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New Perspectives on Olive Oil Residue

Dealing With The Liquid By Products of Olive Oil Production

A resent study conducted by the  Fraunhofer Institute for Interfacial Engineering and Biotechnolog focuses on the potential environmental hazards of olive oil production process. There are two major types of olive residue that are produced as a result of olive oil extraction: Olive Cake (Olive Pomace) and Vegetation Water. Olive Cake has immediate use in the bioenergy industry. However, the vegetation water, or black water as it is called among Turkish farmers pose an environmental conundrum. This waste product is rich in organic content yet not readily usable as liquid fertilizer. Olive vegetable water is rich in phenols which are potentially valuable due to their antioxidant qualities but liquid olive residue is an environmentally dangerous waste product. One liter of olive residue can contaminate several times more volume of water than regular household sewage and thus it is imperative that it should be prevented from leaking uncontrolled into ground water or open streams and rivers.

Olive Oil industry is an important part of the European Union agricultural sector with about 2.2 million metric tons produced every year. Now, it is important to note that for every one hundred kilograms  of olives processed about 20-22 kg of olive oil is obtained. The actual amount varies depending on the production method, the olive breed, and time gap between picking and pressing. Again depending on the method between 85 and 175 kilograms of vegetable water is produced. Traditional olive presses that use only mechanical power to crush and press the olives produce the least amount of liquid residue. In contrast two phase and three phase production methods add water and heat to facilitate oil extraction and therefore produce a higher volume of contaminated liquid residue. Due to the high content of phenols, fatty acids and organic substances the discharge of liquid waste into rivers creates a phytotoxic effect in bodies of water. In some regions the residues are collected in storage ponds, which may also lead to damage to the environment.

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From Olive Residue to Biogas

In an industry that is vital to several economies in the region drastic change does not come easily and actors involved in the sector need some convincing. Any proposal for changing practices needs to be backed up by research immaculately. Fraunhofer’s report is among such studies and it is an ongoing project. Over the recent decades use of olive biomass as a fuel source has been increasing. In fact locals have known and used olive cake as a substitute for firewood for millennia. Gradually the industry started to take notice of the economic potential of olive cake (alperujo, as it is called in Spanish). Today (i.e. 2010s) in many olive producing regions solid olive residue is not an environmental problem anymore. Especially Italian and Spanish olive related industries have integrated olive pomace relatively well in the agricultural and energy sectors. However, Turkey, the fourth largest producer of olives still wastes most of its olive cake (which is called pirina in Turkish, a Greek origin word if memory serves). Nevertheless, the real environmental problem is not the solid by products of the olive oil production. It is the liquid waste (alpechin in Spanish) that worries the environmentalists. Despite the fact that research into a cost-efficient, technically feasible and environmentally sound solution for the disposal of these residues has been going on for over 50 years, it has not yet been possible to find a satisfactory answer which can be comprehensively transferred to industrial applications. Together with nine European partners from research, industry and various associations the Fraunhofer IGB is developing a combined process during which organic substances present in high concentrations, such as polyphenols, are first extracted and reused as natural antioxidants. The residual biomass is then digested for the generation of bio gas.

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Trial and Error

The major problem faced by researchers is the chemical composition of the liquid waste. Olive oil residues are characterized by a high concentration of potassium, organic and sulfur compounds and a low nitrogen concentration. Therefore, these residues constitute a special challenge for anaerobic microorganisms (for futher info check 1 or 2 ).  Since digestion of biomass that comes from every different source needs a different optimal process experiments were carried out  on a large number of solid and liquid waste batches which had been generated during olive oil production using different production methods in Spain, Italy and Greece. The results are generally encouraging. Organic content of both solid and liquid olive residues were successfully reduced to bio gas. In these experiments the methane content of the resulting gaseous by product was around 70 percent.

Where do we go from here?

Olive oil is a vital industry for many countries in the Mediterranean basin. Furthermore it involves millions of families, large and small scale producers and literally hundreds of millions of consumers. Olives and olive oil production will remain an important economic activity and total efficiency of the industries related to olives must be enhanced. Biogas production from liquid olive residue not only utilizes what is generally considered a waste product but also helps thwart an environmental threat.

