Sukarni (2014) Karakteristik Mikroalga Laut Nannochloropsis oculata sebagai Alternatif Bahan Bakar Terbarukan. Doctor thesis, Universitas Brawijaya.
Abstract
Biomassa mikroalga menjadi alternatif yang paling menjanjikan dan menarik untuk menggantikan pemanfaatan tanaman darat sebagai bahan baku bahan bakar biomassa yang terbarukan. Potensi bahan bakar biomassa adalah karena laju pertumbuhan yang cepat dan kemampuan tinggi untuk menyerap CO 2 dibandingkan dengan tumbuhan darat. Dalam disertasi ini, mikroalga laut Nannochloropsis oculata telah diteliti dalam hal potensi kelimpahan biomassa dan sifat fisikokimia yang menentukan kelayakannya sebagai bahan baku bahan bakar biomassa. Perilaku termal pembakaran di udara atmosfer dan karakteristik dekomposisi dalam udara inert juga telah diteliti dengan melakukan percobaan pada STA PT1600 Thermal Analyzer dari temperatur kamar kamar sampai 1200 o C. Perubahan morfologi, struktur dan mineral selama proses dekomposisi juga telah diselidiki. Nannochloropsis oculata yang telah dibudidayakan di kolam terbuka secara tradisional dan alami, memiliki laju pertumbuhan spesifik 0,27 per hari dan memiliki waktu menggandakan diri 2.59 hari. Selama tujuh hari budidaya, ratarata kenaikan biomassa alga adalah sekitar 1.5x10 6 sel/ml/hari. Komposisi kimia biomassa dievaluasi dengan energi dispersif X-ray (EDX) spektrometri. Hasil analisis menunjukkan bahwa kandungan utama unsur anorganik biomassa adalah Mg, Ca, Cl dan Si, sementara Al dijumpai sebagai elemen minor. Satu-satunya alkali yang ada dalam biomassa adalah Na. Kandungan makromolekul sel biomassa diteliti dengan Fourier transform infrared (FTIR) spectroscopy . Pita-pita spektrum FTIR telah menunjukkan kehadiran komponen utama dalam Nannochloropsis oculata , yaitu karbohidrat, protein dan lipid. Analisis proksimat Nannochloropsis oculata , yang dilakukan dengan melakukan percobaan di thermal gravimetric analyzer , menunjukkan bahwa biomassa Nannochloropsis oculata memiliki komposisi kadar air dan karbon tetap rendah, sedangkan kandungan volatil dan kadar abu tinggi, yaitu masing-masing adalah 3,99% ( air-dried basis ), 8.08%, 67.45% dan 24.47% ( dry basis ). Kandungan energi, yang dihitung melalui hasil analisis proksimat, adalah 16.80 MJ/kg. Perilaku termal pembakaran Nannochloropsis oculata dengan udara atmosfer diteliti dengan melakukan percobaan pada STA PT1600 Thermal Analyzer pada laju pemanasan 10, 40 dan 70 o C/menit dengan rentang temperatur dari temperatur kamar sampai 1200 o C. Parameter kinetik dievaluasi dengan menggunakan metode Kissinger dan Ozawa. Hasil penelitian menunjukkan bahwa pembakaran Nannochloropsis oculata terjadi dalam lima tahap. Dimulai dengan tahap devolatilisasi awal, dekomposisi termal utama dan proses pembakaran, tahap transisi, tahap pembakaran arang dan tahap terakhir adalah reaksi lambat-pembakaran sisa arang. Sejalan dengan meningkatnya laju pemanasan, laju kehilangan massa meningkat juga. Demikian juga meningkatnya laju pemanasan menyebabkan proses dekomposisi termal menuju temperatur yang lebih tinggi. Rata-rata energi aktivasi pada tahap dekomposisi termal utama dan tahap pembakaran arang sekitar 251 dan 178 kJ/mol. Mekanisme pembakaran Nannochloropsis oculata ditentukan dengan membandingkan dua temperatur, yaitu temperatur TDTG yang merepresentasikan temperatur awal di mana laju kehilangan massa dari sampel semakin nyata dan yang lainnya adalah temperatur TDTA di mana sinyal kurva DTA naik dengan tiba-tiba. Hasil perbandingan menunjukkan bahwa biomassa Nannochloropsis oculata terbakar secara homogen. Dalam mode homogen, tahap awal adalah pirolisis dan diikuti oleh pembakaran volatil dan selanjutnya adalah pembakaran arang. Perubahan morfologi dari biomassa dan residu setelah 1200 o C diamati dengan scanning electron microscopy (SEM), dan komposisi kimianya ditentukan oleh dengan energi dispersif X-ray (EDX) spektroskopi. Perbedaan morfologi struktural ditemui pada bahan biomassa dan residu, karena adanya proses pemecahan termal komponen dan selanjutnya terjadi penataan ulang ikatan kimia yang mengakibatkan pembentukan senyawa baru. Fenomena ini menyebabkan perubahan struktural dari residu dan juga perubahan warna. Analisis EDX residu menunjukkan unsur-unsur residu yang utama adalah Ca, Mg dan Si. Karbon dan oksigen juga dijumpai dalam residu setelah 1200 o C dalam bentuk senyawa karbonat MgCO 3 dan terak seperti SiO 2 , MgO dan CaO. Al dan Cl telah habis terdekomposisi sampai temperatur 1200 o C, sedangkan Na, yang tidak terdeteksi dalam analisis EDX residu, ditemui dalam senyawa melilite (Ca 6 Na 2 O 15 Si 4 ) dan Na 2 (MgSi) Si 4 O 12 . Perubahan senyawa makromolekul sel biomassa sebagai akibat dari temperatur juga diamati dengan FTIR spektroskopi. Pita spektrum FTIR menunjukkan adanya degradasi intensitas yang progresif dalam spektrum residu biomassa setelah 1200 o C, terutama di sekitar 3590-1630 cm -1 . Menurunnya intensitas tersebut disebabkan oleh hilangnya komponen protein dan lipid bi
English Abstract
