Abstract
The photocatalytic pretreatment of lignocellulosic biomass to oxidize lignin and increase biomass stability has gained attention during the last few years. Conventional pretreatment methods are limited by the fact that they are expensive, non-renewable and contaminate the anaerobic digestate later on. The present study was focused to develop a metal-derived photocatalyst that can work with visible electromagnetic spectra light and oxidize commercial lignin liquor. During this project the advanced photocatalytic oxidation of lignin was achieved by using a quartz cube tungsten T3 Halogen 100 W lamp with a laboratory manufactured TiO2-ZnO nanoparticle (nanocomposite) in a self-designed apparatus. The products of lignin oxidation were confirmed to be vanillic acid (9.71 ± 0.23 mg/L), ferrulic acid (7.34 ± 0.16 mg/L), benzoic acid (6.12 ± 0.17 mg/L) and p-coumaric acid (3.80 ± 0.13 mg/L). These all products corresponded to 85% of the lignin oxidation products that were detectable, which is significantly more than any previously reported lignin pretreatment with even more intensity. Furthermore, all the pretreatment samples were supplemented in the form of feedstock diluent in uniformly operating continuously stirred tank reactors (CSTRs). The results of pretreatment revealed 85% lignin oxidation and later on these products did not hinder the CSTR performance at any stage. Moreover, the synergistic effects of pretreated lignin diluent were seen that resulted in 39% significant increase in the methane yield of the CSTR with constant operation. Finally, the visible light and nanoparticles alone could not pretreat lignin and when used as diluent, halted and reduced the methane yield by 37% during 4th HRT.
Highlights
Sustainable fuel production and the utilization of renewable energy such as biomethane is a demand of the current era
The VFA a ysis and pH was categorized to study the variation caused by pretreatments w lignin derivatives as a result of the POC process (Figure 5). These products correspond to 88% of the lignin oxidation products that were detectable, while previously reported amounts were significantly less compared to our 88% using the UV/TiO2 system [11]
The inoculum was taken from a local biogas plant (PMAS-Biogas Plant, Rawalpindi, Pakistan) at the university that was operated under constant conditions and inoculum degassing was performed prior to use in continuously stirred tank reactors (CSTRs)
Summary
Sustainable fuel production and the utilization of renewable energy such as biomethane is a demand of the current era. (6.12 ± 0.17 m0.g1/7Lm) gan/Ld) pa-ncodupm-caoruicmaacridic(a3c.8id0 ±(3.08.013±m0.g1/3Lm) wg/eLr)e wdeetreermdeinteerdmains ethdeams athine main li derivatives as a result of the POC process (Figure 5) These products correspond to of the lignin oxidation products that were detectable, while previously reported amo were significantly less compared to our 88% using the UV/TiO2 system [11]. The VFA a ysis and pH was categorized to study the variation caused by pretreatments w lignin derivatives as a result of the POC process (Figure 5). These products correspond to 88% of the lignin oxidation products that were detectable, while previously reported amounts were significantly less compared to our 88% using the UV/TiO2 system [11]. Previously it was reported that photocatalysis did not disturb ethanol production and that of other relevant products [25]
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