Synthetic natural gas (SNG)Supercritical water gasification Sensitivity analysis Bioenergy Process economics a b s t r a c t A techno-economic sensitivity analysis of the production of synthetic natural gas (SNG) via catalytic supercritical water gasification (SCWG) of microalgae produced in raceway ponds (RP), tubular-, or flat-panel-airlift photobioreactors (FPA-PBR) has been perfomed. The aim of combining microalgae production with SCWG is to close material flows with respect to water and nutrients, the so called SunCHem process. The sensitivity analysis is based on an annual production of 86,500 t of microalgae biomass yielding 1.14 PJ of methane per year. The sensitivity analysis showed that with an annual algae productivity of 38.5 t per hectare of RP an energy return on energy invested (EROEI) of 1.84 can be achieved for the self-sufficient base case scenario. An SNG production cost of 194 V GJ À1 was obtained forRP. An EROEI of 0.08 was calculated for tubular PBR with a productivity of 75.1 t ha À1 a À1 in the base case scenario and thus was found to be inappropriate for SNG production. EROEI for FPA-PBR with an assumed microalgae productivity of 79 t ha À1 a À1 was found to be 1.01in the base case scenario and an SNG production cost of 266 V GJ À1. With significantly more optimistic assumptions concerning microalgae productivity, energy input and capital requirement with respect to microalgae cultivation, an EROEI of 3.6e5.8 and SNG production costs of 53e90 V GJ À1 were found for RP, whereas for FPA-PBR an EROEI of 2e3.7 and SNG production costs of 30e103 V GJ À1 were obtained.ª 2013 Elsevier Ltd. All rights reserved. IntroductionThe potential of microalgae as a renewable energy source, as a provider of renewable bulk and high value chemicals for the chemical and pharmaceutical industry, as a source of proteins for animal feedstock and fertilizer has made them the subject of considerable research effort in the past [1,2]. However, the economic viability and energy efficiency of biofuels made from microalgae are presently intensively discussed. The main obstacles to large scale introduction of biofuels from microalgae are the high investment costs and energy input required for microalgae cultivation and harvesting [3,4]. b i o m a s s a n d b i o e n e r g y x x x ( 2 0 1 3 ) 1 e9Please cite this article in press as: Brandenberger M, et al., Producing synthetic natural gas from microalgae via supercritical water gasification: A techno-economic sensitivity analysis, Biomass and Bioenergy (2013), http://dx
Purpose-The concept of resilience has emerged recently in scientific debate. The aim of this paper is to outline different notions of the term resilience and explore how the concept of resilience can be applied in order to foster the understanding of complex systems in a learning environment. Design/methodology/approach-Characteristics of the resilience concept used in scientific literature are outlined and a methodology is presented that enables an educated decision to be made upon selection of an indicator set for a resilience assessment. Findings-In this paper, it is argued that vulnerability as well as adaptability shall be the two core components of the resilience concept. It is proposed that resilience is therefore formalised as a function of adaptability and vulnerability. Originality/value-Definitions of resilience, vulnerability and adaptability are very much interlinked and it seems to be not always clear where the line between the different terms is. A novel framework is proposed to foster the understanding of the interlinkage between these three terms in interdisciplinary education, and to cluster indicators to assess system resilience.
Purpose -The purpose of this paper is to show a practical case of dialogic web-based learning that has provided a set of questions analysing two complex technological projects in "southern" countries with effects on multicultural equity. Design/methodology/approach -Structured online review processes in multicultural and systems science curricula allow for high density of literature-based reflection and analysis. Findings -The entirety of the set of over 50 questions developed by the proposed web-based dialogic procedure represents a starting point for an in-depth assessment of the effects of deploying "northern" technology in "southern" countries.Research limitations/implications -The present case study concentrates on energy technology, notably on two hydroelectric plants presently under construction in Ilısu, Turkey, and Belo Monte, Brazil. Practical implications -The multitude of questions calls for complex technological construction projects that have to undertake sound interdisciplinary in-depth analysis of technological, environmental, economic, cultural and social consequences in order to secure a necessary level of economic, environmental and social sustainability. Social implications -Application of widely accepted planning tools such as technology assessment, environmental impact assessment and strategic environmental assessment are useful but have to be complemented by analogous tools at a cultural and social level. Originality/value -This case study operates through questioning, largely in the Socratic tradition. Questions may trigger a broad discussion process within civil societies -which is the intention of the present text.
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