9.4.1 Cost of Algal Biomass and Algal Oil

Currently, commercial processes for the production of microalgae only exist for the production of specialty products such as health supplements, carotenoids, and specific aquaculture feeds. Furthermore, most of the algal species used in these processes are extremophilic algae. Data on the cost of large-scale algal processes are largely based on pre-implementation costing of these. Typical costs estimated are presented in Table 9.4.

From Table 9.4, the disparity in costing that arises from an immature technology position is clear. This was also noted in a comparison of environmental analyses. As a general trend, the algal biomass cost from the raceway system lies in the range of US$0.23 to $0.60 kg-1 DW, with the exception of the estimate of Norsker et al. (2011), for which the biomass was recovered by centrifugation, noted as a major capital and energy cost. The production of algal biomass from photobioreactors was characterized by a greater variation from US$0.42 to $3.04 kg-1 DW. Here it is evident that the two lowest values are based on the same calculations (Chisti, 2007), while the majority of the values (four of the eight available) lie in the range US$3.18 to $9.54. Refinement in this costing is required. Factors impacting the cost­ing are discussed in Section 9.4.2.

These costs are not competitive with the cost of crude oil (US$0.48 to $0.71 L-1; US$76 to $113 bbl-1). Van Harmelen and Oonk (2006) estimated that cost of pro­duction with current technology exceeded potential earnings from algal oil as sole product by 1.7- to 3.9-fold, depending on the assumptions and process decisions made. In costing a production facility for algal oil in South Colorado, Richardson et al. (2012b) indicated that a 60% reduction in CAPEX (capital expenditure) and 90% reduction in OPEX (operating expenditure) are required for a cost-effective pond system with algal oil as the sole product. These reductions increase to 80% on CAPEX and 90% on OPEX using a photobioreactor system. Norsker et al. (2011) translated their costs based on algal biomass to an energy-based cost, yielding val­ues in the range of US$32.60 to $295.50 GJ-1. It is noted that the lower value of US$32 GJ-1 estimated for a high light intensity environment is similar to the cost of delivered electricity.

These costings raise clearly two key considerations:

1. The necessity to operate the algal oil process as a biorefinery, achieving value from multiple products for the same growth costs

2. The need to interrogate component process costs to identify key targets for cost savings and technology development

TABLE 9.4 Cost Estimates for the Production of Algal Biomass and Algal Oil on a Large Scale Biomass Estimated Estimated Productivity Cost of Cost of Algal (g DW m_2d_’) Algal Lipid (L) or [Biomass Lipid Biomass Biodiesel (D) concentration Content (US$ per kg (US$ per Ref. Species Location (g L-1)] (%) biomass) liter) Assumptions wrt Process Benemann and — 30 50 0.241 0.43 (D) Raceway Oswald, 1996 Benemann and 60 50 0.148 0.26 (D) Raceway Oswald, 1996 Molina Grima et al.. Phaeodactylum 30.4 Photobioreactor 2004 Van Harmelen and 27 30 0.37 1.06(D) Raceway Oonk, 2006 Chisti, 2007 72 30 0.47 1.41 (D) Photobioreactor Chisti, 2007 — — 35 30 0.60 1.81 (D) Raceway Norsker et al„ 2011 Spirulina, Eindhoven, the [0.3 g L-4 6.45 Raceway ponds, as wet paste. Dunaliella Netherlands Paddlewheel circulating liquid at 0.25 m s-1 Norsker et al„ 2011 — Eindhoven, the [2.1 g L1] 7.77 Flat-plate photobioreactor, as Netherlands wet paste; aeration at 1 vvm; polyethylene film panels of 1-year lifetime

(Continued)

assumed; circulation at 0.5 m s-1; assume free supply of C02 from flue gas, nutrients from wastewater, and photosynthetic efficiency increased to 60%

Jorquera et al., 2010 Nannochloropsis

Jorquera et al., 2010 Nannochloropsis

Williams and USA 18-37

Laurens, 2010

Richardson et al., 2012

Richardson et al., 2012

0.227 0.419 9.54

15-50 0.36-0.65

US Dept, of Energy’s Office of Energy Efficiency and Renewable Energy using a hybrid reactor system consisting of a front-end PBR “nursery” and “grow-on” raceway stage

3.36 (L) Open ponds

8.34 (L) Photobioreactors

The effect of process variables and process selection on the costing is discussed in Section 9.4.2, while the potential contribution of products other than biodiesel is discussed in Section 9.4.3.