Biomass Valorization: Assessment and Characterization of Biomass Waste for Valuable Products.

Ezealigo, Uchechukwu (2022-04-15)

Main Thesis


Research in the use of biomass residues has a huge interest as their potentials span a wide range of applications. Processed residues are useful as green energy such as biofuel (pellets and briquettes), animal feed, antioxidants, and activated charcoal for filtration and even carbon capture. With this in mind, my doctoral research covers the assessment of biomass residues generated in Nigeria for bioenergy. Also, Ficus benjamina fruit, identified as a biomass waste, was characterized for its value addition in bioenergy application. The latter fruit was further characterized for its value as a potential feed substrate for animals as well as the chemical source for industrial applications. The results from the research within this framework include the following. First, a proper bio-resource assessment, particularly, biomass residues availability and potential were investigated. This is a key requirement for an efficient and functional bioenergy sector in Nigeria, proposing to generate biofuel from agro-waste materials. In this study, computational and analytical approaches with mild assumptions were employed to evaluate the bioenergy potential in agricultural residues, including municipal solid and liquid waste. This assessment was performed using data from 2008 to 2018. The available technical potential of 84 Mt yielded cellulosic ethanol and biogas of 14,766 ML/yr (8 Mtoe) and 15,014 Mm3/yr (13 Mtoe), respectively. The residues gave more biogas than cellulosic ethanol from the same amount of residue potential. The energy potential from residues in Nigeria may be tailored towards biogas production for diverse applications ranging from heat to electric power generation and therefore holds great potential in solving the current electricity crisis in Nigeria. It will also position the nation towards achieving the 7th sustainable development goal (SDG 7) on clean and affordable energy Secondly, having identified that some residues may be limited in supply due to seasonality and multiple applications for various purposes, there is a need to continue a search for more plant waste that is resourceful as a potential feedstock. Ficus benjamina (FB) is an ornamental plant that produces nonedible fruits considered as waste. These fruits have no defined application, hence, identifying the potential in these fruits for possible valorization is necessary. Detailed preliminary characterization was performed to determine its suitability as a biofuel feedstock. The whole fruit (pulverized) was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDS), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and bomb calorimeter. In addition, the physical, thermal, and chemical properties of FB fruits for potential biofuel application was determined using the proximate and ultimate analyses. Pulverized Ficus benjamina fruits (PFB) have a porous morphology that makes them less dense and a crystallinity index of 25.5%. The moisture, ash, volatile matter, and fixed carbon contents were 9.29, 6.26, 64.35, and 20.10%, respectively. The higher and lower heating values are 19.74 and 18.55 MJ/kg, respectively, and are comparable to other biomass feedstock. The results establish the possibility of using PFB as a solid biofuel. Thirdly, another possible approach in valorizing FB fruit focuses on other value products and benefits for livelihood. On this basis, the nutritional analysis, as well as the identification and quantification of micro and macro-nutrients and amino acid profile, were performed. HPLC and GC-MS were used to investigate the sugar profile of the water extract and the chemical content on the extracts obtained with solvents (ethanol, n-hexane, and ethyl-acetate), respectively. Found in FB fruits were: eighteen (18) amino acids, diverse micro- and macro mineral content, metabolizable sugars (such as galactose and glucose), and other chemicals, including phytochemicals. In addition, these fruits showed low anti-nutritional factors such as phytate and tannins. From these findings, FB fruits offer diverse biological potential and functions and may be a prospective bio-resource for animal feed. The high fiber content reveals rich lignocellulose for bowel bulkiness. This result indicates that the fruits of FB can offer health benefits and can serve as a biomaterial. Thus, FB fruits may possess the potential as an additive material for animal feed, and phytochemicals for industrial and pharmaceutical uses.