<p>Algae is regarded as a good potential substrate for biogas production, due to high cells productivity, low cellulose and zero lignin content. Two parts were included in this study: first, cultivations of micro-algae (<em>Chlorella sorokiniana</em> and <em>Tetraselmis suecica</em>) at two different nitrate concentrations, also the effect of addition of CO<sub>2</sub> on algae grow was investigated in this first part. Second, batch fermentations of the cultivated micro-algae as well as a powder <em>Chlorella</em> (obtained from Raw Food Shop) and a dry mix filamentous algae (collected in the pounds in the park at the back of the Tema-building and then dried) were performed. In this part also effects of thermo-lime pretreatment (room temperature, 80<sup>o</sup>C, 105<sup>o</sup>C and 120<sup>o</sup>C) on the algae biogas potentials was investigated.</p><p> </p><p>Both strains of micro-algae cultured at low nitrate gave more CH<sub>4</sub> yield: 319 (±26) mL and 258 (±12) mL CH<sub>4 </sub>per added gVS was obtained during the degradation of <em>Chlorella sorokiniana </em>grown at 0.4mM-N and 2mM-N level, respectively. For<em> Tetraselmis suecica</em> 337 (±37) mL and 236 (±20) mL CH<sub>4</sub> per added gVS was obtained at 2.4mM-N and 12mM-N level, respectively. Powder <em>Chlorella</em> gave the highest biogas production (719 ±53 mL/added gVS) and CH<sub>4</sub> yields (392 ±14 mL/added gVS), followed by the dry filamentou<em>s</em> algae (661 ±20 mL biogas and 295 ±9 mL CH<sub>4</sub> per added gVS) and <em>Tetraselmis suecica</em> (12 mM-N; 584 ±7 mL biogas and 295 ±9 mL CH<sub>4</sub> per added gVS).</p><p> </p><p>A negative effect of lime treatment at room temperature on CH<sub>4</sub> yield of algal biomass was obtained. Lime treatment at 120<sup>o</sup>C showed the fastest degradation rate for <em>Tetraselmis</em> <em>suecica </em>and powder <em>Chlorella</em> during the initial 5 days of incubation. </p><p> </p><p><em>Chlorella sorokiniana</em> and <em>Tetraselmis suecica</em> cultures flushed with biogas containing 70% and also CO<sub>2</sub> enriched air (5% CO<sub>2</sub>) did not increase cells growth (measured as OD<sub>600</sub>) if compared to references grown under air. On the contrary, a clearly inhibition effect on the algal cells growth was observed in some cultures.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:liu-57987 |
| Date | January 2010 |
| Creators | Liu, Yang |
| Publisher | Linköping University, Linköping University, Department of Water and Environmental Studies |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, text |
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