Plant Biotechnology and Global Sustainability - Part 2 of 4
Preventive measures
One way of dealing with the problem of air pollution could be to cut off evil at the root and directly change its main source. Since transport is a major contributor, because of the type of fuel they use, one strategy is to change that fuel. This is where biofuels come on the scene, as they are a source of renewable energy, emit less harmful gases than other fuels (Ghasemi et al., 2012).
Biofuels
Biodiesel and bioethanol are the main biofuels in the market, being, respectively, made from biomass rich in lipids and starch (Ghasemi et al., 2012). The highest production of these compounds comes from Brazil, from sugarcane in the case of bioethanol, and oil palm in the case of biodiesel (National Geographic), both of which are, to a lesser extent, also produced from microalgae.
Among these two, biodiesel presents the best chance of being able to substitute fossil fuels (Chisti, 2008). One of the main reasons is that it can be used as a blend or alone in diesel engines (Demirbas, 2009). This factor proves to be very important in a short-term perspective, since as soon as it is produced it manages to be introduced into the market; and of great environmental importance, since this type of cars corresponds to 1/3 of the total European cars, which on average pollute more than the gasoline (Transport & Environment, 2017).
The process of producing biodiesel through microalgae biomass is done through chemical and physical reactions, succeeded by transesterification (Voloshin et al., 2016), as can be seen in figure 1.
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| Figure 1. Method of production of different biological fuels from microalgae culture. Voloshin et al., 2016. |
Feedstock
Having chosen the most appropriate type of biofuel, it remains to be seen whether it would be better to use terrestrial plants or algae. The raw material for the production of biodiesel is biomass rich in triglycerides (TAGs), since these are more efficient than simple lipids. Therefore, the use of oleaginous plants or algae would be considered the best to do (Nigam and Singh, 2011). Micro-algae can store and produce TAGs in larger quantities and in a smaller space and time period relative to terrestrial plants producing oils (Nikolić et al., 2009; Nigam and Singh, 2011; Ghasemi et al., 2012; Voloshin et al. ., 2016).
The small production of biodiesel obtained from terrestrial plants is merely sufficient for this fuel to be used in admixture with fossil fuels (bioethanol in the USA). Microalgae can provide the necessary amount of fuel to completely replace fossil fuels (Chisti 2007, Chisti 2008). It would take 111 million hectares of palm oil production (to produce biodiesel) to meet current fuel consumption in the United States. This area corresponds to 11,100,000 square kilometers, which is equivalent to the area of Bolivia, the 28th largest country in the world (Mongabay, 2008). In the case of microalgae production, only 5.4 million hectares are needed, which, combined with the operation of outdoor bioreactors and crops, would be much more viable (Chisti 2007, Chisti 2008).
The microalgae are the basis of the third generation of biofuels and have the potential to be able to replace the use of terrestrial plants, but more importantly, the use of fossil fuels (Ghasemi et al., 2012).
Table below shows some more advantages that make the use of microalgae more appealing.
Advantages Reference
Lower need for water Voloshin et al., 2016
Doubling the biomass faster Chisti 2007; Chisti 2008
They do not require fertilizers or pesticides Voloshin et al. 2016
They present great metabolic elasticity Ghasemi et al., 2012
Increased oil production Ghasemi et al., 2012; Voloshin et al., 2016
Production of biomass
Algae cultivation can take place in outdoor systems (where much of the production of microalgae occurs (Ghasemi et al., 2012)), such as natural or artificial lakes or even coastal areas. It may also occur in photobioreactors, which are closed systems and with greater control of the various factors inherent to the growth of the culture. Each is used in different circumstances having inherent advantages and disadvantages. However, both have the objective of always looking for the highest productivity and the lowest cost (Chisti, 2007; Voloshin et al., 2016).
Both in the case of palm oil, whose production has caused much controversy due to its excessive production in tropical forests (Saynotopalmoil.com), as in the case of sugar cane, where the use of pesticides and fertilizers and the damage caused to the land (World Wildlife Fund), are causing harmful impacts on the ecosystems where they are grown. Unlike plant use, algae need less land to produce and can be obtained more regularly than terrestrial biomass (Voloshin et al., 2016). The production of algae in bioreactors has several advantages such as obtaining a controlled environment (control of the amount of light for no photoinhibition, control of CO2 entry and Temperature and pH), a lower risk of pathogenic invasions and the existence of various designs for various desired effects (Chisti, 2007; Kumar et al., 2011; Voloshin et al., 2016). Something that is not so easily obtained in traditional agriculture.
Limitations
One of the problems of producing microalgae and biodiesel, which is not so impacting in the use of terrestrial plants, is costs. These costs are mainly involved with the photobioreactor infrastructure and the production of biodiesel, whose methodology is not yet improved. One of the few ways to counteract this barrier is to combine activities so that a variety of goods can be obtained with a single infrastructure (Chisti, 2008; Nigam and Singh, 2011; Ghasemi et al., 2012).
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