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• Evaluation of the low technology tubular digesters in the production of biogas from slaughterhouse wastewater treatment: Low cost tubular digesters

  J. Martí-Herrero, R. Alvarez, T. Flores

  Journal of Cleaner Production (2018). Vol. 199, pp. 633-642

  
  

  Abstract

  The aim of this research is to identify the operational conditions and performance of low cost tubular digesters producing biogas from the slaughterhouse wastewater treatment. Three full scale sequenced tubular digesters (of more than 8 m3 each), operating in a slaughterhouse in Cochabamba (Bolivia), have been monitored during one year. The Organic Load Rate (OLR) varied from 0.04 to 1.13 kgSV/m3d (0.04–1.07 kgCOD/m3d), and the Hydraulic Retention Time (HRT) from 3.2 to 87.4 days. The passive solar heating design considered drove the slurry temperature to 27 °C, 8 °C more than mean ambient temperature. The first digester has been filled with soda bottle plastic rings in order to increase the internal effective surface and evaluate, obtaining that an increment in 67% of the internal effective surface, more than doubles the biogas production and enables higher OLRs. A Biogas Production Rate (BPR) peak of 0.2 m3/m3d was observed for OLR = 0.37 kgSV/m3d, HRT = 9.7d and Specific Biogas Production (SBP) = 0.55 m3/kgSV. COD removal achieves values above 70% from HRT>19 d. A comparison with other anaerobic digestion technologies demonstrates that low cost tubular digesters with biofilm carriers, are competitive for OLR<0.5 kg COD/m3d of biogas production, and for 0.25 kgCOD/m3d, when the focus is on COD removal.

  Abstract
  The aim of this research is to identify the operational conditions and performance of low cost tubular digesters producing biogas from the slaughterhouse wastewater [...]

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• Biogas from a full scale digester operated in psychrophilic conditions and fed only with fruit and vegetable waste

  J. Martí-Herrero, G. Soria-Castellón, A. Díaz-de-Basurto, R. Alvarez, D. Chemisana

  Renewable Energy (2019). Vol. 133, pp. 676-684

  
  

  Abstract

  The aim of this work was to evaluate the feasibility of treating fruit and vegetable waste from a municipal market in a full-scale anaerobic digester with minimum implementation and operational costs, i.e. without pre-treatment, clean water consumption, active heating or mixing. For this purpose, a 13.9 m3 digester that forces the submersion of solids, gains heat through solar radiation and recirculates effluent was monitored during one year of real operational and weather conditions in Bolivia. The digester was initially loaded with cow rumen (inoculum source), and after eight weeks with only fruit and vegetable waste. The digester operated at an organic loading rate (OLR) of 1 kgVS/(m3d). The normalized specific biogas production averaged 0.26 m3/kgVS and increased to 0.34 m3/kgVS when OLR was halved to 0.57 kgVS/(m3d), while the passive solar design allowed an average digester temperature of 21 °C (4 °C above the average ambient temperature).

  Abstract
  The aim of this work was to evaluate the feasibility of treating fruit and vegetable waste from a municipal market in a full-scale anaerobic digester with minimum implementation [...]

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• Energy use of Jatropha oil extraction wastes: Pellets from biochar and Jatropha shell blends

  V. Ramírez, J. Martí-Herrero, M. Romero, D. Rivadeneira

  Journal of Cleaner Production (2019). Vol. 215, pp. 1095-1102

  
  

  Abstract

  The aim of this paper is to evaluate the use of biochar (SCB) produced through the pyrolysis of Jatropha seed cake in combination with Jatropha shell waste (JSh) to form pellet combustion fuel. Mixtures using different proportions of SCB and JSh (0, 25, 50, 75 and 100% each), were prepared, with each proportion tested using two particle sizes and two different quantities of water added. Combustion characteristics and mechanical durability were analyzed to identify the best blend, for which a thermogravimetric analysis was made. Pellets composed of 50% JSh and 50% SCB, with 25% of additional water and 4 mm particle size, presented the greatest mechanical durability (96.83%), and higher heating value (22.14 MJ kg−1). Combustion of pellets made with these characteristics in an industrial burner showed average temperatures ranging from 300 to 350 °C, with a maximum temperature of 460 °C. The production cost of the selected pellet is estimated at 0.11 USD kg−1, making the energy cost of the pellet [0.005 USD MJ−1] approximately 28% of the energy cost of LPG, demonstrating the commercial viability of the selected pellet as feasible.

  Abstract
  The aim of this paper is to evaluate the use of biochar (SCB) produced through the pyrolysis of Jatropha seed cake in combination with Jatropha shell waste [...]

