Olive cake

Olive cake is a by-product of the second extraction of olive oil. First extraction is done in the olive oil factories by mechanical squeezing of the olives. As a result of it, so called virgin olive oil is received. Remaining brown mass, called pomace, has a moisture of about 60% and oil content of about 7-8%. After the first extraction of olive oil, pomace is then transported to specialized factories, where the second extraction of oil by hexane is completed. As a result of this process, the second extraction oil is produced and the residue consisting of olive meat, olive skin, whole and crushed olive stones with the moisture of around 13-14% is received. This material is called olive cake and it is a biofuel. 

In majority of cases, olive stones are separated from olive cake, but even after this process about 30% of the crushed olive stones still remain in the material.

During several years, starting from 2001, olive cake was widely used in Belgium, UK and later in Poland for co-firing with coal. Usually, about 4-7% of olive cake was admixed to coal before entering the boiler. Later, most of the coal-fired power plants in Europe were converted to wood pellets.  Nowadays, olive cake is not used so widely anymore by big power plants.  Though, it is still utilized for co-combustion in some smaller power stations. It can also be used in biomass dedicated power plants as a single fuel or in combination with other biomass products.

Olive cake’s usual specification:

Parameter Value Parameter Value
Moisture 12-17% Cr. (Chromium) 4-8 mg/kg
Ash 6-8% Cu. (Copper) 10-20 mg/kg
Net calorific value 15-16 Gj/mt Zn. (Zinc) 16-19 mg/kg
Bulk density 650-680 kg/m3 Cl. (Chlorine) <0,4%
K. (Potassium) <3% S. (Sulphur) <0,12%
As. (Arcenic) 0,1-0,9 mg/kg Ni. (Nickel) 4,5 mg/kg
Hg. (Mercury) <0,1 mg/kg V. (Vanadium) <1,0 mg/kg

Oil content is usually about 1,5% and it should not exceed 4%. Combination of moisture and oil in the biomass cargo over 20% (for example, 16% of moisture and 4% of oil) is regarded to be dangerous for transportation, as it can cause self-combustion. 

Learn more:

Olive cake