Techno-economic analysis of integrating sweet sorghum into sugar mills: The Central American case

This paper aims to evaluate the potential for electricity and ethanol production in Central America using sweet sorghum, performing a techno-economic analysis. The study proposes the integration of sweet sorghum into Central American sugar mills, by using the existing machinery to process this crop during off-season. A process simulation and a cost model were developed to estimate the technical and economical feasibility of sweet sorghum integration. The data on various parameters used for techno-economic assessment were collected from an existing sugar mill and distillery in Central America. The results show that a sugar mill operating 2 months during off-season could obtain an average revenue of US$3 M for a crushing rate of 6500 t/d. Ethanol production costs are estimated to be 24.76 ¢US$/L. In case a new CHP plant is built, a sugar mill operating under the integrated scenario would have a payback period of 4.49 years, as compared to 7.47 years for a sugar mill using sugarcane bagasse as the only fuel. Although several studies highlight the potential of sweet sorghum for ethanol production, the results from this work prove that sweet sorghum must also be seen as a viable feedstock for electricity production. A sensitivity analysis was also performed to determine the variation of the average cost of electricity and ethanol with the variables used in the economic analysis. For all analysed scenarios the effects of installed capacity and crop yield prevailed over the increasing costs of land and transportation.Publicad

Switching to efficient technologies in traditional biomass intensive countries: The resultant change in emissions

This paper aims to quantify the benefits of switching from a system dependent on traditional biomass to systems running on more efficient fuels and technologies. It is estimated that even when open fires burning fuelwood are replaced by improved cooking stoves (ICSs) and liquefied petroleum gas (LPG) stoves, and biomass is processed in dedicated biomass power plants, a net reduction in CO2 emissions is still obtained. The ICS/LPG stove/biomass combustion power plant configuration could provide an average net reduction of 84 kg-C-e/tDM. Meanwhile, a net reduction of 105 kg-C-e/tDM could be obtained when implementing a ICS/LPG stove/biomass gasification power plant scheme. Main factors influencing the net reduction of CO2 emissions are technology efficiency and the fraction of non-renewable fuel wood use. The switch from traditional biomass to modern biomass in traditional biomass intensive countries must not only be done to reduce CO2 emissions but also to avoid indoor pollution and energy poverty. Health improvements should be more important than energy savings. Results also indicate that the use of modern biomass systems not only could provide a reduction of local environmental pollution, but also could boost the local economy by the creation of biomass infrastructures

Bioenergy production in Central America: integration of sweet sorghum into sugar mills

This paper aims to evaluate the potential for electricity and ethanol production in Central America using sweet sorghum as an energy crop. Three scenarios were built to analyse sweet sorghum production in terms of the land where it can be cultivated: cropland, sugarcane land in fallow and land in continuous production (intercropping system). The land under permanent crops was not considered for this evaluation. We propose the integration of sweet sorghum into Central American sugar mills, by using the existing machinery to process it. The short growing period of sweet sorghum would allow the Combined Heat and Power (CHP) plants and distilleries to operate outside the sugarcane crushing season using sorghum bagasse and molasses as raw materials. This production could be performed 1 month before, and 1 month after the sugarcane season. Results indicate that by growing sweet sorghum on 5% of Central America's cropland, sorghum could supply around 10% of region's electricity demand. Thus, Central America could increase its CHP share of electricity supply from 4.4% to 5.6%. The increase in renewable electricity production would allow countries such as Guatemala, Honduras and Nicaragua to reduce fossil fuel bills by USD$13, 10 and 20 million, respectively. The ethanol produced from sweet sorghum during off-season can help to implement and maintain a sustainable ethanol program in the region that does not only depend on sugarcane. Sweet sorghum would allow distilleries to easily supply the ethanol required to implement an E5 or ED3 program. Central America could produce about 387 million liters of ethanol by growing sweet sorghum on 5$ 517 million by using ethanol gasoline blends or USD$ 463 million by using ethanol diesel blends.This work was partially founded by the Spanish Agency for International Development Cooperation (AECID) in the development of this research project.Publicad

Energy from Biomass: technology assessment of small-medium scale biomass conversion systems

