Olive and Biofuel Production
17-04-2025
16:38
The final product of olive oil production, olive pomace, is a sustainable potential biomass raw material for the biofuel industry . Therefore, it is more accurate to describe pomace as "residue" rather than "waste". Studies have shown that using pomace in bioenergy production provides both environmental and economic benefits.
The olive pits inside the pomace are a valuable source of biomass (living-based energy, energy stored within the organism) with a high energy content. The pomace, which contains other molecules besides the pit, can be used in heating, electricity production and biofuel production.
In terms of efficiency, it is superior to straw or wood shavings in terms of energy content.
Direct Combustion for Heating
Olive pits have a high calorific value - the energy obtained from burning a unit of fuel - of approximately 4,500-5,000 kcal/kg or ~18-22 MJ/kg. Due to this feature, dried pomace is a sustainable and efficient biomass that can be used in pellet fuel production.
In Spain, some power plants produce energy by co-firing olive pomace with coal.
Provides efficient combustion with minimum ash residue. It can be used in pellet production, pellets are obtained by compressing natural products and agricultural production waste under high pressure, it is a type of fuel that is usually formed in small form (6-10 mm in diameter and 10-50 mm in length). It can be used in stoves, boilers and industrial heating systems.
Some olive oil mills use olive pits as fuel for their own energy needs, making the olive oil production process more sustainable.
Biodiesel Production
The remaining olive oil in the pomace (~5%) can be extracted and used in biodiesel production. This oil, called pomace oil, is converted into biodiesel by the transesterification process (reaction of vegetable oils with short-chain alcohols to form biodiesel; reaction of fatty acids with methanol or ethanol). It has been calculated that ~50-70 kg of biodiesel can be obtained from 1 ton of dry pomace (European Union BIOLIVE Project, 2020).
Bioethanol Production (Alcohol from Agricultural Products)
Olive pits contain cellulose and hemicellulose, which can be broken down into fermentable sugars for bioethanol production. This potential is still under research and development.
Pyrolysis
The process of decomposing organic waste by burning it at high temperatures (~500°C) in an oxygen-free environment is called pyrolysis. There is no combustion during the process, the fuel undergoes a chemical change. When the heating process is over, several different fuels that can be used as an energy source can be obtained from rice; bio-coal, bio-oil and pyrolysis oil.
When biomass is carbonized (bio-char), it traps and stores its carbon content. Therefore, biochar, which is a carbon-rich solid, enriches the soil, prevents the nutrients used by plants from being washed away with water flow and is an excellent carbon absorber.
Pyrolysis oil can be refined and used as liquid fuel, time will tell whether pyrolysis oil can be a possible alternative to petroleum.
Biogas Production (Anaerobic Digestion)
Pomace can be subjected to anaerobic digestion to produce biogas (a flammable gas obtained from the manure of barn animals), in other words, the organic components in it are subjected to bacterial fermentation to produce methane. ~80-120 m³ of biogas can be produced from 1 ton of wet pomace, but the lignocellulosic substances in it cause low yield. In order to prevent this, it has been tried to increase yield by pre-treatment (chemical/thermal hydrolysis) before production.
Advantages of Using Olive Kernels as Biofuel
As a biomass alternative, olive oil production waste appears to be a cheaper source than traditional fuels such as coal or gas.
It leaves a lower carbon footprint compared to fossil fuels, so it is environmentally friendly.
It presents both opportunities and challenges from an economic perspective. Although it is a promising renewable energy source, its economic viability depends on factors such as processing costs, demand and market structure. The raw material cost is low, and olive oil can generally be obtained from production facilities at low cost (transportation cost of the pomace).
Unlike wood or fossil fuels, they do not require large-scale cultivation, reducing raw material costs.
In regions with high olive production, such as the Mediterranean Basin, olive stone biomass is cheaper than fossil fuels and wood pellets, and therefore has competitive price advantages due to its high energy efficiency. For example, in Spain and Greece, olive stone fuel costs around 100-150 euros per tonne, which is significantly lower than wood pellets (200-250 euros per tonne).
