1. Murray Hunter – University Malaysia Perlis ESSENTIAL OILS
The distillation of
essential oils 3: PART
The final part of this series on distillation carries on from the basic principles, stages and types of distillation
to look at harvesting, selection and design of a distillation system, and the scaling up process.
Harvesting However under plantation
The method and timing of cultivation, the whole tree is
harvesting crops will depend coppiced at an early stage,
upon the part of the plant where it will usually re-grow
required, the pre-processing increasing leaf biomass for
preparation required before future harvests. This is also the
extraction, the re-growth case with tea tree (Melaleuca
characteristics of the crop, alternifolia) where initial growth
the changes of chemical from a seedling will have a
constituents in the plant during singular trunk where coppicing
growth, the diurnal variance of after the first year and breaking
chemical constituents in the up the trunk butt at ground
plant, the characteristics of the level, will promote multiple
field and the type of enterprise stem re-growth, promoting
in terms of size, scale and more biomass (Fig. 1). Table 1
socio-economic environment shows the length of the first
it operates within. Figure 1: Broken up tea tree trunk to promote coppice growth. harvest time from planting
As essential oils can be and method of harvest.
sourced from leaves, stems, flowers, bark, combing them from branches in some Some crops like peppermint have a
wood, fruits, rhizomes or seeds, the nature instances. distinct harvest window where phyto-
of the plant material required will have With trees like eucalyptus and lemon chemicals within the leaves synthesise and
great bearing on the mode of harvesting myrtle, a portion of the leaves are usually convert into desirable constituents that
required. lopped off for distillation, leaving the bulk give the oil its commercial value. These
Flowers are more delicate than other of the tree intact for growth. These trees, processes depend upon seasonal factors
plant tissues and mechanisation may if mature in the wild, will have difficulty and temperature conditions, i.e., in the
damage them. Thus many flowers like re-growing if completely chopped down. case of peppermint daylight hours and
rose and cananga must be picked
manually. Some jasmine and boronia are
mechanically harvested through combing Optimum harvest window
80 80
arrays, although the effectiveness of this
is unknown. Bark can be scraped off from 70 70
trees or collected as a by-product of the
timber industry. However many bark 60 Oil yield 60
products come from remote areas in
Yield (kg/ha
tropical countries and are still collected 50 50
% in oil
manually by collectors from both the wild
and plantations. Woods have to be cut in a 40 40
Menthol
similar manner to how the timber industry
30 30
would harvest a tree. Fruits are usually
utilised for other products like citrus juices, Menthone
20 20
and the peels which contain oil are
processed as a by-product. Rhizomes must 10 Methyl acetate 10
be collected from underground, either Menthofuran
manually or through mechanical upturning 1 2 3 4 5 6 7 8 9 10 11 12
of the earth. Seeds are either directly Weeks from 1 January
collected from the ground or plant when
mature via manual or mechanically Figure 2: The harvest window applicable to the Victorian and Tasmanian mint industries.
September 2012 P E R S O N A L C A R E 1
2. ESSENTIAL OILS
night time temperatures. Plants like
Artemisia vulgaris change in constituent
levels throughout their growth cycle, so it is
important to determine the optimal harvest
time based on maturity.1 Determining the
optimal harvest time requires sampling and
graphing of the leaf oil constituents over
the crop lifecycle. Figure 2 shows the
harvest window applicable to the Victorian
and Tasmania mint industry in Australia.2
Some flowers exhibit diurnal variations
in constituents and the daily timing of
harvest is critical. This is the case for
rose and jasmine which may have to be
harvested in the very early hours of the
morning to obtain the optimum
constituents in the flowers for extraction.
Other flowers where this issue is important
include Hoya carnosa, Stephanotis
floribunda,3 Syringa vulgaris,4 Narcissus
tazetta and Osmanthus fragrans.5
Harvesting methods and timing are Figure 3: Paddle arrangement connected to tractor wheel for ‘boggy’ conditions
Table 1: The length of harvest time and method of harvest for some essential oil crops.
Common name Time from initial planting to first harvest Method of harvesting
Australian Tea Tree Usually can make first harvest 8-12 months Usually mechanised harvesting where the whole tree is cut and
Melaleuca alternifolia after planting. Second and subsequent mulched for easy distillation. First harvest tree will be a single trunk,
harvest every 6-13 months, depending but after harvest stump is smashed so tree can coppice many trunks.
upon climate. Manual harvest is undertaken in Malaysia, Cambodia, etc.
