The Distillation of Essential Oils Part 3


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The Distillation of Essential Oils Part 3, Personal Care Asia, Sept 2012

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The Distillation of Essential Oils Part 3

  1. 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 plantationThe method and timing of cultivation, the whole tree isharvesting crops will depend coppiced at an early stage,upon the part of the plant where it will usually re-growrequired, the pre-processing increasing leaf biomass forpreparation required before future harvests. This is also theextraction, the re-growth case with tea tree (Melaleucacharacteristics of the crop, alternifolia) where initial growththe changes of chemical from a seedling will have aconstituents in the plant during singular trunk where coppicinggrowth, the diurnal variance of after the first year and breakingchemical constituents in the up the trunk butt at groundplant, the characteristics of the level, will promote multiplefield and the type of enterprise stem re-growth, promotingin terms of size, scale and more biomass (Fig. 1). Table 1socio-economic environment shows the length of the firstit 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 awood, 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 andgreat bearing on the mode of harvesting myrtle, a portion of the leaves are usually convert into desirable constituents thatrequired. 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 factorsplant tissues and mechanisation may if mature in the wild, will have difficulty and temperature conditions, i.e., in thedamage them. Thus many flowers like re-growing if completely chopped down. case of peppermint daylight hours androse and cananga must be pickedmanually. Some jasmine and boronia aremechanically harvested through combing Optimum harvest window 80 80arrays, although the effectiveness of thisis unknown. Bark can be scraped off from 70 70trees or collected as a by-product of thetimber industry. However many bark 60 Oil yield 60products come from remote areas in Yield (kg/hatropical countries and are still collected 50 50 % in oilmanually by collectors from both the wildand plantations. Woods have to be cut in a 40 40 Mentholsimilar manner to how the timber industry 30 30would harvest a tree. Fruits are usuallyutilised for other products like citrus juices, Menthone 20 20and the peels which contain oil areprocessed as a by-product. Rhizomes must 10 Methyl acetate 10be collected from underground, either Menthofuranmanually or through mechanical upturning 1 2 3 4 5 6 7 8 9 10 11 12of the earth. Seeds are either directly Weeks from 1 Januarycollected from the ground or plant whenmature 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. 2. ESSENTIAL OILSnight time temperatures. Plants likeArtemisia vulgaris change in constituentlevels throughout their growth cycle, so it isimportant to determine the optimal harvesttime based on maturity.1 Determining theoptimal harvest time requires sampling andgraphing of the leaf oil constituents overthe crop lifecycle. Figure 2 shows theharvest window applicable to the Victorianand Tasmania mint industry in Australia.2 Some flowers exhibit diurnal variationsin constituents and the daily timing ofharvest is critical. This is the case forrose and jasmine which may have to beharvested in the very early hours of themorning to obtain the optimumconstituents in the flowers for extraction.Other flowers where this issue is importantinclude Hoya carnosa, Stephanotisfloribunda,3 Syringa vulgaris,4 Narcissustazetta 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. 3. ESSENTIAL OILSaffected by the physical state of the as is in the case of patchouli where it must the tyres of the harvesting equipment, sofields. 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 paramountparticularly if the gradients are high. of any harvesting system is the potential importance as it must be synchronised withThe weather, particularly rain, will degrade damage on the plant material. Some plant the capacity of the distillery to ensure therefield compactness and can lead to delays material is very easily bruised or damaged, is no undesired backlog of unprocessedin 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 almostwaterlogged 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 distillerycan be adapted to waterlogged fields The most efficient method of harvesting is also a consideration and harvest timesthrough paddle arrangements connected is to cut the material in the field and load over a diverse region utilising a centralto the wheels of tractors and bins. it directly into a container that will also act facility, requires very careful logisticalThis method is successfully used in rice as the charge vessel during distillation. This planning. Where crops like mint requirepaddies 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 andbe integrated with the extraction system also being harvested, i.e., twigs and deposited into buns, delays in the twofor 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. Wiltingcomminution required before extraction, harvesting of plant parts. If crops are times may be heavily influenced by dailyas any pre-processes increase the time mechanically harvested, row planting must wind and temperature conditions, requiringlag 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. 