Download Emergy Analysis of Biodiesel and Biogas Production - DiVA Portal PDF

Emergy Analysis of Biodiesel and Biogas Production - DiVA Portal
Name: Emergy Analysis of Biodiesel and Biogas Production - DiVA Portal
Pages: 64
Year: 2013
Language: English
File Size: 1.37 MB
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I Summary The aim of this study was to compare the production of biodiesel or biogas from macro algae harvested from the Baltic Sea from an energy perspective. The macro algae were considered to be harvested from an area along the southern coast of Sweden, between Malm and Simrishamn. The gathering of algae is an attempt to reduce the current eutrophication in the Baltic Sea by removing nutrients that the algae have assimilated. The algae also contain some amounts of heavy metals, so the amounts of heavy metals in the marine environment are also reduced. The evaluation included all processes from harvesting of the algae, transport of the algae to the processing plants, processing of the algae to biodiesel or biogas. An evaluation of the algae residues from the processes can be used as fertilizer in agriculture was also conducted. The inputs of materials and energy into the systems were calculated from values found in literature and estimated from similar studies. The evaluation method used was an emergy analysis where all the energy and material inflows into the processes were converted to solar emergy joules so the inflows can be compared on a common basis. The energy and material inflows into the system, including the harvesting, the transport and the biodiesel or biogas production processes, were converted with the use of transformities, which describes the amount of solar emergy joules per joule of energy, gram of material or cost in euro. The transformities for biodiesel and biogas were calculated and compared to give an indication of which product that is most efficient to produce. The processes were also evaluated using emergy indices, such as environmental loading ratio (ELR), emergy yield ratio (EYR), emergy sustainability index (ESI), emergy investment ratio (EIR) and percent renewability in the systems. The results of the study show that biogas has the lower transformity of the two, which means that the biogas production have utilized less solar emergy joules to produce 1 joule of energy than the biodiesel production. The total amount of solar emergy joules used per year for the biodiesel and biogas systems were calculated to 2.18 1019 seJ/year for biodiesel and 2.75 1019 seJ/year for biogas. The transformities calculated for biodiesel and biogas were 5.04 105 seJ/J and 9.12 104 seJ/J, respectively. The emergy indices, however, showed support for the biodiesel process by indicating lower environmental impacts, a higher economic competitiveness and a higher percent renewability.


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III Sammanfattning M let med studien var att utv rdera och j mf ra processerna att tillverka biodiesel och biogas fr n alger sk rdade i stersj n. M ngden av alger som kan sk rdas varje r har uppskattats till ungef r 215 000 ton v t vikt, p en yta mellan Malm och Simrishamn l ngs med Sveriges sydkust. Algerna kan sk rdas mellan april och september. Insamlingen av alger har syftet att reducera den r dande verg dningen i stersj n genom att ta upp n rings mnen som algerna har tillgodogjort sig. Algerna inneh ller ven tungmetaller som, n r algerna samlas in, kan omh ndertas och d rmed minska m ngderna tungmetaller i stersj n. Utv rderingen inkluderade sk rd av alger, transport av alger till biodiesel eller biogas anl ggningen, tillverkning av biodiesel eller biogas och en utv rdering av algresterna efter processerna. M ngderna av energi och material som processerna konsumerar ber knades fr n litteraturv rden och uppskattades fr n liknande studier. Den utv rderingsmetod som anv ndes var emergianalys, d r all energi och material som har anv nts i systemen konverterades till solemergijoule s att de kunde utv rderas utifr n en gemensam grund. De energier och material som anv nds vid sk rd och transport av alger och produktion av biodiesel eller biogas konverterades med hj lp av omr kningsfaktorer (Eng: transformities) som beskriver f rbrukningen av solemergijoule per energi i joule, material i gram eller kostnader i euro. De ber knade omr kningsfaktorerna/transformities f r biodiesel och biogas anv ndes i sin tur f r att utv rdera vilken av processerna som kan anses mest effektiv. Ut ver omr kningsfaktorerna/transformities anv ndes ven emergiindex som indikerar processernas p verkan p milj n, emergiutbyte, h llbarhet, ekonomisk konkurrenskraft och procent anv ndning av f rnyelsebara material och energik llor. Resultatet av studien visade att biogas har en l gre omr kningsfaktor/transformity n biodiesel, vilket inneb r att det har anv nts mindre solemergijoule f r att tillverka 1 joule energi fr n biogas n f r 1 joule biodiesel. M ngden solemergijoule som f rbrukats per r uppskattades till 2.18 1019 seJ/ r f r biodiesel och 2.75 1019 seJ/ r f r biogas. Omr kningsfaktorerna/transformities ber knades f r biodiesel och biogas till 5.04 105 seJ/J respektive 9.12 104 seJ/J. Emergiindex gynnade biodieselprocessen, d den visades ha en l gre p verkan p milj n, h gre ekonomisk konkurrenskraft och en h gre procentuell anv ndning av f rnyelsebara k llor till material och energi som anv nts i processen.


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V Contents 1. Introduction ............................................................................................................................ 1 1.1 Aim ................................................................................................................................... 3 2. Background ............................................................................................................................ 5 2.1 Emergy ............................................................................................................................. 6 2.1.1 Multi product systems ............................................................................................... 9 2.1.2 Emergy indices ........................................................................................................ 10 2.2 From algae to product: Processes ................................................................................... 11 2.2.1 Harvesting ............................................................................................................... 12 2.2.2 Algae for biodiesel production ................................................................................ 12 2.2.3 Algae for biogas production .................................................................................... 16 2.2.4 Waste assessment .................................................................................................... 18 3. Methods ................................................................................................................................ 19 3.1 System boundaries .......................................................................................................... 19 3.2 Growth and harvesting ................................................................................................... 19 3.3 Transport ........................................................................................................................ 22 3.4 Biodiesel production ...................................................................................................... 24 3.5 Biogas production .......................................................................................................... 27 3.6 Transformities ................................................................................................................ 29 4. Results .................................................................................................................................. 31 4.1 Inflows ............................................................................................................................ 31 4.2 Emergy biodiesel ............................................................................................................ 32 4.3 Emergy biogas ................................................................................................................ 34 4.4 Comparing biodiesel and biogas production .................................................................. 36 4.5 Emergy indices ............................................................................................................... 37 4.6 Sensitivity analysis ......................................................................................................... 37 5. Discussion ............................................................................................................................ 39 5.1 Results ............................................................................................................................ 39 5.2 Processes ........................................................................................................................ 40 6. Conclusions .......................................................................................................................... 43 7. References ............................................................................................................................ 45


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