THE WORLD BANK FAU 10 FAU-10 SECTORAL LIBRAPY INTERNATIONAL BANK FOR RECONSTRUCTION AND DEVELOPMENT FEB 12 1986 Agro-Industry Profiles CASSAVA 0 Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized
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THE WORLD BANK FAU 10
FAU-10
SECTORAL LIBRAPYINTERNATIONAL BANK
FOR
RECONSTRUCTION AND DEVELOPMENT
FEB 12 1986
Agro-Industry ProfilesCASSAVA
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PROFILES IN THIS SERIES:
OILCROPS - OVERVIEW ........... FAU-01
OIL SEEDS ..................... FAU-02
OIL PA LM ...................... FAU-03
COCONUTO ...................... FAU-04
SUGAR ..................... e. FAU-05
EHANOL. ...................... FAU-06
WHEAT o..e.o....ooo.o..eee... FAU-07
RICE o......oo.eo...o.o.ee..oFAU-08
CORN o.ooo.o.oooses..o...o.eeoAU-09
CASSAVA o ...................... FAU-10
ANIMAL FEEDS..o .............oFAU-11
FRUITS AND VEGETABLES..o...o.. FAU-12
RUBBER ...................... FAU-13
COFFEE...o................... FAU-14
TEAeo.eo.o.oooo.....e...o.e.oFAU-15
COCOA ....o.o.ooo...oo..oe.e.oFAU-16
COTTONooooo.eeo.o.o.ooo..o.oo FAU-17
MSEATS AND ESSeNTIAL oILe...- FAU-18
SPICES AND ESSENTIAL OILSo ................ FAU-19
ABSTRACT
The purpose of this Profile is to review the cassava processingindustry, from its initial production and harvesting stages toits final processing and marketing aspects. The Profile includesyields and production figures for various countries, a glossaryof terms, and a bibliography of useful references. It outlinesthe various steps in the processing of cassava for humanconsumption, including debarking, washing, and fermentation. Italso describes the manufacture of both starch and animal feedfrom cassava. A short discussion of the use of cassava inalcohol production is also included. Examples of investment andoperating costs, as well as conversion tables (Metric/US) arefound in Annexes at the end of the Profile.
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FOREWORD
The nature of project and sector work in the World Bank is suchthat staff are often called upon to work outside their majorfields of specialization, if only to make an initial judgement onthe utility of further, often costly, investigation. Under thesecircumstances, up-to-date and authoritative reference material isessential.
The profiles in this series are designed for use by operationalstaff with experience in the agricultural sector but who do nothave a technical knowledge of the particular commodity underdiscussion. Their purpose is not to substitute for technicalexpertise but to provide a reliable inhouse reference which willhelp Bank staff to determine when and what expertise is needed inthe detailed evaluation of investment proposals in agro-processing.
The conditions for any particular proposal are- bound to be uniquein a number of respects, and the use of norms and general data inproject analyses could give rise to significant errors. On theother hand, by providing responsible staff with a guide to theissues on which appropriate expertise should be sought, theseprofiles can contribute to the overall quality of agro processinginvestment. Used with care, they should also facilitate broadpre-screening such as may occur during sector work andreconnaissance.
Questions, comments and further inquiries should be addressed to:
Agro-Industries AdviserFinance and Agro Industry UnitAgriculture and Rural Development Department
The contribution of Minster Agriculture Limited and Mr. D. Fornoin the review of this profile is gratefully acknowledged.
October 1985
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Cassava
CONTENTS
DATAS SHEET.iDAT SHET..............................................
INTRODUCTION ......................... 1
GLOSSARY .......................... 1
RAW MATERIALS ......................... 2
PROCESSING .......................... 11
MARKET CHARACTERISTICS ......................... 27
OTHER FACTORS ......................... 30
BIBLTOGRAPHY ............................ . . . . . . . 33
ANNEX I EXAMPLES OF INVESTMENT AND OPERATING COSTS
ANNEX II CONVERSION TABLES (METRIC/US)
ANNEX III TOXIC SUBSTANCES IN CASSAVA AND PROCESSED CASSAVAPRODUCTS
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Cassava
DATA SHEET
Cassava Yields: Thailand: 18,653 kg/ha (16,660 lbs/acre).(1983) World Average: 9,122 kg/ha (8,118 lbs/acre).
Varieties developed are capable of yielding50-70 tons/ha.
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Processing Conversions: Starch Recovery Conversion Rate*Rate (product/input)
Small-Scale Starch Prod. 50-70% 20%(250 kg starch/day)
Medium-Scale Starch Prod. 60-70% 18%(1-5 tons starch/day)
Large-Scale Starch Prod. 75-93% 20-25%(10-25 tons starch/day)
Chip Production 38-40%* Pellet Production 33-40%
*Moisture and quality levels of starch vary with type ofprocessing.
Approximate Composition of Cassava Roots:
Water - 65-70%Starch - 20-30%Sugars and Fats - 5%Protein - 1.2%Fiber - 1-2%Ash - 0.5-1.0%
Residual Pulp = 10% of cassava root weightApproximate Composition of Residual Pulp
Starch - 56%Fiber - 36%
, Protein - 5.3%Ash - 2.7%Fat - 0.1%
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Composition of Some Cassava Products in Comparison to OtherStaple Foods Source: Bruinsma, et al, (1983)
Composition per 100 g edible portion Adult maleFresh Cassava Rice Maize Potato dailycassava flour (milled and meal requirementtubers polished (95% per day
extr)
Water (g) 60 12 12 12 80Energy (kJ) 658 1470 1522 1557 322 12900Protein (g) 0.7 1.5 7.0 9.5 2.0 37Fat (g) 0.2 - 0.5 4.0 -Carbohydrate (g) 37 84 s0 72 17Fibre (g) 1.0 1.5 0.2 1.5 0.4Calcium (mg) a 55 5 12 10 400-500Iron (mg) 1.0 2.0 1.0 2.5 0.7 5-9Vitamin A (I.U.) - - - - - 7500Thiamin (Vit. Ba) (mg) 0.07 0.04 0.06 0.30 0.1 1.2Riboflavin (Vit. B2) (mg) 0.03 0.04 0.03 0.13 0.03 1.8Nicotinamide (mg) 0.7 0.8 1.0 1.5 1.5 19.8Ascorbic acid (Vit. C) (mg) 30 - - - 15 30
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INTRODUCTION
Cassava, along with rice, sugar cane, and maize, is one of themost important source-crops of calories in the tropics. It ismainly grown by small farmers using labor-intensive methods andis consumed mostly in rural areas close to the production site.It should not be regarded solely as a subsistence crop, however,as most cassava is traded outside the farm where it is produced.
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Traditional methods of producing foodstuffs from cassava have ledto the development of processing activities which convert thefreshly harvested roots into a range of products for industry, aswell as for livestock and human consumption. This reportprovides a brief background to the cassava crop, and some insightinto the various processing technologies currently practiced. Asmall section describing the toxic elements contained in thecassava plant is included to draw attention to the importance oftheir elimination during processing. A bibliography, whichshould be consulted for in-depth information is included.
GLOSSARY
Aipim A sweet variety of cassava.
'Bitter' cultivars Cultivars which are considered to betoxic (although there is noestablished correlation betweentoxicity and taste).
Branded pellets In Thailand, a superior qualitycassava pellet, generally produced byfirms of European origin;characterized by uniformity of qualityand good composition.
Cassava Usually refers to the roots of thecassava plant.
Cassava meal The powdered residue of chips andtubers after processing to extract theedible starch; used as animal feed.
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Cassava chips Dried pieces of sliced or chippedtuber.
Farinha A form of cassava meal processed forhuman consumption in Brazil.
Cassava flour Finely ground dried tubers consistingalmost entirely of starch.
Gari A West African staple made bymacerating, leaching, fementing, anddrying cassava; similar to farinha.
Cassava starch Fine powdery material obtained bywet-extraction from pulped cassavaroots; usually referred to as tapioca.
Starch milk The aqueous solution of suspendedstarch remaining after the removal ofwet cassava pulp.
'Sweet' cultivars Cultivars which are considered to benon-toxic.
Tapioca Usually applies to pearl, flake, orbead forms of cassava starch producedby wet extraction methods; also usedas another general name for cassava.