4. ESSENTIAL OILSmowing 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 onlyis undertaken either manually as is the be distilled, and for a small percentage of actual workingcase in Indonesia, Cambodia and Vietnam ɀ Minimal delays in harvest to distillation field stills in the industry. Most stills areby small holders. ‘Outback’ stills are still times, according to requirements. locally fabricated with local materials takingused in Australia for tea tree, where the advantage of the local topography andfarmer collects wild or small scale Selection and design energy sources, usually fitting in with theplantation material with a tractor and of extraction system socio-cultural way cultivation is undertakentrailer, to be loaded into the still upon The choice of method for essential oil in their geographical location. This wouldreturning from the field. Although some extraction will depend upon: include the majority of small holdercompanies offer state of the art harvesting ɀ The sensitivity of the aromatic production, cultivating small plots orequipment, many producers fabricate their constituents in the plant to heat. collecting from the wild in Indonesia andown specialised equipment, utilising ɀ The sensitivity of the aromatic Vietnam. Similarly, boutique farmsstandard agricultural machinery available. constituents in the plant to moisture. producing specialty essential oils likeOver a period of years during the winter ɀ The volatility of various constituents lavender, tea tree, manuka and lemonmonths, this equipment is rebuilt and within the plant. myrtle in Australia and New Zealand wouldmodified to suit their small to medium ɀ The physical nature of the plant tissue. also in the majority of cases employ simplescale operations. Large scale operations in ɀ The solubility in water of the aromatic designs. Only large extensive farmsthe mint, citrus, eucalyptus and tea tree constituents within the plant. producing large tonnage oil like mint andindustries utilise equipment that brings the the larger Australian tea tree plantationsmost efficiency to the operation, as a low An overview of some of the issues involved would develop capital intensive ‘integratedproduction 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 distillationprocedure 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 materialɀ 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 ofɀ 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 distillation4 P E R S O N A L C A R E September 2012
  5. 5. ESSENTIAL OILSwould apply to this material? What wouldbe the effect of steam and/or water on thephysical state of the material (i.e., will itcongeal or tend to form steam channels)?Will the material have to be pre-processedbefore distillation (i.e., cut up, ground or Influencing Factors Historicalsome other form of comminution)?. Is the Compound characteristicsmaterial sensitive to delay in distillation? (volatility/mol. Weight)Does it have to be wilted? Are the volatile Surrounding Material Compounds Highly volatile mixed with terpenesconstituents subject to damage at waxes, alsoprolonged 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 ColdHow do others distill this material? Extraction Pressing These questions would assist inidentifying the most suitable type of Automateddistillation method and the general harvest andpractices that will be applied during Influencing Factors Harvest and distillation Price vis. Market later load system systemdistillation, such as what type of steam, Volumefor how long should it be distilled, etc. Plant cell structures Field size TopographyThe harvest method and logistics Soil/field characteristicsThe harvest methods used will depend Part of plant (i.e., Extensive rhizome/leaf) Manual large scaleupon the scale of the project, the nature of Coppice High --- Low harvesting farmingthe herb, the local traditions and practices Value due toof farming, the capital investment made scale,into the venture and the amount of the material, Specialties Distillation investmentparticular herb that requires handling andprocessing. Harvest methods can vary frommanual harvesting, mowing and wilting Hydro Materialbefore being picked up from the field by Characteristics ‘Finer’another vehicle, to a fully integrated system CO2 composition spectrumwhere the material is harvesting, mulched Solubility in Water-Steamand spread directly into a cartridge or box water Individualarray, behind the tractor/harvester. Another Fractional aroma Distillationconsideration is the potential damage that compoundscould occur to the plant material through Steam Material Characteristicsharvesting, as in the example of rose petalswhich must be picked by hand to prevent A Basic Harvest to Distillation Flowchart forany 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 beforedistillation. Time between harvest anddistillation 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 onand tea tree oil distillation. Basically a field Fresh herb contains 80%‘time and motion’ flowchart of the logistical moistureaspect of harvest to distillation canbe undertaken, which can assist in Wilting Must wilt to 50% moisturedetermining the amount of integration level where ‘crisp and brittle’between harvesting and distillationsystems. This needs to be quantified with Pick up with forage harvesterexpected volumes on a daily basis to assist Collect 6 tonne of dry herbin determining the required still capacity,steam requirements and overall still design. Must insure that herb is notA flowchart for mint is shown in Figure 5. Deliver to Distillation system bruised. Use cartridge or box to avoid too much handlingAvailable cooling water for condenser Volume of 4 M2 per tonneAn important factor in condenser design is of herb. Distillationthe temperature of the available water If single charge, yield 15kg oilfor cooling. This will greatly influence the Assume 35 minutes distillation time, 10size 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 litresthroughput. Ignoring the condensate water 12 tonnes of dried herb in a vat of 4m 3. water required for distillation.temperature issue when designing thecondenser 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. 