Basil, Ocimum basilicum Plants usually flower at 50-60 cm height Plants are cut immediately upon flowering, either manually or
and sub-species. after 3-6 months. mechanically. Basil should be replanted after harvest.
Black Pepper, Harvested when plants fruit, just when they start to ripen.
Piper nigrum This is usually a manual operation and occurs several times
during the season.
Calamus Oil, Usually can be harvested 6-10 months after Rhizomes must be dug up by spade or plough, washed and dried before
Acorus calamus planting distillation.
Cananga/Ylang Ylang Usually in 2nd year, peak after 5th year. Manual picking: Flowers should be picked when early in the morning to
Cananga odoratum maximise oil content, only after they have turned yellow. Ropes are
sometimes attached to the branches so pickers can pull them down to
pick off the flowers without having to climb the tree.
Cassia Bark, various Cinnamomum cassia: First harvest approximately Cinnamomum cassia: Trees coppiced and pruned by hand to strip leaves
Cinnamomum species 5-7 years when trees coppiced at 3 m height. and bark for oil production.
Cinnamomum verum: first harvest 2-3 years Cinnamomum verum: Tree coppiced at 3 m height after 2 years for
after planting bark by hand.
Citronella, Cymbopogon Usually first harvest can be undertaken between Small holders will manually harvest with a sickle and carry to the
nardus 4-5 months after initial planting, with still for distillation. Foliage harvesters are used on larger fields, which
subsequent harvests every 3-4 months. chop and collect the material. Most oil is in the leaves so cutting
distance set to where the bulk of the leaves are (18-28 cm).
This also allows faster regrowth. Crop can have a commercial life of
4-10 years.
Coriander seed, Usually after 6 months with coordinated spring When the plant is 50-70 cm in height and fruit is 5-7 mm in size
Coriandrum sativum planting and autumn harvest.
Geranium, many species Crop usually grows enough foliage for first Usually mowed around 10-15 cm above the ground as little oil in the
and hybrids of harvesting 6-9 months after planting stems [143] and to allow for re-growth.
Pelargonium
Ginger, Zingiber officinale Harvest can occur anywhere between 150-300 It is important to determine the optimal level of oil and oleoresin content
and other species days after planting, depending upon temperature in the rhizomes before harvesting. Harvesting can be manual or
conditions. mechanised, as whole plant is pulled out, which must be without
damage.
Jasmine, various Jasmine may take 4-5 years before productive. In warm humid areas, flowers can be continually harvested for around
Jasminum species. 6-9 months per year. Flowers should be picked before sun rises 20%
above the horizon and a daily basis to avoid loss of volatiles. This is a
manually process, although combing and suction systems have been
experimented with. Plants are usually pruned after each flowering
season to promote growth.
2 P E R S O N A L C A R E September 2012
3. ESSENTIAL OILS
affected by the physical state of the as is in the case of patchouli where it must the tyres of the harvesting equipment, so
fields. Hilly fields restrict the degree of be stored before distillation. that the crop can be effectively harvested.
mechanisation during harvesting, An important consideration in the design Planning of the harvest is of paramount
particularly if the gradients are high. of any harvesting system is the potential importance as it must be synchronised with
The weather, particularly rain, will degrade damage on the plant material. Some plant the capacity of the distillery to ensure there
field compactness and can lead to delays material is very easily bruised or damaged, is no undesired backlog of unprocessed
in harvesting as conventional harvest which would restrict mechanisation options. material waiting to be distilled. Ideally,
equipment may have trouble operating on This is why some traditional harvesting harvest should be followed by almost
waterlogged fields, particularly in tropical methods are still widely used for a number immediate distillation, where appropriate.
areas. Mechanised harvesting equipment of essential oil crops. The distance of the field from the distillery
can be adapted to waterlogged fields The most efficient method of harvesting is also a consideration and harvest times
through paddle arrangements connected is to cut the material in the field and load over a diverse region utilising a central
to the wheels of tractors and bins. it directly into a container that will also act facility, requires very careful logistical
This method is successfully used in rice as the charge vessel during distillation. This planning. Where crops like mint require
paddies throughout South-East Asia. causes some loss of oil and inefficiency in some time to wilt after being mowed before
The harvesting system should ideally yields due to non oil-bearing plant material being picked up by a forage harvester and
be integrated with the extraction system also being harvested, i.e., twigs and deposited into buns, delays in the two
for maximum efficiency. This is restricted branches in tree crops. But overall this operations can lead to excessive wilting,
by any pre-extraction wilting and/or is much more economic than selective which will greatly reduce oil yields. Wilting
comminution required before extraction, harvesting of plant parts. If crops are times may be heavily influenced by daily
as any pre-processes increase the time mechanically harvested, row planting must wind and temperature conditions, requiring
lag between harvest and extraction, such be coordinated with the distance between great flexibility in the time lag between
Table 1 (continued): The length of harvest time and method of harvest for some essential oil crops.
