Environmental impacts of biofuels and their blends: a case study on waste vegetable oil-derived biofuel blends

The crisis of fossil fuel depletion and environmental pollution has shifted the focus on investigating renewable alternative fuels. Biofuels are interestingly becoming the alternative fuel of choice owing to their renewable nature, ease of availability and handling, and generation of cleaner emissions. Biofuels are deliberated as potential alternate fractions in blend fuels for diesel engines. Vegetable oils are the largest feedstock for biofuel production and biodiesel is the most commonly investigated biofuel. However, biofuel production from straight vegetable oils is a costly affair and is linked with various associated environmental impacts. On the other hand, the waste vegetable oil (WVO) has the potential to be an alternative feedstock for biofuel since WVO is generated in plenty, wins over the food-versus-fuel issue, and has a huge negative CO2 emission potential. Therefore a case study on the various environmental impacts of WVO-based biofuel blends relative to fossil fuel such as diesel is of obvious research interest. Usually, a fuel is assessed upon various environmental impact categories, such as global warming potential, acidification potential, eutrophication potential, ozone depletion potential, and so on. Several linked toxicity potentials such as human toxicity, terrestrial eco-toxicity, and aquatic eco-toxicity, along with abiotic resource depletion potential are also frequently studied. WVO-based biofuels considered for the case study were assessed as blends with different fossil fuels, namely, diesel, and kerosene. The case study showed that direct utilization of WVO in the blend is associated with lesser environmental impact than the WVO biodiesel blend. Also, WVO-kerosene blends are more environmentally benign than WVO-diesel blends. The case study projected WVO-based biofuel blends as a sustainable diesel alternative with significantly lower environmental impact.