Bioenergy and Bioresource:Open Access

The Influence of Algae Cultivation on the Selection of Jet Fuel or Biodiesel

Sofi Wilson^{* *}Correspondence: Sofi Wilson, Managing Editor, Bioenergy and Bioresource:Open Access, Chaussee de la Hulpe 181, Brussels, Belgium, Email:

Author info »

Introduction

Climate change, mainly due to the emission of flue gases from the coal-fired power plant industry, is a critical environmental issue today. Taking into account power demand and downstream emissions, CO₂ fixation with algae becomes an attractive approach for CO₂ capture and additional benefits in downstream algae use due to environmental permit priorities and sustainable potential. Coal-fired power plant flue gas is an ideal carbon source for large-scale algae cultivation due to stable and centralized emission characteristics, which have been qualified as carriers of bioenergy with benefits of bio-nutrients along with CO₂ abatement. However, the algae chain must reconcile economic, energetic, and ecological aspects to be able to make a specific product selection.

The improvement of flue gas cleaning technology for edible bio-nutrients has achieved certain economic benefits, but the energy consumption is very high. The ideal species of algae should be qualified with the characteristics of rapid growth and high lipid content, but the growth rate of algae decreases with increasing lipid content. However, the increase in algal growth benefits CO₂ fixation, while the increase in lipid content in algae benefits biofuel quality and quantity. Most reviews provide the most promising microalgae species for different types of biofuels. Nanochloropsis oceanica is considered the ideal species of algae, characterized by rapid growth and high lipid content. The challenge of tolerance to high CO₂ concentrations was overcome by gradually increasing the CO₂ concentration to even purified CO₂ by combining pH control and aeration control. Pollutants in flue gas have been shown to have a tolerance to SOX less than 60 ppm, NO₂ less than, 300 ppm and NO less than 60 ppm, but an aggregation of specific trace metals in algal cells has been studied. For edible algae, as an edible source of CO₂, the flue gas needs to be further cleaned to remove trace metals to inhibit trace metals in bio-nutrients. Consequently, the need for edible CO₂ increases energy consumption but benefits economics, while the general algal feedstock without the benefit of edible bio-nutrients loses advantage despite improved CO₂ sequestration. Algae farming for target suitable algae products must also find a balance between energy consumption and economics in terms of quality and quantity of algae products.

Currently, the algae industry pursues a wide range of products, from bionutrients and animal feed to biofuels for aeroplanes and biodiesel. However, it is difficult to reasonably derive the available algal end product with an upstream flue gas source and appropriate algal cultivation due to the long and complex value chains and the uncertainty in upstream algal feedstocks for downstream bioenergy conversion systems. LCAs were performed products and processes based on available models and approaches. The current evaluation results are complex, as a complicated system of relevance from the upstream CO₂ source to the product of the downstream consequences is insufficiently discussed.

In this study, a quantitative assessment model was established and uncertainty analysis was performed, and conflicting factors in the application of algae for CO₂ capture were balanced in favour of sustainable biofuel. In particular, mass allocation and energy allocation were included in the dimensionless value-based model for IA assessment. The results would increase interest in both the AI assessment of LCA and CO₂ sequestration for the benefit of sustainable biofuels.

Conclusion

Combining transport distances and cleaning modes with flue gas concentrations, low CO₂ flue gases are suitable for on-site use within 10 km, while more than 95% of CO₂ flue gases are flexible in terms of transport distance and cleaning modes.

Specific productivities and CO₂ fixation meet negative logarithmic relationships with lipid levels, while lipid levels and profile define biofuel delivery outcomes. HTLHRJ, BiodieselRD, and Biodieselwet achieved positive energy gains in the lipid range of 35% -45% from general algae with glycerol by-products. Negative energy gains in the wide range of edible seaweed cultures despite the addition of by-products (bionutrients and glycerol).

By combining solar energy harvesting and by-product effects, positive energy gains have been achieved at 15% to 45% lipid content for both general and edible algae. The algal CO₂ fixation can be further modified with the AI model towards algal cultivation corresponding to the available target biofueL product and the connection of upstream flue gas sources.