Comparison of Different Possibilities for Biogas Use by Life Cycle Assessment

Abstract This contribution aims at introducing the innovative possibility of biogas use through its upgrading to biomethane and to evaluate this process from an environmental point of view, by applying Life Cycle Assessment (LCA), in comparison with direct use of biogas in energy conversion devices, namely, internal combustion engines and molten carbonate fuel cells. Due to their high energy conversion efficiency, fuel cell use resulted the solution with the best environmental performances, followed by internal combustion engines and the by biomethane production. However, when thermal energy is not recovered in the case of both fuel cell and internal combustion engine, the differences with respect to the biomethane case are strongly reduced

environmental evaluation of waste to energy plant coupled with concentrated solar energy

Abstract Life Cycle Assessment (LCA) was applied to evaluate the environmental impact of a hybrid energy system based on the integration of a Waste to Energy plant with concentrated solar energy plant. In the Waste to Energy (WtE) section only saturated steam is produced, while the superheating takes place in an external superheater fed by the concentrated solar energy or, when this is not enough, by a natural gas backup boiler. Different couples of pressure and temperature, for the superheated steam (51 bar, 440 °C; 60 bar, 480 °C; 70 bar, 520 °C), different values for the solar multiple (1.5, 2.0 and 2.5) and different values for the thermal storage capacity (6 h, 10 h and 14 h) were considered, leading to 27 possible cases. Construction, operation and end-of-life phases were included in the LCA system boundary. Calculated global warming indicator, in kg of equivalent CO2 per MJ of produced electricity, slightly decreases for increasing steam parameter cases and for increasing storage hour cases, while a more relevant reduction was observed for increasing solar multiple values. The main contribution to global warming derives from the operation phase of the WtE part (67-86% of the operation), while the remaining part (14-33%) is given by the solar section, for which, in turn, the main contribution is the impact deriving from the natural gas combustion in the backup boiler

Evaluation of the environmental sustainability of different waste‐to‐energy plant configurations

