3.3 Lignin oligomers content in bio-oils
The amounts of light and heavy lignin oligomers in the bio-oils of untreated and pretreated Douglas fir wood are summarized in Fig.3. It can be seen that,in general.the content of ligninh oligomer was higher than the content of heavy oligomer across all pretreatments. A drastic in the amount of lignin oligomers were observed when the biomass was pretreated with acid and the salt. The reduction is most prominent in salt pretreatment. This result is a clear indication that acid and salt pretreatment had affected the thermal degradation pattern of the lignin.It can be postulated that addition of acid and salt catalysed the polycondensation reaction of lignin under the thermal regime,which lead to the increased yield of biochar whereas cellulose contributed less towards formation biochar. ln spite of this,the final amount of biochar( from pyrolysis of acid and salt pretreated biomass) remained more or less the same when compared to untreated biomass,as only the biochar contributing biopolymer changed.