(498e) Evaluation of Sugars and Bio-Oil Production Using Switchgrass Feedstock Grown in Heavy Metal Contaminated Soil

A combination of biochemical and thermochemical process to produce sugars and bio-oil by using switchgrass which was grown in lead contaminated soil was studied. Four different process routes which involve fast pyrolysis, enzymatic hydrolysis, acid hydrolysis, and their combinations were investigated. The first route only involved fast pyrolysis process only. The second route involved an acid hydrolysis pretreatment followed by the fast pyrolysis. In the third route biomass was hydrolyzed enzymatically to produce sugars. The solid remaining then was pyrolyzed to produce bio-oil. In the fourth route, biomass was pretreated with acid hydrolysis prior to the enzymatic hydrolysis to produce sugar followed by pyrolysis of the remaining solid to produce bio-oil. The impact of lead content in the switchgrass feedstock used for the production of sugars and bio-oil along with the recovery of lead through the above mentioned routes were evaluated by using switchgrass grown in regular soil for comparison. The yields of sugars from acid hydrolysis and enzymatic hydrolysis did not seem to be affected by the lead contained in the switchgrass. The chemical product distribution in bio-oil produced from pyrolysis of lead-containing switchgrass and regular switchgrass showed slight differences. As expected, acid hydrolysis and enzymatic hydrolysis prior to fast pyrolysis affected the product distribution by increasing its selectivity towards aromatics and ketones. Aromatic production was increased by 10% and ketones by 5%, while reducing phenols by 10%. The highest overall yields of the liquid products were obtained from the fourth route which utilized all the three process steps, resulting to the lowest bio-char byproduct. On lead recovery, it was found that most of the lead was extracted from biomass into the liquids in the hydrolysis steps, which can later be recovered by precipitation to for salts. Pyrolysis of the solid remaining from the combined both hydrolysis steps resulted in the bio-char which had the lowest content lead (2ppm) which is not believed to be dangerous by EPA standards