Biorefinery as a promising approach to promote microalgae industry: An innovative framework

In response to energy crisis, global warming and climate changes, microalgae have received a great deal of interest as a biofuel feedstock. However, the development of microalgal biofuels witnesses an obvious and serious dilemma. The reported literature shows that “fuel only” option is not economically viable due to the overwhelming investments in capital and operation. Hence, it is questionable whether it is too luxurious to produce microalgae only for biofuel application. In addition, there are some voiced concerns related to the impacts of microalgal biofuel production on the conventional applications, such as cosmetics, pharmaceuticals and nutritious feed. It is therefore questionable whether the microalgal biofuel production will affect the original functions. From a sustainability point of view, the author explores the current challenges in microalgal applications and proposes an innovative framework for microalgal biorefinery, which can realize the production of multiple products in the form of high values and biofuels such as biodiesel, bioethanol and biogas. With the aim at maximizing the value derived from different microalgal components, the innovative microalgal biorefinery concept includes four pathways: high-value products–biodiesel–bioethanol–biogas; high-value products–bioethanol–biogas; high-value products–biodiesel–biogas; and high-value products–biogas. Special attention has been paid to the production of high-value products through system integration and engineering, which is expected to promote the economics of microalgal biofuels. Net energy ratio assessment and cost-effectiveness assessment have been highlighted to testify the feasibility of microalgal biorefinery options, and some crucial actions have been suggested to help establish the process.