Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains viii, 100 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 86-88).

Energy issues in the United States are currently receiving a very high priority. There is a strong desire to replace fossil fuels with alternative sources of energy since fuel prices are rising dramatically, and for the harming effect on the environment. Biomass is one of the most promising alternative sources of energy. In this study, hydrothermal liquefaction with alcohol co-solvents was applied on giant miscanthus (Miscanthus giganteus) feedstock. All liquefaction experiments were conducted in 5500 series Parr® reactor. The most important parameters that affect the liquefaction process were studied. The yield of the liquefaction process was determined gravimetrically and the produced bio-oils were characterized. Bio-oil obtained at the optimum conditions was upgraded using different solid acid catalysts and the chemical composition for the upgraded bio-oil was determined. In a new study, the solid acids were added directly during the liquefaction process to produce upgraded bio-oil in one liquefaction/upgrading step.

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This study investigated In situ biodiesel production with supercritical methanol. A micro-algae based feedstock was used and obtained from a local water treatment plant situated just outside of Bethal, South Africa (S 26° 29’ 19.362” E 29° 27’ 11.552”). The wet feedstock was used as harvested with only the excess moisture being removed. Characterisation of the feedstock showed that a wide variety of macro-algae, micro-algae, cyanobacteria and bacterial species were present in the feedstock. The main algal species isolated from the feedstock were Nostoc sp. and Chlamydomonas. The feedstock was found to have a higher heating value (HHV) of 22 MJ.kg-1 and a lower heating value (LHV) of 16.03 MJ.kg-1 with an inherent moisture content of 270g.kg-1 feedstock. The protein and fat content of the feedstock was determined by the Agricultural Research Council (ARC) and found to be 370.1 g.kg-1 and 61.6 g.kg-1 on a moisture free basis respectively. The high protein and fat content gives a theoretical bio-yield of 430 wt%. The low lignin content and high cellulose and hemi-cellulose content indicated that the feedstock would be suitable for energy production. Three experimental sets were performed to determine the effect certain reaction parameters will have on the bio-char, bio-oil and biodiesel yields. The first set entailed hydrothermal liquefaction without the addition of methanol. The second set involved in situ biodiesel production with supercritical methanol, while both supercritical methanol and an acid catalyst were used during in situ biodiesel in the third set. For the first set of experiments the effect of temperature (240°C to 340°C in intervals of 20°C) on the crude bio-oil and bio-char yields were investigated. The highest bio-char yield was found to be 336g g char.kg-1 biomass at 280°C, while the highest crude bio-oil yield was 470.7 g crude bio-oil per kg biomass at 340°C. In the second set of experiments the dry biomass loading was kept constant at 500 g.kg-1 and the temperature varied (240°C to 300°C in intervals of 20°C) along with methanol to dry biomass ratio (1:1, 3:1 and 6:1). The optimum bio-oil yield of 597.1 g bio-oil per kg biomass for this set was found at 500 g.kg-1 biomass loading, 300°C and 3:1 methanol to dry biomass ratio. The highest bio-char yield was found to be 382.6 g bio-char.kg-1 biomass for a 1:1 methanol to dry biomass weight ratio set with 500 g.kg-1 biomass loading at 280°C. An increase in methanol ratio also led to an increase in crude bio-oil yields however the 3:1 methanol to dry biomass mass ratio was found to give the highest bio-oil yield and the purest biodiesel, with less unsaturated FAME. The 6:1 methanol to dry biomass mass ratio did however increase the FAME yield, which tends to show completion of the in situ production of biodiesel. This was also seen in the amount fatty acid methyl esters (FAME) present in the crude bio-oil as the degree of transesterification starts to increase with an increase in methanol. The FAME content was determined using gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS). During the last set of experiments the temperature (260°C to 300°C in intervals of 20°C) and methanol to dry biomass ratio (1:1, 3:1 and 6:1) was varied at a constant catalyst loading of 1 wt% of the dry biomass. The optimum yields achieved were 627 g crude bio-oil per kg biomass and 376 g bio-char per kg biomass at 300°C and 280°C, respectively. These yields were achieved at 500 g.kg-1 biomass loading and 6:1 methanol ratio. Compared to the experiments where no catalyst was used, a slight increase in the yield was observed with the addition of an acid catalyst. This might be due to the base metals present in the feedstock that can lead to saponification during transesterification without the addition of an acid catalyst. An overall improvement in the extraction of crude bio-oil was observed with in situ production compared to hydrothermal liquefaction. During in situ liquefaction, the bio-oil yield increased by 150 g crude bio-oil per kg biomass higher, while the bio-char yields did not significantly vary at the optimum point of 280°C this finding has a significant value for green coal research. The