43 research outputs found
Using UAV Imagery to Detect and Map Woody Species Encroachment in a Subalpine Grassland: Advantages and Limits
An Enkf-Based Scheme for Snow Multivariable Data Assimilation at an Alpine Site
Abstract
The knowledge of snowpack dynamics is of critical importance to several real-time applications especially in mountain basins, such as agricultural production, water resource management, flood prevention, hydropower generation. Since simulations are affected by model biases and forcing data uncertainty, an increasing interest focuses on the assimilation of snow-related observations with the purpose of enhancing predictions on snowpack state. The study aims at investigating the effectiveness of snow multivariable data assimilation (DA) at an Alpine site. The system consists of a snow energy-balance model strengthened by a multivariable DA system. An Ensemble Kalman Filter (EnKF) scheme allows assimilating ground-based and remotely sensed snow observations in order to improve the model simulations. This research aims to investigate and discuss: (1) the limitations and constraints in implementing a multivariate EnKF scheme in the framework of snow modelling, and (2) its performance in consistently updating the snowpack state. The performance of the multivariable DA is shown for the study case of Torgnon station (Aosta Valley, Italy) in the period June 2012 - December 2013. The results of several experiments are discussed with the aim of analyzing system sensitivity to the DA frequency, the ensemble size, and the impact of assimilating different observations
Building an LCA Inventory: A Worked Example on a CO2 to Fertilizer Process
This worked example is part of a series of examples that are designed to provide practical guidance to the application of the Techno-Economic Assessment and Life Cycle Assessment Guidelines for CO2 Utilization. This worked example provides guidance on best practices and potential pitfalls in the production of a LCA inventory utilizing one or more sources of primary/secondary data. The worked example highlights the dangers of “picking and mixing” data by showing how derived results can vary significantly resulting in inconsistencies and uncertainty when considering direct comparisons for products/services and functions. The worked example considers a CO2 to nitrogen rich fertilizer pathway, with 18 inventories produced for assessment.Global CO2 InitiativeEIT Climate-KIChttps://deepblue.lib.umich.edu/bitstream/2027.42/154989/3/Building an LCA Inventory (CO2 to fertilizer example).pdfDescription of Building an LCA Inventory (CO2 to fertilizer example).pdf : Report documen
A Guide to Goal Setting in TEA: A Worked Example Considering CO2 Use in the Domestic Heating Sector
This worked example is part of a series of examples that are designed to provide practical guidance to the application of the Techno-Economic Assessment and Life Cycle Assessment Guidelines for CO2 Utilization. This worked example provides guidance on goal setting for TEA, with illustrative examples given for each of the perspectives listed in the guidelines (R&D, Corporate, Market). Multiple goals are derived following the advice of the guidelines with CO2 use in the domestic heating sector as the background. The example also provides advice on assessing the feasibility of using, either alongside a new study or in place of, with illustrative examples provided to demonstrate the impact data variance can have on the results of a study.Global CO2 InitiativeEIT Climate-KIChttps://deepblue.lib.umich.edu/bitstream/2027.42/154988/4/Guide to goal setting in TEA (Domestic heating example).pdfDescription of Guide to goal setting in TEA (Domestic heating example).pdf : Report documen
Remote sensing-based estimation of gross primary production in a subalpine grassland
This study investigates the performances in a terrestrial ecosystem of gross primary production (GPP) estimation of a suite of spectral vegetation indexes (VIs) that can be computed from currently orbiting platforms. Vegetation indexes were computed from near-surface field spectroscopy measurements collected using an automatic system designed for high temporal frequency acquisition of spectral
measurements in the visible near-infrared region. Spectral observations were collected for two consecutive years in Italy in a subalpine grassland equipped with an eddy covariance (EC) flux tower that provides continuous measurements of net ecosystem carbon dioxide (CO2) exchange (NEE) and the derived GPP.