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• Future oil extraction in Ecuador using a Hubbert approach

  V. Sebastián, J. Fontalvo, J. Martí-Herrero, P. Ramírez, I. Capellán-Pérez

  Energy (2019). Vol. 182, pp. 520-534

  
  

  Abstract

  Hubbert based models to project future oil extraction in Ecuador were developed. Two values of ultimate recoverable resources (URR) (7860–10,700 million barrels (MMbbl)) are applied to 16 models, considering symmetric and asymmetric Hubbert models and one and two cycles under top-down and bottom-up approaches. Models are discussed based on the best fit to historical data, and year and value of maximum extraction. The peak oil extraction obtained ranges between 196 and 215 MMbbl and would be reached in the years 2014–2025. An analysis of the implications of extraction models in a Business as Usual and Alternative oil demand scenarios up to 2035 was performed. Ecuador could become a net oil importer between 2024 and 2035, depending on the model and demand scenario. Economic oil trade balance could be seriously affected, decreasing from a current positive value of around 2 billion USD to incur deficits of 0.6–16.7 billion USD in 2035. Current and future oil dependence for Ecuador would increase vulnerability and compromise the country in terms of energy security and trade balance. It is critical for Ecuador to consider more ambitious policies focused on energy efficiency, renewables and diversification of the productive structure over the next few years.

  Abstract
  Hubbert based models to project future oil extraction in Ecuador were developed. Two values of ultimate recoverable resources (URR) (7860–10,700 million barrels (MMbbl)) [...]

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• Management and design of biogas digesters: A non-calibrated heat transfer model

  S. Vilms, J. Martí-Herrero, A. Singh, S. Sommer, S. Hafner

  Bioresource Technology (2020). Vol. 296, p. 122264

  
  

  Abstract

  A thermal balance modeling framework is developed, based on heat transfer-resistance networks. The heat transfer model accounts for effects of digester- design, location and operation, including effects of solar irradiance, external heating and ambient climate. We demonstrate extendibility of the framework by using the model in dynamic simulations of substrate temperature for digesters comprising two very different designs. Digester designs modeled include fixed-dome, buried, uninsulated and unheated household digesters in Hanoi, Vietnam, and an industrial-scale anaerobic digester located at a wastewater treatment plant in Esbjerg, Denmark. The modeled temperature profiles were evaluated against measured substrate temperatures over long periods, from 7 months and up. For the two Hanoi digesters, root-mean-square-error were 1.43 °C and 0.92 °C, with Nash-Sutcliffe model efficiency coefficients (NS-C) of 0.87 and 0.93 respectively. For the industrial digester in Esbjerg root-mean-square-error was 0.48 °C with an NS-C of 0.94. The model was not calibrated prior simulation, suggesting good predictive performance.

  Abstract
  A thermal balance modeling framework is developed, based on heat transfer-resistance networks. The heat transfer model accounts for effects of digester- design, location and [...]

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• Performance Analysis of a Small-Scale Biogas-Based Trigeneration Plant: An Absorption Refrigeration System Integrated to an Externally Fired Microturbine

  J. Villarroel-Schneider, A. Malmquist, A. Araoz, J. Martí-Herrero, A. Martin

  Energies (2019). Vol. 12 (20), pp. 3830

  
  

  Abstract

  Trigeneration or combined cooling, heat and power (CCHP) systems fueled by raw biogas can be an interesting alternative for supplying electricity and thermal services in remote rural areas where biogas can be produced without requiring sophisticated equipment. In this sense, this study considers a performance analysis of a novel small-scale CCHP system where a biogas-fired, 5 kWel externally fired microturbine (EFMT), an absorption refrigeration system (ARS) and heat exchangers are integrated for supplying electricity, refrigeration and hot water demanded by Bolivian small dairy farms. The CCHP solution presents two cases, current and nominal states, in which experimental and design data of the EFMT performance were considered, respectively. The primary energy/exergy rate was used as a performance indicator. The proposed cases show better energy performances than those of reference fossil fuel-based energy solutions (where energy services are produced separately) allowing savings in primary energy utilization of up to 31%. Furthermore, improvements in electric efficiency of the EFMT and coefficient of performance (COP) of the ARS, identified as key variables of the system, allow primary energy savings of up to 37%. However, to achieve these values in real conditions, more research and development of the technologies involved is required, especially for the EFMT

  Abstract
  Trigeneration or combined cooling, heat and power (CCHP) systems fueled by raw biogas can be an interesting alternative for supplying electricity and thermal services in remote [...]

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• Biogas based polygeneration plant options utilizing dairy farms waste: A Bolivian case

  J. Villarroel-Schneider, B. Mainali, J. Martí-Herrero, A. Malmquist, A. Martin, L. Alejo

  Sustainable Energy Technologies and Assessments (2020). Vol. 37, 100571

  
  

  Abstract

  This study presents a comparative techno-economic feasibility analysis for two polygeneration plant solutions, applied to low-income dairy farms in Bolivia. The first option considers an internally fired microturbine (IFMT) and, the second, an internal combustion engine (ICE). They are integrated with an absorption refrigeration system and a fertilizer dryer. Biogas, produced with farms waste, fuels these power generators. The levelized costs of biogas for cooking, electricity, cooling and fertilizers were determined. The cost of biogas, for both options, was found to be 0.020 USD/kWh, which is lower than the subsidized price of LPG. The most competitive cost of electricity was determined for the ICE plant option; it was found to be 0.082 USD/kWh and is lower than the subsidized cost of fossil fuel-based electricity. The cost of cooling was found to be around 0.082 USD/kWh, which is slightly higher than the cost of cooling supplied by using grid electricity. In a realistic scenario, the shorter payback period was found to be 4.4 years for the ICE plant option. From this, the ICE-based plant was found as the most feasible option. Additionally, if no subsidies are applied to the fossil fuel-based services, the proposed polygeneration systems are a highly competitive alternative.

