Assessing the Limit of CO2 Storage in Seawater as Bicarbonate-Enriched Solutions.

The dissolution of CO2 in seawater in the form of bicarbonate ions is an attractive alternative to storage in geological formations, on the condition that the storage is stable over long periods and does not harm the marine environment. In this work, we focus on the long-term chemical stability of CO2 absorbed in seawater as bicarbonate by monitoring the physico-chemical properties of the solutions (pH, dissolved inorganic carbon and alkalinity) in six different sets of experiments on both natural and artificial seawater lasting up to three months. The bicarbonate treatment of natural seawater consists of mixing it with pre-equilibrated solutions obtained from the reaction of CO2 and Ca(OH)2, with the same pH as natural seawater. This was achieved with a pilot plant working with tons of seawater, while small-scale laboratory experiments were carried out by adding sodium bicarbonate to artificial seawater solutions. If the increase in the overall carbon concentration in the final mixture does not exceed a critical threshold (about 1000-1500 µmol/L), the resulting bicarbonate-rich solutions are found to be stable for over three months.

Short-term impact assessment of ocean liming: A copepod exposure test.

Ocean liming (OL) is a potential carbon dioxide removal (CDR) method that aims to increase the ocean's capacity to absorb atmospheric CO2 by adding hydrated lime to the surface ocean. Modeling studies indicate that OL may cause temporary pH spikes lasting several minutes, depending on the lime sparging rate. Little is known about the short-term effects of these spikes on marine organisms. Aim of the present study is to investigate these effects on the copepod Acartia tonsa. Copepods were exposed to different pH conditions (9, 10, 11, 12) by dosing different hydrated lime solutions. Copepod mortality, movements, and behavior were recorded. At pH 9 for short exposure times (<6 h), no negative effects were observed indicating a potential tolerable threshold for OL applications. At longer exposure times (>6 h) and pH higher than 9, negative effects (mortality and sublethal effects) were found significantly higher than in the control.

Use of aircraft in ocean alkalinity enhancement.

Ocean Alkalinity Enhancement (OAE) is a proposed Negative Emissions Technology (NET) to remove atmospheric CO2 through the dispersion of alkaline materials (e.g.: calcium hydroxide, slaked lime, SL) into seawater, simultaneously counteracting ocean acidification. This study considers aircraft discharge of SL and its consequent dry deposition, extending to the marine environment a technique used in freshwater. A feasibility analysis assesses potential, costs, benefits, and disadvantages, considering scenarios with different assumptions on aircraft size, discharge height and duration, and wind conditions. Due to the small size of SL particles (median diameter 9 µm), the dispersion from aircraft is highly enhanced by wind drift; the smallest SL particles may drift thousands of kilometres, especially if discharged from elevated altitudes. This could pose problems related to powders particles settling on remote lands. Although calcium hydroxide maximum concentration into water (from 0.01 to 82 mg L-1) is for almost all the scenarios lower than the most stringent threshold for the ecosystem impacts on a 96-h exposure, the ecologically sensitive sea surface microlayer (SML) should be considered in detail. The high CO2 emissions of the Landing to Take-Off Cycle (LTO) of the aircraft and their limited payload lead to a significant CO2 penalty, ranging in analysed scenarios between 28% and 77% of the CO2 removal potential; very fast discharge could reduce the penalty to 11% - 32%. Preliminary cost analysis shows that the cost of the SL discharge through aircraft is high, between € 30 and € 1846 per ton of CO2 removed (neglecting the lime cost), substantially higher than the cost for discharge by surface vessels resulting from previous studies, which restricts the practical use of this strategy.

A climate mitigation action index at the local scale: Methodology and case study.

This paper presents a novel climate mitigation action index to evaluate various aspects linked to the implementation of Sustainable Energy Action Plans (SEAP), which define the carbon dioxide emission reduction targets and outline the key actions to achieve these at the municipal level. A SEAP Implementation Index (SII) is developed and applied to study climate change mitigation actions implemented by 102 Municipalities belonging to the Metropolitan City of Milan (Italy) in the framework of the Covenant of Mayors (CoM). The SII is composed of six categories and 16 sub-indicators and results in a final score ranging from 1 to 10. The average rating obtained in the case study area is 4.2, and only eleven Municipalities achieved an evaluation higher than 6. The sensitivity analysis shows the index robustness against variations in the applied weight factors. The population engagement and the management of the initiative, neglected by many Municipalities mostly because of a lack of funding and personnel, are identified as the most critical aspects. Despite the massive participation in the CoM, no quantitative analysis of the SEAPs implementation has been proposed until now and this study shows some severe shortcomings in their application.

A methodology for elemental and organic carbon emission inventory and results for Lombardy region, Italy.

This paper presents a methodology and its application for the compilation of elemental carbon (EC) and organic carbon (OC) emission inventories. The methodology consists of the estimation of EC and OC emissions from available total suspended particulate matter (TSP) emission inventory data using EC and OC abundances in TSP derived from an extensive literature review, by taking into account the local technological context. In particular, the method is applied to the 2008 emissions of Lombardy region, Italy, considering 148 different activities and 30 types of fuels, typical of Western Europe. The abundances estimated in this study may provide a useful basis to assess the emissions also in other emission contexts with similar prevailing sources and technologies. The dominant sources of EC and OC in Lombardy are diesel vehicles for EC and the residential wood combustion (RWC) for OC which together account for about 83% of the total emissions of both pollutants. The EC and OC emissions from industrial processes and other fuel (e.g., gasoline, kerosene and LPG) combustion are significantly lower, while non-combustion sources give an almost negligible contribution. Total EC+OC contribution to regional greenhouse gas emissions is positive for every sector assuming whichever GWP100 value within the range proposed in literature. An uncertainty assessment is performed through a Monte Carlo simulation for RWC, showing a large uncertainty range (280% of the mean value for EC and 70% for OC), whereas for road transport a qualitative analysis identified a narrower range of uncertainty.