The core has a low ash content, which reduces maintenance and cleaning costs in industrial heating and power plants, and operating costs are low.
The core moisture content (typically below 15%) means it does not require extensive drying before use, reducing energy-intensive processing costs.
Olive-pomace-based fuels emit 50–70% less CO₂ than fossil fuels, so they can provide additional economic benefits by helping to offset CO₂ emissions from industry.
It is a source of additional income for olive oil producers. For example, in Spain, the olive pomace-based biofuel industry is worth ~€200 million per year. Many governments support biofuel initiatives through tax incentives, subsidies or carbon credit programs.
Disadvantages, Economic Challenges and Limitations of Using Olive Kernels as Biofuel
Olive pits are only found in large quantities in olive growing regions. Transporting them over long distances would increase costs. If local demand is low, exporting biomass fuel can be expensive and logistically challenging.
Biomass sources require fossil fuels to be economically efficient. It should be noted that biomass alternatives always contain a considerable amount of water, and energy is consumed for the separation of this water. Therefore, comparisons of carbon emissions released during fuel processing or use should be taken into account. About half of the pomace consists of water, and due to its high moisture content (50-60%) it requires pre-drying (torrefaction), in the torrefaction process the biofuel loses about 20% of its mass, but retains 90% of its energy.
The olive pits in the pomace are a biofuel with low moisture content, which is advantageous in this respect, but pomace is difficult to transport and store. Scientists and engineers believe that it is not economically efficient to transport biomass more than 160 kilometers (100 miles) from where it is processed. "Drying plants" or on-site processing have been suggested as solutions.
The need for processing and standardization will increase costs.
To be used effectively in large-scale energy applications, olive pits must meet the following criteria: uniform size, screening and cleaning to remove impurities. These additional processing steps must be added to the overall cost.
There is limited awareness and infrastructure for using it as a fuel, a fact that reduces the demand from the society.
Pomace seems to be a good alternative in terms of its renewal speed compared to other biomass raw materials (wood, etc.). It can take hundreds of years for a forest to regenerate itself. Olive cultivation, on the other hand, will provide us with raw materials every year - although it may not be possible to obtain the same amount of pomace every year.
It is a cost-effective, renewable and sustainable energy alternative if logistics and processing costs are managed efficiently.
When evaluated in terms of technological infrastructure, there are high investment costs for biogas facilities and pyrolysis systems.
Government regulations are required to ensure that olive pomace-based biofuels meet sustainability criteria. However, careful market analysis, processing investment and local demand assessment can make sense for long-term profitability.
It appears to be an effective fuel production option if production facilities are located in or near olive production areas where transportation costs are low, if there is local demand (e.g. households, industries or biomass-based power plants), and if investment in efficient processing and storage is encouraged – in other words, if access to government subsidies or carbon credits to increase profitability is possible.
It can contribute to energy independence for countries in the Mediterranean Region (Spain, Greece, Italy, Türkiye, Tunisia) that have abundant olive pomace resources.
If the demand for biofuels can be generated in society, it has a very viable economic potential.
Sample Projects and Countries
Spain; Within the scope of the "PIRINASUR" project, olive pomace is used in the production of biogas and thermal energy in Andalusia.
Türkiye; Pilot scale biodiesel plants have been established in the Aegean Region (supported by TUBITAK).
Italy; The "BIOPRIN" project is researching the integrated production of bioplastic and biofuel from olive pomace.
Future Perspective
Integrated Biorefineries; simultaneous production of biodiesel, biogas and fertilizer from olive pomace.
Nanotechnology; use of olive-pomace ash as a catalyst (e.g. production of biodiesel).
Hybrid Systems; integrating drying processes with solar energy.
Compiled by: Uğur Saraçoğlu, Physician, Olive and Olive Oil Producer (ugisaracoglu@yahoo.com.tr)
Source:
1. Synthesis Gas Combustion and Environmental Pollutants, Suat Öztürk, Çukurova University Faculty of Engineering and Architecture Journal, 34(1), pp. 129-138, March 2019.
2. https://education.nationalgeographic.org/resource/biomass-energy/ .