## 3 Results and Discussion
### Analysis of Liquid Condensate from Wheat-Straw Torrefaction  
Results from GC analysis of the initial torrefaction liquid condensate show that carboxylic acid content increased as torrefraction temperature increased from 260 \({}^{\circ}\)C to 300 \({}^{\circ}\)C (Table 3). This suggests that more hemicellulose was degraded via primary thermochemical reactions as temperature increased. Importantly, the greatest amount of acetic acid of 72,998 ppm as a cheap and sustainable source of organic carbon and/or pH adjuster for microalgal cultivation was obtained at the highest temperature of 300 \({}^{\circ}\)C. Although the permanent gases formed during this torrefaction were not analyzed, the composition of these gases mainly includes CO, CO\({}_{2}\), trace amounts of CH\({}_{4}\), and low molecular weight hydrocarbons (CxHy) combined with unreacted H\({}_{2}\), O\({}_{2}\) and N\({}_{2}\). The CO\({}_{2}\) and CO contents \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**Pre-Treatment**} \\ \hline  & **O\({}_{3}\)** & **280 \({}^{\circ}\)C Torrefraction + O\({}_{3}\)** & **O\({}_{3}\) + NH\({}_{4}\)** & **280 \({}^{\circ}\)C Torrefraction + O\({}_{3}\) + NH\({}_{4}\)** \\ \hline
**Carbohydrate** & \multicolumn{4}{c}{**Concentration (ppm)**} \\ \hline Arabinose & 0.39 & 0.33 & 0.73 & 0.59 \\ Galactose & 0.06 & 0.04 & N/A & N/A \\ Glucose & 11.25 & 11.39 & 25.88 & 22.57 \\ Xylose/Mannose & 5.16 & 4.72 & 10.30 & 8.64 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparative reducible and yielded C\({}_{5}\) and C\({}_{6}\) sugar content in both torrefied and non-torrefied wheat-straw using acetate or citrate buffer. Figure 5: \({}^{1}\)H NMR spectra of enzymatic wheat-straw hydrolysate depicting sugars in the 3-4 ppm region and not small molecules in the 6–10 ppm region. normally range \(\sim\)75-80% and 10-12% of all gaseous products [40]. CO represents the majority of the permanent gas heating value during torrefraction [40] and can be used as fuel to achieve the high 300 \({}^{\circ}\)C temperature corresponding to maximal acetic acid yield. The inability of ALP2 to grow on 100\(\times\) diluted condensate made it necessary to remove such inhibitory compounds and coloration with a neutralization, purification, and dilution scheme at the risk of simultaneously lowering the yield of available carboxylic acids. For instance, only 52.17% of the acetic acid remained after de-colorization. Therefore, future work should be conducted to replace or optimize this de-colorization step. In the approach used herein, the O\({}_{3}\) used for biochemical pre-treatment was also used here to treat activated carbon and increase the number of its acidic surface residues to repel desirable acetate ions away from carbon. \({}^{1}\)H NMR analysis of the 300 \({}^{\circ}\)C-torrefraction condensate before and after activated-carbon adsorption revealed a thorough removal of small molecules such as potentially inhibitory furfurals, furans, HMF, and acetol in the leftmost corresponding ppm region (Figure 6). \({}^{1}\)H NMR analysis of vaporized products that were collected during vacuum distillation revealed the presence of acetol (data not shown). The solid char particle product from an integrated wheat-straw slow-pyrolysis process can not only by used by local farms to improve soil and CO\({}_{2}\) sequestration, but also, once activated with KCl pre-treatment, used for this activated carbon adsorption. The GC-based carboxylic acid content of the purified, de-toxified, filtered 300 \({}^{\circ}\)C-torrefraction liquid condensate is presented in Table 4. This was equivalent to 62.25 g L\({}^{-1}\) potassium acetate and was diluted 100\(\times\) for algal growth experiments. \begin{table}
\begin{tabular}{c c} \hline \hline
**Compound** & **Concentration (ppm)** \\ \hline Acetic Acid & 38,082 \\ Propionic Acid & 2689 \\ Isobutyric Acid & 109 \\ Butyric Acid & 99 \\ IsovalericAcid & 244 \\ Caprotic Acid & 45 \\ \hline \hline \end{tabular}
\end{table}