6. ESSENTIAL OILSFigure 6: A small plant designed and built by the author to Figure 7: A glassware still is usually more efficient than aconvert 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 theseor restriction on the steam flow, critical issue for the existing industry and remain pilot projects and may be too fartemperature and pressure that can be used any potential new venture. away to distillery operation. Some distillation At the present, no specific alternative Another alternative is solar in remote areas of Australia and sources of energy stand out as a solution. Solar distillation involves using solar energyIndonesia utilise a nearby pond to run a Bio-diesel as an alternative to fossil fuels to supply heat source to produce steampipe through where exiting vapours from has gained a lot of attention at late, from through a Scheffler mirror reflector tothe charge vessel are condensed and either ethanol or a fixed oil feedstock, but concentrate UV light onto a focal point tocollected on the other side of the pond, pricing is still according to market forces, convert water into steam.7 This method isaway from the distillery. This can be usually around 70% to 90% of fossil fuels. used to clean drinking water and is beingdesigned when one side of a pond is The economics of jatropha cultivation and used experimentally to distill essential oils.8elevated 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 typecondenser pipe through for the same of venture would attract regulation, Required plant material throughputeffect. 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 dependcondenser. 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 aPotential energy source cases collection and processing become continuous or seasonal operation. TheOne of the major challenges facing the issues. Various pilot schemes exist in the factors which should be considered inessential oil industry today is final region producing bio-fuels based on deciding upon the scale of the distilleryeconomical energy sources to produce plastics, spent sugarcanes and other crops would include:steam. Stills in remote areas were directlyfired using firewood collected fromsurrounding areas. However due to the Initial Parameters of Determination of distillationdecline in logging in most places, a Prototype Time (according to various Still diameter conditions)premium has been put on the cost of firewood and for many places it is not free Still height Steam sourceanymore. Plant refuse from the still can Steam typebe used for distillation, but it is only a Determination of distillationsupplement to firewood, as there is not Stop pointenough volume in its own right to maintaina distillery operation. Further there are Initial Distillationalternative uses for plant refuse in Conditions Material preparation Evaluate steammulching and composts which if applied Packing density flow/temp/pressure to yieldcorrectly can save more on labour for Steam flow/temp/pressureweeding 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 ratesboilers. With the crude oil price going Initial Distillation Resultsabove US$100 per barrel at the time of Oil Constituentswriting, up from just US$16 per barrel a Oil Yieldfew years ago, the cost of running a Total oil verses time Further modification of Oil to water ratio stilldistillery in terms of fuel has risen fivefold.Given that the market expects the price ofcrude 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. 7. ESSENTIAL OILSɀ 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, andɀ The overall capital cost of the distillery.If harvesting needs to be undertaken withina short season, as would be the case forpeppermint, a large distillery to cope forthe biomass within the period would benecessary. The number of operating hoursdistillation 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 arrangementwould 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 isrequire 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 tackleusually comes with experimental trial and comminution is required and this cannot pulley, connected to a tractor. Compacterror, and the testing of smaller prototype be undertaken in the field. Most fixed stills packing of the charge into the still is vitalstills in field operation where they can be exist in smaller to medium plantations and in achieving good yields. The charge mustscaled up. Field results will differ from in operations where plant material is be packed efficiently to prevent steam fromlaboratory 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 andistillations will be guided by shut down of paramount importance to the economics adjacent boiler, which can produce sometimes. A laboratory distillation will utilise of the operation, so many family farms in pressure. Steam is introduced into theselected parts of the plant, where the field Australia utilise this method as they are charge vessel through a pipe arrangementdistillation may also incorporate branches owner operated. However, it should be or vapour coils to distribute the steamand twigs because of the economics of noted that due to rapidly rising living evenly. Others utilise a direct fire under theharvesting 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 atdifferently, milder steam will be used in challenges to their economic viability. atmospheric pressure. Such stills usuallylaboratory distillations and hydrophilic and Most fixed stills consist of an open utilise water-steam distillation. Condensersoxygenated compounds will be less in topped tank, usually constructed of mild are either specially built or the naturalscaled 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 separatorstill, a number of design parameters, or mud, which is not heat sensitive and positioned on the other side of the dam.operating procedures and plantcharacteristics should be tried and testedto determine their influence on results. Lid with Clamps Corrugated Iron Condenser TankThese are shown in Figure 