Resumen en Portugués:

Resumo A produção biológica de hidrogênio a partir de resíduos orgânicos representa uma fonte de energia alternativa promissora. Os resíduos de frutas e verduras possuem uma elevada composição orgânica que pode ser aproveitada para estes fins energéticos. Neste sentido, este estudo investigou o efeito do tempo de detenção hidráulica (HRT) na geração de hidrogênio via fermentação escura da fração líquida de resíduos de frutas e verduras. Reator anaeróbio mesofílico de leito fluidizado foi utilizado aplicando HRTs de 12, 6, 3 e 1 h com uma DQO afluente de 10 kgDQO.m-3, correspondendo a taxas de carregamento orgânico de 20, 40, 80 e 240 kgDQO.m-3.d-1, respectivamente. Não foi detectada produção de hidrogênio nos HRTs de 12 e 6 h, apesar do alto consumo de carboidratos (> 79,5%). Nessas condições, ácido lático foi identificado como metabólito predominante, seguido pelo ácido butírico. Com HRT de 3 h, a produção volumétrica de hidrogênio foi de 3,0 m3 H2.m-3reator.d-1, enquanto com HRT de 1 h, a maior produção de hidrogênio foi alcançada, correspondendo a 9,2 m3 H2.m-3reator.d-1. Nesses HRTs mais baixos, os ácidos butírico e acético foram os principais metabólitos detectados. Os rendimentos de hidrogênio permaneceram entre 821,4 e 904,1 mmol H2.mol de sacarose adicionada-1. De modo geral, os resultados demonstram que HRTs mais baixos favorecem a produção de hidrogênio, permitindo a aplicação de taxas de carregamento orgânico mais elevadas sem comprometer o desempenho do reator.

Resumen en Inglés:

Abstract Biological hydrogen production from organic waste represents a promising alternative energy source. Fruit and vegetable waste has a high organic composition that can be used for this purpose. In this sense, this study investigated the effect of hydraulic retention time on hydrogen generation via dark fermentation of the liquid fraction of fruit and vegetable waste. A mesophilic anaerobic fluidized bed reactor was utilized, with hydraulic retention times of 12, 6, 3, and 1 h at an influent chemical oxygen demand of 10 kgCOD.m-3, corresponding to organic loading rates of 20, 40, 80, and 240 kgCOD.m-3.d-1, respectively. No hydrogen production was detected at hydraulic retention times of 12 and 6 h, despite high carbohydrate consumption (> 79.5%). Under these conditions, lactic acid was identified as the predominant metabolite, followed by butyric acid. At the hydraulic retention time of 3 h, the volumetric hydrogen production was 3.0 m3 H2.m-3reactor.d-1, whereas at the hydraulic retention time of 1 h, the highest hydrogen production was achieved, corresponding to 9.2 m3 H2.m-3reactor.d-1. At the lower hydraulic retention times, butyric and acetic acids were the major metabolites detected. Hydrogen yields remained between 821.4 and 904.1 mmol H2.mol sucrose added-1. Overall, the results demonstrate that lower hydraulic retention times favor hydrogen production, enabling the use of higher organic loading rates without impairing reactor performance.

Resumen en Portugués:

RESUMO Gerir resíduos de frutas e verduras (RFV) é desafiador, pois a maior parte desses resíduos é destinada a aterros sanitários. A fração líquida desses resíduos (RFVL) apresenta elevada biodegradabilidade e é adequada à digestão anaeróbia. Entretanto, avaliações técnicas e econômicas comparativas de sistemas anaeróbios de estágio único (SS) e de dois estágios (TS), tratando RFVL, ainda são limitadas. Este estudo avaliou o desempenho técnico e a viabilidade econômica de um reator Upflow Anaerobic Sludge Blanket (UASB) em SS e de um sistema TS composto de um reator anaeróbio de leito estruturado seguido por um reator UASB metanogênico. Reatores em escala de laboratório foram operados sob diferentes cargas orgânicas volumétricas, e as produtividades de hidrogênio e metano subsidiaram simulações de quatro cenários no software SuperPro Designer®: (1) digestão em SS; (2) digestão em TS sem recuperação de hidrogênio; (3) digestão em TS com recuperação de hidrogênio; e (4) um reator de tanque agitado contínuo (CSTR) tratando RFV. A configuração em TS apresentou maior eficiência de conversão de metano (0,80 g DQOCH4 g-1 DQO) e produtividade (3,6 NL CH4 L-1 d-1), incrementando 23% na recuperação energética em comparação ao reator UASB em SS. Já o hidrogênio contribuiu com 5% da produção total de energia. Extrapolando-se para 17,5 toneladas d-1 de RFV na Central Estadual de Abastecimento (CEASA), o reator UASB em SS produziu 193 kWh ano-1, enquanto o sistema em TS com recuperação de hidrogênio alcançou 254 kWh ano-1. Entretanto, as configurações em TS foram onerosas, e o sistema UASB em SS tornou-se alternativa economicamente viável.

