Synthesis of regional networks for biomass and biofuel production Hon Loong Lam
, 2010, doktorska disertacija
Opis: This thesis presents two different approaches to the synthesis of regional networks for biomass and biofuel production and supply: Mathematical Programming and Graph Theoretic approach. The optimisation criterion for both approaches is the maximisation of profit.
The first approach is based on a generic optimisation model of biomass production and supply networks. This superstructure approach is based on a flexible number of network layers: plantation, collection using a pre-treatment, process, and consumption. A Mixed Integer Linear Programming (MILP) model has been successfully developed during this work.
However, the solution of this biomass production network model is very challenging due to the large sizes of the networks and the number of interconnections. The huge number of redundant variables reduces model efficiency (time taken to solve the model and the interpretation of the results). This model when representing very large size networks cannot be solved over a reasonable time even by professional mathematical programming software tools. Several model-size reduction techniques are therefore proposed for the solution of large-scale networks. In particular, methods are proposed for (i) reducing the connectivity within a biomass supply chain network by setting the maximum allowable distance between the supply zones to the collection centres, (ii) eliminating unnecessary variables and constrains to reduce the zero-flows in the full model, and (iii) aggregating the network and hence the synthesis process by merging the collection centres.
The network synthesis is also carried out by P-graph (Process Graph) tools. P-graph is a directed bipartite graph, having two types of vertices — one for operating units and another for those objects representing material or energy flows/quantities. In this procedure, firstly a maximum feasible superstructure for biomass production network is generated from which the optimal structure is then selected by the Branch and Bound method. This graph-based method clearly shows where, how, and what kind of material and energy carriers will be transferred from one supply chain layer to another.
In order to test the efficiency of the model, a small regional renewable network problem was solved using both methods. Their performances were tested and the results confirmed the applicability on a regional scale. The proposed model-size reduction techniques were also tested. A large-scale regional case study was created to demonstrate these techniques. The results are very positive and some suggestions for future work are given in the conclusion.
Ključne besede: Biomass and bioenergy network synthesis, Model-size reduction
techniques, Mathematical Programming, MILP, P-Graph
Objavljeno: 06.01.2011; Ogledov: 2550; Prenosov: 86
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Preliminary estimation of bryophyte biomass and carbon pool from three contrasting different vegetation typesMahesh Kumar Singh
, Anita Juhász
, Zsolt Csintalan
, Mitja Kaligarič
, Michal V. Marek
, Otmar Urban
, Zoltán Tuba
, 2005, objavljeni znanstveni prispevek na konferenci
Opis: Bryophytes are the primary form of carbon storage in many ecosystems. There is growing consensus within the scientific community that increases in atmospheric carbon dioxide (CO2) enhancing the earth's natural greenhouse effect. Because of the potential effects of these gases on the global enery budget and future elimate, there is an urgent need to quantify terrestrial sources and sinks of carbon. There is more carbon stored in some bryophytes than in any other genus of vascular or non-vascular plants (Clymo & Hayward, 1982). Predicting how the vast stores of carbon in moss-dominated ecosystems will be affected by anthropogenic disturbance is critical for models of global climate change (Post et al., 1982). Bryophytes are a prominent feature of many forest and grassland types, where they can make an important contribution to carbon balance (Delucia, et al., 2003). Tropical montane rain forest, because of their complexity and variety of microhabitats, usually harbors a rich diversity of bryophytes. Even though they are often small and inconspicuous, especially in the lowland forest, they may play a significant role in the forest ecosystem (Frahm, 1994). Similarly, bryophytes in the temperate forest and grasslands are thought to be an important carbon sink (O'Neill, 2000). The objective of this research was to estimate components of the bryophyte biomass and approximate amount of carbon stored in it.
Ključne besede: vegetation, habitats, geoelements, carbon, carbon storage, bryophyte, bryophyte biomass
Objavljeno: 07.06.2012; Ogledov: 1017; Prenosov: 66
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SYNTHESIS OF SUSTAINABLE BIOPROCESSES USING COMPUTER-AIDED PROCESS ENGINEERINGLidija Čuček
, 2013, doktorska disertacija
Opis: This doctoral dissertation, which consists of four substantive wholes, presents several syntheses of sustainable bioprocesses using computer-aided process engineering. In the first part the synthesis of different integrated processes of ethanol production from the entire corn plant is presented. The synthesis of different processes is in the second part further extended to the simplified and more comprehensive synthesis of bioproducts in the whole production supply chain network. Synthesis is based on the generic optimisation model of biomass production and supply chain networks.