  Abstract
  This study presents a comparative techno-economic feasibility analysis for two polygeneration plant solutions, applied to low-income dairy farms in Bolivia. The first option [...]

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• Techno-Economic Study of a Biogas-Based Polygeneration Plant for Small Dairy Farms in Central Bolivia

  J. Martí-Herrero, A. Malmquist, A. Martin, J. Villarroel-Schneider, B. Mainali, L. Alejo

  (2019). Renewable Energy and Sustainable Buildings. Innovative Renewable Energy. Springer, Cham, pp. 675-687

  
  

  Abstract

  This paper presents a techno-economic feasibility study of a polygeneration plant proposed for an association of dairy farmers in Bolivia. The systems have been designed in an integrated approach and are based on the resource recovery utilizing available cow dung. The production of biogas is proposed using “low cost” tubular digesters. The biogas is used for the production of electricity and heat in a 40 kWel internal combustion engine. Heat from the exhaust gas is recovered to drive an absorption cooling system for milk refrigeration and for a bio-slurry drying system. The final services are biogas, electricity, cooling and fertilizers. The techno-economic analysis focuses on determining the levelized cost of the services and compare them with the subsidized and non-subsidized prices of other competitive services in the market. Sensitivity analyses for the services prices are carried out to see the influence of the feedstock handling cost and the subsidies on investment capital. Once the selling prices of the services are defined, the payback period of investment capital is determined. The results show that the biogas and electricity costs were found lower than the subsidized prices of similar services in the market while the cost of cooling was found slightly higher. From the sensitivity analysis we have that the feedstock handling cost can be increased from 10 to 18 USD/ton while maintaining the biogas price below the subsidized LPG price, and applying subsidies to the investment capital allows reducing the rest of the services costs. The payback period is around 3.5 years when a subsidy of 15% is applied in the investment capital and the services are sold at the subsidized prices of the conventional services. Our study has shown that under the conditions of the Bolivian market it is feasible the installation of a polygeneration plant. On the other hand, a market without or with reduced subsidies for the conventional services makes the proposed system more feasible and competitive.

  Abstract
  This paper presents a techno-economic feasibility study of a polygeneration plant proposed for an association of dairy farmers in Bolivia. The systems have been designed in [...]

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• Combinación de métodos lagrangianos de elementos finitos y partículas (PFEM) con métodos eulerianos para el análisis del comportamiento de presas de escollera durante un sobrevertido

  A. LARESE, R. Rossi

  (2009). "Congreso de Métodos Numéricos en Ingeniería 2009". Barcelona: Sociedad Española de Métodos Numéricos en Ingeniería (SEMNI), p. 466. ISBN9788496736665

  
  

  Abstract

  El objetivo de este trabajo es desarrollar una herramienta de aplicabilidad general que ayude en el estudio de la estabilidad y seguridad de una presa de escollera en una avenida extraordinaria que origina un sobrevertido. se combinan métodos eulerianos para el cálculo de flujo de agua fuera y dentro de la presa con métodos lagrangianos de elementos finitos y partículas para analizar el comportamiento tenso-deformacional de la presa y su posible rotura y eventual desmoronamiento bajo la acción del agua. Finalmente se presenta un método para la proyección de datos entre mallas no coincidentes que permita el acomplamiento fluido-estructura.

  Abstract
  El objetivo de este trabajo es desarrollar una herramienta de aplicabilidad general que ayude en el estudio de la estabilidad y seguridad de una presa de escollera en una [...]

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• Un método de cálculo para el estudio de la seguridad de presas de escollera durante un sobrevertido

  A. LARESE, R. Rossi

  (2008). "VIII Jornadas Españolas de Presas", p. 1-10. ISBN978-84-380-0406-7

  
  

  Abstract

  El objetivo de este trabajo es desarrollar y validar un nuevo método de cálculo de aplicabilidad general para el estudio de la estabilidad y seguridad de una presa de escollera durante un sobrevertido. Esta nueva herramienta permite analizar con detalle el estado tenso-deformacional de la presa y su posible rotura y eventual desmoronamiento bajo la acción del flujo de agua y combina métodos de elementos finitos avanzados con métodos de partículas. Esta técnica, denominada PFEM (particle finite element method), permite tener en cuenta de las complejas no-linealidades geométricas y mecánicas en problemas de interacción fluido-estructura, incluyendo fenómenos de superficie libre y de erosión. En el trabajo se describen las características esenciales del PFEM y se detalla la aplicación de este método para modelar el sobrevertido en presas de escollera y su eventual desplome. Este tabajo numérico se combina con una parte experimental que se desarrolla en el CEDEX y en la ETS de Ingenieros de Caminos de Madrid en el marco del proyecto XPRES.

  Abstract
  El objetivo de este trabajo es desarrollar y validar un nuevo método de cálculo de aplicabilidad general para el estudio de la estabilidad y seguridad de una [...]

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