Biomass Scenario Research Articles

From Secondary Biomass to Bio-Methanol through CONVERGE Technology: An Environmental Analysis

Owing to residual biomass availability, the share of advanced biofuels produced from secondary biomass is forecasted to increase and significantly contribute towards achieving net-zero emissions. The current work investigates bio-methanol production through a new process configuration designed to improve the environmental performance when compared to the state-of-the art technologies (Base Case). The environmental evaluation is conducted according to the Life Cycle Assessment (LCA) methodology. ReCiPe was employed as an impact assessment method with the aid of GaBi software. Depending on the plant geographical location, wooden biomass and exhausted olive pomace were evaluated as biomass sources. A scenario analysis targeting different energy sources was performed as well. The outcome of the environmental evaluation highlights a better performance in eight of a total of nine impact categories studied in the wooden biomass scenarios compared to the exhausted olive pomace. Moreover, two of the CONVERGE technology cases were compared against the Base Case. As the results show, CONVERGE technology registers a lower score in at least six of the impact categories studied. Concerning the total CO2 emissions, CONVERGE exhibits a better performance compared to the Base Case, if the additional amount of CO2 is either stored, sold as a by-product or vented into the atmosphere.

Modeling the Next Decade of Energy Sustainability: A Case of a Developing Country

The development of any country is closely related to its ability to provide access to electricity for productive labor. Many countries in sub-Saharan Africa have low electrification rates for commercial, industrial and residential consumers. This study focuses on Nigeria, which has one of the largest populations and economies in sub-Saharan Africa. Although Nigeria possesses abundant renewable energy resources that can increase electricity generation, it has suffered a significant setback in electricity generation. However, for Nigeria to become one of the leading industrialized countries by 2030, access to clean, reliable, and sustainable energy sources is vital (Vision 20: 2030). This study assesses the possibility of Nigeria developing and transitioning to the use of various energy sources. Additionally, this study evaluates greenhouse gas (GHG) mitigation plans and future trends in energy sustainability through multi-criteria decision analysis (MCDA), considering the technical, social, economic, and environmental dimensions of the sustainability structure. A total of twelve (12) sustainability indexes were taken into consideration; these consist of two (2) technical, three (3) social, three (3) environmental, and four (4) economic indicators. A scenario-based software called Long-range Energy Alternative Plan (LEAP) was used to integrate the analysis criteria and forecast a sustainable energy generation mix for the future. It considered three scenarios, namely: the business as usual scenario (BAU); renewables, natural gas and biomass scenario (RNB); and renewables and coal scenario (REC). It was concluded that the renewables, natural gas, and biomass scenario (RNB) is the best scenario to solve Nigeria’s energy problem based on the aim of the study.

Simulation process and data flow for a large system dynamics model

This paper documents the workflow and supporting technologies that a large system dynamics model, the biomass scenario model, employs to streamline the data preparation, simulation, quality control, and analysis process at the National Renewable Energy Laboratory. The workflow centers on automation of routine aspects of the flow of data between data stores, simulations, and visualizations. It enforces quality checks on data, reproducibility of computations, and traceability of results, while maintaining complete archives of modeling and analysis artifacts. The resulting frictionless simulation/analysis environment supports large-scale sensitivity analysis, interactive creation of ensembles of simulations, and rapid visualization-based exploration of simulation results.

Operation assessment of a hybrid solar-biomass energy system with absorption refrigeration scenarios