In the third part three methods for sustainable development assessment, suitable for multi-criteria optimisation, are presented: method of sustainability indexes, footprints and combined criteria, such as eco- and total profit. Methods are further upgraded with indirect effects in order to measure the unburdening the environment, associated with the use and replacement of environmentally-harmful products. Methods include the direct, indirect and total impacts on the environment.
In the last part the methodology for reducing a large number of criteria within multi-objective optimisation to a small number of representative criteria is presented. This method is presented on the case of environmental footprints.
Ključne besede: Biomass energy generation, Supply chain networks, Synthesis of sustainable bioprocesses, Life Cycle Analysis, Sustainability assessment, Multi-objective optimisation, Dimensionality reduction, Representative Objectives Method
Objavljeno: 06.05.2013; Ogledov: 1473; Prenosov: 190
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CATALYTIC GENERATION OF HYDROGEN FROM BIOMASS DERIVED LACTIC ACID VIA AQUEOUS PHASE REFORMINGMonika Bosilj
, 2015, magistrsko delo
Opis: Hydrogen production from aqueous phase reforming (APR) of organic acids in aqueous phase and from residue of a biomass decomposition process over 3 wt% Pt/ZrO2 has been studied in the absence and presence of barium ions. The results have been compared with Pt/TiO2, Pt/C and Ni/C catalysts. Having identified barium hydroxide as a promising reagent in combination with Pt/ZrO2 catalyst for the hydrogen production out of organic acids, the method for the lactic acid conversion was extended. Lactic acid (LA) was analysed as a major compound in an aqueous solution after a biomass digestion process with Ba(OH)2.
Gaseous and aqueous products after APR reaction of LA mixture with barium hydroxide were identified by different analytical techniques. Gaseous products consisted mainly of permanent gases such as hydrogen, carbon dioxide and methane. The results showed that mixture of LA in combination with both barium hydroxide and Pt/ZrO2 catalyst had the highest hydrogen production rate and the highest selectivity to hydrogen, whereas low gaseous product amount were observed from mixture of LA and only barium hydroxide or Pt/ZrO2 catalyst. Methane and higher amount of carbon dioxide were detected in gas phase products particular in the presence of Pt/ZrO2 catalyst in the mixture.
Aqueous products consisted mainly of pyruvic acid, acetic acid and salts, such as acetate and propionate. The complete conversion of LA after APR was reached in mixture of LA and Ba(OH)2∙8H2O over Pt/ZrO2 catalyst. Mixture of LA and Ba(OH)2∙8H2O or Pt/ZrO2 catalyst gave lower conversion of LA.
Amount of gaseous products, selectivity to hydrogen and LA conversion were affected by higher reactant mixture concentration. In comparison to low concentrated mixtures, high concentrated mixtures contained larger amounts of barium but the same amount of Pt/ZrO2 catalyst. BET analyses showed much smaller pore volume of spent Pt/ZrO2 catalyst, which was used in APR reaction of high concentrated (1.5 mol/L) mixture. Therefore, lower gas product amounts, lower selectivity to hydrogen and only 63 % conversion of LA were effects of deactivated Pt/ZrO2 catalyst.
The results showed that hydrogen generation from APR of LA and conversion of LA in aqueous phase are hardly influenced by the Pt/ZrO2 catalyst presence, which in combination with barium ions, promotes the catalytic APR reaction.
Ključne besede: biomass, hydrogen production, aqueous phase reforming, lactic acid
Objavljeno: 20.02.2015; Ogledov: 1064; Prenosov: 88
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Contribution of non-troglobiotic terrestrial invertebrates to carbon input in hypogean habitatsTone Novak
, Franc Janžekovič
, Saška Lipovšek Delakorda
, 2013, izvirni znanstveni članek
Opis: Eleven of the most important terrestrial invertebrate species in Slovenian caves were analyzed for differences in their fresh and dry biomass, energy content and carbon bulk during winter. These data were combined with the species abundance in 54 caves and adits in order to estimate their organic carbon bulk and carbon input into these habitats. In Central European caves, Troglophilus cavicola, T. neglectus, Faustina illyrica, Amilenus aurantiacus and Scoliopteryx libatrix are the most important vectors of carbon between the epigean and hypogean habitats. In contrast to the general assumption, carbon total contribution to caves via dead bodies is only 0.15% of total migratory biomass, and it is not directly available to troglobionts because of infection with entomopathogenic fungi. In winter, together with predated migratory specimens, carbon input does not exceed 0.3% of the total migratory biomass. This situation should be carefully examined in every karstic region inhabited by distinctive fauna.
Ključne besede: biomass, carbon flux, caves, non-troglobiotic species, organic carbon, respiration
Objavljeno: 21.12.2015; Ogledov: 580; Prenosov: 52
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