Microalgal biomass is the most promising and attractive alternative to replace the terrestrial crop utilization for renewable biomass fuel feedstock. The potential for biomass fuel is due to its fast growth rate and high ability for CO2 fixation as compared to terrestrial vegetation. In this work, the marine microalgae Nannochloropsis oculata had been investigated in terms of potential abundance and physicochemical properties, which determine its feasibility as biomass fuel feedstock. The thermal behavior in term of its combustion in air atmosphere and its decomposition characteristic in inert had been investigated by performing experiments on STA PT1600 Thermal Analyzer at room temperature to 1200 o C. The morphological, structural and mineralogical change had investigated, as well. The Nannochloropsis oculata, which it had been cultivated in the traditionally natural open pond, had specific growth rate of 0.27 day -1 and had doubling time of 2.59 days. During seven days of cultivation, the average rate of increase in algal biomass was about 1.5x10 6 cells/ml/day. The biomass chemical composition was evaluated by energy-dispersive Xray (EDX) spectrometry. It analysis revealed that the major inorganic constituents of biomass were Mg, Ca, Cl and Si, whilst Al present as a minor element. The alkali that present in biomass was Na. The cellular macromolecular content of biomass was investigated by the Fourier transform infrared (FTIR) spectroscopy. The FTIR bands spectra have specified the presence of the principal components in the Nannochloropsis oculata , namely carbohydrate, protein and lipid. The proximate analysis of Nannochloropsis oculata, which it was done by performing experiments in the thermal gravimetric analyzer, indicated that it had compositions of low moisture content and fixed carbon, whereas high volatile matter and ash content, i.e., 3.99% (air-dried basis), 8.08%, 67.45% and 24.47%, by dry basis, respectively. The energy content, which was calculated through the proximate analysis results, was 16.80 MJ/kg. The thermal behavior of Nannochloropsis oculata combustion in air atmosphere had been investigated by performing experiments on STA PT1600 Thermal Analyzer at heating rates of 10, 40 and 70 o C/min and range of temperatures from room temperature to 1200 o C. The kinetic parameters were evaluated by using Kissinger and Ozawa methods. The result showed that Nannochloropsis oculata combustion occurred in five stages. Started with initial devolatilization, the main thermal decomposition and combustion process, transition stage, the combustion of char and the last stage was the slow-burning reaction of residual char. In line with increasing heating rate, the mass loss rate increased as well, but it caused the thermal decomposition processes delayed towards higher temperatures. The average activation energy at the main thermal decomposition stage and the stage of char combustion were about 251 and 178 kJ/mol, respectively. The combustion mode of Nannochloropsis oculata was determined by comparing the two temperature. One was temperature TDTG that represented the initial temperature at which the mass loss rate of the samples become apparent and other was temperature TDTA at which the DTA signal curve rose suddenly. The comparison denoted that Nannochloropsis oculata biomass was burned by homogeneous mode. In the homogeneous mode, the initial stage was pyrolysis and followed by volatile ignition and subsequent combustion of char. The morphological change of biomass and its residue after 1200 o C was characterized by scanning electron microscopy (SEM), and its chemical composition was determined by energy dispersive X-ray (EDX) spectroscopy. The difference structural morphology was encountered on biomass material and its residue due to the thermal cleavage of its components and subsequent rearrangement of the chemical bond lead to the formation the new compounds. This phenomenon induced the structural change of the residue and its color change, as well. The EDX analysis of residue showed the major residual elements were Ca, Mg and Si. Carbon and oxygen also present in the residue after 1200 o C as carbonate compound MgCO 3 and slag such as SiO 2 , MgO dan CaO. Al and Cl have depleted until the temperature 1200 o C, whereas Na, which it was not detected in the EDX analysis of residue, was encountered in melilite compounds (Ca 6 Na 2 O 15 Si 4 ) and Na 2 (MgSi) Si 4 O 12 . The cellular macromolecular compounds change as an effect of temperature investigated by FTIR spectroscopy. The FTIR bands spectra revealed the progressive degradation intensity in the spectra of biomass residue after 1200 o C, mainly at around 3590-1630 cm -1 . The declined intensity was caused by the loss of protein and lipid components of biomass during thermal processes, as well as their fibrillar component that composed of polymer of
| Item Type: | Thesis (Doctor) |
|---|---|
| Identification Number: | DES/662.88/SUK/k/061407446 |
| Subjects: | 600 Technology (Applied sciences) > 662 Explosives of explosives, fuels, related products > 662.8 Other fuels |
| Divisions: | S2/S3 > Magister Teknik Elektro, Fakultas Teknik |
| Depositing User: | Endro Setyobudi |
| Date Deposited: | 06 Nov 2014 10:01 |
| Last Modified: | 06 Nov 2014 10:01 |
| URI: | http://repository.ub.ac.id/id/eprint/161337 |
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