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 ABSTRACT Garri is a popular food widely eaten in West Africa, including Nigeria.
It is produced from the enlarged root of the cassava plant, Manihot esculenta,
Crantz. The root is rid of outer peels, which could constitute up to 10
% by weight of the root, to expose the white inner fleshy portion which
is then grated to produce a mash. The mash is placed in cloth bags and
allowed to ferment for 18 - 24 hrs. Heavy objects are also placed on the
bags to squeeze fluid out of the cassava mash. At the end of the fermentation
period the mash is heated to
Two important wastes are generated during the processing of cassava for garri production, namely, the cassava peels and the liquid squeezed out of the mash. This paper deals with a proposed integrated system for the disposal of the cassava peels and the liquid expressed of the fermenting mash. It is proposed to crush the peels and to allow this to ferment
with the liquid squeezed out from the mash. The peels contain toxic cyanogenic
glucosides, and the liquid contains a heavy load of microorganisms capable
of hydrolyzing the glucosides. The resulting product can be dried and used
as animal feed, whose wastes can be used biogas production, and the
effluent and sludge as fertilizers for the cassava plant; thus providing
an integrated system.
INTRODUCTION The enlarged root (marked "A" in Photo 1) of the cassava plant,
Manihot esculenta Crantz, is widely eaten in the tropics. In West Africa
and parts of the Caribbean, a granular food known as garri (farinha in
Caribbean) is produced by fermenting mash produced from the grated roots
and heating the fermented mash in a dry basin (Okafor and Ejiofor, 1990).
Before crushing, the roots are peeled to rid them of two outer coverings:
a thin brown outer covering, and a thicker leathery parenchymatous inner
covering. These peels are regarded as wastes and are usually discarded
and allowed to rot. As a rough estimate, about 10 million tonnes of cassava
are processed for garri annually in Nigeria alone. Since these peels could
make up to 10 % of the wet weight of the roots, they constitute an important
potential resource if properly harnessed by a bio-system such as the one
to described in this paper.
 For the fermentation of the roots, the white inner fleshy portion (marked "B" in Photo 1) of the cassava roots exposed after peeling, is grated mechanically or by a hand grater, packaged in cloth bags and rid of fluid by placing heavy objects on the bags containing the mash. The fluid squeezed out of the bags is allowed to drain freely into the soil to waste. This fluid contains large amounts of lactic acid and yeasts which several studies have shown to be responsible for the fermentation of the cassava mash (Ngaba & Lee, 1979; Okafor, 1977; Okafor & Ejiofor, 1990; Okafor & Uzuegbu, 1987). This paper discusses the potential utilization/processing of the
two wastes into animal feed, which upon utilization by farm animals would
result in faecal wastes which can be used to produce biogas, as well as
to fertilize the cassava plant itself.
PROCESSING OF THE PEELS
 Cassava peels derived from garri processing are normally discarded as
wastes and allowed to rot (Photo 2). No economic value is placed on them.
They normally contain about 40 %. It is suggested before putting them to
the use suggested in this paper, they should first be sun-dried to reduce
the moisture content to about 10 % or less. Dried in this manner, they
would be better susceptible to grinding; they would also store better.
The dried peels would now be milled for use in the next stage. (Photo 3)
 Cassava mash being prepared for garri production is put in bags and freed of liquid by pacing heavy objects on the bags (Photo 4). Microorganisms are not normally inoculated into the mash, and the fermentation is thus spontaneous. However, for this work a deliberate inoculation of three microorganisms is proposed. These microorganisms are Lactobacillus delbruckii, Lactobacillus coryneformis and Saccharomyces sp, which were found among 214 organisms isolated from soil, utensils, grating machines etc, associated with cassava mash production, to be the highest producers of linamarase, lysine, and amylase (Okafor et al, 1998 a). The liquid squeezed out of the mash inoculated with these organisms will be expected to contain large numbers of the inoculated organisms. The ground peels will now be mixed with the liquid from the fermenting mash and mixed thoroughly. The white inner peels are known to contain the highest quantities of the cyanogenic glucoside, linamarin, in the entire root, and the organisms will break down this linamarin. The amylase produced by the organisms will break down any starch granules escaping with the fluid, and the lysine will provide nourishment for the organisms. PRODUCTION OF ANIMAL FEED FROM THE TWO CASSAVA WASTES The thin brownish outer peel consists of lignified cellulosic material, whereas the white inner portion consists of parenchymatous material which contains most of the toxic cyanogenic glucosides. The mixture should be allowed to ferment for about 48 hr, during which a slurry rich in sugars, lysine, and protein derived from the microbial biomass, will result. Lysine is usually short in animal feed unless components such as soybean cake are present. The resulting material will be mixed with other feed components (as may be necessary) and fed to pigs. BIOGAS PRODUCTION Biogas production is a well-known process and will not be described in any detail in this presentation. The pig droppings will form the main basis for biogas production. MANURING OF CASSAVA PLANTS WITH EFFLUENT AND SLUDGE FROM BIOGAS DIGESTER The manuring of the cassava plant with the effluent and sludge from biogas digester is a potential agronomic practice for Nigeria as this is a common practice in many countries too where biogas technology has been successfully been implemented and integrated with agriculture and aquaculture. CONCLUSION. In the process described above wastes from cassava which would normally be thrown away can be converted into value-added components in terms of pig meat, methane (biogas), and a better harvest of cassava roots themselves .  REFERENCES Ngaba, P R and Lee, J S (1979) Fermentation of cassava (Manihot esculenta Crantz ) J Fd Sci, 44, 1570 - 1572. Okafor, N (1977) Microorganisms associated cassava fermentation for garri production. J Appl Bact 42, 279-284. Okafor, N & Ejiofor, A O (1990) Rapid detoxification of cassava mash by a yeast simultaneously producing linamarase and Amylase. Process Biochem Inter, 25, 82-86. Okafor, N & Uzuegbu, J O (1987) Studies on the contributions of micro-organisms on the organo-leptic properties of garri, a fermented food derived from cassava (Manihot esculenta Crantz). J Fd Agric 2, 99-105. Okafor, N, Umeh, C, and Ibenegbu, C (1998) Amelioration of garri, a fermented food derived from cassava, Manihot esculenta Crantz, by the inoculation into cassava mash, of microorganisms simultaneously producing amylase, linamarase, and lysine. World Journal of Microbiology and Biotechnology. In press. |
