With the increased availability of CO2 extracts it is important to understand their similarities and differences to essential oils. Let us compare Marjoram CO2 and Marjoram essential oil.

Common to both 

Name: Sweet Marjoram (Origanum majorana)

Family:   Lamiaceae (Labiatae)

Description:  A tender, busy perennial plant, growing up to 2 ft high.  It has a hairy stem, dark green oval leaves and small white flowers growing in clusters.

History/Folklore: The genus name Origanum derives from the Greek words oras, and ganos which roughly translates as Joy of the Mountains. The ancient Greeks believed that if Marjoram grew on one’s grave, the deceased would enjoy eternal peace and happiness. Ancient Romans called marjoram the “herb of happiness”.

Differences

Method of Extraction 

Marjoram CO2 :  Carbon dioxide as the `solvent` to extract the viscous liquid from dried flowering herb.  Yield is around 1.8%. (Kerkhof)
Marjoram Essential Oil:  The essential oil is steam distilled from the dried flowering herb.  Yield around 0.2 – 0.8%.

Color and Appearance 

Marjoram CO2:  A transparent and fluid extract with a yellow color.  (Kerkhof)
Marjoram Essential Oil:
 Depending on where the plant is grown it can be a brown to colorless or pale yellow oil.  (Burfield)

Aroma 

Marjoram CO2:  The aroma is warm, woody, smooth and only slightly camphoraceous and herbal.  The CO2 smells a lot like the aroma emitted when you rub the leaves of the plant with your fingers. (Kerkhof)
Essential Oil:
  The oil produced in Tunisia, Hungary, Bulgaria and Egypt has an herbaceous, fresh aromatic aroma with a thyme-like quality and some woodiness.  The dry-out has a dry leaf quality, reminiscent of dried sage, dried herbs or a mixture of dried sage and dried thyme.  The flavor is herbaceous, warm, and spicy.  Turkish Marjoram oil has a piercing aromatic fresh, somewhat minty aroma with a slight medicinal edge.  The dry-out is first minty-aromatic, woody and then becomes slightly musty and disappears completely after a few days. (Burfield)

Chemistry 

Marjoram CO2:  The CO2 extract consists of over 50 components including monoterpene alcohols (cis-thuja-nol-4, trans-thujanol-r and terpinene 1-ol-4); monoterpenes (sabinene, a-terpinene, ocimene, cymene and terpineols).  (Kerkhof)
Essential Oil:
  2% Esters (linalyl acetate, terpinyl acetate, geranyl acetate); 1% Aldehydes (citral); 3% Sesquiterpene (caryophyllene, cadinene); 40% Monoterpene (β-pinene, α-terpinene, γ-terpiene, ρ-cymene, myrcene, limonene, ocimene, sabinene); 50% Alcohol (linalool, borneol, α-terpineol, terpineol-4-ol) (Caddy)
Madeline Kerkhof says that when dealing with physical conditions she likes to combine both the CO2 and the essential oil in equal parts, as together they make an ideal synergy.

Cautions

Marjoram CO2: Avoid using on large body surfaces (massage) for those who are known to have low blood pressure.  Not sure about its safety in pregnancy.  Precautionary avoid in newborns and infants. (Kerkhof)
Essential Oil:
Hazards: None known.  Contraindications: None know. (Tisserand and Young)
Some sources suggest using caution with depression as it is a very sedative oil.

Indications for Use 

CO2:  Sweet Marjoram CO2-select extract is a strong support of the parasympathetic nervous system.  It can be a gentle invitation to unwind, surrender and slide into the next phase when used for letting go on all levels, from giving birth to clinging to old patterns to passing from this world.  Skin infections, muscle tension, circulatory disorders, abdominal cramps can all be addressed with this extract. (Kerkhof)
Essential Oil:
On a physical level, Sweet Marjoram’s analgesic properties make it very helpful for arthritis, lumbago, muscular aches and stiffness, as well as rheumatism, sprains and strains.  It can also be helpful for some respiratory conditions like asthma, colds and coughs, as well as digestive problems like constipation and flatulence.  Marjoram is also often used in blends created to address menstrual problems and PMS.

Emotional and Spiritual Conditions 

Both the essential oil and CO2 extract have analgesic, balancing and calming properties and can be used to help ease headaches, migraines, stress and nervous tension.  On a subtle level, Sweet Marjoram can impart the ability to embrace unconscious fears, and in reducing fear and providing comfort it adds support for one to move forward.  It can also help to promote courage and confidence. Sweet Marjoram is also an aromatic to consider when creating blends to support grief and the grieving process.   In Dr. Berkowsky’s Spiritual PhytoEssencing, Sweet Marjoram is considered to be specific for problems that are associated with coldness or conditions that require warming.

You might also enjoy the article I have on the website for Sweet Marjoram, as well as the article on Muscle Aches and Pains.  Sweet Marjoram can be an excellent addition to blends created for those who are dealing with Fibromyalgia.

References
Tony Burfield, Natural Aromatic Materials – Odours & Origins, 2000E. 
Joy Bowles, the A to Z of Essential Oils, 2003
E. Joy Bowles, The Chemistry of Aromatherapeutic Oils, 2003
Ernst Guenther, The Essential Oil, Vol I-V, 1948 reprinted 1972
Madeline Kerkhof, CO2 Extracts in Aromatherapy, 2018
Julia Lawless, The Complete Aromatherapy & Essential Oils Sourcebook, 2017
Leung and Foster, Encyclopedia of Common Natural Ingredients, 1996
Tisserand and Young, 2nd Edition Essential Oil Safety, 2014