Biogas, as a product that comes from biodegradability of biomass, both from animal and vegetal origin, is generated in processes of anaerobic digestion with EDAR sludge, agricultural waste, household waste, etc. It has a high energetic value because of its methane content (CH4). This value considerably increases if the concentrations of the rest of components presents reduce, basically carbonal anhydrid (CO2), through upgrading processes (improving performance) of biogas.
The high concentration of methane, greater than 95%, generates a new ‘Bio-Sourced product’ (of biological origin) called biomethane. It has almost identical characteristics in concentration and primary energy to natural gas (of fossil origin) used in the gas network. Therefore, it is likely to be injected into it and/or be consumed as fuel for transport fleets.
Faced with the traditional management of biogas with cogeneration systems, in which the sale of energy or self-consumption prevails, the generation of biomethane provides us with a significant reduction in the emissions avoided in facilities outside our own company.
”Biomethane is likely to be consumed as a fuel for transport fleets”
Baix Llobregat Ecofactory
The project of biometanization that Aigües de Barcelona is promoting, within the context of the 2030 Agenda, is the sum of different initiatives that encompass the entire project and that aim to increase the production of biogas in the Baix Llobregat Ecofactory and, consequently, increase the primary energy available.
This ecofactory has an anaerobic digestion with a usable volume that allows us to provide mud from other facilities within the Barcelona metropolitan area. This is the case of the sludge platform, an installation that will treat up to five trucks a day from the Besòs Ecofactory. This mechanically dehydrated mud, as it that has not been digested, will provide a high potential for methanization to the digestion of Baix Llobregat due to its high volatility.
This platform will receive and rehydrate this mud to be digested together with the mud of the ecofactory itself and will contribute a decrease in the overall management of almost 13% of the total production of dehydrated mud in the set of facilities operated by Aigües de Barcelona, while increasing the production of biogas by 45% compared to the current value. This is the case of codigestion, dosage to anaerobic digestion of non-special liquid waste with high DQO content, basically from the agri-food industry, with a high and rapid potential to generate methane. With an initial contribution of 30,000 tons per year of waste that will increase biogas production by approximately 49% compared to the current value.
With an almost total increase of the production of biogas of 94% due to these two initiatives included in the project, part of this biogas will be used in the annual production of 27 GWh of biomethane that will be transported, directly, in a newly built pipeline from the Baix Llobregat Ecofactory to the maintenance and recharging depots that Transports Metropolitans de Barcelona (TMB) has in the Zona Franca of Barcelona.
This production will allow us to feed and guarantee the daily mobility of about 40 to 50 urban buses that now operate with compressed natural gas (GNC) and will save annually the amount of CO2 absorbed by about 6.000 trees. Selective permeability membranes will be used as the technology to transform biogas into biomethane and will allow separating CO2 and CH4. The rest of the biogas will be used in the cogeneration existing in the Baix Llobregat Ecofactory to guarantee both the thermal energy necessary to heat mesophile anaerobic digestion and to increase the percentage of self-consumption of the installation up to 45%.