Fig. 1

Composition of lignocellulosic conversion residue. Lignocellulosic conversion residue (LCR) was generated from “Cave in Rock” switchgrass harvested in 2016, subjected to AFEX and enzyme pretreatments, fermented by Zymomonas mobilis, and finally distilled to remove ethanol. The total potential chemical energy of the remaining LCR was determined by COD analysis while the remaining carbon sources, Zymomonas waste products, and other compounds that might affect future microbial metabolism were quantified via a combination of different separation techniques combined with HPLC and GC–MS analysis then converted to g/L COD to calculate the percent composition of the LCR. The most abundant components of this LCR were oligomeric sugars shown in shades of green (54.2%), monomeric sugars in shades of blue (14.7%), C1–C4 metabolites in shades of purple (10.8%) and acetamide in red (6.4%). These numbers are the average of five batches of LCR