European strategy for waste management attributes primary importance to waste production prevention and imposes a priority order in waste management based on: “preparing for re-use; recycling; other recovery, e.g. energy recovery; and disposal” [1]. According to this strategy, those wastes for which the material recovery is not effectively applicable, should be used for energy recovery. Unsorted municipal residual waste (i.e. the waste left downstream of separate collection), has an average lower heating value higher than 10 GJ/Mg, in EU, and can be recovered in modern Waste-to-Energy (WtE) plants, producing combined heat and power (CHP) and reaching high levels of energy recovery. CHP is pinpointed as the best techniques for energy recovery from waste and also it is the technical solution that allows reaching high values according to the R1 criteria [1]. However, in some cases, heat recovery is not technically feasible – due to the absence of thermal user (industrial plant or district heating) in the proximity of the WtE plant - and only power production remains as the unique possibility. In these cases, some challenges are posed in order to increase as much as possible the energy performances: high values are obtainable only for large WtE plants [2-3]. High energy recovery efficiency values are very important, not only to comply with the R1 criteria, but also for the environmental sustainability of WtE plants. The highest the electricity and heat produced, the best saving of natural resources may be achieved. Pavlas et al. [3] evaluated the benefits of energy recovery in WtE by CHP applying a method based on Primary Energy Saving (PES). Damgaard et al. [4] showed that CHP is able provide higher saving, in Life Cycle Assessment (LCA) evaluations, than only electricity recovery. Within this frame, the aim of this work is to carry out an environmental assessment, through LCA, of different configurations of municipal residual waste WtE plant, i.e. only power production vs. increasing degree of cogeneration. The size ranging from small to large plants (12.5-300 MW thermal power input) was considered, including gradually the technical improvements that may increase the overall plant performances. Additionally, some specific configurations, related to energy recovery integration into the flue gas treatment (FGT) system, considering acid gas removal dry processes using calcium or sodium-based reactants, were investigated. The WtE process was simulated by a home developed thermodynamic model (using Engineering Equation Solver, F-Chart Software), providing the material and energy streams in input and output to/from the process, allowing the R1 calculation. LCA system boundary also included municipal residual waste transportation to WtE, production processes of input chemicals, bottom ash transport, treatment and recovery, fly ash and air pollution residues transport, treatment and disposal and, obviously, avoided effects of conventional heat and power production. Impact assessment results were calculated using cumulative energy demand (CED) and ReCiPe 2008 methods, even if here we discuss only climate change indicator results. Regarding only power production mode, the improved net electric efficiency along with the size allows for increasing the R1 value and decreasing the CO2 equivalent emissions. However, only medium-large plants (larger than 50 MW) reach R1 values higher than 0,65 and only 200-300 MW size plants reach negative CO2 equivalent emissions, even without cogeneration. Smaller plants need to operate in cogeneration mode – according to different extents - to reach imposed R1 value and to obtain negative CO2 equivalent emissions. As a matter of fact, a plant able to comply with the R1 limit, not always shows neutral carbon balance. Thus, in order to make WtE processes acting as carbon sink, cogeneration should be employed in larger extent than the minimum required for R1 compliance. Some specific configurations, related to energy recovery integration into the FGT system allow enhancing energy efficiency: a FGT line with injection of sodium bicarbonate at 180° C and a tail-end heat recovery used for pre-heating primary combustion air has a positive influence on R1 value and CO2 balance. References [1] Directive 2008/98/EC of the European Parliament and of the Council on waste and repealing certain Directives - Annex II, 19 November 2008. [2] Consonni, S. and Viganò, F., 2012. Waste gasification vs. conventional Waste-To-Energy: A comparative evaluation of two commercial technologies. Waste Manage, 32, 653–666. [3]Pavlas, M., Tous, M., Klimek, P., Bebar, L., 2011. Waste incineration with production of clean and reliable energy. Clean Technol. Environ. Policy 13, 595–605. [4]Damgaard, A., Riber, C., Fruergaard, T., Hulgaard, T., Christensen, T.H., 2010. Life-cycle-assessment of the historical development of air pollution control and energy recovery in waste incineration. Waste Manage, 30, 1244–1250

life cycle assessment lca of landfill gas management comparison between conventional technologies and microbial oxidation systems

Abstract The reduction of landfill gas emissions is a central issue of the Directive 99/31/EC. Biofilters and biocovers have been identified as an alternative and cost-effective technologies to mitigate impacts due to CH4 and NMVOCs emissions. The Life Cycle Assessment demonstrates the environmental sustainability of biofiltration systems, with the aim of improving the environmental impact indicators such as Global Warming (-10.75% for Biofilter and -11.60% for Biocover) and Photochemical oxidation (-7.97% for Biofilter and -8.61%. for Biocover). This paper shows that these treatment technologies are effective for methane oxidation when the calorific value of the LFG is low, thus they maximize the amount of treated gas during the after-care phase

BBCircle – Life Cycle Assessment for innovative biorefinery process evaluation

The BBCircle project1, funded by the Lazio Region (IT), is aimed at integrating different processes to produce biomaterials, biofuels, capturing CO2 and promote circularity, in reference to the suitable and available substrates in the regional territory. Please click Additional Files below to see the full abstract

Main factors affecting climate change, acidification and eutrophication in MSW management systems