RAW MATERIALS
Cassava is widely grown throughout the humid and semi-humidtropics and in some sub-tropical areas. Table 1 presents thearea grown, national average yields, and total production for themain producer countries. Major producers include Brazil (approx.21 million tons annually), Thailand, and Indonesia (approx. 20and 14 millions tons, respectively), Zaire (15 million tons) andNigeria (12 millions tons). Processing is not limited to majorproducer countries and extensive processing industries exist incountries whose production is too small to appear in Table 1,e.g., Malaysia. Similarly the importance of cassava processingdoes not necessarily reflect the size of the national crop;almost all the Thai crop is processed; in comparison relativelylittle is processed in Zaire.
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Table 1: Cassava Production StatisticsSource: FAO (1985)
Area Yield Production('000,000 ha) (tons/ha) ('000,000 tons)
AFRICAZaire 2.15 6.80 14.80Nigeria 1.25 9.44 11.80Tanzania 0.45 12.44 5.60Mozambique 0.55 5.73 3.15Madagascar 0.34 6.02 2.04Angola 0.13 15.00 1.95Ghana 0.25 7.60 1.90Uganda 0.50 3.30 1.65Cent. African Rep. 0.30 3.00 0.90Ivory Coast 0.22 3.55 0.80Kenya 0.08 8.19 0.68Cameroon 0.40 1.55 0.62Congo 0.09 6.38 0.60Burundi 0.04 10.75 0.43Togo 0.01 19.72 0.34
_ TOTAL (Africa) 6.76 7.29 47.26
ASIAThailand 1.33 14.97 19.98Indonesia 1.42 9.85 14.00India 0.30 19.04 5.80China 0.25 16.13 4.06Vietnam 0.50 5.80 2.90Philippines 0.25 8.00 2.00Sri Lanka 0.05 11.81 0.65
TOTAL (Asia) 4.10 12.23 49.39
SOUTH AMERICABrazil 1.81 11.71 21.27Paraguay 0.15 14.66 2.20Colombia 0.21 10.00 2.10Peru 0.03 10.90 0.36
TOTAL (S. America) 2.20 11.81 25.93
Central America 0.16 5.57 0.92& Caribbean
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The size of the national crop only partly indicates cassava'simportance in some countries. There are countries in whichcassava is a very important component of the diet, althoughnational production is too small to merit inclusion in Table 1.The consumption of cassava in selected countries is given inTable 2.
Table 2: Consumption of Cassava in Selected CountriesSource: Cock, 1984
Country Cal/person/ % of dietaryday energy
Zaire 1,287 56Congo 1,128 55Central African Republic 839 39Mozambique 697 36Angola 660 32Tanzania 503 24Liberia 501 21Togo 402 20Ghana 380 19Gabon 439 18
Yields vary and are influenced by climate, soils, diseases,pests, the inherent capability of the cultivar grown, and theskill of the producer. The crop has the potential to produceyields in excess of 25 tons per ha under extensive production andup to 70 tons per ha in small research plots; but as the figuresin Table 1 show, national yields are all well below this level.These low levels probably reflect lack of fertilizer inputs bypredominately subsistence-level producers.
Cassava's importance as a source of calories in the human diet oftropical regions is demonstrated in Table 3 on the followingpage.
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Table 3: Human Dietary Sources of Caloriesin Tropical ZonesSource: Cock, 1984
Crop Content(billion cal/day)
Rice 924Sugar 311Maize 307Cassava 172Sorghum 147Millet 128Wheat 100Potato 54Banana 32Plantain 30Sweet Potato 30
The Plant
The economically useful portion of the cassava plant is thecluster of starchy swollen roots which form underground and areattached to the base of the woody stem. The leaves also play animportant dietary role in some areas but as yet are not used inprocessing. They have significant potential, however, as proteinrich leaf-meal, equivalent in many respects to alfalfa (Webb etal, 1978).
Cassava (Manihot esculeuta Crantz) is a member of theEuphorbiaceae family and a relative of rubber and castor bean.It is native to the tropics of the Western Hemisphere where itwas brought into cultivation in the pre-Columbian era. Its wildancestors are unknown. Its introduction into Africa was relatedto the return of liberated slaves from Brazil. The crop spreadvia traditional trading routes through southern and easternAfrica, reaching India and Southeast Asia during the 18th and19th Centuries.
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The cassava plant is a short-lived perennial woody shrub whichusually branches a number of times during its life. At maturityit reaches 1.5-2.5 m in height, although some non-branching typescan exceed three meters. The stem is characteristically knobbyin appearance and the leaves are dark green, with three to fivelobes appearing during the first few weeks. Leaves increase insize and domplexity, (up to 11 lobes) with age, reverting tofewer lobes when the plant attains maximum size.
The plant is grown commercially by planting a piece of woodystem, normally 15-30 cm in length. This 'cutting' gives rise toone or more shoots within a month and after two-to three monthsswollen roots containing starch can be found in the soil. Thecrop can be lifted for consumption as soon as starchy roots areavailable, but economic yields of processable roots are normallyonly available after nine months of growth.
Under good conditions nine or more swollen roots are produced perplant. They vary in size from 25 to 40 cm in length and 5 to 15cm in diameter. Three main components of the roots areimmediately recognizable:
- the outer brown corky periderm, usually referred to asthe 'bark';
- the white/pinkish 'peel' (three to five mm thick); and
- the white inner cortex or 'flesh'.
The 'bark' is removed in all except the most crude processes(e.g. chipping and sun drying for animal feed) as particles ofbark discolor the resulting starch/meal/gari. The ease withwhich the bark is removed varies with variety. A good processingtype can be 'de-barked' easily using a 'tumbling washer' device.
The peel is only removed during processing in the manufacture ofgari. The cyanide content of the peel is proportionally higherthan the flesh of the root. Peel is not normally removed duringstarch processing as the peel itself contains a proportion ofstarch.
At the core of the 'flesh' of the root lie bundles of fibrousxylem vessels. These become undesirably woody as the rootincreases in age, reducing root acceptability as a foodstuff, andincreasing the fiber content of processed cassava.
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Cassava is limited to cultivation in the hotter parts of theworld and thrives best in areas with long rainy seasons and meantemperatures exceeding 20°C. Lower temperatures reduce growthrate and light frost will defoliate the plant. More severe frostwill kill the above-ground portions of the stem. If the frost isnot too severe, regrowth will occur from the stem base protectedby the soil.
Cassava is well-adapted to areas receiving rainfall exceeding1,000 mm per year, but it requires good drainage as rotting ofthe storage roots occurs after only short periods ofwaterlogging. Once established, cassava will tolerate prolongedperiods of drought; this accounts for its important role as asubisistence crop in areas with unreliable climates. The cropadapts to drought by shedding leaves and reducing shoot growthuntil moisture once more becomes available. Unlike many crops,especially cereals, cassava has no critical growth period duringwhich moisture is essential to prevent crop failure. An extendeddrought results in a delayed harvest rather than a crop failure.
The ability to withstand drought during different phases of itsgrowth means that the crop can be planted virtually any timeduring the rainy season except during the last few weeks. Inorder to harvest a crop within one calendar year, the rainfalland temperature must be adequate to support growth for six tonine months of the year (the higher figure if industrial scaleprocessing is contemplated). If environmental conditions do notpermit this, the growing period can be extended over 18-24months, taking in two or more short rainy seasons.
Agronomy of Cassava
In common with other root crops, thorough land preparationresults in better root yields. However, much of the world'scassava is grown by manual techniques; therefore, inadequate soiltilling results in depressed yields. Cassava cuttings areplanted horizontally, inclined, or vertically, completely coveredor protruding from the soil, according to local preference. Theuse of fresh healthy cuttings is important. They are best takenfrom the woody part of the plants over 10 months old, and shouldbe 2.5-3.5 cm in diameter. Plants are spaced 0.80-1.20 m apart,providing 6-16 thousand plants per hectare. For planningpurposes a plant population of 10,000 per hectare is recommended.