GHGs emissions from waste disposal in Lombardia (Italy): inventory 1975-2008 and projections 2009-2020.

A survey has been conducted across all MSW landfills with gas extraction system in the Lombardia Region (Italy) in order to collect data for an emission inventory assessment of greenhouse gas (GHG) emissions in the timeframe 1975-2008. The survey results identified a large number of landfills opened over the last 35 years and characterized by different kinds and amounts of waste disposed. Using the IPCC methodology, GHG emissions in the year 2008 were quantified to be 1.81 Mt CO(2)-eq, which corresponds to 1.9% of overall GHG emissions in Lombardia. A dependency between collection efficiency and age of the collecting network has been established and used for the projection of GHG emission in the period 2009-2020, and for two scenarios: a business as usual (BAU) and an alternative one that implies policies to reduce biodegradable carbon content in the residual waste. The latter allows for a 45% reduction of the GHG emissions in 2020 compared to the year 2008, whereas in the BAU scenario the expected reduction is 32%. The sensitivity analysis shows that a variation of parameters that represent the carbon content of the waste category and degradation rate constant, within the range reported in the literature, could affect GHG emission level by about ±18%, whereas the uncertainty due to landfill gas (LFG) composition is less relevant.

Traffic emission scenarios in Lombardy region in 1998-2015.

This study assesses and discusses the current and future contribution of road traffic to primary PM10 and PM10 main precursors (i.e. NO(x), SO(2), NH(3), VOC) in the Lombardy region (Italy). It defines a coherent and updated set of input parameters (emission factors, mileage and fleet composition) for traffic emission estimation between 1998 and 2015. 1998-2004 emissions are assessed basing on historical data, while 2005-2015 rely on different hypothesis about mobility development and vehicular turnover rate. The work shows that road traffic emissions of PM10 and PM10 precursors are expected to decrease in the period 2005-2015, with a reduction greater than 70% in scenarios with a fast vehicle turnover and a decrease in fuel usage. Increase in fuel consumption could substantially lower the emission reduction expected, off-setting a substantial part of the new technology benefits. The introduction of DPF (diesel particulate filter) vehicles will determine a reduction of PM10 exhaust, however this could potentially be stalled by the increase in diesel usage in the vehicle fleet and an increase in mileage driven, as the latter causes a rise in the contribution of PM10 from abrasion. Concerning the total atmospheric emissions in Lombardy, SO(2) (-6%) and NH(3) (<-2%) emission will remain constant, while PM10, VOC and NO(x) emission will decrease, respectively by 2-30%, 6-15% and 2-32% in the period 2001-2015.

Air and soil dioxin levels at three sites in Italy in proximity to MSW incineration plants.

Levels of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) in both air and soil samples were measured at three different sites in Italy, in proximity to three municipal solid waste incinerators (MSWIs) to determine baseline contamination and the contributory role of incinerator emissions. At the first site, located in an agricultural, cattle-breeding, typically flattish area of the Po Valley, the dioxin concentrations had already been measured before the start-up of the new MSWI. These dioxin concentrations were then again measured after two years of continual operation of the incinerator. Despite the presence of the plant, the PCDD/Fs concentrations appear not to have been affected and were found to be in a range of 22-125 fg I-TEQ m(-3) in the air samples and 0.7-1.5 pg I-TEQ g(-1) in the soil samples. The second site is located in an industrial district of the Veneto Region, in the surroundings of an old MSWI that is not equipped with Best Available Technology (BAT) dioxin removal system. The PCDD/Fs concentrations in the air samples were between 144 and 337 fg I-TEQ m(-3). This is a typical range of values for industrial areas, while the soil samples showed contamination levels between 1.1 and 1.4 pg I-TEQ g(-1). The third site lies in the Adige Valley, near a MSWI that has been equipped with BAT for flue gas cleaning. The observed values ranged from 10 to 67 fg I-TEQ m(-3) for the air samples and 0.08-1.2 pg I-TEQ g(-1) for the soil samples. The contributory factors of the varying characteristics of the different areas together with the types of technology adopted at each MSWI plant are discussed. The PCDD/Fs levels are subsequently compared with established values from previous studies.

PCDD/Fs emissions inventory in the Lombardy Region: results and uncertainties.

The results of an assessment study of both industrial and non-industrial dioxin and furan (PCDD/Fs) emissions in the Lombardy Region (Italy) are outlined below. The main data source refer to 1997, and are compiled from the Lombardy Emissions Inventory (developed under the framework of the Regional Air Quality Plan) together with documented emissions factors available. Due to the uncertain nature of the emissions assessment, results are provided as a most probable value within a given range. Total PCDD/Fs emissions in Lombardy average 33 g I-TEQ y(-1), ranging from minimum 13 g I-TEQ y(-1) to maximum 88 g I-TEQ y(-1). The main PCDD/Fs sources are waste incineration, electric arc furnace for steel production, vehicle diesel combustion and residential wood combustion. Incineration emission factors are expected to decrease over the period 2005-2010, in compliance with legal requirements. This will prioritize control over the remaining main PCDD/Fs contributors. Due to limited information available concerning this data, the accuracy of which is uncertain, further research is needed to evaluate the future role of these sources.