One of the oldest life forms, algae, holds the highest potential for future energy generation. This third generation (3G) biofuel holds some major advantages over other biomass but it has not yet taken off as once expected. With increased focus and attention, innovative techniques in research and development, and political will, algae can return to the fore-front of future biofuel production.
Higher biofuels yields are a major advantage of algae over first generation (1G) plant crops such as sugar beet or wheat, and second generation (2G) sources for biofuels such as vegetable or animal waste streams. Estimates provided by Rocca et al (2015) in table 1 below indicate the stark differences in estimated oil yield potential per unit area for different terrestrial crops and microalgae. Microalgae also have rapid growth potential and can double their biomass in as short as 3.5 hours, and are capable of year-round grow (Cheng, 2018).
There is a diverse range of biofuels that can be derived from algae. Biomethane, bioethanol and biobutanol can be derived from macroalgae or seaweeds. Biodiesel, biomethane, bioethanol, bio-oil and bio-hydrogen can be derived from microalgae (Rocca, et al., 2015). Microalgae species are favourable for fuel production due to high lipid contents of 50 – 70 % (Khan, et al., 2018). Algae cultivation can be done in open systems such as ponds and lakes, and in more advanced closed-loop systems on land unsuitable for food crops, removing the concern of competition with food producers. Closed-loop systems offer the added advantage of additional control over variables such as light, temperature, nutrients, pH, and the particular species grown, to enable producers to maximize crop production. Algal growth can be combined with wastewater treatment systems to recycle waste nutrients such as nitrogen and phosphorous to help mitigate greenhouse gas emissions and protect our environment. Microalgae also produce valuable coproducts such as proteins and pigments, and the left-over biomass after oil extraction can be used as feed, fertilizer, or fermented to produce methane or ethanol (Cheng, 2018).
b) Considering 70% of oil (by wt.) in microalgal biomass;
Table 1: Estimated oil yield potential of different terrestrial crops and microalgae (Rocca, et al., 2015, p. 35)
With so many advantages it is clear that algae have been held back from their high expectations as no commercial algae-based biofuel currently exists. It can often require more energy to remove moisture from algal biomass to enable lipid separation, than the energy the end product provides. This has long been a point of friction and research continues into a much-needed energy-intensive drying process that would enable algal biofuels to compete for market share. The high operational, maintenance, harvesting and conversion costs, have meant that it has not yet become feasible as a biofuel (Khan, et al., 2018). Rising CO2 prices as a result ofstringent CO2 stabilizing techniques make the economics of microalgal biofuel unattractive, and production and combustion of microalgal diesel releases as much CO2 as is captured from anthropogenic sources and assimilated by microalgae (Takeshita, 2011). There is at present no comprehensive analysis on the deployment potential of optimized harvesting methods at large scale, from the point of view of technical viability, environmental impacts and cost effectiveness (Rocca, et al., 2015). Environmental and social concerns raised by the production of biofuels from algae include the high demands on key resources such as energy, nutrients, water and CO2’ along with the availability of land with suitable characteristics including climatic conditions and an adequate supply of resources (Rocca, et al., 2015).
There is no doubt there are major challenges to be overcome before biofuels from algae are a viable alternative. The potential is there however and with focus on energy efficient and low-cost harvesting and dewatering techniques, there is a positive future ahead for algae biofuel production.
References
Cheng, J., 2018. Biomass to Renewable Energy Processes. 2 ed. s.l.:CRC Press.
Khan, M., Shin, J. & Kim, J., 2018. The promising future of microalgae: current status challenges, and optimization of a suatainable and renewable industry for biofuels, feed, and other products. Microbal Cell Factories, 16(36).
Rocca, S., Agostini, A., Giuntoli, J. & Marelli, L., 2015. Biofuels from algae: technology options, energy balance and GHG emissions, s.l.: European Union.
Takeshita, T., 2011. Competitiveness, role, and impact of microalgal biodiesel ain the global energy future. Applied Energy, 88(10), pp. 3481 – 3491.
The Environmentalization 
The potential of algae is enormous, but as you state in your post, there are still some challenges to make this a viable biofuel. The energy requirements for the process of turning algae into fuel is one of these. Another challenge might be the water requirements and the risks of water pollution. I think there will be solutions to overcome these hurdles, let’s hope that happens sooner than later. We need viable alternatives to replace the fossil fuels.
LikeLiked by 2 people
Hi! you have discussed the properties and limitation of very important biomass. No doubt microalgae has great oil yield potential as obvious from Table 1. In my point of view culturing microalgae in waste water is a best option as it is also helpful in the treatment of waste water. However the downstream processing of microalgae is difficult and the chances of bacterial contamination could make this process more laborious.
LikeLiked by 1 person
Very interesting post! It was surprising to learn that no no commercial algae-based biofuels exist at the moment. On further investigation I stumbled upon an article on the failure of Exxon to produce economically viable algae based biofuels after massive investments of hundreds of millions USD. Perhaps small-scale production combined with environmental cleanup is a more viable route at the moment? By cleanup I mean absorption of nitrogen and phosphorus in waters as a way of combating eutrophication. That way, algae wouldn’t have to compete directly with other fuel sources. It would “only” be a byproduct.
LikeLiked by 1 person
Very interesting! I could understand that although with so many advantages that algae have, there is currently no commercial algae-based biofuel because it has not yet become feasible as a biofuel due to the high operational, maintenance, harvesting and conversion costs. As disadvantages, you highlight the fact that: (1) It can often require more energy to remove moisture from algal biomass to enable lipid separation, than the energy the end product provides; (2) Rising CO2 prices as a result ofstringent CO2 stabilizing techniques make the economics of microalgal biofuel unattractive, and production and combustion of microalgal diesel releases as much CO2 as is captured from anthropogenic sources and assimilated by microalgae.
What can we do in the face of so much potential to enable the production of biofuels from algae?
Thank so much for your contribution.
Fastudo Jorge Mabecua
LikeLiked by 1 person
Thank you for an intresting post! As you clearly state and show in Table 1 microalgaes has a enormous potential for bio oil yield. With regards to the high energy requirment for the drying processes, perhaps hydrothermal carbonization or liquefaction could be suitable options to produce bio oil from algae?
I agree with you that algae will play an important role in replacing fossil fuels with biofuels and perhaps also be an eminent food source as global population rises.
LikeLike