Common name Time from initial planting to first harvest Method of harvesting
Lemon scented gum, First harvest 6-12 months after planting. If grown solely for oil production, trees should be regularly topped and
Eucalyptus citriodora After 2nd year tree can be felled for re-growth. coppiced to maintain growth. A height of around 2.5 m maintained.
Alternatively trees can be felled, leaving the main stem for re-growth of a
coppice of young shoots, which can be re-harvested every 6-12 months.
Lemon Scented Tea First harvest after 2-3 years, subsequent A foliage harvester can coppice the tree when re-growth warrants it.
Tree, Leptospermum harvests each year.
petersonii
Lemongrass, Usually first harvest can be undertaken between Small holders will manually harvest with a sickle and carry to the still for
Cymbopogon flexuosus 4-7 months after initial planting with subsequent distillation. Foliage harvesters are used on larger fields, which chop and
harvests every 3-5 months. collect the material. Most oil is in the leaves so cutting distance set to
where the bulk of the leaves are (15-20 cm). This also allows faster
regrowth. Crop can have a commercial life of 4-5 years.
Nutmeg, Myristica Trees from seed bear fruit between 6-10 years, Fruit is allowed to split and either picked or allowed to fall to the ground
fragrans vegetative propagated trees 5-7 years. and collected on a daily basis. Nets can also be used to catch the
Fruit ripens around 6-9 months after flowering. falling fruits. Long poles with cutters also used.
Reach maximum yields after 20 years.
Palmarosa, Cymbopogon First harvest around 6 months after planting Plants should be mechanically or manually harvested about 10 cm from
martini var. motia Further harvests when flowering occurs every the ground, when flowering begins, around 6 months after planting.
and sofia. 6 months.
Patchouli, Pogostemon Can be harvested 4-8 months after planting Usually the leaves are cut manually or mechanically, dried and stored to
cablin and subsequent harvests at 3-6 month allow some fermentation, before distillation at a later time.
intervals for a 2 to 6 year period.
Peppermint, Mentha Planted in early spring and harvested mid to The crop is usually mowed, allowed to wilt and them scooped up into
piperita late summer. bins for distillation. This is usually an automated process.
Rose, Rosa species Flowers picked manually between 5-10 am in the morning,
(usually R. centifolia while flowers still open.
and damascena)
Sage, Salvia officinalis Trees can be trimmed after first year for Trees can be trimmed for leaves each year and dried.
around 6 years.
Sandalwood, Santalum 30-50 years after planting The oil is contained primarily in the heartwood and large roots, thus the
album and S. spicatum tree must be felled and pulverized.
Tasmanian Blue Gum, Trees can be lopped after 6-12 months, upon Trees either coppiced and lopped when dedicated to oil production
Eucalyptus globulus reaching around 3 m height. Trees then allowed manually or through mechanized lopper. If trees cultivated for timber,
to coppice for lopping and coppicing every harvest after tree felled around 5-8 years of age.
9-15 months.
Vertivert, Vetiveria First harvest usually 18 months after planting to Usually the foliage is cut and slashed prior to the lifting of rhizomes
zizanioides allow rhizomes time to mature. (sometimes burning used). Roots either dug up manually or dug up with
the aid of a mechanical digger. As much vetiver is planted on hill slopes,
harvesting is a very difficult process to mechanise.
September 2012 P E R S O N A L C A R E 3
4. ESSENTIAL OILS
mowing and picking up the foliage for ɀ Efficient collection of the material in the these systems will fulfill their requirements.