Mención Internacional en el título de doctorBioenergy is a key resource to addressing challenges such as climate change (anthropogenic CO₂ emissions), pollution (suspended particles), energy security and human well-being. Currently, most of the biomass produced worldwide is consumed for cooking and space heating which has raised concerns among governments and policy-makers, especially due to threats to human health. The present thesis focuses on studying the technical and economic feasibility of energy systems based on biomass. It is considered that the main problems regarding the deployment of biomass-based energy systems are: (a) use of traditional biomass; (b) selection of a biomass-based technology; (c) low diversification of the biomass portfolio. With regards to the use of traditional biomass, the thesis evaluates the impact of switching from a system dependent on traditional biomass to a centralized system using low-carbon technologies. The outcome is a model capable of estimating the net reduction of CO₂ emissions that could be obtained by displacing fuelwood and introducing modern biomass taking into account the CO₂ released not only in the production, collection, transport, pre-treatment and conversion of biomass but also the anthropogenic CO₂ emissions caused by shifting to alternative fuels to meet basic energy needs. Results show that even when households have to use alternatives fuels, burning biomass in combustion and gasification power plants still provide a significant reduction in CO₂ emissions. With regards to the selection of a biomass-based technology, this thesis includes a methodology to identify, evaluate and select the best suited technology for the conditions of a given biomass value chain. As any system is affected by the conditions where it is developed, biomass-based energy systems are strongly dependent on region/local conditions such as weather, type of biomass resources, among others. Thus, each region demands its own detailed study. Given the lack of studies related to bioenergy in developing regions such as Central America (CA), this thesis entails a full study case presentation for CA where 84% of the biomass produced is used for domestic cooking and heating. In this context, the thesis aims at improving the bioenergy assessment methodology by using a resource-focused approach to determine the key biomass resources in the region and a Multi-Actor Multi-Criteria Decision- Making method to identify a portfolio of thermochemical conversion technologies appropriate for CA, considering parameters that range from technical, economic, environmental to socio-political aspects. Furthermore, it includes a discussion about the barriers that have stopped the progress of biomass technologies and the challenges to achieve modern bioenergy systems in the region. Results reveal that the main source of biomass in CA is in the agricultural sector and the most appropriate technologies to transform CA’s biomass are improved cooking stoves and biomass combustion power plants. With respect to the diversification of the biomass portfolio, currently, sugarcane bagasse is the biomass mostly used in large scale applications for the production of combined heat and power (CHP) in developing countries. Using a demand-driven assessment this thesis aims to evaluate the potential for electricity and ethanol production in CA using sweet sorghum as an alternative sugar crop. Three scenarios were built to analyse sweet sorghum production in terms of the land where it can be cultivated: cropland, sugarcane land in fallow and land in continuous production (intercropping system). The land under permanent crops was not considered for this evaluation. It is estimated that sweet sorghum could supply around 10% of region’s electricity demand or supply the ethanol required to implement a 5% ethanol blending programme. Following this assessment, the thesis studies the integration of sweet sorghum into Central American sugar mills by using the existing machinery to process it. The short growing period of sweet sorghum would allow the CHP plants and distilleries to operate during off-season using sorghum bagasse and molasses as raw materials. This thesis provides a techno-economic analysis of the production of electricity and ethanol from sweet sorghum in a sugar mill. The data on various parameters used for techno-economic assessment were collected from an existing sugar mill and distillery in Central America. Results indicate that modern energy carriers from sweet sorghum can be produced at a competitive price under CA conditions and crucial variables determining the cost of electricity and ethanol are the installed capacity of the plant and crop yield.La bioenergía es fundamental para hacer frente a retos como el cambio climático (emisiones antropogénicas de CO₂), contaminación (partículas en suspensión), seguridad energética y bienestar humano. Actualmente, la mayor parte de la biomasa que se produce a nivel global se utiliza para fines domésticos (calefacción y cocina) lo cual ha generado preocupación entre los gobiernos y responsables de establecer políticas energéticas, especialmente por los potenciales daños a la salud. La presente tesis doctoral se enfoca en el estudio técnico y económico de sistemas energéticos basados en biomasa. Se considera que los principales problemas con respecto al uso de sistemas basados en biomasa son: (a) uso de biomasa tradicional; (b) selección de la tecnología adecuada; (c) baja diversificación del portafolio de recursos biomásicos. Con respecto al uso de biomasa tradicional, esta tesis evalúa el impacto de cambiar de un sistema altamente dependiente en biomasa tradicional a un sistema centralizado utilizando tecnologías con bajas emisiones de carbón. El resultado es una modelo capaz de estimar la reducción neta en las emisiones de CO₂ que se podrían obtener debido al desplazamiento de leña y el incremento en el uso de biomasa moderna. Dicho modelo no solamente toma en cuenta el CO₂ emitido por la producción, recolección, transporte, pre-tratamiento y conversión de la biomasa sino que también considera las emisiones antropogénicas de CO₂ debidas al uso de combustibles modernos para satisfacer las necesidades energéticas básicas de los usuarios de leña. Los resultados indican que aún cuando los consumidores de biomasa tradicional cambian a combustibles alternativos, la conversión de biomasa en plantas de potencia basadas en combustión y gasificación, proporcionan una reducción en emisiones de CO₂ significativa. Con respecto a la selección de una tecnología para transformar los recursos biomásicos, la presente tesis incluye una metodología para identificar, evaluar y seleccionar la tecnología más apropiada bajo las condiciones de un sistema energético dado. Al igual que cualquier sistema que es afectado por sus alrededores y la interacción de las partes que lo conforman, los sistemas energéticos basados en biomasa son fuertemente influidos por condiciones regionales/locales como el clima o los tipos de recursos biomásicos entre otros. Por lo tanto, cada región exige la realización de un estudio detallado que incluya la influencia de variables locales. En este sentido, teniendo en cuenta los pocos estudios técnicos relacionados al uso de bioenergía en regiones en desarrollo como por ejemplo Centroamérica (CA), esta tesis realiza un estudio detallado para CA donde el 84% de la biomasa producida es usada para satisfacer necesidades energéticas básicas. En este contexto, la tesis tiene como objeto proponer soluciones que permitan la explotación de biomasa de manera eficiente utilizando un enfoque basado en los recursos disponibles para determinar las fuentes de biomasa con mayor potencial en la región. A su vez se emplea un análisis multicriterio impulsado por la participación de varios actores para identificar un portafolio de tecnologías apropiadas basadas en procesos termoquímicos para su implementación en CA considerando aspectos que varían desde lo técnico, económico, medioambiental hasta lo socio-político. Así también, discute las barreras que han detenido el progreso en el uso de tecnologías basadas en biomasa y los retos que se tienen que afrontar para incrementar el uso de biomasa moderna en dicha región. Los resultados muestran que la principal fuente de biomasa en CA proviene del sector agrario y que la tecnología más apropiada para transformar dicho recurso son las cocinas mejoradas y las plantas de potencia basadas en combustión. Con respecto a la diversificación del portafolio biomásico, actualmente el bagazo de la caña de azúcar es la biomasa más utilizada para la producción de vapor y electricidad a gran escala en regiones en desarrollo como Latinoamérica. Utilizando un enfoque impulsado por la demanda de electricidad y etanol, esta tesis tiene como objeto evaluar el potencial del uso de sorgo dulce en CA para la producción de vectores energéticos sostenibles. Tres escenarios han sido planteados para estudiar el potencial del sorgo dulce en función de dónde esta planta podría ser cultivada: tierra para cultivos, tierras potencialmente baldías dedicadas al cultivo de caña de azúcar y un sistema de intercultivo de sorgo dulce con caña de azúcar. La tierra dedicada al uso continuo de cultivos ha sido excluida del presente estudio. Se estima que la utilización de sorgo dulce como cultivo energético podría proveer alrededor del 10% de la demanda energética de la región o proveer el etanol necesario para implementar un programa de etanol al 5% en la gasolina. Así mismo, la presente tesis estudia la integración del sorgo dulce a los ingenios azucareros de CA utilizando la misma maquinaria que se emplea en la caña de azúcar para procesar dicho cultivo energético. El corto periodo de crecimiento del sorgo dulce permitiría a las plantas de potencia y destilerías operar fuera de la temporada de caña de azúcar utilizado el bagazo y miel final del sorgo dulce como materia prima. La presente tesis proporciona un análisis tecno-económico de la producción de electricidad y etanol a partir de sorgo dulce en ingenio azucarero. Los datos necesarios como parámetros de entrada para el análisis tecno-económico fueron obtenidos de una planta existente de producción de azúcar y destilería en CA. Los resultados indican que la producción de vectores energéticos con tecnologías modernas puede ser llevada a cabo a precios competitivos bajo las condiciones de CA y las variables que lo determinan, ya sea el costo de la electricidad o etanol a partir del sorgo dulce, son la capacidad instalada de las plantas y el rendimiento del cultivo energético.This work started as part of a project supported by the Spanish Agency for International Development Cooperation (AECID).Programa Oficial de Doctorado en Ingeniería Mecánica y de Organización IndustrialPresidente: Omar Raúl Masera Cerutti.- Secretario: Carolina Marugán Cruz.- Vocal: René M.J. Bender

