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High-solid and solid-state anaerobic digestion are technologies capable of achieving high reactor productivity. The high organic load admissible for this type of configuration makes these technologies an ideal ally in the conversion of waste into bioenergy. However, there are still several factors associated with these technologies that result in low performance. The economic model based on a linear approach is unsustainable, and changes leading to the development of a low-carbon model with a high degree of circularity are necessary. Digestion technology may represent a key driver leading these changes but it is undeniable that the profitability of these plants needs to be increased. In the present review, the digestion process under high-solid-content configurations is analyzed and the different strategies for increasing reactor productivity that have been studied in recent years are described. Percolating reactor configurations and the use of low-cost adsorbents, nanoparticles and micro-aeration seem the most suitable approaches to increase volumetric production and reduce initial capital investment costs.
Marcos Ellacuriaga; José García Cascallana; Rubén González; Xiomar Gómez. High-Solid Anaerobic Digestion: Reviewing Strategies for Increasing Reactor Performance. Environments 2021, 8, 80 .
AMA StyleMarcos Ellacuriaga, José García Cascallana, Rubén González, Xiomar Gómez. High-Solid Anaerobic Digestion: Reviewing Strategies for Increasing Reactor Performance. Environments. 2021; 8 (8):80.
Chicago/Turabian StyleMarcos Ellacuriaga; José García Cascallana; Rubén González; Xiomar Gómez. 2021. "High-Solid Anaerobic Digestion: Reviewing Strategies for Increasing Reactor Performance." Environments 8, no. 8: 80.
This manuscript deals with the detailed design of a small digestion prototype intended as a commercial unit fully operational to cover the demand for decentralized treatment of wastes. These plants are highly affected by the complex nature of wastes giving rise to different operating problems that should be considered in detail. This paper describes the design and start-up strategy of a small-scale digestion plant with a volume of 8 m3 designed to operate with a hydrolysis pretreatment unit. The plant was designed to treat fruit and vegetable wastes as substrates derived from a local processing food factory. The performance of the plant during fed-batch operation was reported. The strategy of inoculating the reactor only to a third of its original volume and subsequently increasing the volume of the reactor by using the fed-batch mode was inadequate. The acid pH of the feeding substrate resulted in the application of a low organic loading rate with a volumetric variation of just 19.7 L/d. The performance of the plant was evaluated at non-steady state conditions and resulted in excessive destruction of volatile solids due to the low nitrogen content of the feeding substrate. The prototype reported a specific methane production of 232 L/kg volatile solids despite the low feeding rate supplemented.
Rubén González; Daniel Blanco; Judith González-Arias; José García-Cascallana; Xiomar Gómez. Description of a Decentralized Small Scale Digester for Treating Organic Wastes. Environments 2020, 7, 78 .
AMA StyleRubén González, Daniel Blanco, Judith González-Arias, José García-Cascallana, Xiomar Gómez. Description of a Decentralized Small Scale Digester for Treating Organic Wastes. Environments. 2020; 7 (10):78.
Chicago/Turabian StyleRubén González; Daniel Blanco; Judith González-Arias; José García-Cascallana; Xiomar Gómez. 2020. "Description of a Decentralized Small Scale Digester for Treating Organic Wastes." Environments 7, no. 10: 78.
Hydrothermal carbonization (HTC) allows the conversion of organic waste into a solid product called hydrochar with improved fuel properties. Olive tree pruning biomass (OTP), a very abundant residue in Mediterranean countries, was treated by HTC to obtain a solid fuel similar to coal that could be used in co-combustion processes. Three different reaction temperatures (220, 250, and 280 °C) and reaction times (3, 6, and 9 h) were selected. The hydrochars obtained were extensively analyzed to study their behavior as fuel (i.e., ultimate, proximate, fiber and thermogravimetric analysis, Fourier-transform infrared spectroscopy (FTIR), activation energy, and combustion performance). The concentrations of cellulose, hemicellulose, and lignin in the samples depict a clear and consistent trend with the chemical reactions carried out in this treatment. Regarding O/C and H/C ratios and HHV, the hydrochars generated at more severe conditions are similar to lignite coal, reaching values of HHV up to 29.6 MJ kg−1. The higher stability of the solid is reflected by the increase of the activation energy (≈ 60 kJ mol−1), and ignition temperatures close to 400 °C. With this, HTC is a proper thermal treatment for the management of raw OTP biomass and its further conversion into a solid biofuel.
Judith González-Arias; Marta Elena Sánchez; Elia Judith Martínez; Camila Covalski; Ana Alonso-Simón; Rubén González; Jorge Cara-Jiménez. Hydrothermal Carbonization of Olive Tree Pruning as a Sustainable Way for Improving Biomass Energy Potential. Effect of Reaction Parameters on Fuel Properties. Processes 2020, 8, 1201 .