New Perspectives on Olive Oil Residue

Olive Oil FAQ : Olive and Olive Oil Facts

This FAQ about Olives and Olive Oil facts first appeared here, as far as I know.  I came across this when I was doing some freshening up for the Olive Biomass post I was writing. I truly believe in the miraculous nature of olives and its importance for the Mediterranean basin. I reproduce the Olive Oil FAQ with minor additions and corrections.

Most Commonly Asked Questions About Olive Oil

Are olives fruits or vegetables?

Olives are fruit, grown on the olive tree, olea europaea. Olive trees have been cultivated for thousands of years, and were already plentiful during biblical times. Plucked from the tree, the olive is extremely bitter, and virtually inedible. Prior to eating, olives are typically cured, either in brine,water or in oil.  The method of curing and the ripeness of the olive when picked gives it its flavor and color. Black olives are not very popular in the US or Northern Europe. In Greece and Turkey some olives are kept on the branch until they are blackish purple. These ripe fruits are then stored in a airtight container with rock salt in a dry and dark place for about a month. Olives release some watery residue over time. This residue must be regularly removed from the container without exposing the olives to fresh air for extended periods. The resulting black, wrinkled product is surprisingly tasty. A staple of breakfasts in the Mediterranean basin. Sometimes, though not popular everywhere, freshly picked olives can also be stir-fried to remove some of the bitterness before eating.

Where are olives grown?
Major olive producers in the world include countries which border the Mediterranean Sea (e.g., France, Greece, Israel, Italy, Morocco, Portugal, Spain, Tunisia, Turkey), as well as California and in South America. It is reported that Thomas Jefferson tried but failed to cultivate olive trees in his native Virginia.

How is olive oil produced?
The traditional method of extracting olive oil from the fruit is virtually the same today as it has been for thousands of years. At harvest time, which varies from region to region, olives are harvested by hand, and collected in nets placed around the foot of the tree. A day or two thereafter, the olives are taken to the mill. Giant stones weighing several tons are used to crush the olives and pits into mash.

The olive mash is then spread onto thin mats. These mats are stacked, and placed into a machine “press.” As the press applies several hundred pounds of pressure, oil and water from the mash seep out of the mats, and drip into collection vats. In the traditional method, no heat is applied in the pressing–hence the term “first cold pressed.” The oil is allowed to settle, and any vegetable water is removed either by centrifuge or decantation.
Oil extracted from the mechanical pressing of the olive is described as “virgin” olive oil, because it is pure, unrefined and unprocessed.

The traditional “press” method yields the best result but it is not the most efficient. Therefore most producers apply heat and add water to better extract oil. In two phase or three phase production facilities the amount of oil extracted is greater then traditional oil presses but the quality suffers somewhat.

What are the differences among extra virgin olive oil, ordinary olive oil, and “light” olive oils?
Extra Virgin Olive Oil. ”Extra” is the highest grade for olive oil–the best you can buy. The virgin oil produced from the mechanical pressing described above may be called “extra” if it has less than 1% free oleic acid, and if it exhibits superior taste, color and aroma. Thus, the “extra” in extra virgin olive oil means “premium,” or simply, “the best.”

Olive Oil. Ordinary “olive oil” is actually a blended oil product. Olive oil producers start with low quality virgin olive oils. For these oils to be fit for consumption, they must be refined using mechanical, thermal and/or chemical processes. The resulting “refined olive oil” is largely colorless and tasteless. Before the resulting product is sold as “olive oil,” the producer blends into the refined olive oil a percentage of quality virgin olive oil to provide color and taste.

“Light” or “Mild” Olive Oil. Light olive oil is a variation on ordinary olive oil. Producers of this product use a highly refined olive oil, and add less quality virgin oil than that typically used to blend olive oil. The only thing “light” about light olive oil is the taste and color; it has the same caloric and fat content as other oils.

Olive-Pomace Oil. Olive-pomace oil is the residue oil that is extracted by chemical solvents from previously pressed olive mash. This oil must be highly-refined to remove chemical impurities. Like ordinary olive oil, refined olive-pomace oil is enriched with virgin olive oil prior to sale.