Where available, fertilizers are applied before, during, or soonafter planting. The crop responds dramatically to fertilisers,especially balanced applications of potassium and nitrogen in
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impoverished soils. The crop will tolerate soil acidity beyondthe range of many crops, which gives cassava an ecologicaladvantage over crops such as maize. High yields at circa pH 4.0are regularly obtained on highly leached soils in Southeast Asia.Cassava reacts unfavorably to high concentrations of salts in thesoil, and at pH levels of 7 and above growth and yield areaffected seriously.
Weeds compete with cassava during the first three months afterplanting. Weeding, during this period, usually by hand, iscrucial to optimize yields. Weeds encroach later in the life ofthe crop when the leaf canopy becomes sparse. They can hinderharvesting operations.
Cassava roots are available for harvest singly, per plant, or perarea, as soon as they are fit for consumption or processing. Theperiod of availability can extend over several months until thefiber content renders the root unpalatable or causes the starchcontent to be too low. Cassava can therefore be 'stored' in theground until required for consumption or when marketcircumstances are most favorable. In famine-prone areas a smallarea of cassava is often maintained by smallholders as a'famine-reserve'. The lack of a distinct harvest time is afactor in favor of cassava as a crop for environmentally fragileareas.
After weed control, harvesting is the single most expensiveoperation in terms of labor input. (Table 4). it has beenestimated that even in a high-yielding crop the maximum that oneperson can harvest per day is 750 kg. This quantity is notlimiting in a subsistence or small farm situation, but can be adrawback in the supply of raw material for large-scaleprocessing, where smallholders are relied upon for root suppply.
Table 4: Labor Requirements for Cassava Production
Method of Land PreparationManual Mechanical
(Man days/hectare)
Land preparation 25 --Planting 11 9Weeding 44 47Harvesting 25 31
TOTAL 105 87
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Mechanization for the crop is available but little used as themajority of the producers are subsistence/small-scale farmers.The few large-scale producers use mechanization for landpreparation and fertiliser application. Mechanical planters andharvesters are available but perform with mixed results.Harvesters generally have a high power requirement and theirsuccess depends on the root distribution pattern of the varietygrown as well as soil type. It is not only necessary to removethe above-ground parts of the plant before harvesting but also toremove weeds and crop debris to prevent blockage of mechanicalharvesters. Mechanical harvesting also requires a machine topulverize the stem and leaves of the crop.
Post-Harvest Behavior and Root Quality
Harvesting for processing normally coincides with maximum starchcontent of cassava roots. Varieties used for processing may betoo dense, because of high starch content, to make-them desirableeating varieties, but this depends on the preferred method ofpreparation. Maximum starch content of the root varies withvariety and conditions under which the crop was grown. Drymatter content of the root typically ranges from 30 to 35 percent and between 85 and 90 per cent of this is in the form ofstarch. The extractability of this starch depends largely on theefficiency of the starch processing equipment.
Over-mature roots become fibrous and starch content falls,resulting in lower recovery during processing. Similarly, rootsproduced in nitrogen-rich soils, such as those recently clearedof forest, may be low in starch compared with roots grown on moreimpoverished soils.
Cassava roots have a very short life once detached from theplant. Deterioration begins after 24-48 hours and firstindications are brown/blue/black streaking in the flesh of roots.Secondary deterioration follows, characterised by a softening ofthe roots, followed by a general decomposition into a rottingmass with a foul stench.
Varieties exist which have a longer root 'shelf life' than most.However, the difference is too small to be of much commercialimportance to processors. Basically, cassava roots must betransported to the processing plant and processed within 24 hoursof being lifted from the ground; otherwise, starch content of
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roots will decrease and the quality of the starch recovered willdeteriorate.
Techniques for extending shelf life for markets demanding freshroots for human consumption have been developed. Methods includedipping into hot paraffin wax, refrigeration, and curing. Thelatter method utilises the natural wound-healing properties ofthe intact root which produces a protective layer to keep outpathogenic organisms responsible for deterioration. Placingroots into a warm humid environment (e.g. boxes of sawdust orpolythene bags) stimulates 'curing' which prolongs shelf life forweeks and even months. The system is, however, uneconomic forthe large-scale storage necessary for processing requirements.
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PROCESSING
Approximately one third of the world's cassava is consumed fresh.The rest is fed directly to livestock or processed into humanfood, livestock feed for export, or converted into starch andstarch derivatives (including alcohol). Table 5 shows how thepattern of utilization varies from continent to continent. InAfrica, more than half of the cassava is processed for humanfood, with little or no industrial utilization. In contrast,Asia processes a similar proportion of its cassava, but themajority of this is converted into animal feed for export(chips/pellets) and starch, etc. The situation in the Americasis influenced by the huge Brazilian cassava industry whichprocesses much of its crop into farinha, flour, and meal forhuman consumption, as well as starch and alcohol.
Table 5: Utilization of Cassava, 1975-1977Source: Adapted from Cock, 1984
(Figures show percentage of total cassava produced)
0 Area Human Food Animal Feed IndustrialArea UJse Other*Fresh Processed Local Exported(starch etc)
Africa 38 51 1 - - 10Americas 19 24 33 - 10 14Asia 34 22 3 23 9 9All World 31 34 .12 7 6 10
* Includes waste and changes in stocksProcessing into Human Food
Cassava is processed at the domestic, artisanal, and industrialscale into a range of human food products in all continents. Therange of products is very wide, but relatively few processes havebeen mechanized to any great extent. Figure 1 shows theprocessing stages required to produce four of the major humanfood-stuffs produced from cassava: Farinha (Brazil); Gari (WestAfrica); Chickwange and Nshima (West and Central/SouthernAfrica); Gaplek (Indonesia); and cassava meal. To date, only theprocessing of farinha, gari, and cassava meal have beenmechanized to any significnt degree, although plans have been
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drawn up for the mechanized processing of nshima meal (Atkinsonet al, 1981). Farinha, gari, and cassava meal processing arediscussed in more detail on the following pages.
Figure 1: Processing Flowchart for Major HumanFoodstuffs Derived from Cassava
DFRESH ROOTS
a,b,d | Soak
e b d cp, e
a,b j _= c d
a c,d
Press # b I|Grind/Poun
a,b c lcd e
DTD PRODUC
(a =Farinha, b =Gari, c .Chickwange/nshima, d =Gaplek, e =meal)
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Farinha Processing
Farinha is an important foodstuff in Brazil where traditional* processing methods have been mechanized on an industrial scale.
Peeled roots are grated and the resulting mash is squeezed toremove much of the hydrocyanic acid released from the rootsduring the grating operation. The liquid also contains starchand soluble materials and is used as a base for stews and soups;cooking drives off the toxic elements. The moist cake of grated
A cassava is then roasted until dry, when it is packed in bags forstorage and sale.
Water is only required-for root washing, but energy is requiredto drive various motors and to roast and dry the finishedproduct. Peeling cassava roots results in a loss of up to 30 percent of the raw material, depending on peel thickness and ease ofpeeling, which are both varietal characteristics. Published workrates for peeling cassava are scarce but estimates from Indonesiaindicate between 3.3 and 4.6 man days are required to peel a tonof cassava roots. The operation is difficult to mechanizeeffectively although some machines exist which indiscriminatelyremove the outer layer of the root by abrasion.
Gari Processing
It is assumed that the techniques for farinha processing weretransferred from Brazil to Africa in conjunction with cassavaplanting material and cultural techniques when freed slaves wererepatriated from Brazil. The indigenous population modified thefarinha process to include a fermentation stage, giving rise toan end-product which resembles farinha in physical appearance,but tastes quite different.
The steps required to process cassava into gari are shown inFigure 1. The procedure is similar to that described previouslyfor farinha and Brazilian equipment designed for farinhaprocessing has been successfully imported into West Africa forgari production.
The additional fermentation stage is achieved by maintaining thewet mash, produced by rasping peeled roots, in anaerobicconditions for three to four days. Traditionally, this wasachieved by placing the mash into sacks which were tied and leftfor two to three days before squeezing out the liquor by pressingthe sack with stones and/or logs. Modern processing factoriesachieve fermentation by allowing the mash to remain in
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plastic/fiber glass bins for three to four days. Thefermentation process involves micro-organisms which reduce the pHlevel of the mash, which in turn brings about the liberation ofhydrocyanic acid from the cassava mash by hydrolysis. Squeezingout the water from the fermented mash removes most of the solublehydrocyanic acid, the rest being driven off when the cake isroasted or fried.
