Production Of Biodiesel Coupling With CO₂Fixation By Microalgae

Reduction of dioxide carbon emission and production of renewable energy have become thehotspot in the sustainable development research field. Microalage has shown its remarkableadvantages in CO₂emission reduction and bioenergy production. Especially, producing bio-oilfor biodiesel by microalgae coupling with CO₂mitigation is showing important significance tosolve the two problems, global warming and energy shortage. In this work biodiesel productioncoupling with CO₂mitigation by microalgae is studied with Chlorella vulgaris as the researchobject.Firstly, the technology for production of biodiesel was developed at laboratory scale.Through analysis and comparison, the determined technique is microalgae cultured in15Lphotobioreactor, harvested by centrifuge, disrupted four times by freezing and thawing method,dried six hours to obtain biomass and extracted oil through organic solvent extraction method.By using this technoloy, the cetane number of microalgal biodiesel is up to57.3, which corformsto calorific value requirements of biodiesel, and it also has good application prospects.Then in order to comprehensive understanding lipid accumulation factors of bio-oilproduction by microalgae coupling with CO₂mitigation, the factors effect on microalgae growthand oil accumulation are investigated. Results shows NaNO₃concentration0.75g/L, K₂HPO₄concentration0.03g/L, culture time5days,5%carbon dioxide concentration, photoperiod18L:6D and IAA added concentration0.5mg/L are the best conditions.Based on the above results, to obtain the optimum procedure parameters of lipidaccumulation, the microalgae culture conductions was optimized by multi-factor experimentusing response surface methodology （RSM）. The optimum conditions are NaNO₃concentration0.67g/L, K₂HPO₄concentration0.03g/L, culture time5days, corresponding lipid content is15.4%. The siginificance test and further research proves that the RSM regression model isfeasible and can be well used for practical systhesis of lipid accumulation.Finally, to discover the mechanism of lipid accumulation, the effect of enzyme promotor onmicroalgal lipid synthesis was discussed deeply with the key enzyme as its starting point. Thestudy on acetyl-CoA carboxylase promters such as citric acid and magnesium ion shows theremarkable promote effect for lipid systhesis especially under the appropriate concentration of30mg/L and1.5mmol/L compared with control group. Thus the lipid is up to15.9%and16.5%,0.7and0.4times higher than control group.This research demonstrates that microalgae can efficiently produce bio-oil used forbiodiesel coupling with CO₂mitigation by microalgal technique. And combustion performanceof microalgal biodiesel is confirmed well, it concludes that microalgae can be used as rawmaterials for biodiesel production. Furthermore, the study can also provide references forlarge-scale industrial application.