Olive Oil Blends. Olive oil blends (e.g., canola oil enriched with some virgin olive oil) are sometimes used as a more economical substitute for olive oil (but not as a substitute for extra virgin olive oil). Because the production of good olive oil is labor intensive–the olives must essentially be picked by hand–the resulting product is more expensive than other vegetable oils. To offer a more economical product with some of the goodness of olive oil, some companies make olive oil blends. In an olive oil blend, the producer uses a base of a less expensive vegetable oil (e.g. canola oil) to which it adds a percentage (e.g. 25%) of virgin olive oil. These products have proven particularly attractive to restaurant and institutional purchasers where the small savings per tablespoon results in big savings due to the large volume they purchase.

What is the difference between filtered and unfiltered extra virgin olive oil?
Extra virgin oil may be consumed either in a filtered or unfiltered state. Filtration is the process by which the microscopic bits of the fruit of the olive are removed from the oil. Unfiltered oil will be cloudy until it settles to the bottom. Some consider unfiltered oil superior because of the added flavor from the fruit, while others say it shortens the oil’s shelf life. Ultimately, it is a matter of personal preference.

Are all extra virgin olive oils the same?
No. Like wines, extra virgin olive oils can vary dramatically in taste, depending upon the type and quality of the fruit that is pressed, the time of harvest, the weather during the growing season, and the region from which the olives were produced.

Connoisseurs generally use the following adjectives in appraising extra virgin olive oils: mild, semi-fruity and fruity, depending on the flavor of the olive that can be detected. Further, some oils, such as the finer oils from Tuscany and Southern Italy, have a peppery finish that many appreciate.

 

What are the nutritional components?
A tablespoon of olive oil contains 120 calories, 14 grams of fat, and no cholesterol. Seventy seven percent (77%) of the fat in olive oil is monounsaturated, and nine percent (9%) is polyunsaturated fat; fourteen percent (14%) is vegetable-derived saturated fat. Virgin olive oils also contain the antioxidants beta-carotene and Vitamin E, as well as the phenolic compounds tyrosol and hydroxytyrosol.

 

What makes olive oil a superior product to other oils?
Three things make olive oil superior to vegetable oils: taste, nutrition and integrity.

Taste is the most obvious difference between olive oil and the commercially popular vegetable oils such as corn, soybean and canola oils. These oils are tasteless fats. You would not want to eat a piece of bread dipped in vegetable oil; for the same basic reason, many chefs refrain from adding tasteless fat to the foods they prepare. When you cook with oil, get the most flavor and texture you can.

Olive oil, especially extra virgin olive oil, adds a flavor and textural dimension lacking in other oils, making it a suitable substitute for butter and margarine in almost any recipe. In fact, more and more restaurants are serving extra virgin olive oil, both plain or flavored with salt and pepper, as an alternative to butter for bread.

Nutritionally, olive oil contains more monounsaturated fat than any of the popular vegetable oils. For more information on the nutritional qualities of olive oil versus other oils and fats, please refer to the last chapter in this booklet.

Moreover, vegetable oils are industrial, processed foods. Vegetable oils are generally extracted by means of petroleum-based chemical solvents, and then must be highly refined to remove impurities. Along with the impurities, refining removes taste, color and nutrients.

Extra virgin olive oils are not processed or refined. It is said that you do not make extra virgin olive oil, you find it. Extra virgin olive oil is essentially “fresh squeezed” from the fruit of the olive tree, without alteration of the color, taste, and nutrients or vitamins. Because of the integrity of the product, and its antioxidant components, olive oil will keep longer than all other vegetable oils.

 

How does olive oil compare with butter or margarine?
Butter and margarine are essentially fats like cooking oils. A tablespoon of ordinary butter contains twelve grams of fat, of which 8 grams (66%) are saturated fat. In addition, a serving of butter contains 33 mgs of cholesterol.

Saturated fat and cholesterol have been linked to increased levels of low density lipoproteins (LDLs)–the “bad cholesterol.” Thus, compared to butter, a serving of olive oil contains much less saturated fat (only 2 grams) and no cholesterol. The comparison with margarine is more difficult because the fat breakdown in margarines varies by manufacturer and ingredient. Margarine typically contains approximately 10 grams of fat per tablespoon. However, to solidify the vegetable oils used to make margarine, the oils have to be hydrogenized. In the hydrogenization process, trans fatty acids are created. Trans fatty acids have a double whammy effect of increasing LDLs and lowering the high density lipoproteins (HDLs)–the “good cholesterol” (see discussion of health issues in last chapter of this booklet).

