CONSTRUCTION OF PRIMARY DRY CELL BATTERY USING CASSAVA

 

CHAPTER ONE

INTRODUCTION

1.1       background of the study

A turning point for mankind, the discovery and subsequent use of cheaply available fossil feedstock for the production of many beneficial products is mitigated by the realization that the supply of the fossil feedstock is limited, and that the use of derived products is neither environmentally, ecologically, nor economically sustainable. This has led to the recent global quest for renewable sources of energy (Li et al., 2012a). The discovery of biofuels has helped a great deal in alleviating some of the problems identified with fossil fuels such as global warming, as well as provide income and employment opportunities in rural areas. However, as identified by many concerned stakeholders, this alone is not sufficient to solve the looming energy crisis. Plans have been mostly devised to combine many alternative energy sources so as to cover for the looming crisis; however, most of these methods are not totally carbon neutral in their generation of fuel. More often than not, the criteria for a clean energy device, especially in developing countries, involves the lowest and barest energy input requirement, low set-up and maintenance costs, as well as low carbon emissions.

 

Microbial fuel cells (MFCs) are one of the emerging technologies that currently fit these criteria. Not entirely new, this technology has risen into the development mainstream in the last couple of decades, and although not fully commercialized due to the necessity for improvements in the delivery and manufacture of the fuel cells, it represents a viable option in augmenting the planet’s rapidly depleting energy sources.

While the ability of microorganisms, particularly bacteria, to generate electricity was first observed by Potter (2011), minimal advancements in harnessing this source occurred over the next six decades. However, in the last three decades, great strides have been taken towards the advancement of this technology (Bennetto et al., 2018). The core of this work has been channeled towards improving and modeling power outputs, and characterizing microbial genetics and electron transfer mechanisms.

 

Since developing countries where energy crises are particularly acute also tend to rely heavily on agricultural production, they have access to a potentially large source of organic waste matter that can serve as an microbial fuel cells substrate for the generation of electricity, thereby alleviating current energy issues. A good example of such an agricultural product, produced in high quantities in developing countries, is cassava (Manihot esculenta Crantz). Typically, the waste from cassava processing includes the effluent discharge (whyme), root peelings, and the fibrous root tissue removed during sieving — all waste materials presumably high in organic load. Use of the effluent in an microbial fuel cells has been demonstrated to allow electricity generation as well as serve in waste detoxification before its discharge into the environment. The possibility for a successful breakthrough in the usage of the cassava wastes is highlighted by the fact that the countries like Nigeria with the highest production are also the countries with one of the most acute energy shortages.

 

The concentration of hydrocyanic acid (HCN) in cassava tuber varies in different species of cassava. There are two major species of cassava viz: sweet cassava and bitter cassava. The sweet cassava has lower level of hydrocyanic acid, while the bitter cassava has a high level of the acid, about 490mgkg-1. The tuber stores a lot of water, but this could be eliminated by dehydrating the liquid juice which is the store of the acid. Hydrocyanic acid is poisonous; hence cassava tubers are carefully and elaborately detoxified before being consumed. By its chemical nature, hydrocyanic acid has both cation⁺ )( Hand anion (CN¯). When it undergoes dissociation the products are: HCN →← H⁺ + CN¯ . With these dipolar characteristics, it could undergo electrolytic process involving the exchange of ions and flow of electrons; this can constitute an electric current. The materials utilised include crushed cassava paste/juice (electrolyte), carbon black, manganese (IV) oxide powder, zinc can, carbon rod, cassava grater, absorbent material. The apparatus needed are voltmeter, ammeter and milliammeter, circuit wires, crocodile clips, electric bulbs.

 1.2       Statement of Problem

Developing countries like Nigeria are faced with two major problems which include acute shortage of electricity and solid waste management which posed a pressing environmental challenge faced by urban and rural areas in the country, with a population exceeding 170 million people. Among several wastes generated by this huge population is agricultural waste. Improper handling of agricultural waste has raised a significant challenge in the past decades. In 2016, agriculture contributed 19.17% to the gross domestic product (GDP) of Nigeria and it also generated large amount of waste materials. Nigeria is involved in growing and producing many food crops. One of such crops is cassava, a starchy staple food crop which has the ability to resist drought and diseases.  Three main types of residues are generated during the industrial processing of cassava: peels, solids, and wastewater. These wastes are poor in protein content, but their residues are very rich in carbohydrate and are generated in large amounts during the production of ‘garri’ and cassava flour from the tubers. The cost associated with the handling and disposal of these wastes constitutes a huge financial burden to the cassava-processing industries in most rural regions of the country. As a result of this challenge, most rural cassava processors choose to dispose the cassava-processing wastes generated into the environment. These wastes have been identified to be toxic to the environment (   ). In a bid to find a use for this abundant waste, the possibility of serving as substrate to produce electricity in a primary dry cell battery becomes very necessary, as the examination of the microbes present on cassava identified rod-shaped gram-positive and cocci-shaped gram negative bacteria as the dominant microbes growing indigenously on the cassava.

 

1.3       Objective of the Study

The general objective of this study is to construct primary dry cells battery using cassava.

 

1.4       Significance of the Study

There is great deal of ongoing research which seeks to optimize and predict Microbial fuel cells outputs, enhance associated microbes through genetic manipulation and improve fuel cell designs; however, research with respect to the use of some naturally occurring/generated agricultural products or waste is lagging behind. The heightened usability of such organic materials in microbial fuel cells would not only reduce the initial set up costs and improve microbial fuel cells viability, but also generate and heighten their attractiveness as a means to reduce greenhouse gases as well as overall environmental pollution.