Microalgae have received significant attention as a biodiesel feedstock. This is in response to energy shortage, climate change and global warming. Microalgae offer many advantages for use in biodiesel production. They have high photosynthetic efficiency, which translates to high growth rate. Moreover, most algal species have high lipid content. Furthermore, it is possible to launch algal biorefinery facilities in lands with low economic value, such as saline and arid lands therefore microalgae cultivation does not compete with food production for farmlands.
Liandong Zhu and colleagues from University of Vaasa in Finland developed a method to determine algal biomass accumulation for biodiesel production when algal cultivation with livestock waste compost was combined. In their work, an optimal concentration level for algal cultivation was found, and the productivities of biomass and lipids was specified. The work is published in peer-reviewed journal, Bioresource Technology.
Chlorella sp. microalgae were used in this study. It was isolated from local fresh-water habits by Utex and grown in a BG11 medium. Livestock waste compost from a local collection point was used. Windrow composting technology was applied to compost cattle waste. The compost was immersed in water, and stirred with a magnetic stirrer. The mixture was then filtered to eliminate non-soluble particulate solids.
Livestock waste compost medium was diluted using fresh water to four varying concentrations (200, 1500, 1000 and 500 mg L-1 COD). The undiluted media and four diluted media were applied as cultures for microalgal cultivation for 10 days. For comparison, BG11 media (control group) were also used to grow algae. The livestock waste compost with the variable chemical oxygen demand concentrations were introduced into 0.4L flasks. The optical density of Chlorella sp. was measured every day using spectrophotometer.
The authors determined the lipid contents of chlorella sp. in five cultures with varying nutrient concentration. The culture with the initial chemical oxygen demand concentration at 500 mg L-1 experienced the highest algal lipid accumulation (44.30% of dry weight). They attributed this to the fact that low biomass concentration in the culture could make more algal cells access and receive more light that triggered and benefited lipid storage. As the initial chemical oxygen demand concentration increased from 500 mg L-1 to 2680 mg L-1 the lipid content decreased from 44.30% to 33.90%.
The authors also found that about one third to one fourth of lipids would be converted into fatty acid methyl esters; efficient biodiesel ingredients. This is because some lipids such as phospholipid, chlorophyll and glycolipid are not efficient ingredients for biodiesel production.
This study successfully found the optimal concentration level for algal cultivation and productivities of biomass. The authors concluded the following parameters: specific growth rate of Chlorella sp. grown in the five cultures ranged from 0.275 to 0.375 day-1. Initial nutrient concentration affected lipid accumulation, and the lipid content ranged from 33.90% to 44.30%. The 2000 mg L-1 chemical oxygen demand culture was found to be the optimum medium for algal cultivation, since the highest biomass and lipid productivities were realized.
This study was possible with partial funding from TranAlgae. A network of relevant stakeholders within the algae industry in the Botnia-Atlantica region with the aim of implementing innovative solutions for the production of micro- and macroalgae biomass from waste streams at industrial scale.
L.-D. Zhu1,2,5, Z.-H. Li1, D.-B. Guo3, F. Huang4, Y. Nugroho2, and K. Xia2. Cultivation of Chlorella sp. with livestock waste compost for lipid production. Bioresource Technology, volume 223 (2017), pages 296–300.Show Affiliations
- Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources, and Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China
- Department of Energy Technology, Faculty of Technology, University of Vaasa, Vaasa 65101, Finland
- School of Environmental Science & Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
- Laboratory of Tropical Agro-Environment, Ministry of Agriculture, South China Agricultural University, Guangzhou 510642, China
- Renewable Energy Research Group, Vaasa Energy Institute, Vaasa 65101, Finland
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