Biofuels – can your car run on plants?

Despite some criticism biofuels are highly regarded as the best alternative to help maintain the transport sector globally and assist in reduction of CO2 emissions. The basic argument for biofuels is very logical indeed; they are derived from plant materials that are working to remove carbon from the atmosphere so they should be reducing the carbon footprint or at least be neutral in this respect. But as is usually the case, especially when we are discussing the environment, things are not that simple.

Dr Carl Peters Dr Carl Peters


What are biofuels?

Quite simply a biofuel is any liquid-based replacement for an existing fuel. The conventional biofuels are bioethanol and biodiesel. Both are currently used as at least partial replacements or additives to fuel derived from oil.

Where do you get these biofuels?

This is where it becomes interesting! 

Bioethanol is made by converting the sugar from plants to alcohol. So nearly any type of plant material can be used as the source of sugar. This can include what is left over after the usually consumable portion is removed. So, for example with corn, the kernels are what is employed as a food source for human or livestock consumption. The remaining biomass is what can then be processed into a form whose sugars can be consumed by micro-organisms and the produced ethanol collected for use as a biofuel. This type of biomass is also called lignocellulose and much work is currently being done to match sources and processing methods with the micro-organism that will be most efficient at converting this material to ethanol. 

Fig. 1: Sources of lignocellulose in biofuel research.

Biodiesel has a couple of interesting sources but what primarily comes to mind is waste oil. Basically, the oil that was used to fry up some delicious chicken yesterday could be converted to diesel fuel tomorrow. Another source comes from the fact processing of food products from plants such as soybeans results in a surfeit of oil. More recently it has been proposed that algal biomass from the ocean could be a useful source of oil. Efforts are ongoing to improve the growth of algal sources while increasing their ability to produce lipids. Certain algae thrive on industrial waste raising the possibility that these wasted gases could be converted to useful biomass. Regardless of the source, since this oil is more viscous than the fuel you put in your vehicle it must go through a process called transesterification.

Fig. 2: Transesterification Process of Biofuels.To better accommodate the blending of bioethanol and biodiesel with petro-fuels they are taken through other processes including hydrodeoxygenation to produced so-called high-quality biofuels.

What are the arguments against the use of biofuels?

The main argument that you will hear is the food vs. fuel debate. It is clear that our global society has a food distribution problem and that hunger in certain regions is the primary concern. With people going hungry it is unconscionable to carelessly take food and make it into fuel instead. The proponents of biofuels could not agree more! That is why they propose that are typically considered waste products of food production. But that brings up another concern, can these sources truly be considered waste? In many cases, these products are re-used, either returned to the soil for maintaining the soil eco-system or used as feed for livestock, for instance, hay for horses and cattle. All that aside, collecting this ‘waste product’ and getting it into the hands of producers of biofuels is an additional step for the farmer. A step for which they ask, rightly so, to be compensated.

Another argument that has been raised against biofuels is that they create such a high demand for source material that it will be easier to simply clear more land to plant products that can be used as the source for the biofuel. This has been an especial concern with regard to biodiesel. Palm oil is an excellent starting point for biodiesel production and as demand rises the price of oil used in biodiesel production increases. However, clearing land in rainforest regions, where oil palms grow well, is counter to the benefits sought by using biofuels. So, as the cost of oil for biodiesel increases there must be an equal increase in vigilance to prevent the use of oil from these sources. There is a consensus that we already have enough oil from recycling used and the excess from food production to meet current and even expanded needs. Making sure that the supply is getting where it needs to go is going to be an ongoing battle.

Arguments about the disruption of the ecosystem are not isolated to the land. Using algal sources for biofuel production also has opponents on the basis of the disruption that this can cause to the ocean environment. Employing this possible source of biofuel will need to be carefully weighed against the impact on commercial fishing and marine life in general.

One argument is undeniable. Biofuels are simply not as efficient from an energy content standpoint. That is the main reason why their use is currently limited to low percentage addition to petro-fuels. Does this cost outweigh the benefit of decreased pollution from emissions?


Despite concerns and important issues that will continue to require our attention biofuels do appear to be a useful way forward as a way to become less reliant on the limited petro-fuel resource. Scientists will continue to work to find better ways to make useful biomass for the production of bioethanol and biodiesel. The search continues for new micro-organisms, or modifications of existing organisms, that can enhance production. As the industry grows the processes involved in producing useful biodiesel and bioethanol will also be further refined to improve the utility of the final product.

In the end, it will come down to economics. If oil companies see a financial benefit to an approach it will be widely implemented, as they control the existing distribution network. With increasing recognition that the impact of our transportation needs is having an effect on our world, there will be an increased benefit for these companies to pursue alternatives. The possibilities are promising for biofuels! But when we see them called into action and used to their full capacity is at this time highly questionable.


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