distillation. field and delivery to the distillery. Fabricated ‘turnkey systems’ are offered by
Still today a large amount of harvesting ɀ Minimisation of backlogs in material to some suppliers, however, they account only
is undertaken either manually as is the be distilled, and for a small percentage of actual working
case in Indonesia, Cambodia and Vietnam ɀ Minimal delays in harvest to distillation field stills in the industry. Most stills are
by small holders. ‘Outback’ stills are still times, according to requirements. locally fabricated with local materials taking
used in Australia for tea tree, where the advantage of the local topography and
farmer collects wild or small scale Selection and design energy sources, usually fitting in with the
plantation material with a tractor and of extraction system socio-cultural way cultivation is undertaken
trailer, to be loaded into the still upon The choice of method for essential oil in their geographical location. This would
returning from the field. Although some extraction will depend upon: include the majority of small holder
companies offer state of the art harvesting ɀ The sensitivity of the aromatic production, cultivating small plots or
equipment, many producers fabricate their constituents in the plant to heat. collecting from the wild in Indonesia and
own specialised equipment, utilising ɀ The sensitivity of the aromatic Vietnam. Similarly, boutique farms
standard agricultural machinery available. constituents in the plant to moisture. producing specialty essential oils like
Over a period of years during the winter ɀ The volatility of various constituents lavender, tea tree, manuka and lemon
months, this equipment is rebuilt and within the plant. myrtle in Australia and New Zealand would
modified to suit their small to medium ɀ The physical nature of the plant tissue. also in the majority of cases employ simple
scale operations. Large scale operations in ɀ The solubility in water of the aromatic designs. Only large extensive farms
the mint, citrus, eucalyptus and tea tree constituents within the plant. producing large tonnage oil like mint and
industries utilise equipment that brings the the larger Australian tea tree plantations
most efficiency to the operation, as a low An overview of some of the issues involved would develop capital intensive ‘integrated
production cost is of great importance to in selecting an extraction process can be production systems’.
survival. seen in Figure 4. A number of factors must be taken into
Good management of the harvesting A summary of the extraction methods consideration when designing a distillation
procedure requires: used for a number of essential oils is listed system for the project:
ɀ The determination of the optimal harvest in Table 2.
time. The comments in the rest of this The nature of the plant material
ɀ Precise mowing or harvesting of the section are primarily related to distillation. This would lead to considerations such as;
herb with minimal damage to the crop. A great number of distilleries tend to be what are the absorption characteristics of
ɀ Consistent and precise wilting, if locally built and designed from what the material? What would the most
required before extraction. information people have in the hope that important distillation fundamentals that
Table 2: Methods of extraction utilised for a number of essential oils.
Essential oil Botanical name Part of plant used for extraction Usual method(s) of extraction
Star anise oil Illicium verum Seeds Steam distillation after seeds are comminuted
Artemisia oil Artemisia vulgaris All the herb Steam distilled after drying
Basil oil Ocimum basilicum All the herb Steam distilled after drying
Bergamot oil Citrus bergamia Fruit Peels Cold expression of nearly ripe fruits
Broom absolute Spartium junceum Flower blossoms Solvent extraction
Cajuput oil Various Melaleuca species Leaves and twigs Steam distillation of fresh material
Calamus oil Acorus calamus Roots Steam distillation of fresh or dried material
Cananga oil Cananga odorata Flowers Steam distillation of fresh material
Cedarwood oil Juniperus virginiana Wood chips, sawdust Steam distillation
Celery Seed oil Apium graveolens Seeds Steam distillation of crushed seeds
Citronella oil Cymbopogon nardus Grass Steam distillation of dried material
Coriander seed oil Coriandrum sativum Seeds Steam distillation fo crushed dried seeds
Fennel oil Foeniculum vulgarie Seeds (in fruits) Steam distillation of the crushed seeds
Ginger oil Zingiber officinale Rhizomes Steam distillation of freshly ground rhizomes
Jasmine absolute Jasminum grandifloram and other Flowers Solvent extraction of the fresh flowers
Lavender oil Lavandula officinalis and others Flowering tops and stalks Steam distillation of fresh material
Lemon oil Citrus medica Peel Cold expression
Lemongrass oil Cymbopogon flexuous and citratus Grass Steam distillation of fresh or mildly wilted grass
Lime oil Citrus aurantifolia Peels Steam distilled or cold pressing
Litsea Cubeba oil Litsea cubeba tree Ripe fruit Steam distillation
Patchouli oil Pogostemon cablin Leaves Steam distillation of dried and fermented
leaves under pressure
Rose oil Rosa centifolia, damascena and others Flowers Water distillation of fresh flowers
Sandalwood oil Santalum album Wood Steam distillation of chipped and powdered wood
Thyme oil Thymus vulgaris Flowering herb Steam distillation
4 P E R S O N A L C A R E September 2012
5. ESSENTIAL OILS
would apply to this material? What would
be the effect of steam and/or water on the
physical state of the material (i.e., will it
congeal or tend to form steam channels)?
Will the material have to be pre-processed
before distillation (i.e., cut up, ground or Influencing Factors Historical
some other form of comminution)?. Is the Compound
characteristics
material sensitive to delay in distillation? (volatility/mol. Weight)
Does it have to be wilted? Are the volatile Surrounding Material Compounds Highly volatile
mixed with terpenes
constituents subject to damage at waxes, also
prolonged high temperatures? Are there lactones,
Low/medium volatility/stable
esters etc.
low and high boiling constituents?
