animal feed and has proven to be an effective natural herbicide, reducing the growth of weeds and grasses.
Environmental Impact
Improper disposal of fresh pomace in quantities exceeding permitted levels can have adverse effects on plant growth, particularly due to the release of vegetative water, posing a serious challenge for the olive oil industry. Classified as waste, fresh pomace can significantly endanger the environment through its biological and chemical pollution, thus requiring proper disposal in accordance with legislation. It is important to note that disposing of it in large quantities on permeable terrain should be avoided to prevent the risk of groundwater contamination and disruption of microbiological activity in the soil. Therefore, disposal on agricultural land is recommended, but in limited quantities of no more than 8 tons per hectare to minimize negative impacts.
Innovative or Emerging Applications
In Andalusia, the Spanish region with the highest concentration of olive trees in the world, it is commonly used as a fuel source for heating or as biomass for energy production. This ecologically clean method of dealing with pomace, while simultaneously producing energy, is employed by Spaniards, Italians, and Greeks. In Croatia, the owner of the Nadin oil mill, Željko Vrsaljko, follows the practices of such plants and powers the entire mill with energy obtained from pomace previously produced in the same mill. The pomace is dried on an asphalt surface in the open air and sun, and then burned in a modified pellet stove. Olive pomace possesses antioxidant properties, making it applicable in the cosmetics industry. Various cosmetic products are produced from olive pomace that slow down skin aging. Olive pomace waste has also proven to be an adequate solution in the polymer industry.

Processing Techniques
During the olive oil extraction process, waste in the form of olive pomace and vegetable water is generated, with the mixture of vegetable water and pomace formed by centrifugation in two-phase centrifuges. Olive pomace consists of the skin of the fruit, pulp, and parts of the pit, and its chemical composition varies depending on the olive processing method. Pomace obtained by pressing typically has a lower water content compared to that obtained by centrifugation, with the main chemical components being cellulose, proteins, water, polyphenols, and oil.
Sustainability and Environmental Considerations
The process of extracting oil from olives results in waste in the form of olive pomace and vegetable water. It is estimated that approximately 6.8 million tons of this waste are generated annually in the EU, posing challenges for its proper disposal and reducing its environmental impact. In Croatia, where approximately 30,000 tons of olives are produced annually, around 12,000 tons of fresh pomace are generated. This process can have a negative impact on the environment, especially when fresh pomace is scattered in orchards in quantities exceeding permissible limits, which can inhibit plant growth and lead to the release of vegetative water.

Current Research and Developments
There is growing attention devoted to researching and developing methods for the optimal utilization of olive pomace as a valuable resource, and in finding sustainable ways to harness it as an energy source. According to the Regulations on Organic Production, waste cannot be used without appropriate processing. Therefore, all progress in researching and developing new technologies for utilizing olive pomace represents a crucial step towards more sustainable energy production.
Regulations or Restrictions
In the European Union, there is a legal obligation for the disposal of waste generated in the olive processing process, but the method of disposal is not extensively regulated. In Croatia, the Regulations on Organic Production in Plant Cultivation and Production of Plant Products specify that agricultural waste cannot be used without appropriate processing. This disposal represents an additional cost for olive oil mills due to legal obligations, but governments strive to provide various support measures to reduce costs and create additional value for these companies.
Relevant Organizations, Associations, Producers
Ponikve Krk (Dejan Kosić), uljara Nadin (Željko Vrsaljko), J.T. Energy (Sven Jeličić)

Pomace is an organic waste material commonly found in areas of coastal regions such as Dalmatia and Istria. It is a by-product of the olive oil production process, formed by pressing olives to extract oil, resulting in a mixture of fruit skin, pulp, and pit residues.

The chemical composition of pomace varies depending on the processing method and olive type, typically containing cellulose, proteins, water, polyphenols, and oil. Historically, pomace was used as fuel for household hearths, and today it has many practical properties, such as being utilized as a source of energy through thermochemical processes.

  • HR_Komina (5) A 898

    A sack filled with crushed olives, Jesenice near Omiš, 1954, Etnographic Museum Split, EMS A 898

  • HR_Komina (6) A 899

    Man treading on the tavulja sack, Jesenice near Omiš, 1954, Etnographic Museum Split, EMS A 899

Pomace is prevalent in Dalmatia, Istria, and various Adriatic islands such as Brač, Hvar, and Korčula. It can also be found in inland areas of Croatia with smaller olive groves, including continental Istria, Primorje, and parts of Lika and Dalmatinska Zagora.

During olive oil extraction, pomace and vegetable water are generated, with the mixture formed by centrifugation. The chemical composition of pomace varies depending on the processing method, with pressing typically resulting in lower water content compared to centrifugation.

Olive mill, Rudine on the island of Hvar, 1930; Women putting olive fruits into the mill, Jesenice near Omiš, 1954; Crushing of olives, Jesenice near Omiš, 1954; Olive mill, Grohote on the island of Šolta, 1964. Etnographic Museum Split: EMS B 3767, EMS A 892, EMS A 894, EMS A 559

Recent research focuses on optimizing pomace utilization as a sustainable energy source, in line with regulations requiring proper waste processing.

Pomace has diverse applications, including its use as fertilizer, a natural herbicide, and a source of energy. In some regions, large energy plants utilize undried pomace for thermal energy production, while smaller operations, such as the Nadin oil mill in Croatia, power their entire facilities with pomace-derived energy. Additionally, pomace is being explored for its antioxidant properties in the cosmetics industry and as a solution in the polymer industry

(Cover photo: Milan Pavić, Olive harvest, 1947, Museum of Arts and Crafts, MUO 37964)