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Keywords:

  • biofuels;
  • butanol;
  • algae;
  • fermentation;
  • ABE

Abstract

This study ascertained the technical potential of producing biofuel from a naturally occurring macroalgae. The algae examined grow in Jamaica Bay, New York City, on water containing nitrates, phosphates, and carbon dioxide that comes from the atmosphere. The process consisted of manual and mechanical harvesting, drying, grinding, and subjecting the algal matter to acid hydrolysis to extract carbohydrates to form an algal sugar solution. Fermentation of that solution to butanol was performed with butanol ultimately removed by distillation. An average of 15.2 g/L of reducing sugars was extracted in the hydrolysate showing that macroalgae (Ulva lactuca) have significant usable carbohydrates after hydrolysis. It was found necessary to remove the excess solids from the hydrolysate prior to fermentation, as the productivity fell by 75% if this was not done. With the bacterial strains (Clostridium beijerinckii and C. saccharoperbutylacetonicum) and the algal sugar solutions used, an acetone butanol ethanol (ABE) fermentation was used to make butanol. The butanol concentration in the fermentation broth reached about 4 g/L, which is close to the theoretical value for the sugar concentration obtained, and compares well (when adjusted for sugar concentration in the media) with values reported in the literature for other systems. The recovery of reducing sugars in the media during the pilot study was 0.29 g butanol/g sugar. © 2011 American Institute of Chemical Engineers Environ Prog, 2012