What considerations must be given to this? Distillation Solvent Cold
How do others distill this material? Extraction Pressing
These questions would assist in
identifying the most suitable type of
Automated
distillation method and the general harvest and
practices that will be applied during Influencing Factors Harvest and
distillation
Price vis. Market later load system system
distillation, such as what type of steam, Volume
for how long should it be distilled, etc. Plant cell structures
Field size
Topography
The harvest method and logistics Soil/field characteristics
The harvest methods used will depend Part of plant (i.e., Extensive
rhizome/leaf) Manual large scale
upon the scale of the project, the nature of
Coppice High --- Low
harvesting farming
the herb, the local traditions and practices Value
due to
of farming, the capital investment made scale,
into the venture and the amount of the material, Specialties
Distillation investment
particular herb that requires handling and
processing. Harvest methods can vary from
manual harvesting, mowing and wilting
Hydro Material
before being picked up from the field by Characteristics ‘Finer’
another vehicle, to a fully integrated system CO2 composition
spectrum
where the material is harvesting, mulched Solubility in
Water-Steam
and spread directly into a cartridge or box water
Individual
array, behind the tractor/harvester. Another Fractional
aroma
Distillation
consideration is the potential damage that compounds
could occur to the plant material through Steam Material
Characteristics
harvesting, as in the example of rose petals
which must be picked by hand to prevent A Basic Harvest to Distillation Flowchart for
any damage which could promote Peppermint Oil
Figure 4: Some of the factors influencing the mode of extraction of essential oils from plants.
hydrolysis, oxidation and resinisation before
distillation. Time between harvest and
distillation is another factor that needs Determination of Harvest time
(Sampling)
consideration. In the case of rose petals,
distillation time after harvest is very crucial,
where time is not as critical for eucalyptus 10 tonne fresh herb per Ha.
Mowing and leaving to wilt on
and tea tree oil distillation. Basically a field Fresh herb contains 80%
‘time and motion’ flowchart of the logistical moisture
aspect of harvest to distillation can
be undertaken, which can assist in Wilting Must wilt to 50% moisture
determining the amount of integration level where ‘crisp and
brittle’
between harvesting and distillation
systems. This needs to be quantified with
Pick up with forage harvester
expected volumes on a daily basis to assist Collect 6 tonne of dry herb
in determining the required still capacity,
steam requirements and overall still design.
Must insure that herb is not
A flowchart for mint is shown in Figure 5. Deliver to Distillation system bruised.
Use cartridge or box to
avoid too much handling
Available cooling water for condenser Volume of 4 M2 per tonne
An important factor in condenser design is of herb.
Distillation
the temperature of the available water If single charge, yield 15kg
oil
for cooling. This will greatly influence the Assume 35 minutes distillation time, 10
size of the condenser along with vapour minutes change over, 6.90 litres/minute If distillate ratio is 0.062/1
steam rate per minute. 9 hours will handle (oil/water), then 241.8 litres
throughput. Ignoring the condensate water 12 tonnes of dried herb in a vat of 4m 3. water required for
distillation.
temperature issue when designing the
condenser could lead to expensive re- Figure 5: A basic harvest to distillation flowchart for peppermint oil.
September 2012 P E R S O N A L C A R E 5
6. ESSENTIAL OILS
Figure 6: A small plant designed and built by the author to Figure 7: A glassware still is usually more efficient than a
convert used cooking oil to bio-diesel. commercial still.
fabrication and modification at a later date to the US$200 per barrel mark, this is a like palm oil wastes, but most of these
or restriction on the steam flow, critical issue for the existing industry and remain pilot projects and may be too far
temperature and pressure that can be used any potential new venture. away to consider.
in distillery operation. Some distillation At the present, no specific alternative Another alternative is solar distillation.
systems in remote areas of Australia and sources of energy stand out as a solution. Solar distillation involves using solar energy
Indonesia utilise a nearby pond to run a Bio-diesel as an alternative to fossil fuels to supply heat source to produce steam
pipe through where exiting vapours from has gained a lot of attention at late, from through a Scheffler mirror reflector to
the charge vessel are condensed and either ethanol or a fixed oil feedstock, but concentrate UV light onto a focal point to
collected on the other side of the pond, pricing is still according to market forces, convert water into steam.7 This method is
away from the distillery. This can be usually around 70% to 90% of fossil fuels. used to clean drinking water and is being
designed when one side of a pond is The economics of jatropha cultivation and used experimentally to distill essential oils.8
elevated from the other. Other ‘field’ or extraction is questionable. The logistics of The system does not work on cloudy days
‘bush’ stills utilise a large single water tank producing your own is enormous due to where a backup system is required.
