Biofuels: Food for thought

What are Biofuels?

Biofuels refer to fuels that are produced from biomass through various chemical processes. There are three major types of biofuels: 1st, 2nd and 3rd generation biofuels, classified according to the type of feedstock used to produce them.

Figure 1: 1st Generation Biofuels1

1st generation biofuels, also known as conventional biofuels are made from food crops such as sugarcane, corn and rapeseed. As seen in figure 1, chemical processes of fermentation, distillation and transesterification are used to convert the sugars and fats present in these food crops into biofuels such as bioethanol and biodiesel. One major producer of 1st generation biofuels is Brazil, where bioethanol produced from sugarcane makes up 27% of their fuel composition2.

Figure 2: 2nd Generation Biofuels1

2nd generation biofuels are made from agricultural and agro-industrial by-products3. Essentially, 1st generation biofuels are created from food crops that you and I consume while 2nd generation biofuels are made from parts of the food crop that would normally go to waste. Using corn as an example, the corn cob would be used to make 1st generation biofuels while the rest of the plant would be used for 2nd generation biofuels. These unwanted parts of the plant contain lignocellulosic material3 such as cellulose, hemicellulose and lignin, which allows the plant to stand upright. As illustrated in figure 2, these materials are first broken down by chemical processes in order to extract simple sugars such as glucose. Then, similar processes to 1st generation biofuel production are applied to obtain the desired products1.

Figure 3: 3rd Generation Biofuels1

Lastly, we come to 3rd generation biofuels. As seen from figure 3, these biofuels are produced from a radically different feedstock as compared to the earlier 2 generations; namely micro-organisms such as algae. These microbes convert solar energy into oils via photosynthesis and these oils can then be extracted to produce a variety of biofuels1.

Why do we use Biofuels?

Carbon neutrality of biofuels8

Biofuels are meant to supplement or replace conventional fossil fuel based transportation fuels such as petrol, diesel and even aviation fuels. They are touted as the solution to two major issues of fossil fuels; namely, their associated greenhouse gas emissions and their finite nature. Although biofuels still produce greenhouse gases and other pollutants when they are combusted, the amount produced is much less as compared to conventional fossil fuels1. Additionally, biofuels are also theoretically carbon neutral4. This is because the carbon dioxide produced during their combustion would be reabsorbed during photosynthesis and used to produce the next cycle of biofuels. Furthermore, given that biofuels are produced in a much shorter timescale than fossil fuels, they are considered to be much more renewable and could help humanity mitigate the looming fossil fuel crisis1.

So Why Haven’t We Replaced Fossil Fuels Entirely Then?

Biofuel related deforestation7

Unfortunately, biofuels have many issues that detract from their promise as the panacea to our fossil fuel crisis. The major issue with all biofuels is that they are simply not as cost competitive as extracting fossil fuels from the ground5. All of them require highly energy and resource intensive processes to grow, extract and process feedstock into useable fuel. Consequently, fossil fuels still have the edge in terms of cost. Furthermore, 1st generation biofuels are produced from food crops. This gives rise to a whole host of issues ranging from socio-economic problems such as threatening food and water security to environmental issues such as deforestation and pollution of the land and water from fertiliser usage1.

What is Being Done About It?

Continued scientific progress in the field of biofuels is certainly helping to solve many of the issues highlighted above. For example, 2nd generation biofuels were developed in an effort to solve the problems of 1st generation biofuels. As mentioned previously, 2nd generation biofuels are primarily produced from agricultural residue and non-food crops. This means that the feedstock used is not in direct competition with the demand for food, thereby avoiding any associated socio-economic conflicts3. Additionally, scientific advancements can help increase the cost competitiveness of 2nd generation biofuels. For example, scientist have found that certain micro-organisms can be used in lieu of conventional energy intensive processes to help break down the cellulosic feedstock3.  However, given that the feedstock ultimately still comes from terrestrial crop sources, 2nd generation biofuels still requires land, water and fertiliser application to produce, hence still has inherent environmental problems1.

3rd generation biofuel9

As such, 3rd generation  biofuels were developed to help solve the shortcomings of the prior two generations. These algal based biofuels have many advantages over the other two types of biofuels. Firstly, they are significantly more energy dense1, meaning that the yield of biofuel would be much greater and that less space is required to cultivate the feedstock. Next, algae can grow in areas that are unsuitable for terrestrial crops and can even be cultivated using saltwater, sewage and waste water1. This means that valuable arable land is not taken up by the cultivation of algae, protecting food security and reducing deforestation. Furthermore, freshwater resources need not be expended to grow these algae, allowing biofuel production to coexist with water security1. Although the main issue with 3rd generation biofuels lie in the energy intensive oil extraction process, recent scientific developments are helping to significantly reduce the energy investment in these processes5.

Lastly, broader economic policies such as the taxation of fossil fuels and the subsidising of alternative fuels such as biofuels must be put in place in order to enable biofuels to be truly cost competitive6.

Overall, biofuels are definitely a promising solution in our quest to shift away from fossil fuels for a cleaner and greener future! Until next time!

Written by: Noel

References:

  1. https://agsci.oregonstate.edu/sites/agsci.oregonstate.edu/files/bioenergy/generations-of-biofuels-v1.3.pdf
  2. https://www.nationalgeographic.com/environment/global-warming/biofuel/
  3. https://www-sciencedirect-com.libproxy1.nus.edu.sg/science/article/pii/S0168165612001721
  4. https://www.eia.gov/energyexplained/biofuels/biodiesel-and-the-environment.php#:~:
  5. https://www.power-technology.com/features/algal-biofuels-challenges-opportunities/
  6. https://www.greenfacts.org/en/biofuels/l-2/2-economic-policy-factors.htm
  7. https://www.transportenvironment.org/press/palm-oil-and-soy-oil-biofuels-linked-high-rates-deforestation-new-study
  8. http://www.viaspace.com/biomass_versus_alternatives.php
  9. https://www.azocleantech.com/article.aspx?ArticleID=406

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