Advanced Bioethanol Production from Source-Separated Bio-waste in Pilot Scale

Abstract

The Sustainable Development Goals along with national policies pave the way to a sustainable, circular, and resource efficient development model. The environmental scenario could change with the promotion of biofuels such as bioethanol. Recent research on bioethanol aspires to reduce the costs production, via the optimization of process variables and the increase in ethanol yields. This study presented a stepwise upscaling of bioethanol production from dried source-separated municipal biowaste. Three different scales (250 mL, 4 L, 100 L) were examined applying advanced ethanol production via simultaneous saccharification and fermentation. The bioprocess runs at each of the three scales and produced very similar ethanol yields, indicating excellent scalability. The validated optimum conditions at the pilot scale were 25% solids loading, Spirizyme 40 μL/g starch, NS87014 175 μL/g cellulose, and 2% S. cerevisiae. The results from the pilot trials were very successful and repeatable. Τhe mean ethanol yield was 86.60 ± 4.91%, while the structural component such as starch and cellulose were efficiently hydrolysed. The produced ethanol was recovered and purified meeting the standards of absolute ethanol, rendering it suitable for industrial uses and for biofuel use as well. Energy consumption aspects were discussed as well. Conclusively, all the stages of the value chain for source-separated biowaste valorisation (collection, treatment, added value product recovery) were successfully showcased.

Piloting Bioethanol Production from Source-Separated Food Waste Boosts Technology Readiness

“…This study focused on the production of bioethanol from wet, "as received" source-separated biowaste after mechanical pretreatment (high-power shredding) and water addition, although most studies also include a thermal pretreatment step (e.g., drying) [5,[29][30][31][32][33][34]. Tsafara et al [12] studied bioethanol production from dried source-separated biowaste. More specifically, in the study of Tsafara et al [12], the biowaste originated from the same municipality (Municipality of Vari-Voula-Vouliagmeni, Attica, Greece).…”

“…Tsafara et al [12] studied bioethanol production from dried source-separated biowaste. More specifically, in the study of Tsafara et al [12], the biowaste originated from the same municipality (Municipality of Vari-Voula-Vouliagmeni, Attica, Greece). In the present study, the bioconversion was carried out in the same pilot plant; the enzymatic formulations (Spirizyme XL, NS87014 by Novozymes) and yeast used were the same, thus a reliable comparison of the results of both studies could be performed.…”

“…Based on the results of extensive experimental work on biowaste [9][10][11], on the bioethanol production trials with dried feedstock [12], and on preliminary lab scale experiments, the enzyme and yeast dosages that were adopted were: 175 µL/g cellulose NS87014 (333 FPU/mL), 40 µL/g starch SpirizymeXL (2337 U/mL), and 2% Saccharomyces cerevisiae (d.b.) (dry baker's yeast).…”

“…The pilot's operation is controlled by a Programmable Logic Controller (PLC) (Siemens S7-1200). The PLC manages and monitors parameters such as temperature, agitation, and distillation [12]. Overall, this pilot plant serves as a controlled environment for conducting experiments related to bioconversion processes, particularly the production and recovery of ethanol.…”

“…The efficiency of the process for every trial was assessed by the ethanol yield and by the ethanol produced per tonne of dried total solids, as presented in Figure 3. The term dried feedstock refers to total solids (TS) and is used in order to calculate yields that can be comparable with the results of a previous study [12] using dry feedstock under similar operational conditions.…”