Resumen en Inglés:

ABSTRACT Managing fruit and vegetable waste (FVW) is challenging, as most of this waste is disposed of in landfills. The liquid fraction of this waste (LFVW) is highly biodegradable and suitable for anaerobic digestion. However, comparative technical and economic evaluations of single-stage (SS) and two-stage (TS) anaerobic systems treating LFVW remain limited. This study evaluated the technical performance and economic feasibility of a UASB reactor in SS and a TS system composed of an anaerobic structured bed reactor followed by a methanogenic UASB reactor. Laboratory-scale reactors were operated under different organic loading rates, and hydrogen and methane productivities supported simulations of four scenarios in SuperPro Designer® software: (1) SS digestion; (2) TS digestion without hydrogen recovery; (3) TS digestion with hydrogen recovery; and (4) a continuous stirred tank reactor (CSTR) treating FVW. The TS configuration showed higher methane conversion efficiency (0.80 g CODCH4 g-1 COD) and productivity (3.6 NL CH4 L-1 d-1), increasing energy recovery by 23% compared to the UASB reactor in SS. Hydrogen contributed 5% of total energy production. When extrapolated to 17.5 tonnes d-1 of FVW at CEASA (Supply Center), the UASB reactor in SS produced 193 kWh year-1, while the TS system with hydrogen recovery reached 254 kWh year-1. However, TS configurations were costly, and the UASB system in SS was the economically viable alternative.

Resumen en Portugués:

RESUMO Este estudo avaliou o biochar derivado de esterco suíno como um material multifuncional para recuperação de nutrientes e imobilização da enrofloxacina (ENR), um antibiótico veterinário comumente detectado em águas residuais de sistemas de produção animal. Os biochars foram produzidos sob diferentes condições: agente ativador (KOH, HCl, MgCl₂), proporção de impregnação (1:1 e 3:1) e temperatura de pirólise (400, 600 e 800°C). O biochar modificado com MgCl₂ produzido a 800°C (3:1) apresentou o melhor desempenho na remoção de amônio e fosfato. Em testes com analitos individuais, o material atingiu a capacidade de adsorção de fosfato (60,1 mg.g-1), amônio (28,9 mg.g-1) e ENR (39,5 mg.g-1). Experimentos multicomponentes demonstraram alta remoção de fosfato (100%) e amônio (93%), atribuída à estequiometria ideal para a formação de estruvita, enquanto a absorção de ENR diminuiu devido à competição por sítios ricos em metais e à especiação alcalina. Ensaios de dessorção mostraram alta liberação de nutrientes (150% de P e 40% de N) e dessorção mínima de ENR (< 7%). Um balanço de massa teórico indica que 317 m3 de águas residuais podem ser tratados por tonelada de biochar produzido, com recuperação de 86 kg de P. Em geral, o biochar de esterco suíno modificado com Mg é uma rota promissora para a reciclagem de nutrientes e mitigação de contaminantes.

