Cost, Cleanliness, Scale-up, and Safety Considerations

The reduced cost of extraction is clearly advantageous for the proposed SFME method in terms of time and energy. Hydrodistillation required an extraction time of 90 min for heating of 6 L water and 500 g aromatic plants to the extraction temperature, followed by evaporation of the water and essential oil for 180 min. The SFME method required irradiation for 3 min only and evaporation for 27 min of the in-situ water and essential oil of the same material. The energy required to perform the extractions is 4.5 kW h for HD, and 0.25 kW h for SFME. The power consumption was determined with a Wattmeter at the microwave generator supply and the electrical heater power supply. 

With regard to environmental impact, the calculated quantity of carbon dioxide emitted to the atmosphere is greater for HD (3600 g CO2 g essential oil) than for SFME (200 g CO2 g essential oil). These calculations were based on the assumption that to obtain 1 kW h by combustion of fossil fuel 800 g CO2 will be emitted to the atmosphere [61]. 

SFME is proposed as an environmentally friendly extraction method suitable for sample preparation before essential oil analysis. SEME is a very clean method which avoids the use of large quantities of water and voluminous extraction vessels, in contrast with HD. SEME could also be used to produce larger quantities of essential oils by using existing large-scale microwave extraction reactors [62]. These microwave reactors are suitable for the extraction of 10, 20, or 100 kg of fresh plant material per batch. These reactors could be easily modified and used for SFME extractions. 

Solvent-free Microwave Extraction Specific Effects and Proposed Mechanisms 

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