• Energy Research

Abstract The paper describes the energy and environmental evaluation of a new patented process for the storage of liquid carbon dioxide (CO2) in glass capsules on the deep seabed. This technology is proposed as a safe option to store CO2 captured from flue gas of industrial processes and power plants, as well as directly from the atmosphere, in order to overcome the obstacles that still today limit the commercial deployment of other CO2 storage techniques, such as the injection in saline aquifers. By keeping the liquid CO2 separated from the seawater, the technology might be an alternative that presents reduced risk associated with the storage in the marine environment when compared to other alternatives proposed in the past. A Life Cycle Assessment carried out with different combinations of the geographical and technological parameters showed an average impact of 0.10 tCO2eq per ton of stored CO2. The process with the highest impact was the capsule production, due mainly to the consumption of natural gas and electricity, as well as to calcination taking place during the production of glass. The availability of space in the seabed for submarine CO2 storage in capsules resulted a minor issue for the development of the technology. Close to most coastal areas where CO2 emission sources are located, large surfaces of the seabed at a suitable depth (between 1500 and 3000 m) and distance from the coast (

In Europe, about 20% of municipal solid waste is incinerated. Large differences can be found between northern and southern Europe regarding energy recovery efficiencies, flue gas cleaning technologies and residue management. Life-cycle assessment (LCA) of waste incineration often provides contradictory results if these local conditions are not properly accounted for. The importance of regional differences and site-specific data, and choice of LCA model itself, was evaluated by assessment of two waste incinerators representing northern and southern Europe (Denmark and Italy) based on two different LCA models (SimaPro and EASEWASTE). The results showed that assumptions and modelling approaches regarding energy recovery/substitution and direct air emissions were most critical. Differences in model design and model databases mainly had consequences for the toxicity-related impact categories. The overall environmental performance of the Danish system was better than the Italian, mainly because of higher heat recovery at the Danish plant. Flue gas cleaning at the Italian plant was, however, preferable to the Danish, indicating that efficient flue gas cleaning may provide significant benefits. Differences in waste composition between the two countries mainly affected global warming and human toxicity via water. Overall, SimaPro and EASEWASTE provided consistent ranking of the individual scenarios. However, important differences in results from the two models were related to differences in the databases and modelling approaches, in particular the possibility for modelling of waste-specific emissions affected the toxicity-related impact categories. The results clearly showed that the use of site-specific data was essential for the results.

This study focuses on the potential energetic and environmental impacts associated with the production of wheat grain-based bioethanol in Lombardia (Italy), with a "seed-to-wheel" approach (i.e. taking into account the production and use phase). Greenhouse gas emissions (GHGs) were estimated through the CML 2 baseline 2000 methodology counting the CO(2) equivalent emissions, while the energy flow indicator was estimated using the Ecoindicator 95 methodology. The impact of the different phases involved in the production and use of bioethanol have been analysed: the agricultural production of wheat grain, its transformation into bioethanol, the production of gasoline and the use of 5 different blends (from pure gasoline to pure ethanol). The results show that ethanol fuel, used in the form of blends in gasoline, can help reduce energy use and GHGs. In particular, the use of pure ethanol was found to be the best alternative presenting the lowest GHGs (saving about 32% of CO(2)eq emissions in comparison to gasoline) and the minor energy use (63% saving). Differences between low-ethanol blends and gasoline are minimal and dependent on the specific fuel consumption of the vehicle. The sensitivity analysis performed to test the robustness of results through the change of some basic assumptions (specific fuel consumption, N(2)O emissions from agricultural phase, allocation method) shows the sensitivity of GHGs saving to the adopted allocation method.

Shredding is the common end-of-life treatment in Europe for dismantled car wrecks. It produces the so-called Automotive Shredded Residue (ASR), usually disposed of in landfill. This paper summarizes the outcome of a study carried out by Politecnico di Milano and LEAP with the support of Actelios SpA on the prospects of a technology based on sequential gasification and combustion of this specific waste stream. Its application to the treatment of ASR allows the recovery of large fractions of metals as non-oxidized, easily marketable secondary raw materials, the vitrification of most of the ash content and the production of power via a steam cycle. Results show that despite the unfavourable characteristics of ASR, the proposed technology can reach appealing energy performances. Three of four environmental impact indicators and the cumulative energy demand index are favourable, the main positive contributes being electricity production and metal recovery (mainly aluminium and copper). The only unfavourable indicator is the global warming index because, since most of the carbon in ASR comes from fossil sources, the carbon dioxide emissions at the stack of the thermal treatment plant are mainly non-renewable and, at the same time, the avoided biogas production from the alternative disposal route of landfilling is minor.