 

Can olive oil be used to replace butter and margarine in recipes?

Yes! Butter and margarine have a pleasant taste, and there are certain uses of butter and margarine for which there is no satisfactory replacement in the American Diet–buttered toast at breakfast comes to mind. ?Extra Virgin Olive Oil has been described as “buttery” by many consumers in taste tests. Extra Virgin Olive Oil can be used in place of butter or margarine in many recipes, such as on vegetables, rice, potatoes, and–yes–even corn on the cob.

 

How do you store olive oil?

Olive oil should be stored in a cool, dark place. Properly stored, olive oil can keep for at least two years. It is, however, at its peak within a year of production, and is its most flavorful for the first two months. Olive oil should not be stored in the refrigerator. If chilled, olive oil will become cloudy and eventually solidify or crystallize. Should this happen, the oil is perfectly fine; just leave the oil at room temperature for a time to restore it to its natural state.

 

Can olive oil be used in baking recipes that call for butter, margarine, vegetable oil or shortening?

Yes! Try olive oil in your muffin and cake and cornbread recipes (but not in recipes in which butter is the principal flavor like butter cookies or pound cake).

Can olive oil be used to “grease” a pan in place of butter or vegetable oil?

Yes! And you will be delighted with the results.

 

Can avacado oil or macadamia nut oil be used in place of olive oil?

Yes! These relatively new oils are very healthy and taste great too! We like to use avacado oil in salad dressings and pan fried potatoes. We use the macadamia nut oil on broiled fish and asparagus.

 

 

 

Olive Oil FAQ : Olive and Olive Oil Facts

Olive Biomass Fuel

 The ultimate salvation of the world lies in transition to a hydrogen based energy regime. This might involve sustainable fusion, third generation nuclear plants, or renewable energy sources (solar, wind, tides and other methods that harness the energy of the waves). However, until the complete overhaul of our energy regimes around the world our best course of action seems to be integrating the use of biomass fuels with our existing infrastructure based on fossil fuels. One such fossil fuel alternative is the co-burning of olive biomass  (olive cake) in power plants.

It is estimated that around five million metric tons of olive pomace (the waste of olive oil industry and the basis for olive biomass fuel) is produced every year. Once the remaining oil extracted using a solvent like hexane gas what we are left with is a clean biomass fuel with high calorific value. The seedy parts (seeds and meaty parts are generally separated) are measured at 4500 – 5000 kCal/kg. At this rate olive biomass is comparable to medium quality lignite and it compares favorably with other biomass fuels produced from woody residues.

 

 Real Net Zero Emission

One great advantage of olive pomace is that it is a truly zero net carbon emission fuel. Net zero emissions usually relate to the fact plants use up carbon dioxide build tissue. When this tissue is oxidized the fuel releases carbon compounds which in turn will be absorbed by the plants. This equation is only true if we burn only the plants we grow. Burning firewood is only potentially a zero emission practice. It all depends on whether we burn more than we grow. A net decrease in forest area that is utilized for biomass fuel production means that we are releasing more carbon than we are absorbing from the atmosphere. Biomass fuels based on crops or agricultural residue generally cannot consume what is not grown. Olive residue fuels are in this category. The industry can only process the remains of already grown and used olives.

In addition unlike the production of bio diesel which is an energy intensive process olive biomass industry is relatively energy shy. In fact in many more traditional plants the energy needed for drying the olive cake and extracting oil is supplied by burning olive cake in the first place. This makes olive pomace (olive cake) a very attractive candidate for a renewable, clean alternative for fossil fuels.

In fact the first olive cake power plant started to operate in Spain in 1995. The share of biomass fuels in Spain’s energy production is around 3 percent (not very admirable) and a substantive portion of this three percent comes from olive cake burning. Similarly, England imports around 200.000 metric tons of olive biomass (mostly from Spain) for co-burning in coal plants.

In short olive biomass offers a clean, sustainable, and truly renewable fossil fuel alternative.

Olive Biomass Fuel