with stationary water inside to run a the plant and land required and this type
condenser pipe through for the same of venture would attract regulation, Required plant material throughput
effect. These methods save substantially licensing and even excise in many legal (Scale)
on the cost of constructing a dedicated jurisdictions.6 However possibilities exist for The required size of a distillery will depend
condenser. the recycling of used cooking and engine upon the required throughput of biomass
oils for diesel fuels. However in these per annum and whether it will be a
Potential energy source cases collection and processing become continuous or seasonal operation. The
One of the major challenges facing the issues. Various pilot schemes exist in the factors which should be considered in
essential oil industry today is final region producing bio-fuels based on deciding upon the scale of the distillery
economical energy sources to produce plastics, spent sugarcanes and other crops would include:
steam. Stills in remote areas were directly
fired using firewood collected from
surrounding areas. However due to the Initial Parameters of Determination of distillation
decline in logging in most places, a Prototype Time (according to various
Still diameter conditions)
premium has been put on the cost of fire
wood and for many places it is not free Still height
Steam source
anymore. Plant refuse from the still can Steam type
be used for distillation, but it is only a Determination of distillation
supplement to firewood, as there is not Stop point
enough volume in its own right to maintain
a distillery operation. Further there are Initial Distillation
alternative uses for plant refuse in Conditions
Material preparation Evaluate steam
mulching and composts which if applied Packing density flow/temp/pressure to yield
correctly can save more on labour for Steam flow/temp/pressure
weeding and maintaining moisture in soils. Stop point of distillation
Larger distilleries have employed diesel,
bunker fuel or natural gas to power their Determination of steam flow/
Temp/pressure rates
boilers. With the crude oil price going Initial Distillation Results
above US$100 per barrel at the time of Oil Constituents
writing, up from just US$16 per barrel a Oil Yield
few years ago, the cost of running a Total oil verses time Further modification of
Oil to water ratio still
distillery in terms of fuel has risen fivefold.
Given that the market expects the price of
crude oil to rise even further, perhaps close Figure 8: Testing procedure for prototype stills.
6 P E R S O N A L C A R E September 2012
7. ESSENTIAL OILS
ɀ Whether the harvest would be seasonal
or staggered over the year.
ɀ The actual size of the plantation, i.e.,
tonnage of bio-mass to be processed
each year.
ɀ Whether labour is an important factor in
the cost of production (operating cost),.
ɀ The value of the crop, and
ɀ The overall capital cost of the distillery.
If harvesting needs to be undertaken within
a short season, as would be the case for
peppermint, a large distillery to cope for
the biomass within the period would be
necessary. The number of operating hours
distillation is carried out in a day, i.e.,
single or double shift or around the clock Figure 9: Manual harvesting and mulching before loading into fixed still arrangement
would also influence the required size. at author’s property in Perlis, Malaysia.
Crops with less critical harvest times,
where harvesting can be staggered would Fixed stills are ideal for operations that clamped during distillation. The foliage is
require a smaller distillery. require water distillation. They are also usually loaded and unloaded manually or
The design of efficient working stills suitable for plant material where heavy with the assistance of a block and tackle
usually comes with experimental trial and comminution is required and this cannot pulley, connected to a tractor. Compact
error, and the testing of smaller prototype be undertaken in the field. Most fixed stills packing of the charge into the still is vital
stills in field operation where they can be exist in smaller to medium plantations and in achieving good yields. The charge must
scaled up. Field results will differ from in operations where plant material is be packed efficiently to prevent steam from
laboratory results because; laboratory collected from the wild. They are also used channelling through the plant material.
distillations will be exhaustive and field in situations where the cost of labour is not Steam is usually generated through an
distillations will be guided by shut down of paramount importance to the economics adjacent boiler, which can produce some
times. A laboratory distillation will utilise of the operation, so many family farms in pressure. Steam is introduced into the
selected parts of the plant, where the field Australia utilise this method as they are charge vessel through a pipe arrangement
distillation may also incorporate branches owner operated. However, it should be or vapour coils to distribute the steam
and twigs because of the economics of noted that due to rapidly rising living evenly. Others utilise a direct fire under the
harvesting them. Plant material in standards in many parts of South East still, built up upon a three sided brick wall.
