Food waste has become an international problem that is currently part of public agendas and policies. This problem has different social, economic and environmental dimensions. The international debate relates food waste to climate change and the Sustainable Development Goals, due to the release of greenhouse gases (GHG) by the inefficient use of resources. This research carries out an analysis of the methodologies to calculate greenhouse gas emissions (Carbon Footprint), for its application to the activities of Food Banks and to estimate the environmental effects. Documentary sources, research and international standards will be reviewed and contrasting methodologies will be analyzed. In addition, a survey will be carried out on the 54 Food Banks to learn about experiences and contextualize. The results allow us to propose a common proven methodology for its application from the Food Banks and to quantify its contribution to the improvement of the environment.