ABSTRACT Refrigeration systems claim increasing research attention as the climate crisis intensifies. One of the most well-established viable and feasible solutions is solar cooling, as the necessary cooling energy is produced by exploiting the available solar irradiance. The utilization of solar thermal energy to produce cooling energy by absorption chillers fed by a driving heat source (such as solar energy) to produce cooling power. Existing works in the literature present mainly case studies and simulations for small-scale systems (less than 50 kWc). The case study presented investigates the performance of a single-effect 316 kWc absorption chiller under different renewable-only driving heat source scenarios (solar-driven, biomass-driven, and a hybrid approach). The results indicate a significantly advantageous performance in combined heat generation (solar field and biomass boiler connected in series) compared to the scenarios of biomass or solar energy as a sole heat source. Moreover, an absorption chiller’s economic indicators appear more fetching than a centrifugal electric chiller of the same capacity, as the payback period is significantly reduced. The Net Present Value (N.P.V. – over 75% greater in the case of absorption chiller compared to the centrifugal electrical chiller) and Return on Investment (R.O.I.) values are increased in the case of the absorption chiller option (18.03% against 15.24% of the centrifugal electrical chiller). The system described in this paper operates in Eastern Macedonia and Thrace, Greece, and is part of one of the largest self-sufficient energy communities. The case study presented is the first attempt at performance evaluation of a large-scale (more than 250 kWc) cooling system operating in a local energy community.

Carbon footprint of biofuels production from forest biomass using hot water extraction and biochemical conversion in the Northeast United States

This study assessed the cradle-to-grave life cycle greenhouse gas (GHG) emissions of ethanol production via the fermentation of sugars derived from hot water extraction (HWE) of forest biomass under two processing energy scenarios (biomass, natural gas). The energy source was a key driver of the climate change benefits of ethanol production. Compared to petroleum gasoline, the lifecycle GHG emissions of ethanol fuel were 78% lower for the biomass scenario while the natural gas scenario resulted in 2% increase of GHG. Monte Carlo analysis revealed that when the input variable parameters were allowed to vary by 20% from their baseline value, the biomass scenario was always compliant with the 60% GHG reduction requirement for cellulosic ethanol. Measures to improve the energy efficiency of the biorefinery per unit of ethanol produced (i.e. increase ethanol yield or reduction in energy consumption) could result in ethanol fuels produced under the natural gas scenario with GHG emissions equal to or less than those of petroleum gasoline. The potential for ethanol from forest biomass in the Northeast United States to contribute to the decarbonization process is heavily dependent on the process energy resources chosen to power the biorefinery and the characteristics of the designed conversion process.

Harnessing the full potential of biomethane towards tomorrow's bioeconomy: A national case study coupling sustainable agricultural intensification, emerging biogas technologies and energy system analysis

Here, we demonstrate the applicability of national strategies towards massive biogas deployment, through a case study Denmark. First, a variety of sustainable agricultural intensification measures to produce additional biomass resources were investigated; as a result, it was found that the biomass currently used in Denmark's biorefineries (including biogas) could be tripled without compromising soil carbon and inducing little to no land use changes. The degree to which these resources could be mobilized for the biogas sector was analysed through examining the extremes, here labelled as LOW and HIGH biomass-to-biogas scenarios. The resulting biomethane production was calculated considering three combinations of biogas production and upgrading technologies: (i) conventional biogas production and upgrading technologies; (ii) plants with prolonged retention time and conventional upgrading technologies and (iii) as in (ii), but upgrading via biological methanation of carbon dioxide in the biogas, using renewable hydrogen. These scenarios revealed a biomethane potential of 24–111 PJ y−1. The key finding of our study is that only the extreme deployment measures, in terms of biomass and technology, allowed to fulfill the emerging gas demands, namely buffering the deficits from fluctuating power and transport (light- and heavy-duty vehicles, urban buses, coaches), quantified at 95 PJ y−1. Yet, just harnessing the full sustainable potential of animal manure, straw and perennial grass allows to supply half of this demand. In the LOW and HIGH biomass scenarios, doubling the retention time brought an increased methane production of 20% (energy-wise), while this increase was 87% when methanation was added.

