Carbon and energy footprint of the hydrate-based biogas upgrading process integrated with CO2 valorization

Beatrice Castellani; Sara Rinaldi; Emanuele Bonamente; Andrea Nicolini; Federico Rossi; Franco Cotana

doi:10.1016/j.scitotenv.2017.09.254

Carbon and energy footprint of the hydrate-based biogas upgrading process integrated with CO₂ valorization

Sci Total Environ. 2018 Feb 15:615:404-411. doi: 10.1016/j.scitotenv.2017.09.254. Epub 2017 Oct 5.

Authors

Beatrice Castellani¹, Sara Rinaldi², Emanuele Bonamente³, Andrea Nicolini¹, Federico Rossi¹, Franco Cotana¹

Affiliations

¹ CIRIAF - Interuniversity Research Center on Pollution and Environment, University of Perugia, Via G. Duranti, Perugia, Italy; Department of Engineering, University of Perugia, Via G. Duranti, Perugia, Italy.
² CIRIAF - Interuniversity Research Center on Pollution and Environment, University of Perugia, Via G. Duranti, Perugia, Italy.
³ CIRIAF - Interuniversity Research Center on Pollution and Environment, University of Perugia, Via G. Duranti, Perugia, Italy; Department of Engineering, University of Perugia, Via G. Duranti, Perugia, Italy. Electronic address: emanuele.bonamente@unipg.it.

PMID: 28988076
DOI: 10.1016/j.scitotenv.2017.09.254

Abstract

The present paper aims at assessing the carbon and energy footprint of an energy process, in which the energy excess from intermittent renewable sources is used to produce hydrogen which reacts with the CO₂ previously separated from an innovative biogas upgrading process. The process integrates a hydrate-based biogas upgrading section and a CO₂ methanation section, to produce biomethane from the biogas enrichment and synthetic methane from the CO₂ methanation. Clathrate hydrates are crystalline compounds, formed by gas enclathrated in cages of water molecules and are applied to the selective separation of CO₂ from biogas mixtures. Data from the experimental setup were analyzed in order to evaluate the green-house gas emissions (carbon footprint CF) and the primary energy consumption (energy footprint EF) associated to the two sections of the process. The biosynthetic methane production during a single-stage process was 0.962Nm³, obtained mixing 0.830Nm³ of methane-enriched biogas and 0.132Nm³ of synthetic methane. The final volume composition was: 73.82% CH₄, 19.47% CO₂, 0.67% H₂, 1.98% O₂, 4.06% N₂ and the energy content was 28.0MJ/Nm³. The functional unit is the unitary amount of produced biosynthetic methane in Nm³. Carbon and energy footprints are 0.7081kgCO_2eq/Nm³ and 28.55MJ/Nm³, respectively, when the electric energy required by the process is provided by photovoltaic panels. In this scenario, the overall energy efficiency is about 0.82, higher than the worldwide average energy efficiency for fossil methane, which is 0.75.

Keywords: Biogas upgrading; CO(2) methanation; Carbon footprint; Clathrate hydrates; Energy footprint; LCA.