Solar biorefinery concept for sustainable co-production of microalgae-based protein and renewable fuel

Microalgae-based renewable fuels offer low carbon alternatives to fossil fuels, and can theoretically support energy and climate security, regional employment and sustainable development. However, to achieve price parity with fossil fuels and fast track scale up, a benchmark production price of US$0.67 L-1 ($2.54 gal(-1)) must be achieved. The financial performance of microalgae systems can be enhanced through the cascaded conversion of biomass into multiple co-products, such as proteins and high-density liquid fuels. Here we evaluate the use of hydrothermal pre-treatment (HTP: 180 ???C, 1 MPa, 10 min) green chemical-based protein extraction processes (acetone and urea treatment) followed by hydrothermal liquefaction (HTL) crude oil production and high-density liquid fuel refining. This experimental data was incorporated into an integrated Techno-Economic and Life-Cycle Analysis (TELCA 2.1) simulation of a 500 ha microalgae production and biorefinery facility to simulate protein and fuel co-production at scale. At a minimum diesel selling price of US$0.67 L-1 the protein co-product (32% purity) required a minimum selling price of US$7.2 kg(-1). The low protein purity can be improved to at least 40% using low carbohydrate biomass and further process optimisation to deliver a more sustainable alternative to cheap protein sources, such as soybean meal or fishmeal. Competitive and green co-production of fuel and food/feed will help achieve a circular bioeconomy and support UN Sustainable Development Goals.

Automated summary

Microalgae-based renewable fuels offer a low carbon alternative to fossil fuels and have the potential to support energy and climate security, regional employment, and sustainable development. Achieving price parity with fossil fuels and scaling up production requires the conversion of microalgae biomass into multiple co-products, such as proteins and high-density liquid fuels. This study evaluates a green chemical-based protein extraction process and fuel refining process to enhance the financial performance of microalgae systems.