## 9 Evaluating Biorefinery Model Scenarios  
There exist many published examples where evaluation of the application of a biorefinery approach has been undertaken for microalgae platforms [100; 101]. Despite these publications on the theoretical algal biorefinery concept from academic groups, the experimental data supporting the theory is often poor and usually related to lab or small-scale experiments and is a long way, therefore, from being realised within any profitable industrial process. Lab-based techno-economic analysis of the processes would seem to support that the biorefinery approach can be profitable on an industrial scale, but this is yet to be convincingly proven. There is clear scientific evidence that emissions of greenhouse gases (GHG), such as carbon dioxide (CO\({}_{2}\)), methane (CH\({}_{4}\)), and nitrous oxide (N\({}_{2}\)O), arising from fossil fuel combustion and land-use change as a result of human activities, are perturbing the Earth's climate [102]. [PERSON] and [PERSON] [100] have evaluated the feasibility to couple the biorefinery concept to wastewater treatment and CO\({}_{2}\) remediation of flue gases in order to lower the production cost of the biomass. The resultant algae, as whole biomass, cannot be used for food and feed because it is effectively derived from waste treatment. The biomass can only be used after fractionation. In this way the purified valuable compounds like EPA and pigments can be used as feed ingredients after appropriate testing to establish the absence of biotic contaminants and heavy metals, while the residual 'waste' biomass can still be used for biogas production. [PERSON] et al. [101] developed a protocol for the isolation of fucoxanthin (a brown-pigmented xanthophyll), eicosapentaenoic acid (omega-3 fatty acid), and chrysolaminarin (storage polysaccharide) from _Phaeodactylum tricornutum_ biomass. In this case, no biomass disruption was adopted; a first step of ethanol extraction of the dry biomass (fucoxanthin partition), a second step of hexane extraction (EPA partition) and a final step of hydro-thermal acid extraction (chrysolaminarin) were performed with a purification step applied for each component. The process is complex and the extraction yield does not support application at large-scale. Furthermore, utilisation of hexane in the process creates a scenario where the EPA would not be useful in many of the highest value commercial applications. Again, this is an example of a nice academic study where many critical constraints that would kill the application within a real industrial context have not been carefully considered. Production of biochar and bio-oil from _Chlorella vulgaris_ biomass through pyrolysis for carbon sequestration was evaluated recently [103]. The products seem to be of good quality as alternative fuels, soil applications, and bio-adsorbent material but, disappointingly, a techno-economic analysis of the overall process is missing and this information is mission critical for industrial application. Within a GM microalgal strain engineering context, as much as 0.2 g betulin (a high value compound of pharmaceutical interest) per kilogram of dry biomass could be produced from an engineered strain of _Phaeodactylum tricornutum_[17], alongside other natural compounds of mid-lowvalue produced naturally by the organism. In engineered yeast (_Saccharomyces cerevisiae_), 10 g of betulin can be extracted, about 50 times more, from an equivalent amount of produced biomass. Under the reported scenario, the calculated cost of biomass production was as much as 9 times higher for the _Phaeodactylum_ platform versus the yeast, largely as a function of relative biomass densities. At the present time, for most phototrophic or mixotrophic microalgae cultivated using photosynthesis where a valuable compound can be produced, even a biorefinery approach will not be considered economically sufficient to compare the microalgal platform with another competitive production platform.