UTILIZATION OF CASSAVA PROCESSING WASTE AS A VIABLE AND SUSTAINABLE STRATEGY FOR

MEETING CASSAVA PROCESSING ENERGY NEEDS: CASE STUDY FROM IBADAN CITY, NIGERIA

A.O. Coker*1 C.G. Achi1 and M.K.C. Sridhar2

1 Department of Civil Engineering, Faculty of Technology, University of Ibadan

2 Department of Environmental Health Sciences, Faculty of Public Health, University of Ibadan

*Corresponding author: cokerwale@yahoo.com

Abstract

Improper management of solid wastes and problems of pollution have been the bane of life of

many urban community residents in Nigeria. Waste generation is an inevitable fact of living.

With increase in population and industrial activities come the increase in waste generation. One

of such industries is the agro-food processing industries. In Nigeria, cassava is a food item

predominantly processed, being a starchy staple food crop which can be converted into myriads

of edible and industrial raw materials.

Recognising the importance of cassava food crop and its growing production rate in Ibadan,

south-western Nigeria, this study focused on evaluating the cassava production activities in six

selected cassava processing sites in the city. The cassava roots delivery rates, the waste

generation rates, waste composition, cassava processing energy needs and the attitudes of the

people towards cassava waste management were some of the issues investigated.

Results showed that the percentage and composition of solid waste (Peels and bagasse) and

liquid waste generated during cassava processing depends on the nature of the final product

and this varied also according to market demand of products. Fufu (cooked cassava paste after

fermentation) produced more liquid waste and baggase than cassava starch and garri (toasted

cassava granules). Fufu was produced more frequently than other products due to its much-

reduced production cost and high market demand as compared to other products. It was found

out that all of the solid wastes produced were organic in nature and can be recycled, recovered

and reused. Between 25 – 30% of the cassava peels and bagasse were utilized as feedstock for

livestock (goat and pigs) while the remaining 70 – 75% of cassava peels, bagasse and waste

effluent were discharged indiscriminately into nearby bushes and water bodies. The only source

of energy for processing fufu and garri is firewood which is usually obtained from cutting down

forest trees.

The study came up with a low-cost, sustainable strategy to provide an alternative renewable

energy source to firewood which will also ensure a proper solid waste management for the

cassava processing industries.

Keywords: Cassava waste, rural regions, sustainable development, renewable energy, Nigeria

1.0 Introduction

The provision of food to meet the world’s growing population has become a global concern in

recent times. Researchers and policy makers have explored and continued to exploit various

ways of providing the best crop-growing conditions and also the most efficient agricultural

food harvesting and processing techniques to meet this growing need for food. Fertile soils and

conducive crop-growing climate are some of the natural factors that promote food production.

Most developing Sub Saharan African countries are endowed with these natural factors and as

such are known to support the growth and production of so many food crops.

One of such crops is Cassava (Manihot esculenta), a starchy staple food crop, which is regarded

as a primary food security crop in Africa due to its resistance to drought and diseases. Cassava

provides a reliable and inexpensive source of carbohydrate for people in Sub-Saharan Africa,

especially in Nigeria where its production, processing and consumption is most predominant

and significant on a global scale (Westby, 2008)

Cassava roots can be processed into myriads of food items and raw materials for industries.

During cassava conversion processes for food such as garri (toasted cassava granules) or fufu

(cooked cassava paste after fermentation), energy and water needs are considered to be vital.

In rural regions of most developing countries, firewoods are usually employed as a heat energy

source for toasting garri and cooking fufu. The sole dependence on firewood for cooking and

toasting cassava products has consistently put pressure on the use of forest trees. This

dependence promotes felling of trees to meet up with the increasing cassava processing rate

and energy demand for cassava production and processing and consequently this practice can

be linked to deforestation.

Besides energy demand and water consumption, waste generation is a key environmental issue

in all food processing industries (EC, 2006) including cassava processing industries. The

continuous growth and thriving of cassava processing businesses in most developing sub-

Saharan African countries has resulted in the generation of large amounts of cassava processing

residues. Three main types of residues are generated during the industrial processing of

cassava: peels, bagasse (solid) and wastewater (liquid). These wastes are poor in protein

content, but are carbohydrate-rich residues and are generated in large amounts during the

production of ‘garri’ and cassava flour (which generates more solid residues) and starch (which

generates more liquid residues) from the tubers. The cost of treatment and disposal of these

wastes constitute a huge financial burden to the cassava processing industries in rural regions

of developing countries. As a result of this challenge, the rural cassava processors resort to

indiscriminate disposal of cassava processing wastes into the environment and water bodies

without any form of treatment. These wastes are known to have high levels of Chemical

Oxygen Demand, Biochemical Oxygen Demand and are often laden with suspended solids that

are considered to be toxic (Plevin and Donnelly, 2004, Barros et al, 2012). The disposal of

these toxic wastes without prior treatment leads to the alteration of the receiving water bodies

and ecological systems.