Different VIs were calculated based on ESA-MERIS and NASA-MODIS spectral bands and correlated with biophysical (Leaf area index, LAI; fraction of photosynthetically active radiation intercepted by green vegetation, f IPARg), biochemical (chlorophyll concentration) and ecophysiological (green light-use efficiency, LUEg) canopy variables. In this study, the normalized difference vegetation index (NDVI)
was the index best correlated with LAI and f IPARg (r = 0.90 and 0.95, respectively), the MERIS terrestrial chlorophyll index (MTCI) with leaf chlorophyll content (r = 0.91) and the photochemical reflectance index (PRI551), computed as (R531 −R551)/(R531 +R551) with LUEg (r = 0.64).
Subsequently, these VIs were used to estimate GPP using different modelling solutions based on Monteith’s lightuse efficiency model describing the GPP as driven by the photosynthetically active radiation absorbed by green vegetation (APARg) and by the efficiency (") with which plants use the absorbed radiation to fix carbon via photosynthesis.
Results show that GPP can be successfully modelled with a combination of VIs and meteorological data or VIs only.
Vegetation indexes designed to be more sensitive to chlorophyll content explained most of the variability in GPP in the ecosystem investigated, characterised by a strong seasonal dynamic of GPP. Accuracy in GPP estimation slightly improves when taking into account high frequency modulations of GPP driven by incident PAR or modelling LUEg with the PRI in model formulation. Similar results were obtained for both measured daily VIs and VIs obtained as 16-day composite time series and then downscaled from the compositing period to daily scale (resampled data). However, the use of resampled data rather than measured daily input data decreases the accuracy of the total GPP estimation on an annual basis.JRC.H.4-Monitoring Agricultural Resource
Interpretation of LCA results: A Worked Example on a CO2 to Fertilizer Process
This worked example is part of a series of examples that are designed to provide practical guidance to the application of the Techno-Economic Assessment and Life Cycle Assessment Guidelines for CO2 Utilization. In this worked example the impact of “picking and mixing” inventory data on results interpretation is explored in detail. The results of 18 LCA inventories (for a CO2 to nitrogen rich fertilizer pathway) are assessed, showing the inconsistencies in the conclusions drawn from the interpretation phase of the studies.Global CO2 InitiativeEIT Climate-KIChttps://deepblue.lib.umich.edu/bitstream/2027.42/154990/4/Interpretation of LCA results (CO2 to fertilizer example).pdfDescription of Interpretation of LCA results (CO2 to fertilizer example).pdf : Report documen
SNG Worked Example for the TEA Guidelines for CO2 Utilization
To meet the high demand for natural gas globally, synthetic natural gas (SNG) can be produced as a substitute for natural gas derived from fossil fuels. Nevertheless, the traditional SNG production process is highly carbon-intensive. In the framework of the Power-to-Gas concept, production of SNG can occur via hydrogenation of CO2, which can be captured from industrial sources. As a result, the reliance of SNG production on fossil fuels can be reduced and, subsequently, associated CO2 emissions can be controlled.
The goal of the present study is to assess the technical viability and economic feasibility of producing SNG via CO2 hydrogenation. Additionally, to prepare for integrating the techno-economic analysis (TEA) with a life-cycle assessment (LCA), the challenges and pitfalls of such integration are also discussed. The TEA in this study was carried out mainly from a research & development perspective. The production cost for SNG based on carbon capture and utilization (CCU) is estimated and key cost drivers are identified. The combined indicator of CO2 abatement cost is also estimated as a quantitative indicator for assessing the TEA and LCA results.
The methanation plant is assumed to be located next to an iron & steel plant in Germany, from which the CO2 feedstock for producing SNG is by means of MEA-based chemical absorption technology, while the hydrogen (which is produced via electrolysis using surplus electricity) is purchased from a production facility located 250 km away. The output capacity of the methanation plant is 148 MW. Aspen Plus software was used for process modelling and data were taken from the literature.
