**8. Acknowledgements**

Simrat Kaur and Charles Spillane acknowledge funding support from Science Foundation Ireland, the Irish Environmental Protection Agency (Fellowship Grant REP957, EPA STRIVE 2009 PHD ET8) and from the Competence Centre for Bio-refining and Bio-energy, Enterprise Ireland (www.ccbb.ie ).

#### **9. References**

172 Biodiesel – Feedstocks and Processing Technologies

problems associated with biodiesel fuels at low temperatures. The maximum temperature at which the first solids appear for a particular fuel is known as the cloud point (CP) and such solids can lead to fuel filter plugging. The pour point (PP) is typically a few degrees below the cloud point and represents the temperature at which the fuel can no longer be poured (Dunn & Bagby, 1996). Key properties of biodiesel fuels at low-temperature are determined by the cold filter plugging point (CFPP) and low-temperature flow test (LTFT) (Dunn & Bagby, 1996; Knothe, 2009). The cloud point (CP) and CFPP are included in the biodiesel standards but as "soft" specifications (Knothe, 2009). For instance, The cloud point in ATSM D6751 requires a report, while the CFPP in UNE-EN 14214 varies with

The properties of biodiesel at low-temperature are correlated with the properties of individual fatty acids, which mostly depend on the saturated ester content. In contrast, the effect of unsaturated fatty acids is considered negligible (Imahara et al., 2006; Ramos et al., 2009). Saturated fatty acids have significantly higher melting points than unsaturated fatty acids and in a mixture saturated fatty acids will crystallize at higher temperature. Therefore, biodiesel fuels derived from fats or oils with significant amounts of saturated fatty

Biofuels can broadly be classified as oxygenated (ethanol, biodiesel) and hydrocarbon biofuels (diesel, jet fuel and gasoline). Based on this classification, the different generations of biofuels are - 1st generation, where biofuels are obtained from natural vegetable oils and greases; 2nd generation of lignocellulosic biomass and algal derived fuels. Two biomass crops, *Jatropha* and *Camelina* bridged, the 1st and 2nd generations of biofuels. The next generations of biofuels will be based on the innovative technologies that improve the processing of biomass into various other types of biofuels and improving the existing feedstock species of biofuel using metabolic/ genetic engineering. For example, application of heat and pressure on algae/biomass/waste using innovative approaches like hydrothermal, catalytic and biological biomass conversions for the creation of cost-effective biofuels as a replacement for fossil fuels. Moreover, the next generation fuels are direct replacements for petroleum and are compatible with the existing infrastructure of the petrochemical industry. Genetic modification of microalgae improves their photosynthetic biomass conversion efficiency and hence can lead to higher biomass productivities, which is necessary for economic scalability. The improvements in the existing infrastructure for microalgae biomass production by photo engineering approaches will also play a key role towards the commercial application of next generation microalgae biofuels. In summary, the replacement of petroleum based fuels by bio-based products depends on several key factors, which include selection of the right bio-based product, process modification or product improvement for indirect substitutions, technological interventions to lower the cost of individual processing steps, scalability of biomass production and bioproduct delivery, and

Simrat Kaur and Charles Spillane acknowledge funding support from Science Foundation Ireland, the Irish Environmental Protection Agency (Fellowship Grant REP957, EPA STRIVE

compounds display higher values of CP and CFPP (Knothe, 2003).

time of year and geographic location.

availability of sufficient and productive land.

**8. Acknowledgements** 

**7. Summary** 


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**9** 

*South Africa* 

**Advantages and Challenges of** 

Christine Richardson and Susan T. L. Harrison

Melinda J. Griffiths, Reay G. Dicks,

**Microalgae as a Source of Oil for Biodiesel** 

*Centre for Bioprocess Engineering Research (CeBER), University of Cape Town,* 

Microalgal oil is currently being considered as a promising alternative feedstock for biodiesel. The present demand for oil for biofuel production greatly exceeds the supply, hence alternative sources of biomass are required. Microalgae have several advantages over land-based crops in terms of oil production. Their simple unicellular structure and high photosynthetic efficiency allow for a potentially higher oil yield per area than that of the best oilseed crops. Algae can be grown on marginal land using brackish or salt water and hence do not compete for resources with conventional agriculture. They do not require herbicides or pesticides and their cultivation could be coupled with the uptake of CO2 from industrial waste streams, and the removal of excess nutrients from wastewater (Hodaifa et al., 2008; An et al., 2003). In addition to oil production, potentially valuable co-products such as pigments, antioxidants, nutraceuticals, fertilizer or feeds could be produced (Mata et al.,

Despite these advantages, algal fuel is not currently in widespread use, largely due to its high cost of production (Chisti, 2007; Miao & Wu, 2006). Despite strong interest from the commercial and scientific sectors, there are currently no industrial facilities producing biodiesel from algae (Lardon et al., 2009). One of the major economic and technological bottlenecks in the process is biomass and lipid production by the algae (Borowitzka, 1992; Sheehan et al. 1998; Tsukahara & Sawayama, 2005). Productive strains and optimized culture conditions able to produce cells with a simultaneously high growth rate and lipid content are required. The high cost and energy demand of harvesting unicellular algae also remains a major challenge. The small cell size (often < 10 m in diameter) and dilute biomass produced requires innovative solutions to minimize the consumption of water and

This chapter provides an overview of microalgae as a source of oil for biodiesel, focusing on:

Mechanisms to enhance lipid productivity of microalgae and future research

A description of algae and their properties with regards to oil production

 Methods and challenges in harvesting and processing of algal biomass Economic and environmental feasibility of microalgal biodiesel

**1. Introduction** 

2010; Rodolfi et al., 2009).

directions.

energy as well as processing costs (Rodolfi et al., 2009).

Requirements and key factors in microalgal cultivation