From the foregoing, there is a need for a better management and utilization of these waste

residues. Due to their rich organic nature, cassava residues can serve as ideal substrate for

microbial processes in the production of different products. Attempts have been made by

various researchers to produce products such as organic acid, flavour and aroma compounds,

methane and hydrogen gas, enzymes, ethanol, lactic acid, bio surfactant,

polyhydroxyalkanoate, essential oils, xathan gum and fertilizer from cassava bagasse, peels

and wastewater (Siddhartha et al, 2012). The use of cassava residues as feedstock for methane

(bioenergy) production could be a viable alternative to firewood.

It is against this backdrop that this study seeks to explore the potentials for utilizing an

integrated cassava production and waste management strategy, through cassava solid waste

reuse and bioenergy recovery, targeted at the cassava processors in the resource-limited sub-

Saharan African region, where cassava production is predominant.

2.0 Potential of producing bio-energy from cassava wastes and other biomasses in

Nigeria

2.1. Cassava roots production in Africa and Nigeria: some basic statistics

According to FAO (2006) estimates, world annual production of cassava roots stood at

approximately 226 million Metric Tonnes (MT), out of which 54% (122 million MT) are

produced in Africa. In this specific context, West African countries produce the majority of

cassava roots: 63 million MT, equal to 52% of the total African cassava production, followed

by Eastern Africa countries with a production of approximately 31 million MT (or 25% of

Africa’s total).

As shown in the table below, with a yearly production of approximately 45 million MT, equal

to 37% of the total cassava produced in Africa, Nigeria is the first African largest producer.

Table 1: Key Figures on Cassava Production in Africa

Cassava Production in the World

Geographic area MT %

World 226,337,396 100

Africa 122,088,128 54

Asia 67,011,365 27

Latin America & Caribean 37,041,521 16

Others 196,382 1

Cassava Production in Africa

Geographic area MT %

Africa 122,088,128 100

Western Africa 63,261,251 52

Eastern Africa 30,757,886 25

Middle Africa 28,057,653 23

Northern Africa 11,338 0

Major Cassava Production Countries in WCA

Country MT %

Africa 122,088,128 100

Nigeria 45, 721,000 37

DRC 14,974,470 12

Ghana 9,638,000 8

Benin 2,524,234 2

Ivory Coast 2,200,000 2

Congo 1,000,000 1

Source: FAOStat 2006

In Nigeria, the cassava-growing belt falls within three agro-ecological zones of the southeast,

southwest and the central areas. (FAO, 2005).

In most part of these zones, cassava is traditionally cultivated by smallholder farmers; in the same

way, its processing is usually done by small-scale processing units, scattered all over cassava

production areas.

In Ibadan (South-western Nigeria) for instance, as elsewhere in Nigeria, small farmers (mainly

males) are mainly responsible for growing cassava, which is a year-round crop.

Traditionally, the bulk of cassava products are processed by women at village level, working

independently or organised into informal groups or co-operatives. At this level of production, the

major products are garri, fufu, starch and lafun (dried cassava meal after fermentation)

Plate 1: Women Processing Cassava at Moniya, Ibadan

Cassava conversion processes

The flow charts below (figures 1 and 2) depict the processes involved in the production of Garri

or attieke, and starch respectively.

Fig 1 Flow chart of garri and attieke processing

Source FAO 2001

Fig 2 Flow chart for the conversion of Cassava to starch

Source FAO 2001

Solid waste is usually generated by all forms of cassava processing. For instance, solid waste

from cassava starch processing is divided into three categories: (i) Peelings from initial

processing, (ii) Fibrous by-products from crushing and sieving (pulp waste) and (iii) Starch

residues after starch settling. The weight of solid waste produced is usually between 10 –

25 % of the total weight of cassava root before peeling.

Renewable Energy Production from cassava wastes

Bio-methanation (biogas production) is a renewable energy technology where organic

materials e.g. animal manure, night soil, agricultural residues, Municipal Solid Waste

landfills and industrial effluents, are biologically fermented in the absence of oxygen to

produce flammable gas consisting predominantly methane (CH4) and carbon dioxide (CO2).

(Sridhar et al 2003). Combustible gases produced can be stored and turned into energy by

means of an electrical generator.