This paper reports the environmental results, integrated with those arising from mass and energy balances, of a research project on the comparative analysis of strategies for material and energy recovery from waste, funded by the Italian Ministry of Education, University and Research. The project, involving the cooperation of five University research groups, was devoted to the optimisation of material and energy recovery activities within integrated municipal solid waste (MSW) management systems. Four scenarios of separate collection (overall value of 35%, 50% without the collection of food waste, 50% including the collection of food waste, 65%) were defined for the implementation of energetic, environmental and economic balances. Two sizes of integrated MSW management system (IWMS) were considered: a metropolitan area, with a gross MSW production of 750,000 t/year and an average province, with a gross MSW production of 150,000 t/year. The environmental analysis was conducted using Life Cycle Assessment methodology (LCA), for both material and energy recovery activities. In order to avoid allocation we have used the technique of the expansion of the system boundaries. This means taking into consideration the impact on the environment related to the waste management activities in comparison with the avoided impacts related to the saving of raw materials and primary energy. Under the hypotheses of the study, both for the large and for the small IWMS, the energetic and environmental benefits are higher than the energetic and environmental impacts for all the scenarios analysed in terms of all the indicators considered: the scenario with 50% separate collection in a drop-off scheme excluding food waste shows the most promising perspectives, mainly arising from the highest collection (and recycling) of all the packaging materials, which is the activity giving the biggest energetic and environmental benefits. Main conclusions of the study in the general field of the assessment of the environmental performance of any integrated waste management scheme address the importance of properly defining, beyond the design value assumed for the separate collection as a whole, also the yields of each material recovered; particular significance is finally related to the amount of residues deriving from material recovery activities, resulting on average in the order of 20% of the collected materials.

The iron and steel industry is responsible for a significant amount of direct and indirect greenhouse gas emissions. The goal of this study is to evaluate the environmental impacts of a new system in which the steel mill gases (Basic oxygen furnace gases BOFGs, Blast furnace gases BFGs, and Coke oven gases COGs) are used to produce both methanol and electricity. In the specific configuration under study, 100% of BOFGs and 90% of COGs are used for methanol production, whereas 100% of BFGs and 10% COGs are used for electricity production. The analysis was conducted by applying the Life Cycle Assessment methodology. The model considered all the processes associated with the treatment of the gases, including the methanol and electricity productions and the corresponding avoided products. The results show that for most of the impact categories (12 out of 17), the benefits associated with the avoided productions are higher than the impacts caused by the process itself. In particular, the avoided methanol gives an important benefit in four impact categories. Focusing on the contributions adding impacts to the environment, the power plant and the chemicals used in some of the units resulted as the most important ones. When considering the use of the methanol as ship fuel in substitution of heavy fuel oil, the avoided impacts are higher than the impacts associated with the process itself for 15 out of the 17 impact categories, and the impact on climate change is reduced from 504 kgCO2eq of the baseline scenario to 491 kgCO2eq per 1000 kg steel mill gases.

This study investigates the environmental improvements associated to the integration of a microalgae unit as a side-stream process within an existing municipal wastewater treatment facility in northern Italy. Microalgae are fed on the centrate from sludge dewatering, rich in nutrients, and on the CO2 in the flue-gas of the combined heat and power unit. The produced biomass is recirculated upflow the water line where it settles and undergoes anaerobic digestion generating extra biogas. A life cycle assessment was performed collecting primary data from an algal pilot-scale plant installed at the facility. Fifteen environmental indicators were evaluated. Compared to the baseline wastewater treatment, the new algal configuration allows an improvement for 7 out of 15 indicators mainly thanks to the electricity savings in the facility. Some recommendations are provided to improve the performance of the algal system in the scaling up.

Abstract This paper analyzes and compares the environmental impacts of biomass combustion in small appliances such as domestic open fireplaces and stoves, and in two types of centralized combined heat and power plants, feeding district heating networks. The analysis is carried out following a Life Cycle Assessment (LCA) approach. The expected savings of GHG (greenhouse gases) emissions due to the substitution of fossil fuels with biomass are quantified, as well as emissions of toxic pollutants and substances responsible for acidification and ozone formation. The LCA results show net savings of GHG emissions when using biomass instead of conventional fuels, varying from 0.08 to 1.08 t of CO2 eq. per t of dry biomass in the different scenarios. Avoided GHG emissions thanks to biomass combustion in Lombardy are 1.32 Mt year−1(1.5% of total regional GHG emissions). For the other impact categories, the use of biomass in district heating systems can again cause a consistent reduction of impacts, whereas biomass combustion in residential devices shows higher impacts than fossil fuels with a particular concern for PAH, VOC and particulate matter emissions. For example, in Lombardy, PM10 emissions from domestic devices are about 8100 t year−1, corresponding to almost one third of the total particulate emissions in 2005.