Prospects, progress, challenges and policies for clean power generation from biomass resources

Worldwide primary energy needs are satisfied basically from non-renewable sources that are limited in supply and innately hazardous to the environment. Biomass-based power systems are very much potent to address the environmental issues fostering sustainable development, while being able to provide a secured and uninterrupted power supply at the same time. Biomass-based power generation systems not only reduce the GHG emissions but also have enormous opportunities of job creation and promote biomass re-growth through sustainable land management practices. This paper overviews the biomass scenario in Southeast Asian and EU countries to give an overview of the potential and scalable energy harnessed from biomass resources. Economic analyses presented on biomass gasification-based power generation have been evaluated with three specific cost estimations, namely low, average and high. Key economic performance metrics of biomass gasification-based dual-fuel internal combustion engine generator with low investment estimates are as follows: a positive net present value of USD 7.5 million; internal rate of return 14.45%; and a payback period of 5.45 years. A review of the technologies can provide a base for strategic energy policy for the next generation of sustainable energy policies and helps policymakers to frame strategies aiming for clean technology and sustainable development. Biomass integrated gasification combined cycle-based systems are found to be most suitable for power generation or biofuel synthesis.

Formation Criteria for Hyporheic Anoxic Microzones: Assessing Interactions of Hydraulics, Nutrients, and Biofilms

AbstractRecent experimental studies have detected the presence of anoxic microzones in hyporheic sediments. These microzones are small‐scale anoxic pores, embedded within oxygen‐rich porous media and can act as anaerobic reaction sites producing reduction compounds such as nitrous oxide, a potent greenhouse gas. Microbes are a key control on nutrient transformation in hyporheic sediment, but their associated biomass growth is also capable of altering hydraulic flux, leading to potential bioclogging. Here, we developed one of the first computational modeling approaches that combined hydraulics and microbial conditions to explore the continuous evolution of microzones in stream sediments. The model assessed stream and sediment conditions with different hydraulic flux (0.1–1.0 m/day Darcy flux), nutrient concentrations (O2 = 8 mg/L, OrgC = 20 mg/L, NO−3 = 1.5–3 mg/L, and NH3 = 0.5–1 mg/L), and biomass scenarios (with and without). The model domain is a pore network model with random sized pore‐throat radii creating heterogeneous and anisotropic flow that is representative of a natural streambed composed of medium sand with a hydraulic conductivity of 0.8 m/day. Results from 30 day simulations indicate that hyporheic microzone formation will occur and microzone distributions are not simply controlled by residence time alone, rather by the complex interactions of hydraulic flux, nutrient concentrations, and biomass, with bioclogging having strong feedbacks on both hydraulics and nutrients. Under all conditions with biomass growth, anoxic microzones were unstable, perishing a few days after formation, because bioclogging primarily occurs near the influent (downwelling) area of the hyporheic zone. In turn, this bioclogging shifts transport conditions from advection‐dominated to diffusion‐dominated transport, removing all oxic regions in the hyporheic zone. Overall, results from the modeling show that anoxic microzones are likely to form under many hyporheic zone conditions, and be dynamic through space and time as they are dependent on both hydraulic flux and nutrient transport.

Using a gate-to-gate LCA to apply circular economy principles to a food processing SME

Abstract The purpose of this study was to assess: what are the circular economy opportunities for small and medium-sized enterprises (SME) in the meat processing sector to reduce their environmental impacts, using Life cycle assessment (LCA) as the analytical method to prevent burden shifting; whether current life cycle inventories and LCA studies adequately represent SMEs such as the study plant; and whether climate change is a suitable proxy for impacts. Life cycle inventory data from a SME meat processing site in regional Australia was used for benchmarking with existing industry data and for risk and opportunity identification along the supply chain. A LCA was conducted of the current operation and possible future energy supply scenarios involving the use of tallow, wastewater methane and biomass production, to identify the best performing option as part of a PhD project on SMEs and sustainability in agribusiness value chains. System expansion was used to handle all coproducts and byproducts. The area of land required to produce biomass was calculated and was compared to the catchment area for livestock, and an estimate was made of the non-arable land area required to produce biomass to offset all greenhouse emissions for the supply chain. Inventory data and LCA results for this SME were significantly different to previous LCAs. The system expansion resulted in large credits, particularly for edible offal. Climate change may not be a suitable proxy for other midpoint impact categories due to the difference in contributing processes. The best future energy appeared to be the biomass scenario, which involved using tallow for biodiesel production, capturing methane generated in the onsite wastewater treatment system for electricity generation, using tallow to generate the remaining electricity needs and using biomass for thermal energy production. Less than 0.5% of the non-arable land area required for producing the livestock for the plant was needed for biomass production, and if all supply chain emissions were offset using biomass, the land area required was 12% for life time grass fed beef. The potential for supply chain integration in the red meat sector appears promising, particularly in terms of offsets from biomethane use for electricity production, tallow use for biodiesel production and biomass production for thermal energy use. Life cycle assessment is a useful tool to screen circular economy options and identify the best future scenario, although a wide range of impact categories should be assessed as climate change may not be a suitable proxy.

