EVALUATION OF GASOLINE GENERATOR MODIFIED FOR BIOGAS UTILIZATION

ABSTRACT

This study addresses the design and modification of a gasoline generator to use biogas as an alternative fuel. The biogas was produced from fresh cow dung using a 10m³ fixed dome bio-digester and the produced biogas scrubbed to improve its energy content per unit volume.  A 1.0 kW Tigmax air-cooled gasoline generator was used for the investigation. The modification involved the fabrication and mounting of a simple external mixing chamber on the air-duct of the carburetor. A comparative analysis of the performance and combustion characteristics of the engine was evaluated separately with petrol and biogas using ten number 100 watts bulb as variable loads. Power output was optimal at 0 to 500 watts, while rapid power output deterioration was noticed above load condition of 500 watts. Overall rated power output reduction of 47% was observed in the study due mainly to high percentage of carbon dioxide. Exhaust gas temperature of the modified engine was comparable to the unmodified engine at load condition of 100-200 W, above 200 W the exhaust temperature lost the linearity. The exhaust emission revealed an improvement in emission at load range of 100-200 W, while 200 W the achieved superiority was lost due to an increased emission of CO and CO₂. Improving the scrubbing capacity of the purification and the external mixing chamber is here-by recommended.

CHAPTER ONE

1.0 INTRODUCTION

Energy is an integral component of any socio-economic development and a central factor for eliminating poverty in any society (Aderemi et al., 2009). In Nigeria located on the west coast of Africa, lack of access to wide range of modern energy services has remained a major barrier to improving key indicators of human development (Onafeso, 2006). Presently over 60% of the country population depends almost entirely on fire wood for cooking, heating and agro-processing activities. Petroleum products such as kigasoline and kerosene are marked by acute shortages and mounting price, with the product sold over 300% above the official pump price (Anonymous, 2008). Additionally, electricity which is the foundation of modern economies is non-available and if available is of poor quality or better still unreliable as less than 4,000 MW of the 7,876 MW installed electricity capacity is been generated (Sambo et al., 2010).

The introduction of mechanization and automation of food processing operations to drive conveyors, pumps, compressors and equipments like steam boilers, dryers, refrigeration equipments, ventilation and ovens has made the use of electricity critical in food industries. The non-availability of electricity supply or poor quality and unreliable nature of electricity supply by Power Holding Company of Nigeria (PHCN) has resulted in the increasing use of stand-by generators of various shapes and sizes (Adegoke and Akintude, 2000), which depends entirely on petroleum products as fuel.  In spite of the obvious advantage offered by these stand-by generators as a dependable solution to erratic power supply; the re-current perennial petroleum products scarcity and it rising cost contribute to high cost of production and loss of competitive advantage of processed foods when placed side-by-side with the imported ones (Aderemi et al., 2009).  Additionally petroleum products are finite in nature and their combustion bye products are major contributors to environmental degradation, climate change and global warmng (Das et al., 2000). Awareness of the limitations of the convectional fuel has enhanced the growing interest in the search for alternate cleaner and sustainable source of energy (Goodger, 1980).  Biogas which has a relatively significant comparative advantage due to the country huge biomass potential estimated to be about 8 x 10² MJ offers a promising sustainable solution (Nwoke and Okonkwo, 2006), however the wastes are usually dumped indiscriminately in landfills and unauthorized areas contributing further to environmental degradation and global warming (Adeola, 1996; Igbinomwanhia and Olanikpekun, 2009). In-order to reduce the current over dependence on fossil fuel, enhance energy availability and safeguard the natural eco-system in the face of Nigeria huge biomass potential (Garba and Sambo, 1992), biogas technology represents a viable alternative due to its simple technology and rural possible adaptability. (Diaho et al., 2005). Biogas is a fuel gas consisting of a mixture of methane (CH₄), carbon dioxide (CO₂) and traces of other gases, produced through microbial processes under anaerobic conditions from bio-degradable materials (Dennis and Burke, 2001). It’s a renewable high quality fuel that burns without leaving soot’s or particulate matter (Merchaim, 1992). Although biogas technology is yet to be adequately exploited in Nigeria and other Africa countries, the technology is a common place in countries like India, China, Pakistan, U.S.A and most European nations (Nwoke and Okonkwo, 2006). Utilization of biogas as fuel in internal combustion engines have witnessed a substantial breakthrough and improvement over the years (Mitzlaff and Mkumbwa, 1980; Mitzlaff, 1988; Huang and Crookes, 1998; Midkiff et al, 2001; Eshan and Naznin, 2005) Although biogas engines are presently not available in Nigeria markets; the crippling fuel prices and high cost of food processing coupled with the growing problem of food wastes management has remain an intractable national problem. Modifying these existing engines via rural adaptable technology to use biogas produced from these food wastes is an essential springboard for a shift to an eco-system friendly technology and sustainable rural development.

1.2 Problem Statement

Energy is a key instrument in accelerating economic growth, alleviating poverty and creating employment opportunities. Epileptic power failure has resulted in an over-dependence on generators driven by fossil fuel. Apart from this, fossil fuel is non-renewable and fast depleting and contributes to ecological degradation. Due to the endemic power shortage in the country and the current fragile enforcement laws governing waste management and use of generators in Nigeria, it is highly appropriate to researched on the use of biogas produced from food and other biodegradable wastes as alternative fuel source for internal combustion engines.

Gasoline generators represented almost 80% of the population source of independent energy supply. Given that over 70% of the country estimated 150 million people are involved in agricultural activities, and producing diverse varieties of plants and animal wastes. Transforming these wastes into biogas energy for use in existing gasoline generator represents a long-term sustainable approach to energy self-sufficiency and economic development.

1.3 Objectives

1.3.1 General Objective

The broad objective of this research was to adapt gasoline generator for biogas utilization for lower cost energy alternatives from available food and agro-allied wastes.

1.3.2 Specific Objectives

The specific objectives of this research were to:

• Modify a generator for biogas utilization
•  Evaluate the electricity voltage output and load bearing characteristics of the modified generator
•  Determine the exhaust gas emission and temperature in comparison to petrol based generator