Resumen en Inglés:

ABSTRACT This study evaluated swine-manure-derived biochar as a multifunctional material for nutrient recovery and immobilization of enrofloxacin, a veterinary antibiotic commonly detected in livestock wastewater. Biochars were produced under different conditions: activating agent (potassium hydroxide (KOH), hydrochloric acid (HCl), and magnesium chloride (MgCl₂)), impregnation ratio (1:1 and 3:1), and pyrolysis temperature (400, 600, and 800°C). The MgCl₂-modified biochar produced at 800°C (3:1) exhibited the best performance in ammonium and phosphate removal. In single-analyte tests, the material reached phosphate (60.1 mg.g-1), ammonium (28.9 mg.g-1), and enrofloxacin (39.5 mg.g-1) uptake. Multicomponent experiments showed high phosphate removal (100%) and ammonium removal (93%), attributed to an ideal stoichiometry for struvite formation. In contrast, enrofloxacin uptake decreased due to competition for metal-rich sites and alkaline speciation. Desorption assays showed high nutrient release (150% P and 40% N) and minimal enrofloxacin desorption (< 7%). A theoretical mass balance indicates that 317 m3 of digestate can be treated per tonne of biochar produced, with 86 kg of phosphorus recovered. Overall, magnesium-modified swine-manure biochar is a promising approach for nutrient recycling and contaminant mitigation.

Resumen en Portugués:

RESUMO A digestão anaeróbia seca (S-DA) tem se destacado como alternativa promissora no tratamento e recuperação energética de resíduos sólidos orgânicos, entre eles os provenientes de frutas e verduras (RFV). Este estudo investigou a adaptação progressiva de um lodo anaeróbio mesofílico, antes utilizado no tratamento de efluentes de uma cervejaria (2,4% sólidos totais), para operar em condições com alto teor de sólidos (13,8%), utilizando a fração seca de RFV (RFVS) como único substrato. A aclimatação foi conduzida em um reator de mistura completa (CSTR) a 35°C, com substituição gradual de sacarose por RFVS e posterior aumento da concentração orgânica de 0,1 a 6,0 kg DQO m-3. A adaptação foi avaliada por meio de parâmetros físico-químicos, teste de atividade metanogênica específica (AME) e análise metagenômica da comunidade microbiana. Os resultados demonstraram uma reestruturação biológica significativa, com redução da diversidade alfa, mas com aumento da especiação funcional, refletindo em maior resiliência aos estresses operacionais da S-DA. A sucessão taxonômica mostrou maior abundância relativa de Proteobacteria e Bacteroidota, e, com a adaptação, Nitrospirota, Chloroflexi e Synergistota se destacaram. Além disso, observou-se enriquecimento dos gêneros Methanothrix (0,13 para 28,9%) e Methanobacterium (0,0 para 2,2%), revelando a produção de metano por vias acetoclásticas e hidrogenotróficas. Nos ensaios de AME,o lodo adaptado apresentou aumento de até 254% na produção real de metano em comparação com o inóculo não adaptado. Esse incremento na capacidade metanogênica, aliado à robusta conversão de ácidos graxos voláteis, confirma a eficácia da estratégia de adaptação gradual para sistemas de digestão anaeróbia seca (DAS). Esses resultados contribuem para a consolidação de protocolos reprodutíveis para o condicionamento de inóculos no tratamento de resíduos orgânicos complexos sob altas concentrações orgânicas.

Resumen en Inglés:

ABSTRACT Dry anaerobic digestion has emerged as a promising alternative for treating and recovering energy from organic solid waste, including fruit and vegetable waste. This study investigated the progressive adaptation of a mesophilic anaerobic sludge, previously used to treat brewery effluents (2.4% Total Solids), to operate under high-solids conditions (13.8%), using the dry fraction of fruit and vegetable waste as the sole substrate. Acclimation was conducted in a mixing reactor at 35°C, with gradual replacement of sucrose by the dry fraction of fruit and vegetable waste and sequential increase in organic concentration from 0.1 to 6.0 kg COD m-3. The adaptation was evaluated through physicochemical parameters, a Specific Methanogenic Activity test, and metagenomic analysis of the microbial community. The results demonstrated a significant biological restructuring, with a reduction in alpha diversity but an increase in functional speciation, reflecting greater resilience to the operational stresses of dry anaerobic digestion. The taxonomic succession showed higher relative abundances of the phyla Proteobacteria and Bacteroidota, and, with adaptation, Nitrospirae, Chloroflexi, and Synergistota stood out. Furthermore, enrichment of the methanogenic archaea genera Methanothrix and Methanobacterium was observed, increasing from 0.13 to 28.9% and from 0.0 to 2.2%, respectively, indicating methane production via complementary acetoclastic and hydrogenotrophic pathways. In Specific Methanogenic Activity assays, the adapted sludge showed an increase of up to 254% in actual methane production compared to the non-adapted inoculum. This increase in methanogenic capacity, coupled with the robust conversion of volatile fatty acids, confirms the effectiveness of the gradual adaptation strategy for dry anaerobic digestion systems. These results contribute to the consolidation of reproducible protocols for inoculum conditioning in the treatment of complex organic waste under high organic concentrations.

