Abstract
Pulp and paper mills have an abundance of underutilized waste wood with the potential for use as feedstock for the production of algae biomass. Enzymatic hydrolysates originating from pine softwood, southern hardwoods, and northern hardwoods pretreated using a proprietary process were tested for their ability to support heterotrophic growth of microalgae. Focusing on Hawaiian Chlorella and Scenedesmus species, growth varied with each type of wood hydrolysate, depending on the pentose (C5) and hexose (C6) sugar composition as well as process residuals such as organic acids and alcohols. Both species were able to utilize pentose sugars. A 1.6-fold higher biomass productivity, of 2.87 g/L/day in batch culture, was obtained on a medium with Bleached Southern Pine (BSP) hydrolysate than with the equivalent C5 and C6 model sugars alone, suggesting enhanced growth stimulation on wood hydrolysates compared to purified sugar streams. Biomass yield per gram of sugar consumed ranged from 0.45:1 in BSP hydrolysate to 1.15:1 in hardwood (similar to Southern Hardwood Chips) hydrolysate in which ethanol was also present. Oil refinery wastewater, on the other hand, represents a different source of feedstock with different nutrients to support algae biomass production. With oil refinery wastewater the goal is to reduce nutrient load for effluent outflow, resulting in the generation of usable biomass. An algae-wastewater pilot facility at an oil refinery was designed and constructed to mimic deep treatment ponds for polishing of wastewater through microalgae augmentation. Operation in batch mode using a mixed microbial consortium enriched for Scenedesmus showed 97% reduction in ammonia-nitrogen; 69% reduction in total nitrogen; 90% reduction in total phosphorous; and 100% reduction in total suspended solids.
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