Gari processing is carried out on different scales throughoutcoastal West Africa. Traditional village-scale processingsatisfies rural areas, with each village claiming to produce thebest quality gari. Urban areas are supplied by surplus gari fromvillage-scale processing plants and increasingly largeindustrial-scale gari factories. These produce up to 10 tons ofgari per day and some types use horizontally rotating drumroasters and dryers which are heated with oil-fired furnaces.
As with farinha, gari requires water for root washing and fuel todrive motors and heat the roasters. Peeling presents the sameproblem and an additional consideration is the press-water fromthe gari process. This is high in starch and dissolved materialfrom the mash as well hydrocyanic acid. The BOD and toxic natureof this liquid makes it a serious pollutant to rivers andstreams.
Processing of Cassava Meal
In many countries, simple processing systems have been developedto produce cereal-type meal from cassava roots. Some systems,e.g. chickwange and nshima) involve leaving the whole cassavaroots under water for a few days before drying. While soaking,the tissues soften and much of the hydrocyanic acid is hydrolyzedto dissolve into the water. Other systems, e.g. gaplek, kokonte,merely dry the chopped-up roots, (usually after peeling), in thesun until the moisture content is reduced to 10-12 percent, atwhich point the material can be stored without the usualdeterioration problems that affect cassava.
The dried chips are then pounded or milled into a meal to be usedin traditional redipes as a dough, porridge or gruel type ofdish. In addition to traditional processing, some countries areeager to produce cassava meal as an extender in bread-making,typically to reduce wheat imports. In Brazil, large mechanizedfactories rasp washed roots, the resulting material being driedin furnaces before milling and using in bread making.
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Animal Feed Processin4
Cassava is valued as a high-energy, easily-digestible animalfeed. Because it is low in protein, vitamins, and minerals, itmust be combined with other feeds for a balanced ration.
Cassava is fed fresh to animals in many parts of the world butcassava roots must be dried for transportation and storage. Mostcassava-derived animal feed which enters international trade isin the form of pelletized sun-dried chips.
Thailand dominates the production and export of cassava foranimal feed. Most exports go the EC as a cereal substitute indairy and pig rations. Other countries exporting pellets andchips include Indonesia and China.
Chip Processing
Roots are chipped and spread to dry in the sun without washing orpeeling. If field conditions are wet at harvesting, soilcontamination increases, but chain elevators used to feedchipping machines remove most of the soil by abrasion andvibration.
Roots are 'chipped' into small pieces by machines equipped withcircular discs in which holes are made to effect the cuttingaction (mimicking the kitchen vegetable shredder). In Thailand,chipping machines are commercially available in different sizes(10-50 tons/hr) and are usually diesel-powered. Each machine hasa short rubber-belt conveyor which carries the chips away fromthe cutting blade. A conveyance for transporting the chips tothe drying yard is located under the end of the belt. This mayrange from a hand cart to a specially constructed 'sprinkler'developed in Thailand to spread chips evenly on the drying floor.Special front-loader type mechanical shovels in Thailand are alsoused.
The drying floor is usually concrete surface and represents themajor investment of a chipping enterprise. Chips are spread in athin layer usually less than five centimeters deep, and areturned at frequent intervals to ensure even drying during the twoto three days of exposure to the sun and wind required to reducemoisture content to less than 18 percent.
Turning the chips is done by pushing wooden rakes through thechips. Recently, small petrol-powered 'go-carts' equipped withmetal rakes have appeared in Thailand.
- 15
During periods of rain, the chips are quickly pushed togetherinto heaps on the drying floor and protected with smallpurpose-built portable roofs or, more recently, plastic sheets.Reduction in chip quality results from such interruptions indrying.
When the chips have dried to less than 18 per cent moisture, theyare collected using motorized shovels (front-end loaders) andloaded into trucks for transport to the pelletizing mills. Theseare ususally located near the port, but some are constructedinland in order to reduce the transport costs of the bulky chips.A number of artificially-heated cassava dryers which startedoperations in Southeast Asia during the mid-1970s have all closeddue to high energy costs.
Cassava chip production in Indonesia is done more on acottage-industry scale. Roots are harvested and peeled in thefield before chipping by hand and sun drying. Surpluses beyondhuman food requirements are put into sacks to be collected by'assemblers' who transport the dried chips to ports. Pelletizers,located at the ports, convert the bulky chips into pellets, whichare, in general, superior in quality to Thai pellets. This isdue to less soil content and to peel removal, which results in awhiter pellet with less fiber.
Pelletizing
Almost all the cassava animal feed entering the export trade ispelletized. This is because pelletizing increases the bulkdensity of the material and reduces shipping costs.
In Thailand early imported pelletizers which produced 'hard'pellets were copied locally and gave rise to poorly-formed 'soft'pellets. The 'soft' pellets, known in the trade as 'nativepellets', break up during transportation and handling and giverise to dust problems which are especially frowned upon byenvironmentalists in Europe. The trade prefers hard pellets,known as 'brand pellets', but price premiums are inadequate tostimulate the use of good-quality pelletizing equipment.
Chips used in pelletizing are processed very crudely in the'native' pellet mills. The chips are pressed through largediameter dies without grinding. The pellets are not cooled;therefore, they tend to break up as the bound-in moistureescapes. Hard pellet mills both grind chips and cool pellets but
16
0
they are expensive to operate.
During the passage of the chips through the pelleting dies,friction heats up the machinery. This heat drives off themoisture from the chips reducing the moisture content from aninitial 18 per cent down to 12.5-13 per cent which is acceptableto importers.
Current EC standards for cassava pellets and chips are:
Fiber - not more than 5%Ash - not more than 3%Starch - a minimum of 62%Moisture - Not more than 13%
(An additional 1/2% of moisture is tolerated during Thailand'srainy season.)
Industrial Processing
By far the most important industrial processing of cassavainvolves the extraction of starch. Starch granules are producedin the cells of the root and it is necessary to rupture the cellto recover the starch. Starch extraction occurs in manycountries but is most common in parts of South America wherecassava starch is used in recipes for speciality breads, etc.,and in Southeast Asia where medium- and large-scale starchfactories are found. It is likely that cassava starch plants inSoutheast Asia have taken over from the sago processing industrywhich has declined in recent years. (Apart from the obviousdifferences between raw materials, the extraction and separationtechniques are relatively similar.)
Traditional starch processing plants relied on sedimentationtechniques to separate the starch granules from the water used towash the rasped-root material. The procedure is slow and laborintensive, however, and is giving way to centrifugal and vacuumseparators.
The two main processing systems for starch extraction are shownin Figure 2. The main steps of this process are describedindividually.
0 17
Figure 2: Flowchart for Starch Extraction UsingSedimentation and/or Centrifugal Separators
| jCASSAVA ROOTS
~~~~~~~~~~~~~~~~~~~~~I
ter Washing
Wter De-barkin
Water pn
1S creening
fl | ~~~~~~~Separating|
Seimentation|1
|De-watering
\1gs ~~~~~~Drying Vt
STARCH l
0Washing
Cassava should be processed according to the order of its arrivalat the factory, to avoid deterioration of root quality. Removalof extraneous soils is the first step in processing. This isaccomplished by hand or by the use of specialized equipment, thesophistication of which is largely determined by the scale ofoperation. Among the machinery employed in cassava washing are:
- simple paddle washers consisting of troughs withagitating paddles along a horizontal shaft;
- perforated cylindrical tanks which are immersed inwater while spiral brushes scrub the roots containedwithin; and
- rotary drums equipped with interior pipes from whichwater sprays are emitted. Washing is a result of thespraying action as well as the abrasive action of rootsrubbing against each other and against the sides of thecylinder.
O Debarking
As the peel of cassava contains significant amounts of starch,only the brown corky outer layer is removed from the roots. Inmost starch factories this is done in conjunction with rootwashing. Rarely is the bark removed entirely, but this is not aproblem in modern factories as the centrifugal separators easilyremove remaining particles of bark. In small traditional starchplants, hand peeling is occasionally practiced, but labor costsseriously constrain this type of operation.