highest HHV for the bio-char of 27 MJ.kg-1 +/- 0.17 MJ.kg-1 was found at 280°C and a 3:1 methanol ratio. The HHV of the bio-char decreases with an increase in temperature as more of the hydrocarbons are dissolved and form part of the bio-crude make-up. The highest HHV recorded for the crude bio-oil was 42 MJ.kg-1 at a 6:1 methanol ratio, a temperature of 300°C and an acid catalyst. The crude bio-oil HHV, which increased with an increase in temperature, is well within the specifications of the biodiesel standard (SANS, 1935). The highest FAME yield of 39.0 g.kg-1 was obtained using a 6:1 methanol ratio and a temperature of 300°C in the presence of an acid catalyst. The crude oil contained 49.0 g.kg-1 triglycerides with alkenes (C13, C15 and C17) making up the balance. The purest biodiesel yield was achieved at 3:1 methanol to dry biomass mass ratio, as it had the lowest yield unsaturated methyl esters. The overall FAME yield increased with an increase in methanol ratio. The derivatised FAME yields were the highest during hydrothermal liquefaction (55.0 g.kg-1 biomass). The in situ production of biodiesel from waste water clarifier effluent stream was found to be possible. Further investigation is needed into sufficient harvesting methods, including the optimum harvesting location, as this will result in fewer impurities in the stream and subsequent higher yields. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Biochar, a carbon-rich and a potential solid biofuel, is produced during the liquefaction of biomass. Biochar can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. It is very important and advantageous to produce biochar under controlled conditions so that most of the carbon is converted. The main objective of the study was to investigate the effect of solvents, reaction temperature and reaction atmosphere on biochar production during the liquefaction of sunflower husks. The liquefaction of sunflower husks was initially investigated in the presence of different solvents (water, methanol, ethanol, iso-propanol and n-butanol) to study the effect of solvents on biochar yields. The experiments were carried out in an SS316 stainless steel high pressure autoclave at 280°C, 30 wt.% biomass loading in a solvent and starting pressure of 10 bar. Secondly, sunflower husks were liquefied at various temperatures (240-320°C) to assess the influence of reaction temperature on the biochar yield. Experiments were carried out under either a carbon dioxide or nitrogen atmosphere with a residence time of 30 minutes. Biochar samples obtained from sunflower husk liquefaction were structurally characterised by scanning electron microscopy (SEM) and Brunauer-Emmet-Teller (BET) analysis to compare surface morphological changes and pore structural changes at different reaction temperatures. Compositional analysis was done on sunflower husk biochar samples by proximate analysis, Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Elemental analysis. The results showed that biochar produced through the liquefaction of sunflower husks was significantly affected by the type of solvent used. The highest biochar yields were obtained when ethanol was used (57.35 wt. %) and the lowest yields were obtained when n-butanol was used as a solvent (41.5 wt. %). A temperature of 240°C was found to produce the highest biochar yield (64 wt. %). However, biochar yields decreased with increasing liquefaction temperature and the lowest yield was 41wt. % at 320°C. Temperature had the most significant influence on biochar yield in an N₂ atmosphere, while solvent choice had the most significant influence on biochar yield in a CO₂ atmosphere. Temperature also had an effect on the structure of biomass, as the SEM analysis shows the biochar became more porous with increasing temperature. Generally, results from the CO₂ adsorption analysis, suggested that CO₂ develops microporosity to a greater extent than N₂ reaction. The results of sunflower husk compositional analysis show that sunflower husks contain a high lignin content (34.17 wt. %), of which the high lignin content in biomass is associated with high heating value and high solid yield product. Sunflower husks as waste product can be used to produce useful products such as biochar through liquefaction, and biochar can be used to generate heat and as a soil amendment due to its high heating value and high porosity. While these preliminary studies appear promising for the conversion of sunflower husks to biochar, further studies are needed. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2014

This study investigated In situ biodiesel production with supercritical methanol. A micro-algae based feedstock was used and obtained from a local water treatment plant situated just outside of Bethal, South Africa (S 26° 29’ 19.362” E 29° 27’ 11.552”). The wet feedstock was used as harvested with only the excess moisture being removed. Characterisation of the feedstock showed that a wide variety of macro-algae, micro-algae, cyanobacteria and bacterial species were present in the feedstock. The main algal species isolated from the feedstock were Nostoc sp. and Chlamydomonas. The feedstock was found to have a higher heating value (HHV) of 22 MJ.kg-1 and a lower heating value (LHV) of 16.03 MJ.kg-1 with an inherent moisture content of 270g.kg-1 feedstock. The protein and fat content of the feedstock was determined by the