Resumen en Inglés:

ABSTRACT Ineffective and unregulated management of fruit and vegetable waste contributes significantly to greenhouse gas emissions. In this context, biological routes for hydrogen generation represent a sustainable strategy for waste valorization and energy production. This study investigated the effectiveness of ultrasonic pretreatment followed by enzymatic hydrolysis to enhance the valorization of fruit and vegetable waste for biohydrogen production by increasing the release of fermentable sugars. Ultrasonic pretreatments were applied at 70% amplitude for 5 to 30 minutes, and the most promising conditions were selected based on physicochemical characterization and subsequently subjected to enzymatic hydrolysis using Celluclast and α-amylase. Among the evaluated conditions, the 10-minute ultrasonic treatment significantly improved carbohydrate solubilization. Enzymatic hydrolysis further increased glucose and xylose release, maximizing the availability of fermentable sugars. These findings demonstrate that the combined ultrasonic-enzymatic strategy enhances substrate accessibility and sugar recovery, highlighting its potential to improve subsequent dark-fermentation processes for biohydrogen production. However, fermentation assays are still required to confirm this potential.

Resumen en Inglés:

ABSTRACT This study evaluated the effects of hydrothermal pretreatments, steam explosion, and autohydrolysis, on the anaerobic digestion of secondary sludge, with emphasis on organic matter solubilization, methane production, and antibiotic removal. Secondary sludge samples from conventional activated sludge systems treating municipal wastewater in Belo Horizonte, Brazil, were pretreated at different temperature combinations (135–200°C) and residence times (5–40 min). These were defined by response surface methodology using a central composite rotational design. Pretreated samples were then characterized physicochemically and assessed through biochemical methane potential assays. All steam explosion pretreated samples exhibited enhanced organic matter solubilization and methane production, with the best performance observed at 167.5°C for 20 minutes (636.5 NmLCH₄ gVS-1; +229% relative to the control), as well as the highest antibiotic removal (BR: 27–76%). In contrast, autohydrolysis resulted in lower methane yields (47.7–135.1 NmLCH₄ gVS-1; -35 to -78% relative to the control) and did not remove fluoroquinolone, which persisted even after anaerobic digestion. Overall, these findings suggest that of the two hydrothermal pretreatments tested, only steam explosion improved energy recovery and antibiotic removal from secondary sludge.

Resumen en Inglés:

ABSTRACT Contaminants of emerging concern, such as linear alkylbenzene sulfonate (LAS), pose persistent challenges to anaerobic wastewater treatment systems due to their recalcitrance and inhibitory effects on microbial consortia. Strategies based on redox mediators and controlled microaeration have been proposed to enhance anaerobic degradation pathways and mitigate surfactant toxicity. This study aimed to evaluate the combined effects of anthraquinone-2-sulfonate (AQS) and microaeration on LAS removal, biogas production, and metabolic responses in upflow anaerobic sludge blanket (UASB) reactors. Three operational conditions were assessed over 45 days each: a traditional UASB reactor, a UASB reactor supplemented with AQS, and a microaerated UASB reactor with AQS. Methane production remained similar between the conventional UASB (2.0 ± 0.2 L·day⁻¹) and UASB + AQS (1.9 ± 0.3 L·day⁻¹), with methane fractions of 67.2 ± 2.7% and 67.6 ± 2.7%, respectively. Microaeration markedly increased methane generation (5.6 ± 0.7 L·day⁻¹), though methane purity decreased to 33.5 ± 4.3% due to biogas dilution. LAS removal improved from 34.9 ± 14.4% in the traditional UASB to 65.6 ± 4.2% with AQS and to 76.5 ± 1.7% under microaeration combined with AQS. Overall, the integrated use of AQS and microaeration promoted a more favorable redox balance in the reactors, resulting in faster LAS degradation kinetics, improved system stability, and maintenance of methane production. These findings demonstrate the potential of combined microaeration and redox-mediator strategies to improve the treatment of surfactant-rich wastewaters while enabling energy recovery.