Literature is replete with various studies on the conversion of cassava peels mixed with other

substrates to generate biogas. Although biogas generation rates vary according to the kind of

substrate used and the ratio of mixture. For instance, Ofoefula et al, (2009) investigated

biogas production from blends of cassava peels mixed with some animal waste. The result

showed that the low biogas yield and slow onset of gas production / flammability of digested

cassava peels can be enhanced significantly when combined with animal wastes. The blend

with cow dung and poultry droppings had the fastest onset of gas flammability while that

with swine dung had the highest cumulative volume of gas production. Hence, he concluded

that cassava peels which is considered a nuisance can be converted to a useful source of

energy by combining it with these or any other animal wastes.

In a documented research (Eze, 2010) it has been demonstrated that anaerobic fermentation

is an environmentally friendly technology that could be used to generate biogas from cassava

peels. (Adelekan and Bamgboye, 2009) established the possibility of generating biogas from

cassava peels mixed in selected ratios with major livestock wastes. This was demonstrated

using a mix of cassava peels with poultry, piggery and cattle waste at different ratios, the mix

with piggery waste at the ratio of 1:1 produced the highest biogas yield.

Cuzin et al, (1992a).carried out anaerobic digestion of raw cassava peels using a 128 L plug

flow digester. The results showed that a biogas yield of 0.661 m3 per l kg volatile solids (VS)

was obtained. Energy-saving calculations showed that a bioreactor of 88 m3 is sufficient to

produce the methane necessary for drying one ton of cassava meal.

3.0 .Material and methods

Study Locations

Six cassava processing sites were visited in Ibadan, South western Nigeria to assess their

cassava processing operations. The sites are as follows: Moniya, Eleyele 1, Eleyele 2, Ojoo,

Agbowo, Egbeda.

Study Design

The methodology adopted to carry out this study includes the implementation of:

(i) field visits in Ibadan for collecting primary and secondary data from small and

medium-sized cassava industries,

(ii) face-to-face meetings with local cassava producers and processors, and assessment

of current practices

(iii) Assessment of daily cassava delivery and production rates

(iv) Characterization of cassava processing waste

The sites were randomly selected within Ibadan Metropolis. This was done so as to capture the

true picture of the current cassava processing scenario in Ibadan.

During data collection from the sites the following methods were employed.

1.) Key Informant Interview

2.) Direct Personal Observation

The following data were collected and used to make comparison as regards management and

waste disposal practices

1. Name/ Location of the cassava processing site

2. Operations and major cassava products

3. Challenges faced by the workers

4. Number of the workers and Scale of the processing system

5. Cassava processing rate

6. The volume of cassava wastewater effluent produced per unit Kg of cassava

7. The weight of solid waste produced per unit Kg of cassava

8. The amount and volume of solid and liquid waste produced respectively in a cassava

processing site

9. Comparative cost analysis of processing garri and fufu

10. Solid waste disposal method employed

The major products from cassava processing at these selected site are: Garri (Yoruba & Igbo

customary types), Fufu, and Lafun.

Conversion Processes

Cassava conversions processes involves all the processes employed to achieve a desired food

product from cassava tuber. The processes are as follows;

Garri Processing

Cassava tubers Peeling Washing Crushing Squeezing Sieving Frying

Fufu Processing

Cassava tubers Peeling Washing Fermentation Sifting Collection of sediments of

fermented cassava pulp and removal of excess water Cooking and subsequent pounding.

Lafun Processing

Cassava tubers Soak for a day for cyanide removal & slight fermentation peeling

Washing Crushing store in bags for 4days to allow for draining and further fermentation

Sun drying Crushing of dried crumbs into fine flour particles Prepare like semovita or

wheat meal.

Table 2 below shows the general practice recorded in six (6) randomly selected cassava

processing sites.

Assessment of the amount of waste produced

For the purpose of this experiment, two heaps were purchased so as to determine unit weight

of cassava and peels and also quantity of water used for cassava conversion processes into garri

and fufu.

Cost of one heap of cassava as measured by the farmers is 660 Naira (3.5 USD)

During the processing of cassava tubers >10% of the tubers result in peelings whereas 3.25%

pulp is produced

These common features were recorded in all the sites visited.

1. All the sites were located close to a stream or flowing river. This usually serves as a

final disposal point for the waste effluents.

