ABSTRACT
This research work focused on the production of bio-based products and response optimization of bio-oil yield operating parameters from shea butter shell. The Thermogravimetry Analysis (TGA) was used to determine the thermal stability of the shea butter shell and found to be stable at temperature 400 °C. Also, for the bio-char produced, it was found to be stable at temperature 700 °C. Design of Experiment (DOE) was applied to establish optimal pyrolysis conditions for the biomass (shea butter shell) using 23 factorial design module of Response Surface Methodology (RSM)  available  in  Design  Expert®   Software  version  7.0.0.  Furthermore,  the  effect  of temperature  (300-600  °C),  residence  time  (10-60  min),  and  heating rate  (10-30  °C/min)  at constant feedstock mass of 100g per run was studied. The results of operating variable effects shows that bio-oil yield depends on significant variables of the process. Temperature and heating rate were found to be significant to obtain optimum bio-oil yield experimentally. Optimum yield of the  study was  51.50  %wt.  against  71.00  %wt.  of the  predicted  model.  Physicochemical analysis shows that the bio-oil has pH 3.14 and Heating values of 26.03 MJ/kg. The Gas Chromatogram revealed phenolic and carboxyl compounds are dominant in the bio-oil with alcohol, ketones, aldehydes and aliphatic hydrocarbons were equally present. Characterization of the bio-based products using Fourier-Transform Infra-Red (FTIR) revealed that bio-oil contains predominantly the organic functional groups of alkanes, alcohol, acids, aldehydes, ketones, some phenolic compounds and water impurities from the studies. Bio-char was characterized to determine  the  external  surface  area  and  BET  surface  area,  following  values  were  obtained 196.022 m2/g and 170.025 m2/g. Moreover, the values obtained for the pore volume and pore size of the bio-char were 0.0055cm3/g and 1.410 nm respectively. Bio-char from shea butter shell pyrolysis can be upgraded as potential adsorbent in waste water treatment as bio-adsorbent.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of Study
World patronage of a particular energy source depends on its availability, accessibility of technology, quantity of energy obtainable and fuel source. Fossil fuels is the primary source of energy supply worldwide. However, the use of fossil fuel energ is associated with emission of gases which have negative impact on the environment, finding an alternatives use of environmental friendly and economical viable renewable sources of energy and chemicals become necessary (Yaman, 2004; Smets et al., 2013).
Biomass is a renewable resource with great potential as an alternative to fossil fuels for supplying energy (Kumar et al., 2009; Garba et al., 2018). The potential of biomass to supply much larger amounts of useful energy with reduced environmental impacts compared to fossil fuels has stimulated substantial research and development of systems for handling, processing, and converting biomass to heat, electricity, solid, liquid and gaseous fuels, and other chemicals and products. The use of biomass to substitute fossil resources results in low sulphur dioxide emissions and almost no net atmospheric carbon emissions. Hence, it serves to mitigate greenhouse gases (GHG) and global climate change impact (Kumar et al., 2009).
Biomass has the potential to offer alternative sources of energy and chemicals, with agricultural wastes being better alternative to residues from consumable food products. Agricultural waste could be converted into chemicals by thermochemical conversion processes such as combustion, gasification and pyrolysis (Bulushev and Ross, 2011).
Shea butter shells are a major source of agricultural waste in West Africa and were used as raw material. It is non consumable for both man and animal. Therefore, use of shea butter shell as biomass for alternative  source of energy will help in the  environmental waste management
(Noumi et al. 2013; Ouedraogo, 2017).
However, the pyrolysis process is regarded as a promising process for the biomass utilisation at suitable operating process parameters. The process offers an important opportunity for the utilisation of the biomass from agricultural and forestry residues. (Auta et al., 2014).
Pyrolysis is a thermal conversion process in the absence of oxygen, at atmospheric pressure and temperature range of (300-600 °C). It has been practiced for thousands of years to produce charcoal by slowly heating at temperature ranging between 300 °C and 400 °C, which is known as slow pyrolysis (Tamer et al., 2018). High temperature and longer residence time favours the formation of gas than liquid fuels, this technology is known as gasification (Venderbosch, et al., 2011; Garba et al., 2018). Fast pyrolysis is the volatilisation of biomass at high temperature (400- 700 °C) and heating rate (50-1000 °C/min) under inert atmosphere (Demirbas et al., 2008).
Fast pyrolysis is an irreversible thermo-chemical process in which a biomass is thermally heated at high temperature in the absence of oxygen, whereby the biomass decomposed and can be separated into distinct fractions of bio-oil, char and gas. Fast pyrolysis processes produce 40-75 wt. % of liquid bio-oil, 15-25 wt. % of solid char, and 10-20 wt. % of non-condensable gases, depending on the feedstock used (Demirbas et al., 2008).
Many studies had been carried out to determine the operating parameters that influence the distribution of pyrolysis products as well its composition. Temperature, heating rate, residence time, biomass initial moisture content, particle size, and type of biomass are parameters that can affect the yield of the pyrolysis products (Hu et al., 2018). Therefore, it is important to study the effects of these parameters in order to optimise the pyrolyzed products from biomass shea butter shell (SBS) (Chadwick et al., 2014; Heidenreich and Foscolo, 2015).
1.2 Statement of Research Problem
The challenge of finding an alternative source of energy to meet global demand of energy need to be considered. Exploring the potential of Shea Butter Shell (SBS) biomass to produce bio-oil. However, protection of environment against emission from fossil fuel based energy with use of eco-friendly bio-energy from biomass has been consider for this research study.
1.3 Aim and Objectives
The aim of this study was to evaluate the potential of Shea Butter Shell (SBS) as a source of bio- based products. This was achieved through the following objectives:
1.  To characterise shea butter shell (SBS) for its proximate, ultimate and thermal properties; heating values and stability temperature.
2. To evaluate the effects of pyrolitic operating conditions (temperature, heating rate and residence time) on the yield of the bio-oil.
3. To evaluate the optimal devolatisation operating parameters (temperature, heating rate and residence time) on the yield of the bio-oil.
4. To determine the physicochemical properties of the bio-oil produces from shea butter shell (SBS).
1.5 Justification
It was projected that the global supply of energy reserves of fossil fuel may be exhausted by 2050 (McKendry 2002;  Sexana  et  al.,  2009).  Biomass  from  shea  butter  shell  (SBS)  have  high utilisation potential among renewable energy resources. It is cheap and largely available in most rural communities in Nigeria with no secondary usage after it has been removed from the kernel. Therefore, bio-oil from this biomass as a close substitute for the depleting fossil fuel, is very promising to halt the increase of carbondioxide, CO2 concentration in the atmosphere.
1.6 Scope of the Research
The scope of this research is to develop a novel scientific framework and operating parameters for the efficient conversion and utilisation of shea butter shell biomass to obtained optimal bio-oil yield in a laboratory scaled pilot plant (pyrolyser).
This material content is developed to serve as a GUIDE for students to conduct academic research
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