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The rapid urbanization that took place in the last 60 years has led to a dramatic increase in the generation of Municipal Solid Waste (MSW). The biodegradable fraction of MSW mainly consists of food waste (FW) and corresponds to about 50% of the total MSW. The disposal of FW in the environment has become a significant challenge. On the other hand, FW is an excellent substrate for anaerobic digestion (AD). This manuscript reviews the different AD technologies for the treatment of FW. Different types of bioreactors and pretreatment methods used to enhance methane production through AD of FW are discussed. The current review gives special emphasis on the methods for biogas upgrading and on technologies for FW digestate valorization. Food waste valorization through anaerobic digestion offers a wide variety of options in all process steps. From the pre-treatment of the feedstock and the selection of the suitable anaerobic digestion technology to the configuration of the process based on the desired products and the valorization of the generated digestate, the design of an integrated anaerobic digestion plant is a challenging task, which necessitates a systematic design. A systematic approach is necessary for FW valorization. The simple single-stage AD process leads to underutilization of the feedstock. There are plenty of available technologies that could be combined for the development of an integrated biorefinery that will be optimized in terms of FW valorization towards the production of biofuels and high-added value products, while introducing a circularity in the nutrients contained in the FW. FW-to-biofuel conversion technologies are high Technology Readiness Level (TRL—9) technologies and anaerobic digestion is applied worldwide at commercial scale.

This study concerns the production of hydrogen and methane from a Food Residue Biomass (FORBI) product (Papanikola et al. in 5th international conference on sustainable waste management systems, Athens, 2017), generated from pre-sorted HFW in a CSTR and in a PABR respectively. FORBI is generated by drying and shredding the fermentable fraction of household food waste collected door-to-door in the Municipality of Halandri, Greece. Hydrogen production from FORBI through anaerobic fermentation under acidogenic mesophilic conditions was carried out using a 4 L CSTR, operated at 12 h HRT under an organic loading of 15 g TS L−1. The H2-CSTR was operated for 40 days. During the operation of H2-CSTR the production of biogas reached up to 0.1026 Lbiogas gFORBI−1 and the percentage of hydrogen in the gas up to 48.2%. The conversion of FORBI into methane was carried out through the operation of a 77 L PABR operated under mesophilic methanogenic conditions at various operating parameters (OLR, HRT, T). Two different approaches were adopted for the pre-treatment of the feedstock. For the two first phases of the experimental procedure, a liquid extraction step was carried out before feeding the bioreactor with the separated liquid fraction, while in the subsequent three phases, a whole suspension of FORBI was used as feed. The mean biogas production rate was 0.158 ± 0.02 Lbiogas gFORBI−1 and the mean methane percentage in the biogas was 67.5 ± 2.1%, in the first two phases. The mean biogas production rate was 0.519 ± 0.03 Lbiogas gFORBI−1 and the mean methane percentage in the biogas was 66 ± 2.8%, when a whole suspension of FORBI was fed to the PABR.

This research work concerns the production of Hydrogen and Methane from a Food Residue Biomass (FORBI) product, generated from pre-sorted Fermentable Household Food Waste in a Continuous Stirred Tank Reactor (CSTR). FORBI is generated by drying and shredding the fermentable fraction of household food waste, collected door-to-door in the Municipality of Halandri, Greece. Hydrogen production from FORBI through anaerobic fermentation under acidogenic mesophilic conditions was carried out using a 4L CSTR (H2-CSTR), operated at 4 hr and 3 hr Hydraulic Retention Times (HRT), with a feed concentration of 15 g TS/L. Volatile fatty acids (VFAs), Total and Volatile Suspended Solids (TSS and VSS), Total and Soluble Chemical Oxygen Demand (tCOD and sCOD), Total and Dissolved Carbohydrates, pH and hydrogen content in the biogas were monitored. The H2-CSTR operated for 32 days. During its operation, the biogas productivity reached 7.78 L/d, out of which 4.13 L/d was hydrogen (60%). This corresponds to a yield of 22Lbiogas/kgFORBI. The conversion of FORBI into methane was carried out through the operation of a CSTR (CH4-CSTR) with working volume 4L (CH4-CSTR). the reactor operated under mesophilic methanogenic conditions at 20,15 and 10 days HRT and an organic loading of 15 g TS/L. TSS, VSS, tCOD, sCOD, pH, alkalinity, VFAs and methane content in the biogas were monitored. The mean methane percentage in the biogas was up to 65%, with an average biogas productivity of 0.5Lbiogas/Lreactor/day, during the optimum operational conditions. The biogas productivity corresponds to a productivity of 477 Lbiogas/kgFORBI. The experimental results obtained were used as a basis for the development of a model by using AQUASIM [1] software, which was able to adequately simulate the operation of the bioreactors. Conclusively, FORBI was proved as a suitable feedstock material both for hydrogen and methane production, resulting in high biogas yields in both cases.