2. No strict measures have been put in place for the management of solid and waste

effluent and as such are disposed indiscriminately or dumped without check, the vast

majority of cassava peels resulting from the processing of this root is either

abandoned nearby the processing sites, used as land fill or burnt. Between 20-25%

of cassava peels and fibrous waste (bagasse), are sun dried (after having being

washed, to remove dirtiness, and drained) and fed to pigs and goats

3. All the cassava processors depend solely on firewood as the only source of energy

for cooking and toasting cassava products

Table 2: General cassava processing and waste disposal practice in six different sites in

Ibadan

Site/para

meters

Qu

an

tity

o

f C

ass

av

a

sup

pli

ed

da

ily

(to

nn

es)

No

. o

f W

ork

ers

Fin

al

Pro

du

ct

So

lid

w

ast

e (p

eels

) d

isp

osa

l p

ract

ice

Fib

rou

s w

ast

e d

isp

osa

l p

ract

ice

Ca

ssa

va

wa

stew

ate

r d

isp

osa

l p

ract

ice

Pro

xim

ity

to r

iver

/ s

trea

m

wei

gh

t o

f p

eels

pro

du

ced

da

ily

Vo

lum

e o

f ca

ssa

va

wa

stew

ate

r

pro

du

ced

da

ily

(li

tres

)

Eleyele 1

(Temidire

)

6 – 8 200 –

250

Garri,

fufu &

starch

Peels

sold to

goat

rearers,

10 – 25

%

disposed

as waste

Disposed

of as

waste in

nearby

bushes

Discharg

ed inside

drains

and

waterwa

ys

leading

to

nearby

streams

Appro

x

200met

ers

1464 –

2049kg

>5712

Eleyele 2

(Ologuner

u road,

besides

kappan

filling

station)

1 – 2 20 –

30

Garri

& fufu

“

“

“

100m 244 –

512 kg

>1428

Ojoo

Barracks

4 – 5 70 –

80

Garri

& fufu

“

“

“

150m 976 –

1281kg

>3570

Moniya 3 – 5 40 –

50

Garri,

fufu,

starch

and

lafun

“

“

“

200m 732 –

1281

kg

>3570

Agbowo 4 – 5 80 –

100

Fufu

only

“

“

“

50m 976 –

1281

kg

>3570

Egbeda/N

ew ife

Road

7 – 9 500 –

550

Garri

fufu,

lafun

and

starch

“

25 % is

used as

pig feed,

the rest

are

disposed

in

nearby

bushes

“

100m 1708 –

2305.

kg

>6426

Plate 2: Cassava waste dumpsite

Plate 3: Typical cassava waste dumpsite

Identified Challenges and Energy needs in a cassava processing industry

According to the observations made, garri is fried in shallow cast-iron pans, or in the more

traditional areas in earthenware pans, over an open wood fire. The sieved cassava mash is

spread thinly in the pan in 2-3kg batches. A piece of calabash is often used to press the mash

against the hot surface of the pan but it must be scraped quickly and stirred constantly to keep

the material moving to prevent it burning until frying is completed when it reaches a

temperature of 80° to 85°C. The rapid heating partially gelatinises the gari which is dried during

the operation of frying. The process takes 30-35 minutes, with the moisture content of the final

product reduced to about 18% (Muchnik and Vivier 1984, Bencini 1991). During the frying

process, women are forced to lean on the roasting pans to turn around gari, thus inhaling the

smoke from the wood fire.

Plate 4: Women frying garri and cooking fufu using firewood

Plate 5: Bundles of firewood waiting to be used

During roasting operations, the challenge of maintaining a uniform heating using firewood was

observed. Smouldering of firewood exposes workers (mostly women) to toxic fumes.The

major issue being the pressure put on forest tress amidst the growing cassava production rates,

sole dependence on forest woods and current issues and trends as regards the global climate

change and the need to discourage deforestation. These are some of the issues that have

necessitated the search for alternative heating methods

Conclusion

In Nigeria, the problem of poor infrastructural facilities, especially of energy has been

identified among many other challenges currently facing subsistence cassava farmers. In order

to prevent environmental impacts arising from the huge waste streams generated during

cassava processing, various agricultural wastes should be gathered and converted to useful

products.

Based on the current assessment of cassava production rate and waste generation in Ibadan

city, there is a significant potential of utilizing cassava waste as a sustainable energy source for

heating and electrification of the cassava processing environment. The daily supply of cassava

waste (< 1 tonne) is sufficient to maintain a steady supply of substrates for biogas production

to meet up with basic energy demands. Furthermore, use of cassava wastes as substrate for

producing biogas would decrease the potential damages to forests as it reduces the overall

amount of firewood employed to produce heat (for cooking or other purposes).

Apart from the already stated energy need for heating, the bioenergy recovered could be used

to power generators, which will be used to light up the processing environment during dark

working hours. It would also provide a more convenient means of supplying water to the

cassava processors from wells. Most cassava processing industries usually suffer from scarcity

of water supply. In most cases, when water is available in wells, the women involved in cassava

processing would have to go through the drudgery of drawing water from these deep wells.

A sustainable supply of energy from the conversion of cassava waste would go a long way in

meeting these demands and make life easier for the rural farmers.

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