AMA StyleJudith González-Arias, Marta Elena Sánchez, Elia Judith Martínez, Camila Covalski, Ana Alonso-Simón, Rubén González, Jorge Cara-Jiménez. Hydrothermal Carbonization of Olive Tree Pruning as a Sustainable Way for Improving Biomass Energy Potential. Effect of Reaction Parameters on Fuel Properties. Processes. 2020; 8 (10):1201.
Chicago/Turabian StyleJudith González-Arias; Marta Elena Sánchez; Elia Judith Martínez; Camila Covalski; Ana Alonso-Simón; Rubén González; Jorge Cara-Jiménez. 2020. "Hydrothermal Carbonization of Olive Tree Pruning as a Sustainable Way for Improving Biomass Energy Potential. Effect of Reaction Parameters on Fuel Properties." Processes 8, no. 10: 1201.
The performance of a small-scale prototype digestion plant (7.2 m3 working volume) intended for decentralised operation was evaluated considering energy efficiency and technical suitability for biogas valorisation in producing electrical and thermal energy. The digester operated in recirculation mode to enhance organic matter conversion and improve volatile solid degradation. An energy assessment of the process assumed the incorporation of a combined heat and power (CHP) unit. The coefficient of overall performance of the plant for electrical energy (COPel) was 0.95 — this values was estimated at an electrical efficiency of 22.5% and represents the ratio between energy production and consumption — for a methane yield of 360 L/kg VS and an organic loading rate (OLR) of 1.06 g VS/L d. This parameter was slightly lower than the unit thus indicating that the micro-plant was close to attaining self-sufficiency regarding electrical energy use. The temperature increase of the feed to process conditions supposed a significant amount of thermal energy which highly compromised the efficiency when operating at low organic load, thus accounting for more than 80% of the total energy demand of the installation. When the energy assessment of the process was performed at higher OLR of 2.7 g VS/ L d, the resulting COPel value was1.68, demonstrating the feasibility of this configuration for decentralised digestion.
Rubén González; Jesus Ernesto Hernández; Xiomar Gómez; Richard Smith; Judith González Arias; Elia Judith Martínez; Daniel Blanco. Performance evaluation of a small-scale digester for achieving decentralised management of waste. Waste Management 2020, 118, 99 -109.
AMA StyleRubén González, Jesus Ernesto Hernández, Xiomar Gómez, Richard Smith, Judith González Arias, Elia Judith Martínez, Daniel Blanco. Performance evaluation of a small-scale digester for achieving decentralised management of waste. Waste Management. 2020; 118 ():99-109.
Chicago/Turabian StyleRubén González; Jesus Ernesto Hernández; Xiomar Gómez; Richard Smith; Judith González Arias; Elia Judith Martínez; Daniel Blanco. 2020. "Performance evaluation of a small-scale digester for achieving decentralised management of waste." Waste Management 118, no. : 99-109.
Changes in consumer demand due to preferences for a healthier lifestyle have led to a new market offering fruit and salad products ready to eat. This affects the agro-industrial sector and the characteristic of waste streams generated having the organic fraction higher quality and representing a new opportunity of valorisation. This study experimentally evaluated the digestion of wastes derived from the fourth range product sector. It was also proposed the use of this digestate as a fermentation medium for producing plant growth-promoting cultures. Three digestion scenarios were studied: Scenario 1 considered biogas valorisation using a combined heat and power (CHP) unit. Scenario 2 featured biogas upgrading to be used as vehicle fuel. Finally, scenario 3 evaluated the transport of waste materials to the digestion plant by a network of pipes and pumps directly from the production chain. All three scenarios included the land application of a biostimulator based on the production of a plant growth-promoting culture derived from digestate. Life cycle analysis and life cycle costing were used to determine potential environmental impacts and costs over a lifetime of 25 years. The study showed that scenario 1 was the most favourable option for valorising this type of waste, although the economic assessment resulted in negative values for all three alternatives.
Rubén González; José Guillermo Rosas; Daniel Blanco; Richard Smith; Elia Judith Martínez; Raquel Pastor-Bueis; Xiomar Gómez. Anaerobic digestion of fourth range fruit and vegetable products: comparison of three different scenarios for its valorisation by life cycle assessment and life cycle costing. Environmental Monitoring and Assessment 2020, 192, 1 -19.