Agricultural Research Council (ARC) and found to be 370.1 g.kg-1 and 61.6 g.kg-1 on a moisture free basis respectively. The high protein and fat content gives a theoretical bio-yield of 430 wt%. The low lignin content and high cellulose and hemi-cellulose content indicated that the feedstock would be suitable for energy production. Three experimental sets were performed to determine the effect certain reaction parameters will have on the bio-char, bio-oil and biodiesel yields. The first set entailed hydrothermal liquefaction without the addition of methanol. The second set involved in situ biodiesel production with supercritical methanol, while both supercritical methanol and an acid catalyst were used during in situ biodiesel in the third set. For the first set of experiments the effect of temperature (240°C to 340°C in intervals of 20°C) on the crude bio-oil and bio-char yields were investigated. The highest bio-char yield was found to be 336g g char.kg-1 biomass at 280°C, while the highest crude bio-oil yield was 470.7 g crude bio-oil per kg biomass at 340°C. In the second set of experiments the dry biomass loading was kept constant at 500 g.kg-1 and the temperature varied (240°C to 300°C in intervals of 20°C) along with methanol to dry biomass ratio (1:1, 3:1 and 6:1). The optimum bio-oil yield of 597.1 g bio-oil per kg biomass for this set was found at 500 g.kg-1 biomass loading, 300°C and 3:1 methanol to dry biomass ratio. The highest bio-char yield was found to be 382.6 g bio-char.kg-1 biomass for a 1:1 methanol to dry biomass weight ratio set with 500 g.kg-1 biomass loading at 280°C. An increase in methanol ratio also led to an increase in crude bio-oil yields however the 3:1 methanol to dry biomass mass ratio was found to give the highest bio-oil yield and the purest biodiesel, with less unsaturated FAME. The 6:1 methanol to dry biomass mass ratio did however increase the FAME yield, which tends to show completion of the in situ production of biodiesel. This was also seen in the amount fatty acid methyl esters (FAME) present in the crude bio-oil as the degree of transesterification starts to increase with an increase in methanol. The FAME content was determined using gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS). During the last set of experiments the temperature (260°C to 300°C in intervals of 20°C) and methanol to dry biomass ratio (1:1, 3:1 and 6:1) was varied at a constant catalyst loading of 1 wt% of the dry biomass. The optimum yields achieved were 627 g crude bio-oil per kg biomass and 376 g bio-char per kg biomass at 300°C and 280°C, respectively. These yields were achieved at 500 g.kg-1 biomass loading and 6:1 methanol ratio. Compared to the experiments where no catalyst was used, a slight increase in the yield was observed with the addition of an acid catalyst. This might be due to the base metals present in the feedstock that can lead to saponification during transesterification without the addition of an acid catalyst. An overall improvement in the extraction of crude bio-oil was observed with in situ production compared to hydrothermal liquefaction. During in situ liquefaction, the bio-oil yield increased by 150 g crude bio-oil per kg biomass higher, while the bio-char yields did not significantly vary at the optimum point of 280°C this finding has a significant value for green coal research. The highest HHV for the bio-char of 27 MJ.kg-1 +/- 0.17 MJ.kg-1 was found at 280°C and a 3:1 methanol ratio. The HHV of the bio-char decreases with an increase in temperature as more of the hydrocarbons are dissolved and form part of the bio-crude make-up. The highest HHV recorded for the crude bio-oil was 42 MJ.kg-1 at a 6:1 methanol ratio, a temperature of 300°C and an acid catalyst. The crude bio-oil HHV, which increased with an increase in temperature, is well within the specifications of the biodiesel standard (SANS, 1935). The highest FAME yield of 39.0 g.kg-1 was obtained using a 6:1 methanol ratio and a temperature of 300°C in the presence of an acid catalyst. The crude oil contained 49.0 g.kg-1 triglycerides with alkenes (C13, C15 and C17) making up the balance. The purest biodiesel yield was achieved at 3:1 methanol to dry biomass mass ratio, as it had the lowest yield unsaturated methyl esters. The overall FAME yield increased with an increase in methanol ratio. The derivatised FAME yields were the highest during hydrothermal liquefaction (55.0 g.kg-1 biomass). The in situ production of biodiesel from waste water clarifier effluent stream was found to be possible. Further investigation is needed into sufficient harvesting methods, including the optimum harvesting location, as this will result in fewer impurities in the stream and subsequent higher yields. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Biochar, a carbon-rich and a potential solid biofuel, is produced during the liquefaction of biomass. Biochar can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. It is very important and advantageous to produce biochar under controlled conditions so that most of the carbon is converted. The main objective of the study was to investigate the effect of solvents, reaction temperature and reaction atmosphere on biochar production during the liquefaction of sunflower husks. The liquefaction of sunflower husks was initially investigated in the presence of different solvents (water, methanol, ethanol, iso-propanol and n-butanol) to study the effect of solvents on biochar yields. The experiments were carried out in an SS316 stainless steel high pressure autoclave at 280°C, 30 wt.