The study of waste management strategies is increasing worldwide due to the necessity of a more sustainable environment. In this framework, guaranteeing cleaner energy is the key parameter for cleaner production, especially for reducing the emissions of greenhouse gases and other pollutants to the environment, which are directly related to the types of the energy sources used. Through the methodology of LCA it can help in the study of the environmental part. This study is based on the methodologies ISO 14040 and 14044 for obtaining quantitative results on the environmental impact, from cradle to grave, of different waste collection systems. A sensitive study of the influence of the energy source on the life cycle assessment (LCA) is analysed for six different waste collection systems (trucks - electric, gas, diesel, diesel-electric, gas-electric - and stationary pneumatic waste collection) and five energy sources (Spanish energy mix 2008, hydropower, photovoltaic, wind, and a renewable energy mix). The results show that the energy source has a big impact in the results of the LCA with variations up to 80%. The environmental impact of each collection system depends strongly on the source of the energy used and thus, decision-makers should consider the energy source and the expected evolution of energy mix when considering the best waste collection systems from an environmental point of view. In a framework with a majority of fossil-sourced energy, the truck collection shows lesser environmental impact, due to its lower electricity use, whereas in a renewable energy environment, the stationary pneumatic waste collection shows better performance.