Resumen en Inglés:

ABSTRACT This study presents a technical and experimental evaluation of a pilot-scale unit for low-carbon hydrogen production via dry reforming of methane (DRM) using biogas derived from Upflow Anaerobic Sludge Blanket (UASB) reactors at a municipal wastewater treatment plant (WWTP). Computational modeling was conducted using Aspen Plus® V. 14 to define energetic profile and mass balance of the system and to validate the simulation parameters. Experimental DRM tests were conducted by varying the feed flow rate and biogas molar ratios. Simulation results indicated a biogas demand of 120 m³.day-1 to yield a purified hydrogen output of 14.23 kg.day-1 via Pressure Swing Adsorption (PSA). The unit required thermal loads of 12.90 kW for heating and 4.09 kW for cooling. Experimental validation using a Ni/MCM-41 catalyst confirmed that a stoichiometric CH4/CO2 ratio of 1.0 at a feed flow rate of 6 mL.s-1 optimized conversion efficiency, achieving 94% conversion for CH4 and 98% for CO2.

Resumen en Inglés:

ABSTRACT Optimizing the carboxylate platform during continuous sugarcane vinasse fermentation requires overcoming hydrolytic bottlenecks and steering metabolic pathways. This study investigated kinetic patterns and metabolic flux redirection in response to strategic interventions: lactate and glycerol supplementation and effluent recirculation. First-order modeling revealed that while carbohydrate hydrolysis is the baseline rate-limiting step (kapp = 0.4-1.8 h⁻¹), glycerol co-fermentation triggered a redox-driven “flash consumption” (kapp of 23 h⁻¹), bypassing hydrolytic constraints. Targeted lactate supplementation shifted the mixed-acid profile toward butyrogenesis, generating metabolic-derived alkalinity (pH > 7.0) and preventing acidification. Co-supplementation of glycerol and lactate created a controlled hybrid spectrum of propionate and butyrate. Furthermore, effluent recirculation activated in situ chain elongation via reverse β-oxidation, leveraging endogenous electron donors to double valerate production. Crucially, these strategies governed sulfur dynamics by partitioning toxicity between gaseous H2S or dissolved sulfide based on environment buffering. Principal Component Analysis (PCA) revealed that these interventions do not merely increase yields but deterministically restructure the microbial metabolic network. These findings provide a robust, kinetic-based framework for scaling up stable and selective sugarcane biorefineries.

Resumen en Portugués:

RESUMO Este estudo aplicou o Modelo de Digestão Anaeróbia nº 1 (ADM1) à digestão anaeróbia de resíduos de frutas e hortaliças (RFH), com foco no ajuste de parâmetros específicos do substrato e na configuração do modelo utilizando o AQUASIM 2.0. O substrato foi caracterizado para a definição das frações de carboidratos, lipídios, proteínas e inertes. A análise de sensibilidade identificou a velocidade de decaimento da biomassa (kdec), a velocidade de desintegração (kdis), a velocidade de hidrólise de carboidratos (khyd,ch), a constante de meia saturação do acetato (ks,ac) e as velocidades máximas de consumo de acetato (km,ac), ácidos graxos de cadeia longa (km,fa) e açúcares (km,su) como os parâmetros mais influentes na produção de biogás. Esses parâmetros foram calibrados com dados experimentais de um reator anaeróbio de fluxo ascendente com manta de lodo (UASB), resultando em elevado desempenho do modelo, com R2 de 0,99 e erro quadrático médio (RMSE) de 0,34. A análise de inibição revelou o papel-chave do acúmulo de acetato e indicou a interferência da amônia livre na assimilação de acetato, afetando a produção de metano. O ADM1 ajustado reproduziu com sucesso as tendências de produção de biogás e metano observadas experimentalmente, demonstrando sua adequação para a modelagem da digestão anaeróbia de RFH. Os resultados reforçam a importância da calibração específica do substrato e confirmam o ADM1 como ferramenta robusta para a análise de processos, otimização e identificação precoce de potenciais limitações operacionais em sistemas de digestão anaeróbia.

