Techno-economic assessment of anaerobic co-digestions of livestock manure with agro-industrial by-products

• Autores: Seyed Mostafa Imeni
• Directores de la Tesis: Joan Colón Jordà (dir. tes.), Sergio Ponsá Salas (codir. tes.)
• Lectura: En la Universitat de Vic - Universitat Central de Catalunya ( España ) en 2019
• Idioma: español
• Tribunal Calificador de la Tesis: Antonio Sánchez Ferrer (presid.), Ivet Ferrer Marti (secret.), Lorenzo Bertin (voc.)
• Programa de doctorado: Programa de Doctorado en Ciencias Experimentales y Tecnologías / Experimental Sciences and Technology por la Universidad de Vic-Universidad Central de Catalunya
• Materias:
  • Ciencias agrarias
    • Ingeniería agrícola
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• Resumen

  • Deposition of excess amount of livestock waste when they are not properly treated has a notable environmental impacts specially on soil and undergrounds water. Livestock waste as a biodegradable waste can be treated and recycle to finally obtain compost or biogas which means green energy and fertilizer/soil-amendment products. In general biodegradable waste receives especial attention in the European Legislation (Revised Framework Directive 2008/98/CE) and therefore, is necessary to develop suitable facilities to treat these types of waste and assure the correct and efficient operation of such treatment and management facilities. Anaerobic digestion of dairy cattle manure is a common practice; however, the low biogas yield of manure can hamper the profitability of anaerobic digestion systems in small to medium dairy cattle farms. To make this technology more attractive to farmers, an increase in biogas yield per cubic meter of reactor could be achieved by co-digesting animal manure with an abundant and easy accessible co-substrate such as agricultural by-products like wheat straw (in its raw form or pre-treated) and dairy industry by-products like cheese whey. In addition of increase in biogas production which can be translated to production of more energy, economic feasibility of implementation of anaerobic digestion plants in the farms is a must. However, there is scarce information provided in scientific literature about economic feasibility of implementation of such plants in small to medium cattle farms. Thus, in this thesis a techno-economic assessment of anaerobic co-digestion of animal manure and wheat straw (in the raw form and pretreated) or cheese whey was carried out. The technological assessment was carried out at lab scale using batch and semi-continuous reactors. With the data obtained, an economic model was developed in order to investigate the profitability of anaerobic co-digestion plants in small to medium dairy cattle farms, sensitivity analyses were carried out to investigate important parameters (e.g. electricity price) on the overall economic performance of the system. The results obtained from the techno-economic assessment showed that for a farm of 250 adult cattle heads the revenues generated in an anaerobic mono-digestion process are not able to offset the initial required investment. However, the co-digestion of manure with raw or briquetted straw showed positive economic performance and positive returns (Net Present values > 0, Internal Rate of Return > 9 % and a Return of the investment in 11 years) as well as the co-digestion of manure with 30% of cheese whey which showed positive returns (Net Present values > 0, Internal Rate of Return > 11% and a Return of the investment in 9 years). For farmers willing to implement anaerobic digestion, Electricity selling price, and the price of the straw are the key parameters to determine the profitability of the system. Moreover, pre-treatments to increase the straw biogas production have been assessed and evaluated from a technic and economic perspective. Alkali and microwave-alkali straw pre-treatments showed the best results with an increase in biogas production of 156 % and 92 % compared to raw straw.