Rasping and Pulping
Rasping is the mechanical tearing of the flesh of the cassavaroot into a fine pulp in order to rupture all cell walls andrelease the starch granules contained within. The percentage ofstarch released in this way is known as the rasping efficiency.Final recovery of starch in processing is largely dependent onrasping efficiency.
A range of rasping exquipment exists, from the locally-constructed, hand- or foot-driven roll or disc rasps with amaximum capacity of 1 ton/day, to the sophisticated,electrically-operated revolving drum rasps which are fitted withreplaceable blades. All operate by pressing the tubers against a
0 19
rapidly-moving surface which is punctuated at regular intervalswith sharp protrusions. Since only 70-90% of the starch isusually released during rasping, double or triple rasping iscommon.
Due to the presence of hydrocyanic acid in the rasped rootmaterial, contact with iron is often detrimental to starchquality. Hence, stainless steel rasping equipment isrecommended.
Separation of Starch
Once the cassava cells have been ruptured, the starch must bewashed out of the cells with water. The starch milk, or starchsuspended in solution, is then separated from the pulp and fiber.Wet screening combines both of these operations, as the raspedmass is rinsed with water on a screen.
Wet screening can be performed in a variety of ways:
- by hand, in a cloth bag which is formed by attachingthe four corners of the cloth to four poles;
- with a shaking flat-bed screen, which is a slightlyinclined gauze-covered horizontal frame, mechanicallyshaken at regular intervals;
- with multi-stage DSM-screens (sieve bends), in whichthe mass of pulp is rinsed in several counter-currentstages;
- with centrifugal sieves, in which the mass of pulp isrinsed two to five times in a conical-framed, quicklyrotating screen; and
- with a jet extractor, or continuous perforated-basketcentrifuge.
The separated starch milk contains a concentration of about 54 kgof dry starch per cubic meter.
Sedimentation/Purification
In addition to starch, starch milk contains fruit water (anaqueous extract of soluble sugars, proteins, salts, and amino
20
acids). Fruit water must be removed to prevent:
(i) chemical and enzymatic reactions which lower the valueof the starch; and
(ii) micro-organism growth, resulting in fermentation.
Purification is accomplished through sedimentation or centrifugalseparation.
Chemicals are sometimes added to the starch milk to facilitatesedimentation, to lower starch milk viscosity, and to whiten thefinal starch. Among those used are sulphuric acid, sulphurdioxide (0.3-0.4 g/liter starch milk), aluminum sulphate (21g/liter), and chlorine (1 ml/liter).
Purification of the starch milk is generally accomplished by oneof the following methods:
_ Gravity Sedimentation. This is the oldest andsimplest method. The starch milk is washed with cleanwater in a large wooden or concrete tank. It is thenallowed to settle; over a period of six hours, most ofthe starch accumulates at the base of the tank. Thefruit water, which may contain 5-10 percent of thetotal starch, is removed by decanting (stoppers areremoved from holes in the upper portion of the tank).More water is added to the remaining starch and theoperation is repeated for a cleaner final product.Usually the top layer of the settled flour is removed,since it contains a high concentration of anyremaining impurities. The resulting layers of starchare often sold at price differentials reflecting thequality (the highest quality is at the bottom).
- Settling Tables. In this method the starch milk isfed in at one end of a long (50-100 m) table at acontrolled rate. As it flows to the other end, thestarch slowly settles out along the length of thetable. -This is an improved method of gravitysedimentation since the contact time between thestarch and the fruit water is reduced. Also, sincethe vertical sedimentation path is shorter anddrainage is gradual, starch losses from decanting arelower. With gravity sedimentation in tanks or tables,however, contaminating particles which are heavierthan the starch, e.g, sand and clay, are not
* 21
separated. The final moisture content of the starchfrom settling tables is 450-500 grams water per kg.
- Centrifugal Separation. A variety of centrifuges canbe used, with the principal classification being batchor continuous. The advantages of this method are thatit:(i) further reduces the time starch and fruit water
are in contact;(ii) increases processing capacity; and(iii) eliminates the impurities in colloidal
suspension.Centrifugal separation is sometimes followed bygravity settling to free the starch from any solidimpurities which may remain.
- Hydrocyclones. These are centrifuges with counter-current washing.
In modern starch-producing plants, the time lapse between raspingand drying has been reduced to about one hour.
De-watering
The starch in pure water solutions resulting from purification isfurther concentrated by mechanical means in an operation known asde-watering. The moisture content of the thickened slurry isthus reduced to 35-40% prior to drying.
De-watering is achieved.through centrifugal action. Abasket-type centrifuge consisting of a perforated bowl lined witha cloth filter or fine-mesh wire netting is generally used.While the starch collects along the sides of the bowl, the wateris filtered out. A fine layer of fiber and dirt which oftencovers the centrifuged starch, is scraped off and discarded.
Vacuum de-waterers are also used. In these, a perforated drumcovered with a muslin cloth is rotated in a shalllow tank intowhich concentrated starch milk is allowed to run. A vacuum iscreated inside the drum which attracts the starch milk to themuslin. Water passes through the muslin and the perforation intothe drum and is ejected. The deposit of starch is scraped fromthe muslin cloth as the drum rotates.
22
Drying
The de-watered starch receives a final drying by evaporation inits final transformation to a stable, transportable starch.Three principal methods are used:
(i) sun-drying;(ii) hot air drying; and(iii) contact drying.
Sun-drying on flat, shallow baskets is the cheapest and simplestmethod. The de-watered starch-cake is spread manually, usuallyearly in the morning, so as to take full advantage of the day'ssunshine. Lumps of starch should be crumbled to facilitatedrying. Depending on the weather conditions, a single day may besufficient to dry the starch to a moisture content of 15-20%. Ifnot, the baskets are moved inside, where they are stacked duringthe night, and moved outside again the next day. Drying capacityis usally limited to three to five tons of dry starch per day,with limits imposed by internal transport and space requirements.Disadvantages of this method include contamination by dust and achemical degradation which adversely affects the starch quality.An advantage is the bleaching action of the ultra-violet rays ofthe sun; a whiter product results.
Hot air dryers are used in larger, more modern operations. Ovenand chamber dryers are among the most common types of batchdryers; belt, revolving drum, and tunnel dryers are examples ofcommonly-used continuous hot air drying systems. The advantagesof hot air dryers lie in their expanded capacity, independence ofweather conditions uniformity in drying, and in the cleanlinessof the starch thus obtained. This must be weighed against theincreased costs of energy which result.
Larger operations often use pneumatic 'flash' dryers, in whichthe starch is dried in a matter of seconds as it is pneumaticallyconveyed upwards from the bottom of the drier, and then deflecteddownwards6 The air through which it is transported is heated toabout 200 C.
In contact drying, wet starch is dried on a heated surface inplate ovens and with roller driers. Care must be taken to avoidgelatinization (cooking) of the starch due to the hightemperatures involved.
In general, starch moisture contents should be reduced to 10-13%.At higher levels, the risk of mold development and subsequent
i * 23
spoilage increases. Lower levels may damage the starch andreduce its re-moistening capacity.
Packaging
Crude dry cassava starch generally contains hard lumps. It mustbe pulverized and dry-screened for ease in handling and use.This is known as 'bolting'. Bolting is only profitable forlarge-scale operations with substantial output. Otherwise,several smaller mills are typically serviced by a single boltingfactory.
Roller bolting involves the passage of crude dry starch through apair of rollers going in opposite directions at the same speed.This pulverizes lumps of starch while fiber and impurities areleft intact. A conical rotary screen (100-200 mesh/inch) thenremoves small lumps, fiber, and impurities, which are dischargedand re-fed into the rollers. The rollers may be hand-driven formedium-scale operations.
Disintegrater bolting, a faster and more efficient process, isused in large-scale operations. Beater disintegrators pulverize-all starch lumps, fiber, and impurities; hence, the purity of thefinal product is much more dependent on the purity of thestarting material.
Cassava starch is usally packaged in gunny sacks with polytheneliners for shipment, although multi-wall paper bags are becomingmore and more popular. Cassava starch is known in the trade ascassava 'flour' which causes considerable confusion. It isfrequently confused with cassava 'meal' - milled dried wholeroot.
Foodstuffs Produced from Cassava Starch
A range of products are manufactured from cassava starch, oftenon the same premises in which the starch is extracted.
