Results of the International Energy Agency Bioenergy Round Robin on the Analysis of Heteroatoms in Biomass Liquefaction Oils

A round
robin study evaluating the analysis of biomass liquefaction
oils (BLOs) from fast pyrolysis and hydrothermal liquefaction (HTL)
was performed, receiving data from 14 laboratories in seven countries
in order to assess the current status of analytical techniques for
the determination of nitrogen, sulfur, and chlorine content in BLOs
and to evaluate potential differences in origin (i.e., fast pyrolysis
versus HTL). The BLOs were produced from a range of feedstocks including
pine, mixed softwoods, forest residues, microalgae, miscanthus, and
wheat straw to cover a variety in nitrogen, sulfur, and chlorine content
and speciation. Nine samples were distributed, comprised of eight
separate BLOs and one blind duplicate produced by five producers.
The samples were analyzed for water, carbon, hydrogen, nitrogen, sulfur,
and chlorine content. No analytical test method was mandated; laboratories
were encouraged to utilize whichever method they determined would
be most applicable, relying on the existing body of BLO literature
as a guide. The results of this round robin study are presented in
this paper. The results of the carbon, hydrogen, and water measurements
as reference analyses had relative standard deviations (2.9, 3.5,
and 5.6%, respectively) that were comparable to those found in past
round robin studies on fast pyrolysis bio-oil. The analysis of nitrogen,
sulfur, and chlorine showed higher levels of variability. Laboratories
mostly chose the same method for water, carbon, hydrogen, and nitrogen
determination, whereas there were a variety of methods chosen for
sulfur and chlorine determination. The results suggest that specific
analytical methods for the determination of nitrogen, sulfur, and
chlorine should be further refined to ensure reproducible and accurate
results for BLO analysis due to their importance in emissions, material
selection, and catalyst activity.