This research work concerns the production of Hydrogen and Methane from a Food Residue Biomass (FORBI) product, generated from pre-sorted Fermentable Household Food Waste in a Continuous Stirred Tank Reactor (CSTR). FORBI is generated by drying and shredding the fermentable fraction of household food waste, collected door-to-door in the Municipality of Halandri, Greece. Hydrogen production from FORBI through anaerobic fermentation under acidogenic mesophilic conditions was carried out using a 4L CSTR (H2-CSTR), operated at 4 hr and 3 hr Hydraulic Retention Times (HRT), with a feed concentration of 15 g TS/L. Volatile fatty acids (VFAs), Total and Volatile Suspended Solids (TSS and VSS), Total and Soluble Chemical Oxygen Demand (tCOD and sCOD), Total and Dissolved Carbohydrates, pH and hydrogen content in the biogas were monitored. The H2-CSTR operated for 32 days. During its operation, the biogas productivity reached 7.78 L/d, out of which 4.13 L/d was hydrogen (60%). This corresponds to a yield of 22Lbiogas/kgFORBI. The conversion of FORBI into methane was carried out through the operation of a CSTR (CH4-CSTR) with working volume 4L (CH4-CSTR). the reactor operated under mesophilic methanogenic conditions at 20,15 and 10 days HRT and an organic loading of 15 g TS/L. TSS, VSS, tCOD, sCOD, pH, alkalinity, VFAs and methane content in the biogas were monitored. The mean methane percentage in the biogas was up to 65%, with an average biogas productivity of 0.5Lbiogas/Lreactor/day, during the optimum operational conditions. The biogas productivity corresponds to a productivity of 477 Lbiogas/kgFORBI. The experimental results obtained were used as a basis for the development of a model by using AQUASIM [1] software, which was able to adequately simulate the operation of the bioreactors. Conclusively, FORBI was proved as a suitable feedstock material both for hydrogen and methane production, resulting in high biogas yields in both cases., The data set of the publication can be accessed at: http://doi.org/10.5281/zenodo.3906241

This research work concerns the production of Hydrogen and Methane from a Food Residue Biomass (FORBI) product, generated from pre-sorted Fermentable Household Food Waste in a Continuous Stirred Tank Reactor (CSTR). FORBI is generated by drying and shredding the fermentable fraction of household food waste, collected door-to-door in the Municipality of Halandri, Greece. Hydrogen production from FORBI through anaerobic fermentation under acidogenic mesophilic conditions was carried out using a 4L CSTR (H2-CSTR), operated at 4 hr and 3 hr Hydraulic Retention Times (HRT), with a feed concentration of 15 g TS/L. Volatile fatty acids (VFAs), Total and Volatile Suspended Solids (TSS and VSS), Total and Soluble Chemical Oxygen Demand (tCOD and sCOD), Total and Dissolved Carbohydrates, pH and hydrogen content in the biogas were monitored. The H2-CSTR operated for 32 days. During its operation, the biogas productivity reached 7.78 L/d, out of which 4.13 L/d was hydrogen (60%). This corresponds to a yield of 22Lbiogas/kgFORBI. The conversion of FORBI into methane was carried out through the operation of a CSTR (CH4-CSTR) with working volume 4L (CH4-CSTR). the reactor operated under mesophilic methanogenic conditions at 20,15 and 10 days HRT and an organic loading of 15 g TS/L. TSS, VSS, tCOD, sCOD, pH, alkalinity, VFAs and methane content in the biogas were monitored. The mean methane percentage in the biogas was up to 65%, with an average biogas productivity of 0.5Lbiogas/Lreactor/day, during the optimum operational conditions. The biogas productivity corresponds to a productivity of 477 Lbiogas/kgFORBI. The experimental results obtained were used as a basis for the development of a model by using AQUASIM [1] software, which was able to adequately simulate the operation of the bioreactors. Conclusively, FORBI was proved as a suitable feedstock material both for hydrogen and methane production, resulting in high biogas yields in both cases.