laboratory distillations will be packed Asia, these operations could face A direct fire will only produce steam at
differently, milder steam will be used in challenges to their economic viability. atmospheric pressure. Such stills usually
laboratory distillations and hydrophilic and Most fixed stills consist of an open utilise water-steam distillation. Condensers
oxygenated compounds will be less in topped tank, usually constructed of mild are either specially built or the natural
scaled up distillations.9 steel or other locally available scrap topography around a pond or dam is used
During the working life of each prototype metals. The lid is usually sealed with cork as a cooling reservoir with the separator
still, a number of design parameters, or mud, which is not heat sensitive and positioned on the other side of the dam.
operating procedures and plant
characteristics should be tried and tested
to determine their influence on results. Lid with Clamps
Corrugated Iron Condenser Tank
These are shown in Figure 8. Vapour Outlet Running
Still scale varies from plantation to into Corrugated Tank
plantation, with different ideas and
philosophies about the optimum size.
Some systems distil small batches at a Distillation Vat
Vapour Outlet Running Pipe for
“T”
time within a cartridge or bin system, Counterweight into Corrugated Tank Pressure
usually handling multiple units at a time. Equalisation
Other systems distil a large charge at a
time. System design appears to be more
influenced by the logistic flow than the
technical issues of distillation. Most
Oil
designs in larger scale operations are Welded Steel Mesh Bottom
more concerned about continuous Water
operational flows, minimising labour and
handling. No widespread conclusions have
been made about this issue. In plantations Brick
Compartment “Firebox” for wood fire
of medium size, one of three types of
systems are usually employed; a fixed
still operation which requires manual Constant Level Separator
loading and unloading, a cartridge system Tank
or a box system. Figure 10: Simple design layout of a fixed still.
September 2012 P E R S O N A L C A R E 7
8. ESSENTIAL OILS
Figure 11: A cartridge distillation system at the former ‘Maincamp’ Figure 12: Box coupled to the steam source at the distillery for
property in Australia. peppermint distillation at Myrtleford, Victoria.
Alternatively a stationary tank is used to Box distillation systems are usually used inlet pipe is connected at the bottom of the
house cooling water for the condenser for extensive high biomass crops like mint box and another pipe (or lid) connected at
pipe. Figure 10 shows a simple design and fennel, where a number of growers the top flowing to the condenser system.
diagram of a fixed still. over a particular area may share the Once the distillation has been completed,
Cartridge distillation systems were facilities. A central distillery is made up of a the box is pulled out of the distillation
developed as a labour saving process over steam boiler and a station to park and station and through hydraulics, tips out
fixed stills which have to be loaded and connect up boxes to the steam and the spent plant material into a designated
unloaded manually. This system can exist condenser. The box is mobile on a trailer refuse area, before being returned to the
in two basic forms. One is where plant that can be carted behind the harvester in field.
material is brought in from the field and the field for direct filling of Some producers use small compact
loaded into the cartridges at the distillery the harvested plant material. The box will boxes which are easier to use on fields,
and loaded into the still, once the previous have a lid that can be elevated towards especially during rainy conditions. Smaller
cartridge has completed its distillation. the harvester, so the harvested material boxes can be distilled quicker and are
The other is where the cartridge is actually can be deposited or with no lid, where a lighter in weight for handling and most
taken into the field behind the harvester suspended lid at the distillery will be suitable when the distillery is nearby.
and loaded directly during the harvest. lowered onto the box during the actual Smaller boxes also create less pressure at
These systems greatly improve the distillation. Once the box is full of plant the beginning of a distillation when the
logistics of distillation, where cartridges material, it is disconnected from the massive air volume in the top of box heats
can be positioned ready for exchange with harvester and attached to a truck or tractor up and is expelled through the condenser
the previously distilled cartridge, almost (depending on the distance) for transport system. Larger boxes, although more
immediately without having to wait for the to the distillery. At the distillery, a steam difficult to handle on the field, lend
spent plant material to cool. themselves to longer distance
Distilled cartridges are lifted to hauls to a central distillery.
a refuse area where the spent The box must be designed so
foliage is tipped into a compost Each box can be distilled on rotation
that steam will circulate
or both together, governed by boiler
heap, before the cartridge is capacity. throughout the space inside the
returned to the field. In some box. Design of the internal
systems, the cartridges Boiler
piping array to inlet the steam is
themselves critical. The herb material rests
form the still, where the steam on a false mess bottom above
inlet pipe and vapour outlet the steam inlets to prevent any
are connected directly to the burning of foliage that could
steam boiler and condenser create unpleasant odours and
respectively, for immediate assist in even distribution of the
distillation. steam vapour throughout the
These designs greatly internal space of the box. Box
improve daily production stills are suitable for logistic
throughput, as loading, cooling situations where crops are
and unloading times between grown in distributed areas, as
Box No. 1. Box No. 2.