Assessing the role of benthic filter feeders in in the food web of the Gulf of Gdansk (Sothern Baltic) – an Ecopath with Ecosim exercise

Event Abstract Back to Event Assessing the role of benthic filter feeders in in the food web of the Gulf of Gdansk (Sothern Baltic) – an Ecopath with Ecosim exercise Aleksander Drgas1* and Joanna Całkiewicz1 1 National Marine Fisheries Research Institute, Poland Benthic filter feeders are an important link in energy and matter flow between pelagic and benthic part of the ecosystem. Their role is particularly important in highly eutrophicated water bodies, where they may control phytoplankton biomass. On the other hand, benthic organisms are important part of benthivorous fish diet and may affect the availability of food for zooplankton. Possible changes in the biomass of benthic filter feeders due to changes in environmental conditions, changes in the structure of the food web or the appearance of alien species may cause effects on different trophic levels of the ecosystem. The analysis of biomass changes of individual food web elements in the Gulf of Gdansk (Southern Baltic) in response to various scenarios of filter feeders biomass was carried out using the dynamic Ecosim model. This model is based on the Ecopath trophic model constructed for the biomass values of individual ecosystem components observed in 2004-2006. The model is composed of 17 groups, including detritus. The pelagic part consists of fish (cod, flounder, herring, sprat, other predatory fish, other non-predatory fish, and round goby), zoo- and phytoplankton. Benthos is represented by four groups (deposit feeders, predators, filter feeders and meiofauna). The model was also completed by piscivorous and benthivorous birds. Subsequent runs of the Ecosim model were carried out for different biomass values of benthic filter feeders, starting with a drastic decrease through intermediate states to a fourfold increase in biomass in relation to the real values observed in 2004-2006 period. In addition, model runs were carried out at a set of vulnerability values to simulate different control mechanisms (top-down vs bottom-up). The simulations carried out for the period 2017-2050 showed a significant effect of benthic filter feeders biomass change biomass on the other elements of the food web. It concerned not only those groups of organisms directly affected by filtrators (phytoplankton) and those for whom this group of organisms is food (benthivorous fish) but also elements more distant trophic levels such as herring or sprat. Acknowledgements This work resulted from the BONUS BLUEWEBS project which has received funding from BONUS (Art 185), funded jointly by the EU, the Academy of Finland, Projektträger Jülich (PtJ), Germany, the State Education Development Agency of Latvia, the National Centre for Research and Development, Poland, and the Swedish Research Council Formas. Keywords: Benthic filter feeder, Gulf of Gdanńsk, food web, modelling, Ecopath with Ecosim (EwE) Conference: XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019. Presentation Type: Poster Presentation Topic: Oceanography, Modelling and Dynamics of Ecosystems Citation: Drgas A and Całkiewicz J (2019). Assessing the role of benthic filter feeders in in the food web of the Gulf of Gdansk (Sothern Baltic) – an Ecopath with Ecosim exercise. Front. Mar. Sci. Conference Abstract: XX Iberian Symposium on Marine Biology Studies (SIEBM XX) . doi: 10.3389/conf.fmars.2019.08.00040 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 13 May 2019; Published Online: 27 Sep 2019. * Correspondence: Dr. Aleksander Drgas, National Marine Fisheries Research Institute, Gdynia, Poland, adrgas@mir.gdynia.pl Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Aleksander Drgas Joanna Całkiewicz Google Aleksander Drgas Joanna Całkiewicz Google Scholar Aleksander Drgas Joanna Całkiewicz PubMed Aleksander Drgas Joanna Całkiewicz Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Lessons from a large‐scale systems dynamics modeling project: the example of the biomass scenario model

