Fossil fuel production and use contribute to air, water and soil pollution and global warming. According to Enerdata Global Energy Statistical Yearbook 2016, more than 31,000 megatons of CO2 was emitted globally in 2015. It is generally agreed that reduction of fossil fuel uses requires alternative, economical energy sources that are less carbon-intensive. One such alternative source is biofuels, or fuels derived from contemporary biological processes, such as plant or microbial growth processes. These processes takes in CO2 from the atmosphere and converts the carbon into potential fuels.
The two most common types of biofuels in use today are ethanol and biodiesel. Biodiesel can only be burnt in diesel engines. Ethanol is mostly used as blending agent with gasoline to increase octane and cut down carbon monoxide and other smog-causing emissions. It cannot be burnt directly in the vast majority of car engines today. Even specially modified vehicles, called Flexible Fuel Vehicles, can only run on E85, an alternative fuel with 85% ethanol content. In addition, ethanol has about half the energy per mass of gasoline. Butanol is considered better than ethanol because butanol’s energy content is close to gasoline, and can run in any car that uses gasoline without the need for modification to engine components.
First generation biofuels refers to fuels that have been derived from sources like starch, sugar, fats and vegetable oil, found commonly in arable crops. The fuel is obtained using the conventional techniques of production. Research has shown that energy must be invested into producing crops and converting them into biofuels before any energy is obtained. A 2005 study from Cornell University found that producing ethanol from corn used almost 30% more energy than it produced. In other words, invested energy is lost in creating them in the first place, breaking even is impossible according to the 2nd law of thermodynamics.
In contrast, second generation biofuels are made from lignocellulosic biomass or woody crops, agricultural residues or other waste materials. It is more difficult to extract the required fuel from waste than from virgin materials because more processing steps are required to break down the lignocellulose or woody waste matter.
However, current research into second generation biofuels production has achieved several breakthroughs. At the NUS Environmental Research Institute (NERI), the work of several research groups such as those of A/Prof He Jianzhong has been successful in butanol production via fermenting biomass.
According to Prof He, the secret lies in the successful cultivation of a wild-type solventogenic Clostridium species, which could utilize lignocellulosic waste such as its feedstock. This Clostridium directly converts biomass (such as sugarcane bagasse, food waste, horticultural waste hydrolysate) into butanol. This bacterium possesses hydrolysis enzymes (e.g., amylase, hemicellulase, etc) which could efficiently hydrolyze these organics into monosugars for following on fermentation
There are other advantages of this new Clostridium strain, according to Prof He.
Prof He added that wild type microbes have advantages over genetically modified microbes in that they are more resilient to invading species in the open environment, and can replicate and sustain its populations over many generations. This has implications for scale-up production of butanol in large reactors, which are basically open systems that operate continuously. Under these industrial settings, wild type organisms might survive better and have greater practical uses.
Therefore, the approach of identifying wild type organisms and optimising their biofuel production potential, such as butanol, might be one of the ways to combating many environmental challenges, including climate change.
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