Until the middle of 19th century, animal force was the driving source of transportation. The industrial revolution that followed was sparked by the invention of the internal combustion engine, promising to deliver autonomous power to individual vehicles, thereby releasing their owners from the need to use livestock. But with the current challenges imposed by climate change, and the amount of carbon dioxide released in the atmosphere by burning gasoline through the engine of a car, our current modes of transportation no longer seem like realistic ways to live sustainably.
However, getting rid of a system of distribution that encompasses a large network of filling stations and refineries is far from the most efficient way to ensure that more vehicles will be powered by carbon-neutral sources. The natural successor of gasoline is the still relatively new biofuel – fuel derived from biomass, such as agricultural crops – that can be used in current combustion engines with no need for modifications. Recently, researchers from the Oak Ridge National Laboratory have developed genetically engineered switchgrass in an effort to produce a plant with a higher energy density and a simpler conversion process.
Most biofuels, like ethanol, are produced by releasing sugars from stored starches in agricultural products such as corn or sugarcane. This is accomplished by the method of enzyme digestion, which breaks down polymeric macromolecules into their smaller building blocks. The sugars are left to ferment, and then distilled and dried – a long process requiring a lot of energy. The Oak Ridge researchers were able to limit the amount of lignin – a chemical compound found in the cell wall of plants – by encoding a piece of RNA that would limit three quarters of the lignin production and placing it into the switchgrass’s DNA. Since lignin is the main element that keeps the cells together, decreasing the production makes it easier to access the sugars that are trapped inside plants. As a result, the conversion rate from biomass to fuel shoots up significantly, with up to a 40 per cent improvement.
But is it possible to completely replace the fossil fuels used in transportation with biomass products? Risks associated with the conversion to biomass include a potential change in biodiversity, since a bigger portion of land would need to be used to cultivate the appropriate plants. According to the Millennium Ecosystem Assessment, converting land for biofuel production would translate into a massive burst of greenhouse gases. The conversion of a hectare of prairie land could liberate up to 300 tonnes of carbon dioxide, and this number goes up to 1,000 tonnes if a forest is removed to make room for biofuels.
Then there is the question of the energy efficiency of biofuels. For certain agricultural products, the energy savings can vary from about 25 to 70 per cent, and for others – such as corn – there are no energy savings when compared to traditional gasoline. Ethanol, on the other hand, is usually mixed with gasoline because its energy density – the amount of energy stored in a unit of volume – is 34 per cent lower, but this is made up by its higher octane rating, which makes it overall more efficient.
Another major factor in choosing a biofuel replacement will be its ability to reduce greenhouse gas emissions. There is a 75 per cent net reduction in emissions when using ethanol instead of gasoline, and a 90 per cent reduction when compared to diesel emissions. But according to the International Energy Agency, the biofuels would need to account for 26 per cent of global fuel produced in order to limit the atmospheric concentration of carbon dioxide to 450 parts per million by 2050.
When it comes to genetically modified crops, the controversial nature of GM foods undoubtedly becomes a factor, and many farmers are still proceeding with caution. The challenge of creating ecosystems with genetically modified crops can seem daunting, as there have been many cases of regular crops being contaminated by GM ones. This might then put the entire biofuel market in the hands of a couple big producers of genetic crops who have patented the lignin-reducing technology.
In the coming years, ethanol and other biofuels will inarguably be a part of the alternative energies explored for use in the transportation industry. Biofuel production does have the ability to distribute energy sources geographically, but given the initial carbon emissions associated with converting land into biofuel crops – along with the decrease in space available for food production – another fuel source may need to replace biofuels as frontrunner in the alternative energy race.