There is a variety of baked, partially-gelatinized products fromcassava starch in which the starch molecules are radicallytransformed in arrangement and properties. Prior togelatinization, cassava starch molecules are almost insoluble,and of a semi-crystalline structure; afterwards, they areswollen, amorphous, and miscible with water at high temperatures.Upon coooling, the starch assumes the texture of a gel or jelly.
24
Flake, pearl, and seed production involves drying, partiallygelatinizing, and shaping of the starch. It begins at the wetstage of starch production, following sedimentation. The starch
* used must be of the highest quality. If a sulfurous acid hasbeen added during sedimentation, it must be thoroughly rinsed outin order to maintain the quality of the-end product. The use ofactive chlorine preparations should be avoided duringsedimentation.
Following sedimentation the starch is in a cake form, with amoisture content of about 45 percent. It is broken into largepieces with a small roller milll, spades, or a very coarse-meshwire screen and then passed through a 20 mesh/inch screen. Theresulting coarse-grained moist starch is then ready for flakeproduction.
Starch flakes are gelatinized 1/ in shallow pans placed in abrick oven at a moderate heat. The pans are wiped with oil orfat to prevent burning. Shorea (tentawang fat) or bassia (illipefat), which are similar to cocoa butter, are preferred; groundnutoil is also used. The starch must be raked periodically duringbaking to ensure uniform gelatinization.
0 'Pearl' and 'seed' production requires an additional step, inwhich the coarse, moist starch grain are built up andconsolidated to the size and level of strength desired. This isaccomplished in cylindrical rotating pans, typically 0.9 metersin diameter and 1.2 meters deep. As the pans rotate, the starchgrains form small particles or beads, the size of which dependson the speed and period of rotation. This is followed byscreening and sorting.
Beads and pearls are spread on plates or trays in a thick layerand transported through a steam-charged tunnel. This ensuresuniformity in gelatinization.
Gelatinized flakes, beads, and pearls must be dried to a moisturelevel of about 12%. This is accomplished in chamber driers withcirculating air. Drying of pearls and beads should begin at a
i/ Gelatinization is caused byoheating the starch in an aqueousmedium. It begins at about 60 C and is completed at 80 C,depending in part on the size of the starch granules. Flake andpearl production requires gelatinization of only the outer layerof starch. Hence, each flake, bead, or pearl consists of a rawstarch base enclosed by an outer coating of tough, gelatinizedstarch.
0 25
temperature of no more than 400C to prevent furthergelatinization and bursting. Towards the end of 8he dryingcycle, this temperature should be raised to 60-70 C. In anefficient system, drying can be accomplished in as little as twohours.
Sixteen tons of wet starch yields about 10 tons of tapiocaproducts (Grace, 1977).
ALCOHOL PRODUCTION
Cassava is an attractive source of alcohol for countries withoutfossil fuels, as it can be produced on marginal land andtherefore need not compete for land used for food production.Sugar cane is a marginally more efficient source of fermentablematerial for alcohol than cassava but sugar cane requires primeagricultural land and usually requires irrigation, both of whichare needed for food production. (Brazil is one of a number ofcountries using cassava as a source of alcohol, but sugar cane ismore efficient as the bagasse [woody debris remaining after sugarextraction] can be burnt to generate heat required during theprocess.)
The conversion of cassava to alcohol involves rasping the washedroots into a mash. This is then heated to gelatinize the starchin the mash, which is then liquefied by addition of an enzyme,alpha-amylase. Following hydrolysis of the liquefied starch tosugars, yeasts are added to convert the sugars to alcohol byfermentation. Alcohol is removed by distillation. (For a moredetailed discussion of this process, see the Ethanol Profile inthis series.)
Brazilian alcohol plants have produced 170 liters of alcohol perton of fresh cassava. These high yields are achieved by usingenzymes to convert starch to sugar in place of the acidhydrolysis method which is less efficient.
26
MARKET CHARACTERISTICS
Fresh cassava must be sold to the consumer within one to two daysof harvesting the roots. In fact, the rapid post-harvestdeterioration of the crop is a major factor which has led to themany processing alternatives. After the market for freshcassava, and processed cassava products for human consumption,the third major market is for animal feed products for export,and the fourth market is for starch and starch-derivatives.
Market for Cassava Processed into Human Foods
Farinha and gari play an important role in the nutrition of theurban as well as rural population. Gari, especially, is popularin the large cities of West Africa, where going to the marketevery day to obtain fresh cassava is inconvenient. It is aconvenicence food which only requires the addition of boilingwater to convert it into a hot doughy staple. The growing urbanmetropolis promises to provide an increasing outlet for gari andother processed cassava foodstuffs. In addition, expatriate WestAfricans in Europe and North America represent a small but steady
* source of demand.-
This demand for gari is being satisfied by the installation offactory-scale gari processing plants (Nigeria, Ghana, Guinea,etc.); the large daily requirements of fresh roots usuallynecessitate a cassava plantation, however, as an integral part ofthe processing facility.
As cities in the tropics increase in size, it is likely thatmedium to large-scale processing plants for indigenous crops suchas cassava will become a viable commercial venture. The currenttrend towards wheat-flour based convenience foods involvesspending scarce foreign exchange.
There is a recent trend towards small-scale mechanization ofcassava processing using locally manufactured equipment. Thistrend is likely to take the drudgery out of of some operationsperformed traditionally by hand, e.g. root rasping and gariroasting. It also caters for a pragmatic scale of operationsintermediate between 'cottage industry' and 'factory-scale'.
Market for Cassava Processed into Livestock Feed
The EC has paved the way to demonstrate cassava's utility as acheap source of dietary energy for livestock. However, the
* 27
market exists mainly because of the artificially high prices forcereals within the EC. This means that the advantage offered bycassava pellets to European feed millers is not necessarilyavailable for feed millers elsewhere.
Nevertheless, there are many Third World countries spendingscarce foreign exchange to import corn and other cereals for usein animal feeds, when they could be replacing at least aproportion with locally grown and processed cassava.
The international trade in cassava feedstuffs is dominated by thetrade between Thailand and the EC, which is currently around 5.5million tons per year. Other countries also export to the EC,notably Indonesia, China, and Brazil. Vietnam is likely toattempt to enter the world market in the near future.
Although the prices are less attractive than those offered in theEC, other countries import cassava pellets and chips, mainly forlivestock feed, but also as raw material for alcoholfermentation, and other industrial uses. The USSR, faced withchronic cereal shortages, finds it difficult to maintain itslivestock production and imports cassava pellets from time totime. South Korea and other eastern countries have also madepurchases.
The Market for Cassava Starch
The largest importers of cassava starch are the United States,Japan, and Canada, although imports to the U.S. have declined inrecent years. The cassava starch market has been adverselyaffected by problems of poor product quality and erratic supply.Thailand, the largest supplier, has, however, modern factoriescapable of sustaining a steady flow of high-quality starch.
The international starch market is highly complex and with newlydeveloped 'modified' and 'specialty' starches entering the arenait is likely to become even more complex.
-Cassava starch enjoys a relatively small overall share of thetotal starch market and experiences a relatively high level ofvariation in demand because of a number of factors including:
- substitute starches from corn, potato, and wheat areavailable at competitive prices;
- corn starches are available for specialty uses withoutmodification;
28
- traditional markets for cassava starch are protected,e.g. Japan, or monopolized by large companies, e.g.the U.S.A. and Canada; and
- freight rates from Southeast Asia across the Pacificare expensive, making cassava starch less competitive.
Quality specifications for cassava starch have been compiled fora number of countries in Table 6:
Table 6: Quality Specifications for Cassava StarchSource: Edwards (1974)
USA India UK _F Sri Lanka
Grade Grade Grade Edible Cotton Commercial Papermaking PapermakingA B C use textiles use Grade A Grade B
Moisture (max) Z3.5 IZ.5 14.0 13.0 15.0 8-1Z.0 15.0 15.0Ash (max) 0.15 0.25 0.50 0.4 0.4 - 4.0 4.0Fibre (max) - - - 0.2 0.6 - -Protein (max) _ _ _ - 0.3 -Ether extract (max) _- - - O.Z -Viscosity g/ml water (max) 11/150 17/150 Z0/150 I _ sViscosity of Z% paste in SeCS - - - 44.0 - -
in RedwoodNo. I Viscometer at 75°C (min) pH 4.5-6.5 4.5-6.5 4.5-6.5 4.5-7.0 4.8 . 5-8.3 5-8.5
Cassava starch is preferred for the preparation of certain foods,for papermaking, and the cardboard industry, indicating that asmall export demand will continue.
