| Résumé | Several forms of energy, such as hydrogen gas, butanol, biogas, and ethanol can be produced from renewable, biological resources. However, many bioenergy technologies are currently at the lab scale and the list of commercial operations successfully producing bioenergy in Canada is much shorter. Currently, Canada's bioenergy production is dominated by biofuels such as ethanol and biodiesel, biomass for combustion and the use of anaerobic digesters for biogas production. Bioenergy production in Canada is relatively new, especially in comparison to other renewable energy technologies like hydroelectricity, and therefore opportunities exist to improve bioenergy's economic and environmental impact. One route for improvement is through the valorization of co-products, and our efforts to use fungi to convert biodiesel wastewater and biodiesel derived crude glycerol to the value-added product single cell oil is reviewed. Wastewater is generated during biodiesel production through water washing of the unfinished biodiesel, and COD values for biodiesel wastewater are reported to range from approximately 31,000 to 590,000 mg L-1 . Glycerol is generated in biodiesel production during the tranesterification reaction of intact triacylglycerol molecules with an alcohol and a strong base. This glycerol is a crude co-product, and can contain high levels of methanol, residual oils and water. Cultivation of the newly described oleaginous fungus Galactomyces geotrichum in 50 g L-1 crude glycerol, 10 g L-1 casein and 200 mL L-1 biodiesel wastewater yielded fungal biomass with an average single cell oil content of 51.1%. We also review our data on the use of microalga Nannochloropsis granulata as a feedstock for anaerobic digestion. This work was completed in a 2.2 m3 pilot anaerobic digester and is unique as it is much larger in scope than the vast majority of literature sources reporting on the use of algae in anaerobic digestion applications. The use of N. granulata as a co-digestion substrate with swine manure reduced the methane yield as compared to swine manure alone. Algal biomass added at 0.5 kg volatile solids per day, 1.1 kg volatile solids per day and 1.6 kg volatile solids per day reduced methane yield by 48.4%, 55.9% and 64.7% respectively. The observed reductions may have been due to inhibitory metabolites produced during algal digestion or because of recalcitrance of the algal cell wall. The digester inoculum was not pre-adapted to microalgae degradation and this may have also played a role. Use of algal biomass as a feedstock for anaerobic digestion is still in its infancy, and biomass pre-treatments, different algal strains or different digestion techniques could be needed for the successful utilization of algae. Microalgae have other positive attributes including the ability to remediate waste streams and recycle nutrients as well act as a single source for multiple products and more research is needed in order to successfully exploit this versatile feedstock. |
|---|
