www.futurenviro.es | Julio-Septiembre July-September 2022 46 Bioenergía. Gases Renovables | Bioenergy. Renewable Gases Dependiendo de cada materia prima, la biometanización ofrece distintas características y propiedades. La gran oportunidad del biometano Una planta de biometano consiste básicamente en una planta de biogás a la que se le ha añadido una unidad de upgrading para purificar el biogás desde un contenido de aproximadamente el 60% de metano hasta más del 97%. El desarrollo del biogás en Europa, pese a las innumerables ventajas medioambientales que ofrecían, ha necesitado de impulso y ayuda de las respectivas administraciones para poder avanzar, especialmente en lo que respecta a los residuos de origen agrícola y ganadero que no han internalizado o no ha podido internalizar los costes derivados del tratamiento de sus residuos. Por ello, solo se ha desarrollado significativamente el biogás procedente de residuos agroganaderos y agroindustriales en aquellos países en que ha recibido suficientes ayudas e incentivos de sus administraciones, aspecto que no se ha dado en España. De las aproximadamente 20.000 plantas de biogás que operan en Europa, en España apenas lo hacen 260 pese a que la Comisión Europea lo considera que es el tercer país con mayor potencial. El desarrollo del biometano ha seguido una línea consecuente con el desarrollo del biogás. Alemania es el país con mayor desarrollo y en España todavía es una tecnología incipiente, pese a que ya existen 5 plantas inyectando en red. Principales problemas y barreras para el desarrollo del biometano La biodigestión y el upgrading son procesos técnicamente muy maduros sea cual sea la materia prima, ya sean lodos de depuradora, fracción orgánica de residuos sólidos urbanos o residuos agropecuarios y agroindustriales. Por ello las problemáticas y barreras no están ligadas a la tecnología de biodigestión sino a dos aspectos externos al propio proceso que son: • La gestión y suministro de materias primas. • La gestión de los digeridos. Estos dos aspectos del proceso son especialmente problemáticos cuando las materias primas son residuos agropecuarios y agroindustriales como vamos a analizar a continuación. The great biomethane opportunity A biomethane plant basically consists of a biogas plant to which an upgrading unit has been to purify the biogas and increase the methane content from around 60% to over 97%. Despite its countless environmental advantages, the development of biogas in Europe has required impetus and help from the respective public authorities, especially with regard to agricultural and livestock waste, which comes from a sector that has not internalised or has not been able to internalise the costs associated with the treatment of the waste it produces. For this reason, biogas from livestock and agro-industrial waste has only developed significantly in countries where it has received sufficient aid and incentives from public authorities, which has not been the case in Spain. Just 260 of approximately 20,000 biogas plants operating in Europe are located in Spain, despite the fact that the European Commission considers it to be the country with the third-highest potential. The development of biomethane has followed a line consistent with the development of biogas. Germany is the country with the greatest development, while it is still an incipient technology in Spain, despite the fact that there are now five plants injecting into the grid. Main problems and obstacles to the development of biomethane Bio-digestion and upgrading are technically very mature processes, regardless of whether the feedstock is sewage sludge, the organic fraction of municipal solid waste or agricultural and agro-industrial waste. Therefore, the problems and obstacles are not associated with the bio-digestion technology but rather with two factors that are external to the process itself: • Feedstock management and supply. • Digestate management. These two aspects of the process are particularly problematic when the raw materials are agricultural and agro-industrial waste, as is outlined below. Management and supply of feedstock The management and supply of raw materials is subject to different complexities associated with geographical dispersion, seasonality and varying characteristics. The issue of dispersion is an obvious one. Spain has a very large surface area compared to most European countries and, although farms are geographically concentrated in some cases, the raw materials, especially slurry and manure from livestock farming, which have a relatively low biomethane production potential, can only be transported over short distances. Seasonality is another key issue, because some alternative products with higher C/N ratios and higher production potential are seasonal and not always easy or cheap to store (crop waste, straw or pomace). The waste and raw materials have different characteristics in terms of C/N ratio and solids concentrations. The feedstock fed to the bioreactors depends on these characteristics and is conditioned by them. Public authorities can act on this. The dispersion exists, but much of the waste that should be managed is not. If the authorities were to make it compulsory for the waste to be Planta de biogás Vall d´Uixó (Castellón). Fuente Biovic Biogas plant Vall d´Uixó (Castellón). Source: Biovic
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