Catalytic Hydrothermal Liquefaction of Water Hyacinth Using Fe3O4/NiO Nanocomposite: Optimization of Reaction Conditions by Response Surface Methodology

This research aimed at optimizing the reaction conditions for the catalytic hydrothermal liquefaction (HTL) of water hyacinth using iron oxide/nickel oxide nanocomposite as catalysts. The iron oxide/nickel oxide nanocomposite was synthesized by the co-precipitation method and used in the hydrothermal liquefaction of water hyacinth. The composition and structural morphology of the synthesized catalysts were determined using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic absorption spectroscopy (AAS). The particle size distribution of the catalyst nanoparticles was determined by the Image J software. Three reaction parameters were optimized using the response surface methodology (RSM). These were: temperature, residence time, and catalyst dosage. A maximum bio-oil yield of 59.4 wt% was obtained using iron oxide/nickel oxide nanocomposite compared to 50.7 wt% obtained in absence of the catalyst. The maximum bio-oil yield was obtained at a temperature of 320°C, 1.5 g of catalyst dosage, and 60 min of residence time. The composition of bio-oil was analyzed using gas chromatography-mass spectroscopy (GC-MS) and elemental analysis. The GC-MS results showed an increase of hydrocarbons from 58.3% for uncatalyzed hydrothermal liquefaction to 88.66% using iron oxide/nickel oxide nanocomposite. Elemental analysis results revealed an increase in the hydrogen and carbon content and a reduction in the Nitrogen, Oxygen, and Sulphur content of the bio-oil during catalytic HTL compared to HTL in absence of catalyst nanoparticles. The high heating value increased from 33.5 MJ/Kg for uncatalyzed hydrothermal liquefaction to 38.6 MJ/Kg during the catalytic HTL. The catalyst nanoparticles were recovered from the solid residue by sonication and magnetic separation and recycled. The recycled catalyst nanoparticles were still efficient as hydrothermal liquefaction (HTL) catalysts and were recycled four times. The application of iron oxide/ nickel oxide nanocomposites in the HTL of water hyacinth increases the yield of bio-oil and improves its quality by reducing hetero atoms thus increasing its energy performance as fuel. Iron oxide/nickel oxide nanocomposites used in this study are widely available and can be easily recovered magnetically and recycled. This will potentially lead to an economical, environmentally friendly, and sustainable way of converting biomass into biofuel.

Production of Fuel Briquettes from Bamboo and Agricultural Residue as an Alternative to Charcoal

The study was done to explore the potential of producing fuel briquettes that could meet the need for energy in Uganda, especially Kampala city. The primary objective of this work was to produce fuel briquettes from homogeneous and heterogeneous combinations of carbonized maize cobs, Bamboo poles and charcoal dust. For the primary objective to be achieved, the main activities which were performed included;chopping bamboo poles, sorting maize cobs, carbonization, crushing, binder preparation, mixing, extrusion, drying and quality assessment of the fuel briquettes. The maize cobs and charcoal dust used for this work were purchased from the farmers and charcoal sellers respectively from the districts of Luwero and Nakaseke. Bamboo poles were provided by Divine bamboo group. The homogenous combinations included 100% maize cob char, 100% bamboo char and 100% charcoal dust. Heterogeneous combinations included 75% bamboo char + 25% charcoal dust and 25% bamboo char + 75% charcoal dust. The test results for both homogenous and heterogeneous combinations of fuel briquettes had ranges of moisture content 8% - 11%, Volatile matter 12% - 23%, Ash content 33% - 39%, Heating Value 16 - 22 MJ/Kg, Fixed Carbon 30% - 51% and moisture content 8% - 9%, Volatile matter 13% - 19%, Ash content 27% - 44%, Heating Value 16 - 18 MJ/Kg, Fixed Carbon 30% - 51% respectively. The test results for drop resistance, density and Compressibility strength for both homogeneous and heterogeneous combinations had ranges of 7% - 56%, 214 - 941 kg/m3, 0.077 - 0.544 N/mm2 and 12% - 28%, 869.1 - 958.3 kg/m3, 0.124 - 0.295 N/mm2 respectively. These results were within the ranges reported in the literature especially for the heterogeneous combinations. Therefore, there is the possibility to use bamboo woody feedstock in combination with other agricultural waste feedstock for the production of fuel briquettes. We can increase the quality and production of fuel briquettes by using alternative feedstock sources rather than degrading the environment through deforestation.

Hydrothermal Liquefaction of Water Hyacinth: Effect of Process Conditions and Magnetite Nanoparticles on Biocrude Yield and Composition

In this work, an efficient way of converting the water hyacinth to biocrude oil using magnetite nanoparticles (MNPs) as potential catalysts was demonstrated for the first time. MNPs were synthesised by co-precipitation and used in the hydrothermal liquefaction (HTL) of water hyacinth at different reaction conditions (temperature, reaction time, MNPs to biomass ratio and biomass to water ratio). The best reaction conditions were as follows: temperature— 320, reaction time—60 minutes, MNPs to biomass ratio – 0.2 g/g and biomass to water ratio – 0.06 g/g. HTL in presence of MNPs gave higher biocrude yields compared to HTL in absence of MNPs. The highest biocrude yield was 58.3 wt% compared to 52.3 wt% in absence of MNPs at similar reaction conditions. The composition of biocrude oil was analysed using GC-MS and elemental analysis. GC-MS results revealed that HTL in presence of MNPs led to an increase in the percentage area corresponding to hydrocarbons and a reduction in the percentage area corresponding to oxygenated compounds, nitrogenated compounds and sulphur compounds. Elemental analysis revealed an increase in the hydrogen and carbon content and a reduction in the nitrogen, oxygen and sulphur content of the biocrude when HTL was done in presence of MNPs compared to HTL in absence of MNPs. The nanoparticles were recovered from the biochar by sonication and magnetic separation and recycled. The recycled MNPs were still efficient as HTL catalysts and were recycled five times. The application of MNPs in the HTL of water hyacinth increases the yield of biocrude oil, improves the quality of biocrude through removal of hetero atoms, oxygen and sulphur compounds and is a potentially economical alternative to the traditional petroleum catalysts since MNPs are cheaper, widely available and can be easily recovered magnetically and recycled. This will potentially lead to an economical, environmentally friendly and sustainable way of producing biofuels from biomass.