% biomass loading in a solvent and starting pressure of 10 bar. Secondly, sunflower husks were liquefied at various temperatures (240-320°C) to assess the influence of reaction temperature on the biochar yield. Experiments were carried out under either a carbon dioxide or nitrogen atmosphere with a residence time of 30 minutes. Biochar samples obtained from sunflower husk liquefaction were structurally characterised by scanning electron microscopy (SEM) and Brunauer-Emmet-Teller (BET) analysis to compare surface morphological changes and pore structural changes at different reaction temperatures. Compositional analysis was done on sunflower husk biochar samples by proximate analysis, Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Elemental analysis. The results showed that biochar produced through the liquefaction of sunflower husks was significantly affected by the type of solvent used. The highest biochar yields were obtained when ethanol was used (57.35 wt. %) and the lowest yields were obtained when n-butanol was used as a solvent (41.5 wt. %). A temperature of 240°C was found to produce the highest biochar yield (64 wt. %). However, biochar yields decreased with increasing liquefaction temperature and the lowest yield was 41wt. % at 320°C. Temperature had the most significant influence on biochar yield in an N₂ atmosphere, while solvent choice had the most significant influence on biochar yield in a CO₂ atmosphere. Temperature also had an effect on the structure of biomass, as the SEM analysis shows the biochar became more porous with increasing temperature. Generally, results from the CO₂ adsorption analysis, suggested that CO₂ develops microporosity to a greater extent than N₂ reaction. The results of sunflower husk compositional analysis show that sunflower husks contain a high lignin content (34.17 wt. %), of which the high lignin content in biomass is associated with high heating value and high solid yield product. Sunflower husks as waste product can be used to produce useful products such as biochar through liquefaction, and biochar can be used to generate heat and as a soil amendment due to its high heating value and high porosity. While these preliminary studies appear promising for the conversion of sunflower husks to biochar, further studies are needed. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2014

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The use and research of renewable fuels has become more important due to the connection between climate changes and the use of fossil fuels. With risks of decline in petroleum production derived from fossil fuels due to limitation of resources in the future, the renewable fuels are even more important in the transport sector. Research regarding gasification of biomass to create a syngas that can be upgraded to a biodiesel for cars is one of the approaches. By gasifying black liquor, it is possible to create a 100 % green fuel diesel. However, as this black liquor might be in limited quantities the idea to create a synthetic black liquor was sparked. The pulp industry where the black liquor originated from also has quantities of wastewater, containing a biomass sludge. Otherwise containing water in so large quantities that it is not possible to combust it without ending up with a negative energy output. One of the paths could be to recover the biomass from the sludge and convert it to a liquid similar to black liquor. Catalytic hydrothermal liquefaction has been recognized as a potential method. While biocrude is usually the target in hydrothermal liquefaction for direct upgrade to biofuel, the aqueous product could prove to be used for the gasification process. This would create a combined liquefaction-gasification process. Using model compounds possibly existing in the waste sludge, hydrothermal liquefaction was performed at different temperatures, together with varied alkali loads (K2CO3) and water the content to see how the different compounds reacted. Model compounds included cellulose and lignin as major compounds. Although the temperature was increased from 240 °C to 340 ° the lignin conversion was lower at 340 °C than at 240 °C. Re-polymerization took place and around 40 % of resulted in solid residue, while the remaining 60 % was partially converted to aqueous phase, oil phase or gas in the process. By not performing the hydrothermal liquefaction it is however possible to dissolve Kraft lignin directly in water and alkali. Cellulose showed an almost full conversion at 290 °C with similar results at 340 °C, with 4 – 5 % remaining as solid. At the higher temperature more gas was produced, which is not optimal for this process where liquid product is wanted. This suggest that 290 °C is enough for cellulose conversion in this process. Using an alkali load of 0.3 times the cellulose mass in the solution the final aqueous product contained about 26 % alkali, which is similar to black liquor. Increase the alkali to 0.9 times however increased the sought aqueous product, in both terms of energy and carbon content. Fiber sludge from a pulp mill, containing mainly cellulose, could therefore most likely be converted to a liquid product that is similar to black liquor for further upgrade