The continuous increasing of solid waste generation worldwide calls for management strategies to support environmental sustainability. Life Cycle Assessment (LCA) is a decision-support tool for quantifying environmental impacts of systems (product systems). Among the most important and discussed output-based impact categories of waste management, there are: global warming potential (GWP), acidification potential (AP) and eutrophication potential (EP). The aim of this work is to identify which are the most important factors in the Municipal Solid Waste (MSW) management affecting to GWP, AP and EP and what kind of conditions in the operating environment are essentials to these factors. After a review of available literature on this topic (more than thirthy rarther recent papers were analyzed in details even if the reference list is not reported here for length constraints), the work was concentrated at evaluating two rather different study cases: i) the territory belonging to the province of Siena in the south of Tuscany region (Italy) and ii) the territory of South Karelia, the region in the southern Finland on the border with Russia. The total amount of MSW generated in the province of Siena in 2013 was 163 823 t, of which 94 963 t are residual waste, which is processed in a mechanical and biological treatment (MBT) plant. Dry fraction from MBT is sent for waste-to-energy (WtE), while humid fraction is landfilled after aerobic biological stabilization. Source separated wastes (about 45%) are refined locally by mechanical treatment and sent away for material recovery, in particular the organic fraction is processed locally for compost production. Concerning South Karelia region, the total amount of MSW generated in 2013 was 75 280 t, of which 22 500 t are residual waste. Separate collection is reserved for recoverable materials (cardboard, glass, metal, and paper) as well as for biodegradable waste. Residual urban waste is partly disposed to landfill and partly burned into WtE plant. Landfilling has been the only way to treat the residual MSW in the South Karelia region up to 2012, when it was decided to route part of them to a WtE plant. In the end of 2013 about one third of total residual waste was burned into the plant, producing district heating and electricity for the grid. Since 2015, all the residual waste has been directed to the WtE plant. The results obtained in the case study analysis are partially consistent with the literature review. For instance, it was observed that collection and transportation contribution to the total balance is likely to be negligible, as also recognized by different authors. However, as others LCA practitioners point out, it is important to evaluate its contribution mainly when recycling treatment is operated, in order to assess the real benefits of recycling, especially for AP and EP related emissions. As expected, direct emissions from the WtE and from the landfill generate the largest contribution in the whole waste management system, concerning GWP, AP and EP. The same conclusion can be made when considering the energy recovery from WtE and from landfill gas combustion. It was observed that assumptions about waste composition have a considerable influence on the final LCA results. Even assumptions regarding displaced energy can largely affect the LCA final results, such as in both the case studies (i.e. displaced energy mix and energy recovery efficiencies), and this outcome is consistent with the reviewed literature. In particular the real replaced fuel by heat recovery has an important weight on the final results. Additionally, the recovery or disposal of the rejects from MBT plant plays an important role: in this regard, heat recovery can be crucial for improving the environmental performance significantly with respect to landfilling. However, it should be kept in mind that the great variance between different waste management systems prevents a meaningful generalization of the LCA results, which always need context-specific assessments

Evaluation of gas production in a industrial anaerobic digester by means of biochemical methane potential of organic municipal solid waste components

The Biochemical Methane Potential (BMP) of several components of the Organic Fraction of the Municipal Solid Waste (OFMSW) were tested in order to assess the possibility to obtain a good estimate of the biogas production of a real scale anaerobic digestion plant. In particular, five different fractions and a mixed food waste sample were tested with batch anaerobic digesters at 37°C and both the BMP after 21 days (BMP21) and final BMP (BMPf) were measured. Regarding the mixed food waste substrate it was found an average BMP21 of about 405 NL/kgVS and a BMPf of 484 NL/kgVS with an average methane content of 57%. From the experimental results, some industrial potential biogas production were defined to compare them with data from real anaerobic digestion plants. In particular two different plants were considered: one located in a rural area that treats the source selected OFMSW from a public collection point, another located in a city area with a curbside collection system. Furthermore, studying the BMP of the pre-treatment reject of these plants, it was possible to study the pre-treatment efficiency and the difference performance of the two real plants

Mycobacterium lentiflavum Infection in Immunocompetent Patient

Mycobacterium lentiflavum is a recently described nontuberculous mycobacterium that has mainly clinical importance in young children with cervical lymphadenitis and in immunocompromised patients. We describe a case of chronic pulmonary infection in an immunocompetent patient. Our observation confirms clinical, diagnostic, and treatment difficulties in the management of M. lentiflavum infection