Resumen en Inglés:

ABSTRACT This study applied the Anaerobic Digestion Model No. 1 (ADM1) to anaerobic digestion of fruit and vegetable waste (FVW), focusing on substrate-specific parameter adjustment and model configuration using AQUASIM 2.0. The substrate was characterized to define carbohydrate, lipid, protein, and inert fractions. Sensitivity analysis identified the biomass decay rate (kdec), disintegration rate (kdis), carbohydrate hydrolysis rate (khyd,ch), acetate half-saturation constant (ks,ac), as well as maximum uptake rates for acetate (km,ac), long-chain fatty acids (km,fa), and sugars (km,su) as the most influential parameters affecting biogas production. These parameters were calibrated using experimental data from an Upflow Anaerobic Sludge Blanket (UASB) reactor, resulting in strong model performance, with a R2 of 0.99 and a root mean square error of 0.34. Inhibition analysis highlighted the key role of acetate accumulation and indicated that free ammonia interferes with acetate uptake, thereby influencing methane production. The adjusted ADM1 successfully reproduced biogas and methane production trends observed experimentally, demonstrating its suitability for modeling FVW anaerobic digestion. These results reinforce the importance of substrate-specific calibration, confirming ADM1 as a robust tool for process analysis, optimization, and early identification of potential operational limitations in anaerobic digestion systems.

Resumen en Inglés:

ABSTRACT This study evaluated the integration between two technologies, a demonstration-scale desorption chamber (DC) and microaeration, in a demonstration-scale UASB reactor treating real domestic sewage, aiming to enhance methane recovery and reduce hydrogen sulfide. The DC removes dissolved CH₄ and H2S from liquid, generating a waste gas (containing CH₄, CO₂, H2S, and air - O₂ and N2), which was used in this study to microaerate the UASB reactor. The DC achieved median removal efficiencies of 55% for dissolved methane and 79% for dissolved hydrogen sulfide, despite the low gas-to-liquid ratio applied (rQ ≈ 0.042). Waste gas extracted from the DC was successfully reused as the microaeration source in the UASB reactor, resulting in a median 28% reduction in H₂S mass flow and a 60% decrease in biogas H₂S concentration, while also increasing methane mass flow by approximately 37%, even though the doses of O₂ and operational conditions varied substantially throughout the study. The integration of a desorption chamber and a microaerated UASB reactor produced biogas with a typical composition of ~50-54% CH₄ and ~800 ppmv H₂S, suitable for thermal energy recovery without any additional treatment or reducing the required treatment for energy recovery (biogas generator). The demonstration-scale conditions highlighted both the technical feasibility of the approach and the operational challenges of controlling microaeration under real wastewater variability, indicating a need for further research to standardize dosing strategies (L O2/L biogas instead of L O2/L effluent) to support full-scale implementation.

Resumen en Inglés:

ABSTRACT Wastewater treatment plants may act as environmental reservoirs and dissemination pathways for clinically relevant fungal pathogens. However, information regarding the occurrence and fate of yeasts in wastewater treatment systems remains limited. This study investigated the occurrence, removal, reduction, and solid-liquid partitioning of yeasts in a pilot-scale upflow anaerobic sludge blanket reactor treating domestic wastewater. Yeast concentrations were determined in raw sewage, treated effluent, and reactor sludge using culture-based methods, and the isolated species were identified by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry. The geometric mean concentration of yeasts in raw sewage was 1.15 × 10³ CFU·mL-¹, decreasing to 3.89 × 10² CFU·mL-¹ in the upflow anaerobic sludge blanket reactor effluent, corresponding to an average reduction of 0.74 log10. Yeasts were also detected in the reactor sludge, with a geometric mean concentration of 6.82 × 104 CFU·gTSS-¹. Solid-liquid partitioning analysis indicated that approximately 99.5% of the yeast load left the system through the liquid phase. In comparison, only 0.5% remained associated with the sludge, suggesting that adsorption may represent one of the removal mechanisms. Potentially pathogenic species, including C. krusei, C. glabrata, C. tropicalis, and F. oxysporum, were identified. These findings highlight the importance of monitoring pathogenic yeasts in wastewater treatment systems from a One Health perspective.