8. Vapour Outlet Running Still scale varies from plantation to into Corrugated Tankplantation, with different ideas andphilosophies 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 Pressureusually handling multiple units at a time. EqualisationOther systems distil a large charge at atime. System design appears to be moreinfluenced by the logistic flow than thetechnical issues of distillation. Most Oildesigns in larger scale operations are Welded Steel Mesh Bottommore concerned about continuous Wateroperational flows, minimising labour andhandling. No widespread conclusions havebeen made about this issue. In plantations Brick Compartment “Firebox” for wood fireof medium size, one of three types ofsystems are usually employed; a fixedstill operation which requires manual Constant Level Separatorloading and unloading, a cartridge system Tankor 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. 8. ESSENTIAL OILSFigure 11: A cartridge distillation system at the former ‘Maincamp’ Figure 12: Box coupled to the steam source at the distillery forproperty 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 thehouse cooling water for the condenser for extensive high biomass crops like mint box and another pipe (or lid) connected atpipe. 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 distillationdeveloped as a labour saving process over steam boiler and a station to park and station and through hydraulics, tips outfixed stills which have to be loaded and connect up boxes to the steam and the spent plant material into a designatedunloaded manually. This system can exist condenser. The box is mobile on a trailer refuse area, before being returned to thein 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 compactloaded 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. Smallercartridge has completed its distillation. the harvester, so the harvested material boxes can be distilled quicker and areThe other is where the cartridge is actually can be deposited or with no lid, where a lighter in weight for handling and mosttaken 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 thelogistics of distillation, where cartridges material, it is disconnected from the massive air volume in the top of box heatscan be positioned ready for exchange with harvester and attached to a truck or tractor up and is expelled through the condenserthe previously distilled cartridge, almost (depending on the distance) for transport system. Larger boxes, although moreimmediately without having to wait for the to the distillery. At the distillery, a steam difficult to handle on the field, lendspent plant material to cool. themselves to longer distanceDistilled cartridges are lifted to hauls to a central distillery.a refuse area where the spent The box must be designed sofoliage is tipped into a compost Each box can be distilled on rotation that steam will circulate or both together, governed by boilerheap, before the cartridge is capacity. throughout the space inside thereturned to the field. In some box. Design of the internalsystems, the cartridges Boiler piping array to inlet the steam isthemselves critical. The herb material restsform the still, where the steam on a false mess bottom aboveinlet pipe and vapour outlet the steam inlets to prevent anyare connected directly to the burning of foliage that couldsteam boiler and condenser create unpleasant odours andrespectively, for immediate assist in even distribution of thedistillation. steam vapour throughout the These designs greatly internal space of the box. Boximprove daily production stills are suitable for logisticthroughput, as loading, cooling situations where crops areand unloading times between grown in distributed areas, as Box No. 1. Box No. 2.distillations are saved. Still transport of herb material is aheights range between 1.3-2.0 crucial issue. Box systems are Condensersmetres with a suitable diameter also very efficient from thefor handling. Still design is labour point of view, requiring Boxes driven in by tractorgreatly influenced by handling and coupled up to steam only one person to drive theconvenience. The steam supply inlet and condenser. harvester, one person to driveshould be sufficient to handle Separators the transporter, one person tomultiple charges at one time operate the steam and onefor best efficiency. Figure 13: Layout plan for a box system distillery. person to couple and uncouple8 P E R S O N A L C A R E September 2012
  9. 9. ESSENTIAL OILSthe 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 Congresspolluting 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 Scienceand 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 theprotection authorities. Smoke discharges certain distillate waters, although these are headspace volatiles of some importantmay require filters to trap excess carbon limited to a few crops like lavender, rose, fragrance and flavor raw materials. Journal ofemissions 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 ana 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. Essentialthe distillation process References oil extraction from herbs using solar energy – aThe production of any possible by- 1 Clark RJ, Read C. Production of peppermint oil: thesis summary. 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 7thof 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 solarrevenue 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 diversitydistillation can by utilised as mulch. Mulch on the Asia-Pacific Region. New York: Nova in land use systems: Sustainable and organicis 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. irrigation. Using spent foliage as mulch emission in flowers. Planta 1988: 174: 2007/abstracts/links/Hensel_4GdqiE2W.pdfis 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, Lourencoafter 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