It is likely to be the local markets for starch and starchderivatives which offer the best opportunities to the cassavastarch industy. Many cassava growing countries import corn andpotato starch for their textile and pharmaceutical industries.The increase consumption of soft drinks is likely to create ademand for fructose syrup which can be derived from cassavastarch. For countries which are not self-sufficient in sugar,there is an opportunity for import substitution.
29
OTHER FACTORS
There are a number of factors which influence the cassavaprocessing industry. The following section presents a briefdiscussion of some of these.
Location
The cassava processing plant should be located in an areaproducing regular supplies of surplus cassava of a quantity andquality suitable to support operations for as near as year-roundoperation as possible. Estimates of raw material requirementsare presented in Table 7:
Table 7: Estimated Raw Material Requirementsand Necessary Cultivated AreaSource: Bruinsma, et al (1983)
Raw Raw Yield CultivatedSca fproduction material perating material of areaScale of requcio.Ire period
reqtured (d/y) required tubers required(t/d) Y W(t/y) (t/ha per y) (ha
Starch small 1.0 150-170 150-200 10 15-Z0Starch intermediate 6-30 250 1,500-7,500 10 150-750Starch large 40-100 250 10,000-25,000 15 700-1,700Chips pellets small 10 Z00 2,000 10 200Chips pellets large 56 250 14,000 15 1,000
Water Quality and Quantity
Most cassava processing factories require supplies of water.Only chipping and pelleting operations are independent of therequirement. Roots require washing in most factory processes,and in modern starch manufacture processes up to 4,300 liters ofwater are required for every ton of starch recovered. In older,less efficient processes, as much as 16,000 liters of water perton of starch are required.
The quality of water is important as it comes into direct contactwith the starch granules. The water should be free of toxic
30
bacteria and mould spores, and should also be free of copper andiodine ions which discolor the starch.
Accessibility
The desire to site a processing plant close to the productionarea sometimes results in it being in a remote location. Anall-weather road and/or rail link is necessary to facilitate theprovision of inputs and raw material as well as providing thefinished products with access to the market.
Availability of Labor
A processing plant must be located where labor is available,preferably without the need to construct housing for staff, whichcan significantly increase the capital cost of the processingscheme.
Environment
Waste disposal problems will depend on the production processutilised, the plant treatment capacity, and the location of the* operation. Large-scale operations will have to make provisionfor treatment of waste before it is discharged. This isparticularly relevant due to the concentration of cyanide andsuspended organic solids in unutilised cassava peels and in thewater used for cleaning and processing.
Economies of Scale
A comparison of technical data on starch processing at differentscales of operation is presented in Table 8:
It is claimed that large-scale operations:
- make more efficient use of raw materials;- have higher recovery rates and conversions rates, and
lower handling costs;- have higher labor productivity;- make more efficient use of energy; and- produce starch of more uniform quality.
9 31
Competition for Raw Materials
The availability of cassava roots for processing will depend onthe outcome of the following competitive situations (Bruinsma, etal., 1983):
(i) The farmer's decision between planting cassava andplanting all other crops;
(ii) The availability of surplus cassava after foodrequirements have been met; and
(iii) Competition for roots among different processingplants, e.g., starch vs. pellets.
As a result of the above, raw material supply is particularlysusceptible to fluctuation.
Table 8: Comparison of Technical Data on Starch Processingat Different Scales
Source: Bruinsma et al, 1983
Criteria Small Scale Intermediate Scale Large Scale
Raw material required (tonne/year) 150 - 200 1,500 - 7,500 10,000 - Z5,000Production starch (tonne/year) 30 - 40 Z70 - 1,350 Z,000 - 6, ZS0Recovery rate of starch (%;) 50 - 70 60 - 70 75 - 93Conversion rate produce/input (57) 20 18 Z0 - Z5Number of employees 4 40 50 - 60Production per employee (tonne/year) 7.5 - 10 6.5 - 33 33 - 1Z5Required operating skills low low highPercentage of unskilled labour (&) 75 70 4ZUse of energy,Electricity (kwh/starch) (not essential) 100 - 175Fuel oil (tonne/tonne starch) 0.0Z 0.02 0.04 - 0.07Use of water (m'/tonne starch)- ZS 43 12 - 35Quality of product Variable, good to Reasonable - not Good - export
reasonable - not for export qualityfor export
Origin of machinery and equipment Locally made Locally made ImportedMaintenance requirements High Medium MediumOrigin of spare parts Local Local ImportedOrganisational complexity Small Small ModerateAmount of waste produced:- pulp and peel (tonne/year) 100 - 130 1,150 - 5,780 20,000 - 50,000- waste water (m'/year) 750 - 1,000 11,250 - 56,250 80,000 - 160,000
32
0BIBLIOGRAPHY
01. Atkinson, D. R., D. W. Wholey, T. R. W. Jarman & J. W.Turnbull (1983) A Factory Concept for Integrated CassavaOperations.Vienna : UNIDO
02. Baker, J. C. (1981) "Structure and Outlook: TapiocaProcessing Industry in Thailand" IN The Planter No. 57(66), September 1981Kuala Lumpur
03. Black, R. P., W. Peyayopanakul & S. Piyapongse (1979)"Thailand: Cassava Pelletising Technology" IN IndustrialResearch Institutes: Their Role in the Application ofAppropriate Technolocry and Development.Boulder: Westview Press.
04. Bruinsma, D. H., W. W. Witsenburg & W. Wurdemann (1983)Selection of Technoloay for Food Processing in DevelopinqCountries.9 Wageningen: PUDOC
05. Cock, J. H. (1984) Cassava: New Potential for a NeglectedCrop.Boulder: Westview Press
06. Considine, D. M., Editor (1982) Food and Food ProductionEncyclopedia.New York: Van Nostrand Reinhold Co.
07. Dalton, G. E. & F. Akwetey (1971) Cassava Production andProcessing in S.E. Ghana.Legon: University of Ghana
08. Edwards, D. (1974) The Industrial Manufacture of CassavaProducts: An Economic Study.London: TPI
09. FAO (1985) FAO Agricultural Production Yearbook 1984.Rome: FAO
10. Grace, M. R. (1977) Cassava Processing.Rome: FAO
11. Nestel, B. & R. MacIntyre (1973) Chronic Cassava
9 t 33
Toxicity: Proceedings of an Inter-Disciplinary WorkshorLondon, England: January 29-30, 1973.Ottawa: IRDC
12. Nestel, B. & M. Graham (1977) Cassava as Animal Feed:Proceedings of a workshop held at the University ofGuelph, April 18-20, 1977.Ottawa: IRDC
13. UNCTAD Secretariat (1982) Technology and Food Processingin Thailand: The Case of Cassava Pelletising andPineapple Canning.Geneva: UNCTAD
14. UNIDO (unpublished) Evaluation of Cassava Chip ProductionConsultancy Study.Vienna: Available from UNIDO
34
0
ANNEX I:
EXAMPLES OF INVESTMENT AND OPERATING COSTS
#I
'I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I
t
II
CASSAVAEXAMPLE 1
Page 1 of 2
Representative Investment and Operating Costs
CASSAVA PELLET PRODUCTION
Establishment of a factory to produce soft cassavapellets.
COUNTRY: Thailand
NOTE: These data are intended as representative only andunique to the time, country and circumstance of theidentified investment. Their applicability to othersituations may vary considerably.
ANNUAL FULL DEVELOPMENT PRODUCTION:4,800 tons of pellets
PER CENT OF FULL CAPACITY UTILIZATION: not available
US$ '000Total
(1978 prices)I. Investment Costs
Land 4.90Land Improvement 0.98Factory (1300 m2) 31.88Machinery & Equipment
pressing machine & 7.85accessories
motor, 160 h.p. 5.89motors for conveyor 2.21transformer 9.81magnetic switch 3.43payloader 8.34scales 0.32carts 0.15
Sub-Total Machinery& Equipment 37.98
Total Investment Costs 75.75
Ip
CASSAVAEXAMPLE 1
Page 2 of 2
Representative Investment and Operating Costs
NOTE: These data are intended as representative only andunique to the time, country and circumstance of theidentified investment. Their applicability to othersituations may vary considerably.