Resumen en Inglés:

ABSTRACT The study evaluated the co-digestion of vinasse and cattle manure, using slaughterhouse sludge as inoculum through biochemical methane potential assays, demonstrating that the technique is effective for energy production and mitigating industrial environmental impacts. In phase 1, the amount of cattle manure in the co-digestion assays varied from 2 to 20% in terms of volatile solids, considering vinasse as the main substrate. In the monodigestion reactors, vinasse or cattle manure was added as the sole substrate. The adaptability of the inoculum was evaluated in a sequential biochemical methane potential assay (phase 2). At the end of phase 1, the contents of each reactor were centrifuged, and the inoculum was subjected to the same conditions as the previous phase, initiating phase 2. The highest specific methane production in phase 1 was 1327±50 ml NCH4/gTVS for the reactors containing 90% VN:10% cattle manure. In phase 2, an adaptive effect was observed. The specific methane production of the tests with 90:10% increased to 2100 ± 93 ml NCH4/gTVS, followed by the reactors with 80:20% and 95:5% (1986 ± 97 ml NCH4/gTVS and 1885 ± 32 ml NCH4/gTVS, respectively). Sequential monodigestion, however, did not result in a significant increase in specific methane production. In the case of vinasse, there was a 15% increase from Phase 1 to Phase 2. For cattle manure, a 24% increase was observed. In this study, the long-term biochemical methane potential assay allowed for the degradation of recalcitrant organic fractions and a more complete conversion of organic matter, increasing methane yield. The application of centrifugation and sequential inoculation in mono- and co-digestion systems favors the adaptation of the microbial consortium, consolidating itself as a promising strategy for energy recovery and treatment of poultry slaughterhouse sludge.

Resumen en Inglés:

ABSTRACT Australia’s red meat processing sector is under increasing pressure to decarbonise, strengthen water security, and transition toward circular resource management. This paper reports outcomes from a comprehensive feasibility assessment conducted at two large-scale facilities (New South Wales and Western Australia), evaluating an integrated Bio-resource Recovery Facility combining anaerobic co-digestion (AnCoD) of complementary organic streams (paunch, dissolved air flotation sludge, under-utilised solids, and manure) with advanced water recycling, CO2 recovery/valorisation and digestate processing into a marketable biofertiliser. Substrates were characterised and tested using biochemical methane potential (BMP) assays, as well as site-specific mass, energy, and economic models that were developed to quantify recoverable resources, avoided costs, and potential revenue streams. Co-digestion increased methane yields up to 0.6 m3 CH4 kg-1 VS, representing a 50% uplift relative to the VS-weighted ‘sum-of-parts’ BMP predicted from the individual substrates. This is projected to offset approximately 70% of the site’s energy demand. The proposed water treatment train (DAF, ultrafiltration, and disinfection) enables up to 60% internal water reuse. CO2 recovery from biogas/CHP systems could capture ~9,200 t/yr of high-purity CO2, while digestate nutrient value supports pelletised fertiliser production. Overall, integrated resource recovery offers a practical pathway for processors to deliver measurable reductions in emissions, operational resilience, as well as strong economic performance.

Resumen en Inglés:

ABSTRACT Electron-conducting materials (ECMs) stimulate syntrophic microbial interactions and facilitate interspecies electron transfer, thereby promoting the degradation of organic matter and accelerating methane (CH4) production in anaerobic reactors. The objective of this review was to present the benefits of applying ECMs, such as granular activated carbon, zero-valent iron, magnetite, and graphene-based materials, in anaerobic digesters based on their physicochemical properties and electron transfer mechanisms. The literature review was conducted by analyzing scientific papers identified through keyword searches across databases such as Google Scholar, ScienceDirect, and Scopus. The studies indicated that carbon-based additives tend to improve methanization kinetics but commonly decrease CH4 yield due to the adsorption of organic matter. Iron-based additives stand out for increasing CH4 production and raising the CH4 content in biogas. The combination of different ECMs can favor multiple electron-transfer mechanisms, thereby enhancing the overall performance of anaerobic reactors. ECMs are a promising strategy for boosting anaerobic treatment of organic waste.