Carbon Capture and Storage (CCS) technology is seen as an effective technique to decrease significant amounts of CO₂ from stationary sources. Many efforts are being put towards developing new techniques to capture CO₂ from industrial emitters. However, it is necessary to store CO₂ in a safe manner. Techniques applied to develop a suitable emplacement are well known, since these are similar to that for oil or gas explorations. Nonetheless, successful site selection (screen phase) will decrease the inherent risk in the geological exploration (assessment and select phase). In this process, many criteria should be taken into consideration, including technical and socio-economical aspects. For this purpose, different mathematical algorithms have been developed to solve multicriteria problems and to help the decision-makers. This article describes a methodology for the selection of site areas or structures for storing CO₂ based on a multicriteria algorithm, which will rank the areas under consideration, in order to select the most suitable or promising emplacement.

Biogas is a renewable gas with low heat energy, which makes it extremely difficult to use as fuel in conventional natural gas equipment. Nonetheless, the use of hydrogen as a biogas additive has proven to have a beneficial effect on flame stability and combustion behavior. This study evaluates the biogas–hydrogen combustion in a conventional natural gas burner able to work up to 100 kW. Tests were performed for three different compositions of biogas: BG70 (30% CO₂), BG60 (40% CO₂), and BG50 (50% CO₂). To achieve better flame stability, each biogas was enriched with hydrogen from 5% to 25%. The difficulty of burning biogas in conventional systems was proven, as the burner does not ignite when the biogas composition contains more than 40% of CO₂. The best improvements were obtained at 5% hydrogen composition since the exhaust gas temperature and, thus, the enthalpy, rises by 80% for BG70 and 65% for BG60. The stability map reveals that pure biogas combustion is unstable in BG70 and BG60; when the CO₂ content is 50%, ignition is inhibited. The properties change slightly when the hydrogen concentrations are more than 20% in the fuel gas and do not necessarily improve.

Deep saline aquifers are amongst the most promising emplacements for CO2 storing, since theoretically these structures offer the highest value in terms of capacity, the risk associated with the exploration of these potential sites is greater than that for already investigated depleted oil or gas fields.In such cases, it is likely that multicriteria algorithms can facilitate the evaluation of the best alternative under consideration and the results from this process will, therefore, help the decision-maker in decreasing the risk associated with the exploration of these potential emplacements.Site selection phase comprises the identification, characterization and selection of emplacements which could be suitable for CCS among a list of candidates. In this article we propose a methodology based on (i) data recompilation and (ii) mathematical algorithm to define criteria and to hierarchy all of them in a quantitative methodology.Multicriteria decision tool could complement the collection of data: It is necessary to evaluate and to hierarchy each region or area, in order to improve the economic and technical efforts into CO2 storage characterization. To make it possible, both technical and socio-economic criteria should be defined and weighted through a criteria ranking process.In order to help decision maker mathematical algorithm and hierarchy process has been implemented in software: CO2SITEASSESS is a program based on Visual Basic. It connects with a Data Base (CO2 sources and storage alternatives), and it allows to compare different areas and structures, in order to hierarchy them or to compare with other projects (it easily might be used to standardize the site selection phase). Results can be implemented in a Geographical Information System, and it allows to geo-reference the alternatives.This tool has been used to evaluate different areas in Spain: The Guadalquivir basin in southern Spain. Five structures were defined, and the results showed that the methodology is useful to compare different alternatives, and the software may describe the criteria which need more accuracy (lack of data). In this case, the software helps project manager to define the characterization activities, in order to focus on those parameters which needs to be explore

The increase in pig production is a key factor in the fight against climate change. The main problem is the amount of slurry which causes environmental problems, therefore optimal management is needed. This management consists of an anaerobic digestion process in which biogas is produced and a subsequent upgrading process produces biomethane. In this study, a comparison of different biomethane production systems is completed in order to determine the optimum for each pig farm, determining that conventional upgrading systems can be used on farms with more than 11,000 pigs and, for smaller numbers of pigs, the biological upgrading system. The implementation of these technologies contributes to reducing fossil energy demand and greenhouse gas emissions by using biogas and biomethane as heat, electricity or vehicle fuel.