**4. Extraction**

In addition to the thermochemical and biochemical process, the extraction method indeed is applied to oil from oil seeds or nuts materials such as hazelnut, almond nut, sesame seed, sunflower seed, or rapeseed. Traditionally, the oil can be extracted through cold pressing, hot pressing, or solvent extraction methods where the pressing is a mechanical method while solvent extraction is a chemical method [107, 108]. The pressing technique (solvent-free) is traditionally applied to extract edible oil from various sources such as nut or seed samples. Before the extraction sample preparation through various pretreatments on the sample is required before extraction in order to enhance the extraction efficiency [109]. The objectives of the pretreatment process are to destroy or soften the cellular structure of the sample and reduce the moisture content, which can increase the efficiency of the later extraction stage by destroying or softening the cellular structure of the sample and reduction

*Biomass and Energy Production: Thermochemical Methods DOI: http://dx.doi.org/10.5772/intechopen.102526*


#### **Figure 3.**

*General technical readiness level of each conversion process of biomass to bioenergy.*

of the seed moisture content [110]. The process is normally continued with solvent extraction (use solvent polar or non-polar) process due to the significant amount of oil remaining in the press cake, which is around 20–30%100. However new techniques such as microwave-assisted extraction [111], supercritical fluid extraction [112], ultrasound-assisted extraction can be applied in order to extract separate desired oil liquid from a solid–liquid sample [113].