Assessment of biomass energy sources and technologies: The case of Central America

This paper reviews and assesses conditions for increased and efficient use of biomass in Central America (CA), providing an overview of conditions for biomass supply in each country. Then, a Fuzzy Multi-Actor Multi-Criteria Decision-Making (MCDM) method is applied to identify a portfolio of biomass conversion technologies appropriate for CA, considering technical, economic, environmental and socio-political aspects. The work is motivated by the relatively large availability of biomass in CA at the same time as current conversion of biomass is carried out in inefficient processes. The assessment of technologies includes thermochemical processes (pyrolysis, combustion and gasification) for production of different energy carriers, including improved cooking stoves (ICSs). The most promising biomass feedstocks in the region are residue based; animal (manure), forest and agricultural origin. We show that around 250 PJ/year could be available for the energy sector, which is equivalent to 34% of primary energy supply for CA. It is concluded that in the short term promoting and implementing ICSs will give the largest improvement in the efficiency of biomass use, whereas on the long term small combustion plants seem to be the best choice for transforming CA's biomass into a clean and sustainable energy carriers, boosting economy and industrial development. Results show that the introduction of ICSs will result in an annual saving in the range of 4-8 Mt of fuelwood (59-113 PJ). Moreover, even when the investment cost of the cooking stoves is considered, ICSs yield economic savings to fuelwood consumers compared to traditional stoves. The total savings during the first year of implementation would be in the range of 19-152 US$/stove. (C) 2016 Elsevier Ltd. All rights reserved