Biofuels production from Microalgae after heterotrophic growth
(藻类异养转化制备生物质液体燃料) Qingyu Wu (吴 庆 余) Xiaoling Miao (缪晓玲)
Department of Biological Sciences and Biotechnology, Tsinghua
University, Beijing 100084, P.R.China (清华大学生物科学与技术系）
BIOMASS -BIOFUEL higher plants or woody materials : pine wood, rice and cotton straw and stalk, energy crops Microalgae advantages: Higher photosynthetic efficiency, larger biomass, faster growth, easy industry culture 5days 10 years cell culture engineering
1. Materials and biotechnolgy
(in liquid medium)
(on agar plates)
By cell biotechnology to change the nutrition metabolism pathway, green autotrophic cells (AC cells) were transformed to heterotrophic growth.
Yellow heterotrophic cells (HC cells) under light microscope (10×40) lipid vesicles
Fig. 7 Differences in cell organization between HC and AC cells. （图7 小球藻异养和自养转化细胞结构变化示意图）
The contents of main chemical components in cells of AC and HC. （表1 AC、HC细胞主要生化成分含量）
Strain (%) Protein (%) Lipid (%) Carbohydrate (%) Ash (%) Moisture (%) Others (%)
The culture process of the HC cells by “Two Step” method.
12 9 OD 540 6 3 0
0 24 48 72 Time (h) 96 120
10L下口瓶半无菌培养 10L下口瓶补料半无菌培养 20L下口瓶半无菌培养 20L下口瓶补料半无菌培养
6 3 0
48 72 Time (h)
Comparison of the HC cell growth under axenic, half-axenic and no-axenic culture conditions
2. Fast pyrolysis of HC cell
Dry cells powder
Fast pyrolysis system and conditions
Pyrolysis system: the fluid bed reactor Temperature ：500℃ Heating rate ：600 ℃/s Vapor residence time：2-3 s biomass-feeding rate ：4 g/min particle size < 0.5 mm
The diagram of fast pyrolysis system of fluid bed
Yields of fast pyrolysis at temperature of 500 ℃, heating rate of 600 ℃ /s and the sweeping gas flow rate of 0.4m3/h. Strain AC HC Microcystis Gas (%) 29.6 31.6 55.2 Bio-Oil (%) 16.6 57.2 23.7 Char (%) 53.8 11.2 21.1
All the yields were expressed on the basis of the dry weight of samples.
Product yields of microalgae by fast pyrolysis at temperature of 500 ℃, heating rate of 600 ℃ /s and the sweeping gas flow rate of 0.4m3/h.
Product Yield (%)
50 40 30 20 10 0
AC HC M
Char Gas Bio-oil
Bio-Oil products of AC, HC and Microcystis by fast pyrolysis.
Comparison of typical properties of fossil oil and fast pyrolysis oil of wood and HC.
Typical value Properties Wood C H O N S Density (kg l-1) Viscosity (Pa s) Heating value (MJ kg-1) Stability 56.4% 6.2% 37.3% 0.1% n.d. 1.2 0.04-0.20 (at 40oC) 21 Not as stable as fossil fuels Bio-oils AC 62.07% 8.76% 19.43% 9.74% n.d. 1.06 0.10 (at 40oC) 30 HC 76.22% 11.61% 11.24% 0.93% n.d. 0.92 0.02 (at 40oC) 41 83.0-87.0% 10.0-14.0% 0.05-1.5% 0.01-0.7% 0.05-5.0% 0.75-1.0 2-1000 42 Fossil oil
Not as stable as fossil fuels, but more stable than the bio-oil from wood
3. Biodiesel production from microalgal oil
1. Biodiesel （生物柴油） 2. The preparation of microalgal oil （微藻油脂的制备） 3. Acidic transesterification of microalgal oil （酸催化酯交换法制备微藻生物柴油） 4. Characteristics of biodiesel from microalgal oil （微藻生物柴油的特性）
Fatty acid methyl esters originating from vegetable oils and animal fats are known as biodiessel. Biodiesel from transesterification can be used directly or as blends with diesel fuel in diesel engine
Oil from microalgae (微藻油脂的提取)
Growth of HC cells (A), powder of HC cells (B) and microalgal oil from HC cells (C).
Method of Acidic transesterification for biodiesel preparation from microalgal oil: (微藻生物柴油制备: 酸催化酯交换技术)
The reaction mixture consisted of oil, methanol and concentrated sulfuric acid
The separation of the reaction mixture (A) and the biodiesel from microalgal oil (B,C)
Comparison of biodiesel from microalgal oil and diesel fuel
Propertis (特性) Density 密度（kg l-1） Visicosity 粘度（Pa s） Flash point 闪点（ °C ） Solidifying point 凝点（ °C ） Cold filter plugging point 冷滤点（ °C ） Acid value 酸值 (mg KOH g-1) Heating value 热值（MJ kg-1） H/C ratio Biodiesel from microalgal oil (微藻生物柴油) 0.864 5.2×10-4 (40 °C ) 115 -12 -11 Diesel fuel (石化柴油) 0.838 1.9-4.1 ×10-4 (40 °C ) 75 -50 – 10 -3.0 (-6.7 max)
0.374 41 1.18
0.5 max 40-45 1.81
1 Heterotrophic growth of Chlorella protothecoides resulted in the accumulation of a large amount of lipid in cells, which is about 4 times of that in control. By using HC cells rich in lipids as biomass for pyrolysis and biodiesel preparation, we got high yield and high quanlity bio-fuel. 2 The results suggests that the new process, which combines biotechnology with biofuel production, is a feasible and effective method for the production of high yield and high quality fuel oils from microalgae. 3 The study could contribute to the creation of a system to produce biofuels from microalgae which might have great commercial potential for liquid fuel production.
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