fundamentals of water removal from the product are critical in any discussions about largescale fuel production. Laboratory-scale or pilot-scale techniques that use solar drying are relatively slow, require large land areas, and are not likely to scale up commercially.
This chapter describes and contrasts pathways that lead from algae cultivation to fuel production. Many technical options exist for each individual component in the processing pathway (for example, algae can be cultivated in an array of open ponds or closed photobioreactor systems with different designs). This chapter illustrates how particular individual components are linked together to constitute the pathway for algal biofuel production and how categorizing these processes into several distinctive pathways can help with the analysis of the sustainability impacts of algal biofuels. This chapter further discusses the potential fuel products and coproducts from various production pathways. In concert with Chapters 4 and 5, the reference and alternate pathways demonstrate the sustainability issues for the photosynthetic methods of producing fuels from microalgae and highlight potential improvements that might alleviate critical sustainability concerns.
Though this chapter focuses on describing algal biofuel production pathways that are further considered in following chapters, it is the only part of the report that considers the value-added propositions associated with coproducts. The committee believed that coproducing high-value products, such as nutraceutical products, with algal biofuels would be viable only on a small scale. If large quantities of high-value algal products are coproduced with biofuels, the value of coproducts likely decreases with market saturation. Animal feedstuff is the only coproduct that is likely to have a large enough market to absorb the large quantities produced if algal biofuels are produced at commercial scale. The coproduct value depends on the composition of the animal feedstuff and the characteristics of the market in which it would be sold. In general, coproduct volumes swell with the scaling up of algal biofuel production, potentially saturating markets for these products unless a wide variety of coproducts for different markets are produced.
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