Biofuels produced from renewable energy sources have become a hot topic in the pursuit of finding a replacement for fossil fuels. This is motived due to the high dependency of fossil fuels in the transportation sector, which releases large amounts of greenhouse gases. After many years of attempts and research, progression can finally be seen and actual energy efficient biofuel options are out on the market. There still an ongoing discussion of which biomass is the most suitable to produce biofuels from and from there biofuels have been divided into four different generation. The generation of biofuel is based on the composition or origin of the biomass it is produced from, to simplify, take a look at the figure below.
Figure 1. Different generations of biofuels (Ertem, Kappler, Neubauer, & Acheampong, 2016).
However, a biofuel produced from a renewable energy source does not automatically equal to an sustainable alternative. In fact, there are some down sides to them as well. First generation biofuels are cheap but have received some criticism, where the sustainability of it have been questioned. Besides repurposing arable land for fuel instead of food production, producing ethanol from sugar canes or maize is not effective enough and the process can in some cases require more energy than it generates (Olaganathan, Lee, Tong, Cheston, & Yi, 2014). Looking into other renewable resources, the energy efficiency increases. Since I live in Sweden, the first biomass that comes to mind is wood, an energy source with high availability. Wood, and plants in general, are considered lignocellulosic materials consisting of lignin and polysaccharides cellulose, hemicellulose (Zafar, 2020). Lignocellulosic materials are considered biomass for second generation (2G) biofuels, since it is produced from non-edible plants. Being able to use wood scraps (and even agricultural waste) is one of the advantages of lignocellulosic materials, creating a more circular process for e.g. the forest industry. Other advantages include these plants not needing as much fertilizer, not exhausting the soil they grow in as much and can be grown on marginal land. Besides growing trees not compromising food security, they can be grown in a carbon neutral way, meaning that the carbon being released when burned is captured when new trees are being planted. Furthermore, depending on where in the world production occurs the type of wood may vary. In China and South America it is more common to use fast growing trees (Potters, Goethem, & Schutte, 2010).
The process scheme of turning lignocellulosic biomass into ethanol is summarized in Figure 2. First, the polysaccharides needs to be hydrolyzed and broken down into simple sugars (saccharides), this is done by adding enzymes or acid. The following step differ from different producers, but in general microbes are added in order to ferment the sugars into ethanol. Finally, this ethanol is purified through distillation and the ready to be prepared for distribution (Zafar, 2020).
Figure 2. The production process of producing bioethanol from lignocellulosic materials.
2G biofuels are more sustainable, but one of its biggest drawbacks is its limited possibility of commercial upscaling (Olaganathan et al., 2014). Since the resources exist it is of great importance that the governments and politicians take action and start to see the benefits of using lignocellulosic biomass instead of food for fuel production purposes. Hopefully, with the need for new technologies and fight towards climate change, the 2G bio fuel industry will have a leading position in the race of replacing fossil fuels.
References
Ertem, F. C., Kappler, B., Neubauer, P., & Acheampong, M. (2016). In pursuit of Sustainable Development Goal (SDG) number 7: Will biofuels be reliable?
Olaganathan, R., Lee, A., Tong, D., Cheston, M. Z. J., & Yi, Z. H. X. (2014). Is Biofuel a Feasible Long-Term Chief Energy Source? A Global Perspective. Retrieved September 20, 2020, from https://commons.erau.edu/cgi/viewcontent.cgi?article=1920&context=publication#:~:text=Another major drawback for second,%2C a non-food crop.
Potters, G., Goethem, D. Van, & Schutte, F. (2010). Promising Biofuel Resources: Lignocellulose and Algae.
Zafar, S. (2020). Biofuels from Lignocellulosic Biomass. Retrieved September 20, 2020, from https://www.bioenergyconsult.com/what-is-lignocellulosic-biomass/
The Environmentalization 
Very interesting and relevant post. When you mentioned that forest biomass is carbon neutral, I was wondering how many tree you would have to plant in order to compensate for the carbon released by that one tree that has been growing and taking up carbon for decades?
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I see your point of view, and the more you think about it the more questions occurs. Not only will the newly planets trees not take up as much as the other trees that have grown for decades, but the quality of that tree is also not going to be the same. I do not have exact numbers to answer you question, but what I do know is that many established companies (E.g sca) who owns their own forrests plant two trees for every harvested tree. Again, the quality and the carbon up take may not be as effective as letting the trees gros for several hundered years, but it does count for a something.
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Hi! Your blog makes me think about the possibility of transforming wood sawdust into ethanol and doing a comparative study of the yield with ethanol produced from sugar cane and thus assessing the potential of sawdust in ethanol production. And not only, think of ways to optimize the process. Thank you for your contribution!
Fastudo Jorge Mabecua
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This is a well-written blog where you mainly focus on the first and second generations of biofuels. I agree that we should get away from the first generation biofuels as these compete with food resources that we need to feed our growing populations around the world. You mention wood from the forest as a viable generation 2 biofuel. The use of the forest for bioenergy worries me a bit as it is the same resource we need to stay on the land, to absorb the CO2 from the atmosphere. Yes, you are right, burning wood is better than fossil fuel as the living biomass absorbs the CO2 released from the dead biomass, but is it sustainable? How much forest can we consume before we reduce the forest’s ability to absorb CO2 significantly? What do you think about 3rd and 4th generations of biofuel, could these be the solution?
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