US$ '000Total
(1978 prices)
II. Annual Full Development Operating Costs(excluding raw materials)
Fixed Costsadministration . 1.71depreciation 2.47repair & maintenance 3.24
Sub-Total Fixed Costs 7.42
Variable Costspacking materials 4.71other raw materials 0.65labor 3. 73utilities 8.35
Sub-Total Variable Costs 17.43
Total Operating Costs 24.85
DATA SOURCE: All information was adapted fromBlack, Ronald P. Wanawan P. and Sachee P.THAILAND: Cassava Pelletizing Technology,University of Denver Research Institute/U.S. Agency for International Development,December, 1979.
NOTES:1. Exchange rate - Thai Baht 20.39 - US $ 1.00
IMF International Financial Statistics, May, 19852. Data are net of contingencies.3. Full development production based on 200 working
days/year @ 24 tons/day.4. Foreign/local cost breakdown not available.
CASSAVAEXAMPLE 2
Page 1 of 2
Representative Investment and Operating Costs
PRODUCTION OF GARI FROM CASSAVA TUBERS
Establishment of a factory to produce gari from freshcassava tubers.
COUNTRY: Nigeria
NOTE: These data are intended as representative only, and areunique to the time, circumstance, and country of theidentified investment. Their applicability to other sit-uations may vary considerably.
ANNUAL FULL DEVELOPMENT PRODUCTION:
5,400 tons of gari
PER CENT OF FULL CAPACITY UTILIZATION: not available
US $ '000Total
(1983 prices)I. Investment Costs
Site Preparation 21.55Building 239.40Equipment 478.80Transport & Installation 13.41Installation of Utilities 222.64Drainage Facilities 14.36
Total Investment Costs 990.16
CASSAVAEXAMPLE 2
Page 2 of 2
NOTE: These data are intended as representative only, and areunique to the time, circumstance, and country of theidentified investment. Their applicability to other sit-uations may vary considerably.
US $ '000Total
(1983 prices)
II. Full Development Annual Operating Costs(excluding raw materials)
Fixed Costsadministration 6.44insurance 19.85maintenance 14.48
Sub-Total Fixed Costs 40.77
Variable Costslabor 26.28fuel 8.31utilities 5.36packaging materials 10.19
Sub-Total Variable Costs 50.15
Total Operating Costs 90.92
DATA SOURCE: Nyanin Ph.D., Ohene OwusuSome Economic Aspects of Industrial Processing ofCassava. Paper presented at FAO Workshop onProcessing Technologies for Cassava and OtherTropical Root Crops, 28 Nov. - 2 Dec., 1983,Abidjan, Ivory Coast. -
NOTES:1. Data are net of contingencies.2. Full development production based on 36 work weeks per year,
at five shifts per week producing three tons of gari/shift.3. Costs converted from Naira to US $ at exchange rate of
US $ 1.49 - Naira 1.00.
CASSAVAEXAMPLE 3
Representative Investment and Operating Costs
CASSAVA CHIPPER AND DRYING FLOOR
Construction of a cassava chipping machine, powered by a 3-hpgasoline engine, and of a 100 m2 concrete drying floor orbamboo trays and frames for drying cassava.
COUNTRY: Colombia
NOTE: These data are intended as representative only and are uniqueto the time, country and circumstance of the identifiedinvestment. Their applicability to other situations may varyconsiderably.
US$ '000Total
(1977 prices)I. Investment Costs
Cassava Chipping Machine 220.003-hp Gasoline Engine 180.00Total 400.00
Concrete Drying Floor - 100 m2
cement (forty 50 kg sack) 60.00sand (5 m3) 15.00gravel (10 m3) 41.00black pigment (20 kg) 28.00wood boards (30) 33.00
Total Concrete Drying Floor 177.00
Bamboo Trays and Frame
(60 trays at 1.85 x 0.90 x0.025 m/tray)wood (42 boards) 113.40one inch chicken wire 60.50
(3.2 0.90 x 36m rolls)mosquito netting (plastic) 43.70
* (3.8 30 x 0.90 m rolls)nails (10 kg) 8.20bamboo (255 m) 35.70
Total Bamboo Trays and Frame 261.50
DATA SOURCE: Rupert Best, Cassava Drying, Cassava InformationCenter, Centro Internacional de AgriculturaTropical, Cali, Colombia, 1977.
NOTES:1. Data are net of contingencies.2. Operating costs information is not available.3. Foreign/local cost breakdown is not available.
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ANNEX II:
CONVERSION TABLES
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METRIC SYSTEM
Square kilometer sq km or km2;1,000,000 square meters;0.3861 square mile.
Hectare ha;10,000 square meters;2.47 acres.
Hectoliter hl;100 liters; 3.53 cubic feet; 2.84 bushels;
Liter 1;1 liter; 61.02 cubic inches; 0.908 quart(dry); 1.057 quarts (liquid).
Deciliter dl;0.10 liters; 6.1 cubic inchs; 0.18 pint(dry); 0.21 pint (liquid).
Centiliter cl;0.01 liters; 0.6 cubic inch; 0.338fluidounce.
Metric ton MT or t;1,000,000 grams; 1.1 US tons.
Quintal q;100,000 grams; 220.46 US pounds.
Kilogram kg;1,000 grams; 2.2046 US pounds.
Gram g or gm;1 gram; 0.035 ounce.
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WEIGHTS AND MEASURES
avoirdupois
Ton: short ton 20 short hundredweight, 2000 pounds;0.907 metric tons;
long ton 20 long hundredweight, 2240 pounds;1.016 metric tons.
Hundredweight cwt;short hundredweight 100 pounds, 0.05 short tons; 45.359
kilograms;long hundred weight 112 pounds, 0.05 long tons; 50.802
kilograms.
Pound lb or lb av; also *;16 ounces, 7000 grains; 0.453 kilograms.
Ounce oz or oz av;16 drams, 437.5 grains; 28.349 grams.
Dram dr or dr av;27.343 grains, 0.0625 ounces; 1.771 grams.
Grain gr;0.036 drams, 0.002285 ounces; 0.0648 grams.
Trov
Pound lb t;12 ounces, 240 pennyweight, 5760 grains; 0.373kilograms.
Ounce oz t;20 pennyweight, 480 grains; 31.103 grams.
Pennyweight dwt also pwt;24 grains, 0.05 ounces; 1.555 grams.
Grain gr;0.042 pennyweight, 0.002083 ounces; 0.0648 grams.
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ANNEX III:
TOXIC SUBSTANCES IN CASSAVA AND PROCESSEDCASSAVA PRODUCTS
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When the cells of cassava roots are ruptured, an enzyme isreleased which converts glycocides, which also occur in thecells, into hydrocyanic acid (also known as prussic acid).Although this is potentially fatal, raw roots are seldom eatendue to the bitterness of the hydrocyanic acid and the generalunpalatability of raw cassava. If normal preparation methodsinvolving high temperatures are used in cooking, the hydrocyanicacid is driven off leaving the food safe for consumption.However, in areas where large amounts of cassava are consumed ona regular basis, small regular intake of hydrocyanic acid canresult in chronic cyanide toxicity.
The problem is accentuated if the diet is deficient in iodine andprotein, especially animal protein, as the body requires bothiodine and sulphur (from sulphur-bearing amino acids) to detoxifycyanide in the bloodstream. Chronic cyanide toxicity is linkedwith goiter in women and neurological disorders in children.Additional iodine in the diet and a proper balanced diet issufficient to overcome the problem in high-risk areas.
Most processed cassava products have been roasted or boiledadequately. However, some of the meals made from sun-driedcassava, which has not been soaked, may represent a healthhazard, especially if it is not cooked throoughly before eating.Sun drying is sufficient to drive off any free hydrocyanic acidin the chips at the time of drying. It does not denature theenzymes responsible for the release of the acid, and so thereaction can continue once the dried -cassava is moistened eitherprior to cooking or in the stomach.
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