AMA StyleRubén González, José Guillermo Rosas, Daniel Blanco, Richard Smith, Elia Judith Martínez, Raquel Pastor-Bueis, Xiomar Gómez. Anaerobic digestion of fourth range fruit and vegetable products: comparison of three different scenarios for its valorisation by life cycle assessment and life cycle costing. Environmental Monitoring and Assessment. 2020; 192 (8):1-19.
Chicago/Turabian StyleRubén González; José Guillermo Rosas; Daniel Blanco; Richard Smith; Elia Judith Martínez; Raquel Pastor-Bueis; Xiomar Gómez. 2020. "Anaerobic digestion of fourth range fruit and vegetable products: comparison of three different scenarios for its valorisation by life cycle assessment and life cycle costing." Environmental Monitoring and Assessment 192, no. 8: 1-19.
Anaerobic digestion is an established technological option for the treatment of agricultural residues and livestock wastes beneficially producing renewable energy and digestate as biofertilizer. This technology also has significant potential for becoming an essential component of biorefineries for valorizing lignocellulosic biomass due to its great versatility in assimilating a wide spectrum of carbonaceous materials. The integration of anaerobic digestion and pyrolysis of its digestates for enhanced waste treatment was studied. A theoretical analysis was performed for three scenarios based on the thermal needs of the process: The treatment of swine manure (scenario 1), co-digestion with crop wastes (scenario 2), and addition of residual glycerine (scenario 3). The selected plant design basis was to produce biochar and electricity via combined heat and power units. For electricity production, the best performing scenario was scenario 3 (producing three times more electricity than scenario 1), with scenario 2 resulting in the highest production of biochar (double the biochar production and 1.7 times more electricity than scenario 1), but being highly penalized by the great thermal demand associated with digestate dewatering. Sensitivity analysis was performed using a central composite design, predominantly to evaluate the bio-oil yield and its high heating value, as well as digestate dewatering. Results demonstrated the effect of these parameters on electricity production and on the global thermal demand of the plant. The main significant factor was the solid content attained in the dewatering process, which excessively penalized the global process for values lower than 25% TS.
Rubén González; Judith González; José G. Rosas; Richard Smith; Xiomar Gómez. Biochar and Energy Production: Valorizing Swine Manure through Coupling Co-Digestion and Pyrolysis. C 2020, 6, 43 .
AMA StyleRubén González, Judith González, José G. Rosas, Richard Smith, Xiomar Gómez. Biochar and Energy Production: Valorizing Swine Manure through Coupling Co-Digestion and Pyrolysis. C. 2020; 6 (2):43.
Chicago/Turabian StyleRubén González; Judith González; José G. Rosas; Richard Smith; Xiomar Gómez. 2020. "Biochar and Energy Production: Valorizing Swine Manure through Coupling Co-Digestion and Pyrolysis." C 6, no. 2: 43.
Co-digestion of swine manure with glycerine was studied by thermal analysis (TA) and differential scanning calorimetry (DSC). Co-digestion experiments were performed under batch conditions at different organic loadings by increasing the volumetric percentage of glycerine in the mixture. Batch results were used for evaluating the performance of the process under semi-continuous conditions in an attempt to study the characteristics of the digested material. Batch tests demonstrated a successful digestion at a glycerine volumetric addition of 16% (v/v), whilst failure of the semi-continuous digestion process was reported at 8%. The different operating regimes explained the discrepancy in these outcomes, therefore, indicating that results from batch tests should not be directly extrapolated to estimate continuous performance. The addition of glycerine at high percentage negatively affected the digestion under semi-continuous conditions, resulting in the accumulation of volatile fatty acids and high H2S evolution in biogas. These characteristics were accompanied by a decrease in the conversion of the organic matter as reported from the thermal evaluation of digested samples. TA represents a good indicator of the stabilisation attained when evaluating the fate of complex materials during biological transformations. DSC demonstrated to be a superior tool when evaluating the course of digestion and the quality of the organic material obtained. The failure stage (8% glycerine content) reported a mass change of 25.3 ± 0.5% for the complex materials, which represented an increase of 17% when evaluated against the successful digestion at 4% glycerine content. In this same line, when the enthalpy is considered, these complex materials contribute an increase of 22% in the digested sample of the failure stage. This enthalpy value calculated for the complex materials (temperature region of 370–575 °C) greatly aids in assessing degradation. Therefore, the need of a stabilisation stage for co-digestion systems with a high content of readily degradable material was highly recommended.
Rubén González; Richard Smith; D. Blanco; J. Fierro; X. Gómez. Application of thermal analysis for evaluating the effect of glycerine addition on the digestion of swine manure. Journal of Thermal Analysis and Calorimetry 2018, 135, 2277 -2286.