AbstractThe biomass scenario model (BSM) is a dynamic model of the biomass‐to‐biofuels supply chain in the U.S.A., developed during a multi‐year analysis effort conducted by the National Renewable Energy Laboratory (NREL), under sponsorship from the United States Department of Energy (DOE) Bioenergy Technologies Office (BETO). The BSM project, which received the 2018 Applications Award by the International System Dynamics Society, has supported collaborative analyses, developed scenarios for industry development and facilitated stakeholder engagement. We summarize insights gained from the BSM project that may be useful to other large‐scale dynamic modeling efforts. We summarize the project focus, the analysis process, key outcomes and observations on successful execution of such a product. Key points include the value of a multidisciplinary team with clear roles, engagement of experts and stakeholders, and use and reuse of simple, modular structures. The overall effort suggests that these practices may aid long‐term, team‐focused, multi‐stakeholder modeling efforts.© 2019 System Dynamics Society

US alternative jet fuel deployment scenario analyses identifying key drivers and geospatial patterns for the first billion gallons,

AbstractThe aviation sector's commitments to carbon‐neutral growth in international aviation starting in 2020, and the desire to improve supply surety, price stability, and the environmental performance of aviation fuels, have led to broad interest in sustainable alternative jet fuels. Here, we use the system‐dynamics‐based biomass scenario model (BSM), focused on alternative jet fuel production capacity evolution, and the geospatially explicit Freight and Fuel Transportation Optimization Tool (FTOT), focused on optimal feedstock and fuel flows over the transportation system, to explore the incentive effects on alternative jet fuel production capacity trajectories and potential geospatial patterns of production and delivery in the USA. Scenarios presented here focus on readily available waste feedstocks (waste fats, oils and greases, municipal solid waste, and crop and forestry residues) and conversion technologies included in the ASTM D7566 synthesized aviation turbine fuels specification. The BSM modeling of possible deployment trajectories from 2015 to 2045 suggests that up to 8 billion gallons may be available by 2045 depending on the policies and incentives implemented. Both approaches suggest that 200 million to 1 billion gallons per year of alternative jet fuel production are possible in 2030 given multiple incentives and a favorable investment climate, and that capital costs and technology maturation rates will affect deployment of different fuel production technologies, and therefore the feedstocks needed. Further collaboration on these modeling approaches would reduce methodological blind spots while providing insights into future industry trajectories. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd

A review of the current state of biofuels production from lignocellulosic biomass using thermochemical conversion routes

Abstract The rapid increase in energy demand, the extensive use of fossil fuels and the urgent need to reduce the carbon dioxide emissions have raised concerns in the transportation sector. Alternate renewable and sustainable sources have become the ultimate solution to overcome the expected depletion of fossil fuels. The conversion of lignocellulosic biomass to liquid (BtL) transportation fuels seems to be a promising path and presents advantages over first generation biofuels and fossil fuels. Therefore, development of BtL systems is critical to increase the potential of this resource in a sustainable and economic way. Conversion of lignocellulosic BtL transportation fuels, such as, gasoline, diesel and jet fuel can be accomplished through various thermochemical processes and processing routes. The major steps for the production of BtL fuels involve feedstock selection, physical pretreatment, production of bio-oil, upgrading of bio-oil to transportation fuels and recovery of value-added products. The present work is aiming to give a comprehensive review of the current process technologies following these major steps and the current scenarios of biomass to liquid facilities for the production of biofuels.

