Starting from Aja’s last articles, we have seen that algae can produce a large quantity of biodiesel. 

The large production of biodiesel (mixture of methyl esters of fatty acids) occurs when algae are in a stress condition and so, high biomass doesn’t mean high biodiesel production. 

But why do algae prefer to produce lipids, from which we can extract biodiesel, in stressful conditions?

You must think that when a microalga is exposed to a stress condition, such as nutrient limitation, it generates a series of responses that depend on the microalgae examined. Microalgae that naturally produces a high quantity of lipids in stressful conditions prefer to store carbon molecules in this metabolite instead of carbohydrates despite of the energetical expense. And so why should an alga chose a much more energy demanding way to store carbon?

• lipids can be a way to accumulate a large quantity of carbon because they take up less space than carbohydrates
• an excess of lipids can be a way to dissipate metabolic energy 

Moreover, another important question is: why don’t we use biodiesel in our daily life?

Never like now, the use of resources different than fossil fuels can be a good strategy to avoid the dependance from another state (politically) and the use of massive and destructive extraction methods of fossil fuels. 

From and economical point of view the biodiesel production from algae makes absolutely sense. 

• the production of biodiesel from microalgae requires much smaller spaces than the ones necessary for the production of biodiesel from rapeseed (example)

• because of the ecological and functional plasticity of microalgae, these can be cultivated in unproductive areas, that don’t have value for agriculture and livestock
• microalgae have a faster growth and metabolic plasticity that can induce a higher and faster lipid and so biodiesel production

On the other hand, there are many disadvantages related to the biodiesel production from microalgae: 

• microalgae require attention much more than the cultivation of terrestrial plants; this means that specialists and workers must be present during the entire production cycle
• cultivation plants still have very high costs as well as they require maintenance
• the drying process requires a lot of energy

Overall, considering costs of oil and other fossil fuels the use of biodiesel is an advantage but the overall process of production is not as convenient as fossil fuel extraction. 

Furthermore, the industry world thinks of his fossil fuels alternative as something away from our days simply because nowadays we can extract, and we will be able to extract oil from every kind of terrestrial and marine substrate. 

So, what we consider now non-renewable could be available for a long time and only when these resources will be in short supply our governments will invest in this and other alternative ways. 

Maria Bruno