AMA StyleRubén González, Richard Smith, D. Blanco, J. Fierro, X. Gómez. Application of thermal analysis for evaluating the effect of glycerine addition on the digestion of swine manure. Journal of Thermal Analysis and Calorimetry. 2018; 135 (4):2277-2286.
Chicago/Turabian StyleRubén González; Richard Smith; D. Blanco; J. Fierro; X. Gómez. 2018. "Application of thermal analysis for evaluating the effect of glycerine addition on the digestion of swine manure." Journal of Thermal Analysis and Calorimetry 135, no. 4: 2277-2286.
The removal of colour and organic compounds from vinasses derived from the wine distillery industry was studied using boron-doped diamond-based electrodes and dimensionally stable anodes. The maximum reduction of organic compounds and colour was attained with the use of boron-doped diamond-based electrode after 10 h of operation at a current density of 6.6 mA cm−2. The current efficiency obtained was about 90% with a specific energy consumption (measured in terms of removal of chemical oxygen demand) of 17 kWh kg−1 COD removed. The dimensionally stable anodes were capable of removing 6–47% of the organic material and reached 60% decolourisation but with a lower current efficiency (between 85 and 10%) and much higher specific energy consumption values. The anaerobic digestion of vinasse after 1 h of treatment using boron-doped diamond-based electrode showed an effective mineralisation of the organic matter contained in the sample leading to an increase in methane production during anaerobic digestion.
E. Judith Martinez Torres; J. G. Rosas; Rubén González; D. Garcia; X. Gomez. Treatment of vinasse by electrochemical oxidation: evaluating the performance of boron-doped diamond (BDD)-based and dimensionally stable anodes (DSAs). International Journal of Environmental Science and Technology 2017, 15, 1159 -1168.
AMA StyleE. Judith Martinez Torres, J. G. Rosas, Rubén González, D. Garcia, X. Gomez. Treatment of vinasse by electrochemical oxidation: evaluating the performance of boron-doped diamond (BDD)-based and dimensionally stable anodes (DSAs). International Journal of Environmental Science and Technology. 2017; 15 (6):1159-1168.
Chicago/Turabian StyleE. Judith Martinez Torres; J. G. Rosas; Rubén González; D. Garcia; X. Gomez. 2017. "Treatment of vinasse by electrochemical oxidation: evaluating the performance of boron-doped diamond (BDD)-based and dimensionally stable anodes (DSAs)." International Journal of Environmental Science and Technology 15, no. 6: 1159-1168.
The potential of using anaerobic digestion for the treatment of poultry blood has been evaluated in batch assays at the laboratory scale and in a mesophilic semi-continuous reactor. The biodegradability test performed on residual poultry blood was carried out in spite of high inhibitory levels of acid intermediaries. The use of activated carbon as a way to prevent inhibitory conditions demonstrated the feasibility of attaining anaerobic digestion under extreme ammonium and acid conditions. Batch assays with higher carbon content presented higher methane production rates, although the difference in the final cumulative biogas production was not as sharp. The digestion of residual blood was also studied under semi-continuous operation using granular and powdered activated carbon. The average specific methane production was 216 ± 12 mL CH4/g VS. This result was obtained in spite of a strong volatile fatty acid (VFA) accumulation, reaching values around 6 g/L, along with high ammonium concentrations (in the range of 6–8 g/L). The use of powdered activated carbon resulted in a better assimilation of C3-C5 acid forms, indicating that an enhancement in syntrophic metabolism may have taken place. Thermal analysis and scanning electron microscopy (SEM) were applied as analytical tools for measuring the presence of organic material in the final digestate and evidencing modifications on the carbon surface. The addition of activated carbon for the digestion of residual blood highly improved the digestion process. The adsorption capacity of ammonium, the protection this carrier may offer by limiting mass transfer of toxic compounds, and its capacity to act as a conductive material may explain the successful digestion of residual blood as the sole substrate.
Maria José Cuetos; E. Judith Martinez; Rubén Moreno; Rubén González; Marta Otero; Xiomar Gomez. Enhancing anaerobic digestion of poultry blood using activated carbon. Journal of Advanced Research 2016, 8, 297 -307.
AMA StyleMaria José Cuetos, E. Judith Martinez, Rubén Moreno, Rubén González, Marta Otero, Xiomar Gomez. Enhancing anaerobic digestion of poultry blood using activated carbon. Journal of Advanced Research. 2016; 8 (3):297-307.
Chicago/Turabian StyleMaria José Cuetos; E. Judith Martinez; Rubén Moreno; Rubén González; Marta Otero; Xiomar Gomez. 2016. "Enhancing anaerobic digestion of poultry blood using activated carbon." Journal of Advanced Research 8, no. 3: 297-307.