The possibility of 100% utilization of the brown grease waste for
producing biofuels was explored. The brown grease oil layer was
transformed into biodiesel with a mesporous solid acid catalyst.
The catalyst was synthesized from a polymeric base using a templating
method that led to an ordered pore structure with narrow
pore size distribution and high surface area. Acid functionalization
was controlled to yield a hydrophobic material with superior catalyst
properties compared to homogenous catalysts and commercial
heterogeneous catalysts. Esterification of the FFA in the brown
grease oil with the solid acid catalyst, followed by conventional
transesterification of the triglycerides produced biodiesel that
passed the critical ASTM quality tests of acid number and free
and total glycerin.
The bio-solids separated from the aqueous layer of the brown
grease were analyzed and found to have a H/Ceff ratio greater than
wood, implying excellent potential for producing higher aromatic
and olefin yields via pyrolysis. When pyrolyzed at 600 C, the
bio-solids yielded liquid products that were mostly long-chain
hydrocarbons according to GC/MS analysis. Almost 99% of the
bio-solids were combustible implying the feasibility of producing
synthesis gas from the bio-solids through gasification. These
results establish the feasibility of converting 100% of the raw
brown grease to valuable energy products.