distillations are saved. Still transport of herb material is a
heights range between 1.3-2.0 crucial issue. Box systems are
Condensers
metres with a suitable diameter also very efficient from the
for handling. Still design is labour point of view, requiring
Boxes driven in by tractor
greatly influenced by handling and coupled up to steam only one person to drive the
convenience. The steam supply inlet and condenser. harvester, one person to drive
should be sufficient to handle Separators the transporter, one person to
multiple charges at one time operate the steam and one
for best efficiency. Figure 13: Layout plan for a box system distillery. person to couple and uncouple
8 P E R S O N A L C A R E September 2012
9. ESSENTIAL OILS
the boxes and pipes during the operation. mulch as it has been sterilised during flowers: live or dead – which do we want? In:
distillation. The farm enterprise has the Lawrence BM, Mookherjee BD, Trenkle RW eds.
Distillation effluent option of either using the mulch back on Flavors and fragrances: a world perspective.
A distillation plant will have two types of its own fields or selling it as a commercial Proceedings of the 10th International Congress
polluting effluent, smoke from a steam product. There is usually high demand for of Essential Oils, Fragrances and Flavors,
generator (unless electrically powdered) good mulches in the horticulture, Washington DC. Amsterdam: Elsevier Science
and the water distillate from the charge agriculture and home gardening sectors. Publishers, 1986: 415-24.
bin. These effluents fall under the Other potential by-products from 5 Mookherjee BD, Trenkle RW, Wilson RA. Live vs.
jurisdiction of local environmental distillation wastes include hydrosols from dead (Part II): a comparative analysis of the
protection authorities. Smoke discharges certain distillate waters, although these are headspace volatiles of some important
may require filters to trap excess carbon limited to a few crops like lavender, rose, fragrance and flavor raw materials. Journal of
emissions and distillation effluent may and other florals. Spent foliage can be Essential Oil Research 1989; 2: 85-90.
require aerobic or anaerobic treatment in used as cattle feed base, ferro-cement 6 Menage E, Nicholson K. Used oil as an
a pond before discharge into the filler for green bricks and buildings, and as alternative boiler fuel- promises and problems,
environment. a source of fuel for steam production in Southeastern apos; 93, Proceedings, Charlotte,
the distillation plant. PC NC. IEEE, 4-7 April, 1993.
Potential by-products from 7 For layouts and plans see: Dupont F. Essential
the distillation process References oil extraction from herbs using solar energy – a
The production of any possible by- 1 Clark RJ, Read C. Production of peppermint oil: thesis summary. http://www.uni-kassel.de/fb11/
products from the waste products of a model of best practice for Tasmania and agrartechnik/Fachgebiet/personal/Florent/
distillation, not only assists in the handling Victoria, Canberra. A report for the Rural Florent_Thesis_summary.pdf (accessed 7th
of wastes, but in adding value to the Industries Research and Development January 2009).
process through either savings or extra Corporation, August 2000, p61. 8 Munir A, Hensel O. Development of a solar
revenue gained. 2 Hunter M. Essential oils: art, agriculture, distillation system for essential oils extraction
The spent foliage of many plants after science, industry and entrepreneurship: a focus for herbs – Conference on Utilisation of diversity
distillation can by utilised as mulch. Mulch on the Asia-Pacific Region. New York: Nova in land use systems: Sustainable and organic
is very beneficial in weed control and Scientific Publishers, 2009: p417 approaches to meet human needs. Tropentag,
maintaining moisture in the soil after rain 3 Matile P Altenburger R. Rhythms of fragrance
, 9-11 October 2007. http://www.tropentag.de/
or irrigation. Using spent foliage as mulch emission in flowers. Planta 1988: 174: 2007/abstracts/links/Hensel_4GdqiE2W.pdf
is also part of a sustainable farming 242-7. (accessed 7 January 2009).
system and encouraged. Spent foliage 4 Mookherjee BD, Trenkle RW, Wilson RA, 9 Mateus EM, Lopes C, Nogueira T, Lourenco
after oil extraction usually makes good Zampino M, Sanads KP Mussinan CJ. Fruits and
, JAA, Curto MMJ. Pilot steam distillation of
September 2012 P E R S O N A L C A R E 9