Developing a carbon footprint model and environmental impact analysis of municipal solid waste transportation: A case study of Tehran, Iran.

The greenhouse gas emitted due to transportation is the third greatest emitter globally, and its impact has become a threat to the environment, public health, and economic development. Waste transportation is excluded in studies of waste management despite its significant environmental impacts such as global warming and human toxicity. The objective of this study is to develop a quantification model to estimate the carbon footprint of waste transportation and environmental impact assessments in three categories applied in Tehran using IPCC guidelines. In Tehran, light and heavy vehicles ran on diesel fuel. Data on fuel and waste characteristics were provided by Tehran's department of transportation and municipality, respectively. In this study, transport-related emissions are 8.47 k tonCO2eq/y, and the carbon footprint of waste transportation is 93.57 g of CO2 eq per ton of waste transported (t.km), which is relevant to three main parameters: the amount of waste transported annually, the freight shipped from the temporary station to the disposal landfill site, and fossil fuels consumed. Also, an environmental impact assessment in three categories - human health (global warming, abiotic depletion, and ozone layer depletion), resources (fossil fuels), and ecosystem quality (acidification and eutrophication) - using SimaPro, a Life Cycle Assessment (LCA) tool is presented. Global warming (3.49 kg CO₂ eq/t MSW), human toxicity (0.95 kg 1,4-DB eq/t MSW), and freshwater aquatic eco-toxicity (0.04 kg 1,4-DB eq/t MSW) have the greatest impact among categories. Sensitivity analysis of the effective parameters allows us to conclude one of the potential implications of this study would be the introduction of natural gas or biogas-based trucks replacing diesel fuel vehicles to improve air quality and mitigate the greenhouse gas emission.Implications: This paper addresses the significant issue of global warming, particularly in Iran, a developing country that ranks among the top contributors to greenhouse gas emissions. The study emphasizes the importance of evaluating emissions across various sectors such as electricity, waste, etc., Specifically, in this paper we focus on developing a model to quantify the environmental impact resulting from the combustion of fossil fuels in vehicles, focus on the metropolitan city of Tehran as a case study. By examining the waste transportation process, we aim to provide decision-makers with effective strategies to mitigate the environmental consequences. In this paper, we develop a simple quantification term of Carbon Footprint to calculate total greenhouse gas emission of waste transportation process. Carbon Footprint is a fraction which, its numerator is total greenhouse gas emission and its denominator is total waste transported in traveled distance. Effective parameters have been investigated and based on parameters and emission factors taken out of IPPC, the carbon footprint model have been developed. The total greenhouse gas emission of this study and the carbon footprint has estimated at 8.47 k tonCO2eq/y and 93.57 g CO2eq/t.km respectively. Furthermore, the paper explores additional environmental impacts beyond global warming, including abiotic depletion, ozone layer depletion, acidification, eutrophication, human toxicity, photochemical oxidation, and freshwater aquatic eco-toxicity. Using SimaPro software these eight impact categories have been estimated. in this study we identify fossil fuel consumption, traveled distance, and mass transported are the primary parameters influencing greenhouse gas emissions and the carbon footprint. To reduce emissions in the waste transportation system, we suggest promoting renewable biofuels, highlighting Iran as a suitable candidate due to its high percentage of biodegradable material in municipal solid waste. Additionally, the study assesses nonrenewable energy and mineral extraction using the IMPACT 2002+ V2.15/IMPACT 2002+ method, revealing that global warming (100 years), human toxicity (100 years), freshwater aquatic eco-toxicity, nonrenewable energy, and mineral extraction have the most significant impacts on the municipal solid waste transportation system. Overall, this research underscores the need for quantifying environmental impacts and recommends strategies to mitigate them in waste transportation processes, particularly in developing countries like Iran.