本研究測試以鳥糞石作為培養微藻（小球藻）之肥料。實驗用之鳥糞石以磷酸銨和氯化鎂混合來製備，並測得其水中溶解度為0.2 mg/l，這個平衡只需10分鐘即達成。本研究設計七種不同含鳥糞石之配方，並以BBM（Bold’s Basal Media）為對照組，比較藻類生長情形。經過OD（光密度）測試，其中六種顯示增長，再挑出生長最好的四種反覆實驗，選出其中最佳者。結果發現最佳配方是與對照組最相近的一種。用鳥糞石培養的小球藻使用兩種不同的碳源進行測試：二氧化碳（10%）及空氣。結果發現，以二氧化碳培養者生長程度僅比只使用空氣者略高，但空氣中生長的藻類呈現黃色（通常視為不健康的指標）。經測試不同含量的鳥糞石對藻類培養的影響，發現雙倍與三倍含量的鳥糞石讓藻類生長期更長且達到較高的OD。最後將鳥糞石和雙倍含量鳥糞石與標準BBM和含雙倍劑量磷酸、氨、鎂之BBM（等同於雙倍鳥糞石含量之BBM）比較，發現儘管培養於BBM的藻類有最低的OD，但也同時擁有最高的TSS（總懸浮固體）；鳥糞石和雙倍含量鳥糞石之TSS大約相同，而兩倍鳥糞石含量之BBM有最低的TSS。至於以鳥糞石培養藻類OD較高但TSS較低之原因仍未知。粒徑測定顯示，不同培養基之藻類粒徑並無差別。藻類可用脂質含量測試結果，最高者為BBM，其次為鳥糞石，再次為雙倍含量鳥糞石，最低者為雙倍鳥糞石含量之BBM。綜上結果得到可用脂質濃度如下：BBM為3.98 g/l，鳥糞石為2.85 g/l，雙倍含量鳥糞石為1.85 g/l，雙倍鳥糞石含量之BBM為1.01 g/l。本研究發現使用鳥糞石替代BBM中的磷、鎂和氨可降低成本。經計算，肥料價格可降低97.8%，藻類生質生產成本降低6.7%，藻類生物燃料生產成本降低1.8%。

The use of struvite as a fertilizer for the cultivation of microalgae (Chlorella vulgaris) was tested. The struvite was prepared by mixing ammonium phosphate and magnesium chloride. The solubility was tested in water, which was found to be 0.2 mg/l. This equilibrium was reached after only 10 minutes. Different recipes were designed to supplement the struvite, using BBM (Bold’s Basal Media) as reference. These 7 recipes were tested with BBM as a comparison. Out of these recipes, 6 recipes displayed growth, detected by OD (optical density). The 4 best recipes were repeated experimentally, out of which the best one was selected. This recipe was the one most similar to the reference. Cultivation of Chlorella vulgaris was tested with 2 different carbon sources: CO2 (10%) and air. It was found that the growth using CO2 was only slightly higher than using air, but the algae grown on air had a yellow color (usually an indicator of bad health). Different amounts of struvite were tested. Here it was found that double and triple amounts of struvite allowed the algae to grow longer and reach a higher OD. In the final comparison struvite and a double amount of struvite were compared to standard BBM and BBM with a double dose of phosphate, ammonia and magnesium (equal to the double amount of struvite). Here it was found that although algae cultivated on BBM had the lowest OD, it also had the highest amount of TSS (total suspended solid). Struvite and double struvite were about equal while double BBM had the lowest amount of TSS. It is unknown why the OD increases when using struvite, while TSS is lower. The algae particle size was measured, there was no difference in size found for different media. When measuring the algal usable lipid content, BBM scored the highest. This was followed by struvite, then double struvite, while double BBM was the lowest. When combining these results to get the concentration of usable lipids per liter, this was as follows: 3.98 g/l for BBM, 2.85 for struvite, 1.85 for double struvite and 1.01 for double BBM. Using struvite to replace phosphorus, magnesium and ammonia in BBM would reduce the cost. This was calculated at a potential reduction in the fertilizer price by 97.8%, the production cost of algal biomass by 6.7% and that of algal biofuel by 1.8%.

Chapter 1: Introduction 1
Chapter 2: Literature study 2
2.1 Struvite properties and natural occurrence 2
2.2 Struvite as a phosphate source 3
2.3 Waste as fertilizer 6
2.4 Struvite as fertilizer 8
Chapter 3: Materials and methods 9
3.1 Analytical methods 9
3.2 Preparation of struvite 10
3.3 Testing the solubility of struvite 10
3.4 Growing of algae 11
3.5 Initial testing 12
3.6 Further testing the selected recipes 13
3.7 Comparison: CO2 vs air 14
3.8 Varying amounts of struvite 14
3.9 Final comparison 15
Chapter 4: Results 16
4.1 Preparation of struvite 16
4.2 Testing the solubility of struvite 17
4.3 Initial testing 19
4.4 Further testing the selected recipes 21
4.5 Comparison: CO2 vs air 22
4.6 Varying amounts of struvite 24
4.7 Final comparison 27
4.8 Price comparison 32
Chapter 5: Conclusion 37
5.1 Discussion 37
5.2 Conclusion 38
5.3 Future research 40

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