Turkey's greenhouse gas (GHG) emissions reached 341 million tones CO2 equivalent in 2008, with road transportation alone contributing to over 10% of the total amount. Securing the energy needs and reducing the GHG emission generation of a country are two major components of national sustainable energy utilization. Within this frame, a life cycle assessment (LCA) has been performed using GaBi 4 LCA software to compare the environmental performance of biodiesel and conventional diesel fuel mixtures for the Istanbul City, Turkey.
Life Cycle Impact Assessment (LCIA) interpretation has been performed for the 5 and 20% blends of waste cooking oil (WCO) and rapeseed biodiesels with petroleum-based diesel and the results have been evaluated in terms of their potential environmental impacts with main focus on global warming through climate change. Eco-indicator 95 LCIA Methodology was used for the normalization and weighting of the obtained environmental impact potentials. Considering the normalized impact assessment results, the blends of WCO biodiesel have lower global warming potentials, with up to 21% reduction in B20 WCO biodiesel, compared to petroleum-based diesel, mainly due to the biogenic origin of the carbon contained within methyl esters of biodiesel. The reduction in global warming potential for B20 rapeseed biodiesel is 11% compared to petroleum-based diesel. The eutrophication potential of B20 rapeseed biodiesel is 53% higher compared to B20 WCO biodiesel and 45% higher compared to petroleum-based diesel. In addition to this, the weighted acidification potentials of the petroleum-based diesel, B20 rapeseed and B20 WCO biodiesel blends are determined as 0.101, 0.115 and 0.094 mPE respectively. Higher impact scores of the rapeseed biodiesel blends in both acidification and eutrophication categories are explained by the usage of nitrogen rich fertilizers during the cultivation step of the rapeseed plant. The weighted carcinogenic potentials of B20 rapeseed, B20 WCO and petroleum-based diesel are 0.025, 0.022 and 0.026 mPE, respectively. The carcinogenic potential is mainly associated with the combustion of fuel in the car engine and both of the biodiesel blends have been found to be applicable alternatives for decreasing the heavy metal emissions associated with diesel fuel combustion. Photochemical oxidant formation potentials of the B20 rapeseed and B20 WCO biodiesel blends are 7.5% and 18.5% lower compared to the petroleum-based diesel. The higher photochemical oxidant potential of the rapeseed biodiesel blend is explained by the hexane emission during the oil extraction step of rapeseed biodiesel life cycle. B20 WCO biodiesel blend has a lower winter smog potential (0.005 mPE) than the petroleum-based diesel (0.007 mPE) and B20 rapeseed biodiesel blend (0.006 mPE).
Considering the positive environmental performance of the WCO biodiesel in the global warming impact category along with the advantages of having lower acidification and eutrophication impacts (both below 0.005 mPE) due to lack of the cultivation, harvesting and oil extraction steps, it is concluded that the replacement of petroleum-based diesel with B20 WCO biodiesel in road transport vehicles is a viable option for combating the climate change along with an array of other environmental challenges. In addition, WCO utilization for biodiesel production is an alternative way of waste vegetable oil minimization.
On the other hand, while biodiesel made from WCO does not involve any changes in agricultural land use, it does require a well-developed infrastructure for efficient collection of waste vegetable oils from food factories, restaurants and fast food chains. Producing biodiesel from edible oil feedstocks such as rapeseed oil, however, raises the already well-known fuel vs. food dilemma and it is of utmost important to ensure that the primary role of the agricultural industry is to provide food security for the population. Efficient utilization of agricultural and industrial by-products such as straw and glycerin produced during biodiesel's life cycle is another significant step towards increasing the sustainability of the biodiesel fuels. Overall, a multi-stakeholder approach that will include the governmental policymakers, environmental institutions and organizations, community activists and biodiesel companies is needed to fully address the issue.