Author: Toma Ogawa
Artist: Nirvan Marathe
Editor: Catherine Turnbull
Biofuels are fuels made from living matter, and they are an important alternative to traditional fossil fuels. As fossil fuels contribute around 90% of global carbon dioxide emissions, there is a huge incentive to develop viable biofuels. The ideal biofuel must be close to carbon neutral, meaning that the gases released when the fuel is burned equal the gases absorbed in its production. To be able to replace fossil fuels, the biofuel must be energy-dense, producible in large volume and affordable. The potential of biofuels for creating a sustainable future is immense. So, why don’t we have a reliable biofuel yet?
Over the years, researchers have come up with three generations of biofuels. The first-generation biofuels, ethanol, are produced from edible biomass like corn and sugarcane through fermentation by yeast. There is an interesting debate about the use of food crops for biofuel production. As discussed in the Green Alliance Report, the invasion of Ukraine has exacerbated concerns of worldwide undernourishment, making this debate even more important. According to the report, about 3.5 million people could be fed per year if the production of crop-based biofuels in the UK ceased. Second-generation biofuel solves this problem by using non-edible plant dry matter, known as lignocellulosic biomass. The ingredients for these fuels are non-food crops and non-traditional commodities.
However, both first- and second-generation biofuels are not able to power aircrafts and heavy automobiles as they are less energy-dense and often get diluted by water. According to David Pimentel, an agricultural scientist, to produce 1 litre of ethanol by corn, you would require 6600 kcal of energy; this is highly inefficient considering that a litre of ethanol contains just 5130 kcal. This is essentially a negative energy process, so it could be argued that this is not a green technology. Furthermore, harvesting crops for an energy inefficient process wastes scarce resources, such as freshwater. Research by the University of Twente found that the water footprint of biomass production (m3/GJ) is approximately 72 times more than crude oil and 240 times more than solar. Ethanol comes with additional disadvantages. For instance, its corrosive properties mean it cannot be readily used in engines and is expensive to ship.
A more complicated form of alcohol has been sought as an alternative, such as butanol. Butanol, as a result of its longer carbon chain, wouldn’t mix with water and is less corrosive. Producing large volumes of butanol is the limitation as yeast has long been adapted to produce ethanol. There are other organisms that produce more complex alcohol but only in small quantities.The challenge is to devise a method to equal ethanol productionThe last form of biofuels, also known as third-generation biofuels, are produced from algal biomass. Chlorella vulgaris is a popular choice because of its high lipid composition of more than 40% and its fast rate of generation. Although some of these algae can be grown using saltwater or wastewater, it requires large amounts of water and energy to harvest the algae and extract lipids. Currently, algae-based fuel costs 300-2600 USD per barrel, which is significantly higher than petroleum. Despite the current limitations, biofuels have the potential to be the fuels of the future. Much more research is needed to make these fuels affordable and energy-dense. Every development in this field brings us a step closer to a world that can be powered by biofuels.
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