Through discussions, it was found that setting the system boundaries was a central challenge for aligning the TEA and LCA. While LCA tends towards encompassing the full life cycle of products (cradle-to-grave or -gate), it is not necessary to include the upstream and downstream processes to conduct a TEA in the present study. The information on upstream processes is reflected in the characteristics of the input flows entering the product system. Setting identical system boundaries for TEA and LCA would require solving problems of multi-functionality, which can be very challenging for TEA when the market for the products to be analyzed is still uncertain. To align inventories, the relevant environmental parameters (e.g., CO2 emissions) should be documented in addition to the technical and economic parameters. For calculating CO2 abatement cost, system expansion can be used to account for the reduced CO2 emissions, or the CO2 feedstock can be regarded as negative emissions.
The results show that the SNG production cost for the analyzed product system is 0.0748 €/MJ and the minimum selling price is 0.271 €/kWh. The production cost is more than 10 times greater than that of the benchmark product (coal-based SNG). The selling price of SNG produced by the proposed system is also significantly higher than that of natural gas in the German market. The CO2 abatement cost, as a combined indicator of TEA & LCA, was calculated as 0.75 €/kgCO2. Sensitivity analysis reveals that the hydrogen purchase price represents the most significant uncertainty for the analyzed system. At a 95% confidence interval, the estimated production cost ranges between 0.065 and 0.173 €/MJSNG. Current legislation of the European Union Emissions Trading Scheme (EU ETS) is found to be inapplicable to the product system investigated. Thus, the analyzed CCU system cannot benefit from the emissions trading scheme. To drive CCU-based SNG forward in the future market, it is essential to reduce the production cost of hydrogen.Global CO2 InitiativeEIT Climate-KIChttp://deepblue.lib.umich.edu/bitstream/2027.42/167382/1/TEA of Synthetic Natural Gas production - worked example.pdfDescription of TEA of Synthetic Natural Gas production - worked example.pdf : Report documentSEL
Multi-Attributional Decision Making in LCA & TEA for CCU: An Introduction to Approaches and a Worked Example
This worked example considers only the elements of the whole process relevant for the integrated assessment in greater detail. This worked example builds on a prior study, covering CO2 to methanol conversion, and as such a more detailed overview of the technology can be found there. A brief overview of the methanol technology is included for familiarization, along with details on the alignment approach taken to ensure that a ‘preference-based’ integration can be completed. The focus of this worked example is the application of multi-attribute decision making (MADM) approaches and their potential use within combined LCA & TEA studies. The practical part of this examples sees the application of one MADM method to a multi-criteria problem with relevancy in CCU that utilizes the outputs of both an LCA & TEA study.This worked example has been released at an intermediate timeframe within the CO2nsistent project, fitting in between the release of version 1.1 and 2.0 of the ‘Techno-economic Assessment & Life Cycle Assessment Guidelines for CO2 Utilization’. This means the subject matter of this worked example (combined assessment, in particular multi-criteria approaches to decision analysis/making) remains to a degree uncovered by the overarching guidelines associated with this project until the release of version 2.0. As such this worked example will include more contextual sections than has been typical in previous examples, in part bridging the gap until a more detailed guidance section on combined assessment can be included in version 2.0.
This does not mean that no guidance can be drawn from version 1.1 of the guidelines document in the intermediate timeframe. Version 1.1 contains some guidance on both combined LCA & TEA studies (see section A) and the individual TEA section itself also contains a brief section and guideline rules on multicriteria decision analysis (MCDA) for use within the field. Ultimately this guidance is useful even for application in a combined study, as ultimately the same concept applies with the complication of needing to ensure that both the LCA & TEA study are aligned with suitable precision.Global CO2 InitiativeEIT Climate-KIChttp://deepblue.lib.umich.edu/bitstream/2027.42/167009/3/Multi-attributional Decision-Making in LCA and TEA for CCU and Worked Example.pdfedda1cab-631e-4ed3-880e-28ed1c223cc3SEL