Environment or catches? Assessment of the decline in blackspot seabream (Pagellus bogaraveo) abundance in the Strait of Gibraltar

Abstract In this study we carried out an analysis of the relationship between the variation in environmental and oceanographic parameters and the changes in the abundance of blackspot sea bream (Pagellus bogaraveo) in the Strait of Gibraltar between 1983 and 2016. A discrete dynamic model was applied to simulate different scenarios of blackspot sea bream biomass on a monthly time scale. ARIMA models were applied to the simulated biomass time series in order to extract the effect of the fishing component and then correlate the residual series with each of the environmental and oceanic parameter sets. Regardless of the scenario analysed, the error terms provided by the ARIMA models indicated a strong auto-regression dependence on the series and that the fishing component accounted in the worst case scenario for 73% of the variation in sea bream biomass in the Strait of Gibraltar. Throughout the study period, part of the variation not explained by the fishing component was explained in certain years by environmental parameters. These correlations were particularly significant for the water temperature anomaly, salinity anomaly and the NAO index. Our analyses therefore suggest that the main factor responsible for the drastic decline in the abundance of sea bream in the Strait of Gibraltar is over-exploitation of the resource and that environmental conditions had a one-off effect which, depending on the year, favoured or harmed the recovery of the stock.

Innovative Combustion System for Economic and Ecological Thermal Utilization of Solid Fuel in Heating Boilers

AbstractAn innovative combustion system, the so‐called low‐emission combustion system (LEVS), with integrated exhaust gas treatment measurement for thermal utilization of biomass‐fueled boilers is presented. It comprises an intelligently controlled three‐fan combustion air supply and exhaust gas system, a cyclone combustion chamber, and packed‐technology, ensuring high combustion efficiency and stable low‐emission combustion. The technology was tested by preliminary experiments for various application scenarios of biomass, and the current environmental and health‐related aspects were also evaluated. The relevant emission reduction through the system results from improved combustion in critical operating phases, in which the total emissions produced in conventional gasification boilers are drastically reduced. A minimum increase of the boiler efficiency of 15 % in practice with corresponding fuel and CO2 savings can be guaranteed.

Modeling the impact of biota on polychlorinated biphenyls (PCBs) fate and transport in Lake Ontario using a population-based multi-compartment fugacity approach

Organisms have long been treated as receptors in exposure studies of polychlorinated biphenyls (PCBs) and other persistent organic pollutants (POPs). The influences of environmental pollution on organisms are well recognized. However, the impact of biota on PCB transport in an environmental system has not been considered in sufficient detail. In this study, a population-based multi-compartment fugacity model is developed by reconfiguring the organisms as populated compartments and reconstructing all the exchange processes between the organism compartments and environmental compartments, especially the previously ignored feedback routes from biota to the environment. We evaluate the model performance by simulating the PCB concentration distribution in Lake Ontario using published loading records. The lake system is divided into three environment compartments (air, water, and sediment) and several organism groups according to the dominant local biotic species. The comparison indicates that the simulated results are well-matched by a list of published field measurements from different years. We identify a new process, called Facilitated Biotic Intermedia Transport (FBIT), to describe the enhanced pollution transport that occurs between environmental media and organisms. As the hydrophobicity of PCB congener increases, the organism population exerts greater influence on PCB mass flows. In a high biomass scenario, the model simulation indicates significant FBIT effects and biotic storage effects with hydrophobic PCB congeners, which also lead to significant shifts in systemic contaminant exchange rates between organisms and the environment.

