Steve S. Helle

Extraction and hydrolysis of levoglucosan from pyrolysis oil.

Fermentable sugar obtained from lignocellulosic material exhibits great potential as a renewable feedstock for the production of bio-ethanol. One potentially viable source of fermentable sugars is pyrolysis oil, commonly called bio-oil. Depending on the type of lignocellulosic material and the operating conditions used for pyrolysis, bio-oil can contain upwards of 10 wt% of 1,6-anhydro-beta-D-glucopyranose (levoglucosan, LG), an anhydrosugar that can be hydrolyzed to glucose. This research investigated the extraction of levoglucosan from pyrolysis oil via phase separation, the acid-hydrolysis of the levoglucosan into glucose, and the subsequent fermentation of this hydrolysate into ethanol. Optimal selection of water-to-oil ratio, temperature and contact time yielded an aqueous phase containing a levoglucosan concentration of up to 87 g/L, a yield of 7.8 wt% of the bio-oil. Hydrolysis conditions of 125 degrees C, 44 min and 0.5 M H(2)SO(4) resulted in a maximum glucose yield of 216% (when based on original levoglucosan), inferring other precursors of glucose were present in the aqueous phase. The aqueous phase contained solutes which inhibited fermentation, however, up to 20% hydrolysate solutions were efficiently fermented (yield=0.46 g EtOH/g glucose; productivity=0.55 g/L h) using high yeast inoculums (1 g/L in flask) and micro-aerophilic conditions.

Wood pellet fly ash and bottom ash as an effective liming agent and nutrient source for rye grass (Lolium perenne L.) and oats (Avena sativa)

Fly ash (FA) and bottom ash (BA) from a softwood pellet boiler were characterized and evaluated as soil amendments. In a greenhouse study, two plant species (rye grass, Lolium perenne L. and oats, Avena sativa) were grown in three different treatments (1% FA, 1% BA, non-amended control) of a silty loam soil. Total concentrations of plant nutrients Ca, K, Mg, P and Zn in both ashes were elevated compared to conventional wood ash. Concentrations of Cd, Cr, Pb, Se and Zn were found to be elevated in the FA relative to BA and the non-amended soil. At 28 d, oat above-ground biomass was found to be significantly greater in soil amended with FA. Potassium and Mo plant tissue concentrations were significantly increased by addition of either ash, and FA significantly increased Zn tissue concentrations. Cadmium and Hg tissue concentrations were elevated in some cases. As soil amendments, either pellet ash is an effective liming agent and nutrient source, but high concentrations of Cd and Zn in FA may preclude its use as an agricultural soil amendment in some jurisdictions. Lower ash application rates than those used in this study (i.e. <1%) may still provide sufficient nutrients and effective neutralization of soil acidity.

Increased biogas production in a wastewater treatment plant by anaerobic co-digestion of fruit and vegetable waste and sewer sludge - a full scale study.

Anaerobic digestion is a well established technology for the reduction of organic matter and stabilization of wastewater. Biogas, a mixture of methane and carbon dioxide, is produced as a useful by-product of the process. Current solid waste management at the city of Prince George is focused on disposal of waste and not on energy recovery. Co-digestion of fresh fruit and vegetable waste with sewer sludge can improve biogas yield by increasing the load of biodegradable material. A six week full-scale project co-digesting almost 15,000 kg of supermarket waste was completed. Average daily biogas production was found to be significantly higher than in previous years. Digester operation remained stable over the course of the study as indicated by the consistently low volatile acids-to-alkalinity ratio. Undigested organic material was visible in centrifuged sludge suggesting that the waste should have been added to the primary digester to prevent short circuiting and to increase the hydraulic retention time of the freshly added waste.

Pretreatment and enzymatic hydrolysis of recovered fibre for ethanol production

Recovered fibre from pulp mills represents a potentially significant feedstock for conversion to ethanol. Enzymatic hydrolysis of untreated recovered fibre (86.5 Kappa, 13% lignin) resulted in a hexose yield of approximately 23%, which highlighted the need for an effective pretreatment. Recovered fibre was pretreated as a substrate for enzymatic hydrolysis using oxygen delignification. An experimental design was used to optimize temperature (90-150 degrees C), caustic loading (2-10%), and reaction time (20-60 min). The post-delignification Kappa values ranged from 76.7 (11.5% lignin) under the mildest pretreatment conditions, to 20 (3% lignin) under the most severe pretreatment conditions. The effect of caustic load appears to have an increased effect at higher temperatures, with the Kappa numbers ranging from 76.7 (90 degrees C, 2% caustic, 20 min) to 56.0 (150 degrees C, 2% caustic, 20 min) and from 64.7 (90 degrees C, 10% caustic, 20 min) to 38.0 (150 degrees C, 10% caustic, 60 min). These changes in Kappa number reflect changes in the lignin fraction of 3.1% and 4%, respectively. Increasing the caustic load from 2% to 10% decreased the oxygen delignification yield from 93.5% to 87.9% at 90 degrees C and 20 min reaction time, and 80.3% to 74.7% at 150 degrees C. The effect of time on oxygen delignification yield was found to be most significant in the first twenty minutes, which correlates with the drop in Kappa number that was observed. The pretreated fibre was subjected to enzymatic hydrolysis using commercial enzymes Celluclast (80FPU/mL, 20.1CBU/mL) and Novozym (640.5 CBU/mL). A series of enzyme loadings ranging from 19 to 77 FPU/g were utilized on solids loading ranging from 20 to 100g (dry fibre)/L. Based on the pretreatment and hydrolysis results an empirical model was developed that can predict hydrolysis sugar concentrations based on the Kappa number, enzyme loading, and initial recovered fibre concentration.

Comparison of methane production by co-digesting fruit and vegetable waste with first stage and second stage anaerobic digester sludge from a two stage digester

Fruit and vegetable waste (FVW) was co-digested with first stage (FSS) and second stage anaerobic digester sludge (SSS) separately, over the course of 10 days, in batch reactors. Addition of FVW significantly increased the methane production in both sludges. After 10 days of digestion FSS + FVW produced 514 ± 57 L CH(4) kg VS(-1)(added) compared with 392 ± 16 L CH(4) for the SSS + FVW. The increased methane yield was most likely due to the higher inoculum substrate ratio of the FSS. The final VS and COD contents of the sewer sludge and FVW mixtures were not significantly different from the control values suggesting that all of the FVW added was degraded within 10 days. It is recommended that FVW be added to the first stage of the anaerobic digester in order to maximize methane generation.