An Assessment of Biomass Supply Chain: A DEA Application

Renewable energy generation reduces carbon emissions and responds to the targets for renewable energy sources of most EU countries; it also enhances infrastructure resilience and creates flexibility of the energy matrix. However, the availability of biomass may drastically differ from country to country within the EU. In most cases, the most challenged countries to achieve high targets for sustainability are not those with a sufficiently large supply of biomass. Because of this, it is necessary to design new biomass supply chain networks and improve the existing networks. This paper aims to assess the efficiency of biomass alternative pathways of the supply network from South America to Europe. In this particular work, three scenarios of biomass using two transportation systems were investigated, i.e., transportation of wood logs, pellets and torrefied biomass in the country of origin by truck and train transportation. Efficiency was measured using a data envelopment analysis (DEA) model derived from CCR. The results present the most efficient supply chain alternatives and highlight the feasibility of establishing closer cooperation between Brazil and countries in Europe for green energy generation. This information can assist in the process of planning and decision-making to determine the practicability of the implementation of torrefaction facilities using the most efficient logistical pathways

Application of a variance‐based sensitivity analysis method to the Biomass Scenario Learning Model

AbstractVariance‐based sensitivity analysis can provide a comprehensive understanding of the input factors that drive model behavior, complementing more traditional system dynamics methods with quantitative metrics. This paper presents the methodology of a variance‐based sensitivity analysis of the Biomass Scenario Learning Model, a published STELLA model of interactions among investment, production, and learning in an emerging competitive industry. We document the methodology requirements, interpretations, and constraints, and compute estimated sensitivity indices and their uncertainties. We show that application of variance‐based sensitivity analysis to the model allows us to test for non‐additivity, identify influential and interactive variables, and confirm model formulation. To enable use of this type of sensitivity analysis in other system dynamics models, we provide this study's R code, annotated to facilitate adaptation to other studies. A related paper describes application of these techniques to the much larger Biomass Scenario Model.

Acanthoecid choanoflagellates from the Atlantic Arctic Region - a baseline study.

The examination and statistical analysis of loricate choanoflagellate material collected from Greenland waters during the period 1988–1998 represents a de facto baseline study of heterotrophic nanoflagellates from the Atlantic Arctic Region. The geographic sites sampled are Disko Bay (West Greenland) and the high-arctic North-East Water (NEW) and North Water (NOW) polynya. The analyses encompass close to 50 taxa. Some of these are described as new species, i.e. Acanthocorbis glacialis, A. reticulata and Diaphanoeca dilatanda. Two distinct clusters of species that are separated in time and space occur at all three sampling sites. A PCA analysis of NEW and NOW data points to that one community is linked to e.g. an early season high nutrient and low phytoplankton biomass scenario, whereas the other is predominant when nutrient levels are exhausted and the phytoplankton biomass high or declining. The material additionally allows for a comprehensive examination of e.g. the Cosmoeca ventricosa morphological variability encountered, as well as puts on record bimodal size variability within a number of species.

Indicators and assessment of ecosystem health of Bakreswar reservoir, India: An approach through network analysis

Artificial water bodies like reservoirs are unique in sense that they encompass hybrid characters of both lakes and streams. Detailed study of reservoir ecosystem is necessary in order to understand and evaluate the health of such systems. A universal characteristic of any ecosystem is its ability to counter stress conditions and this ability is termed robustness which signifies the systems sustainability. Exergy or eco-exergy, measuring the amount of stored workable energy in the system is another important descriptor of an ecosystem. Both robustness and eco-exergy are good indicators of ecosystem health and also they are dependent on the magnitude and type of the inflicted stress. Robustness of Bakreswar reservoir system has been studied here following hypothetical perturbation scenarios that represent possible real situations of eutrophication (nutrient loading) and overfishing. Quite a few descriptive ecosystem indices have also been considered for the current study including Total System Throughflow (TST), Finn Cycling Index (FCI), Redundancy (R), Ascendancy (A), Developmental capacity (C), Total Primary Production to Total Respiration ratio (TPP/TR), Total Primary Production to Total Biomass Ratio (TPP/TB), detritivory to herbivory ratio and also the Exergy of the system. It is concluded from this study that the Bakreswar reservoir is a moderately stable ecosystem with fair maturity level and is able to withstand stress for a reasonable extent. The network indices revealed that variation in robustness of the system is related more with fish biomass perturbation scenario rather than that for the autotroph biomass perturbations. This is confirmed by the network indices as well as the change in the system exergy values which shows more variation in the fish biomass scenario.