No specific set of emissions must be considered, so the choice is up to those carrying out the process, though it is common to consider greenhouse gas emissions (predominantly carbon dioxide and methane) and regulated pollutant emissions (e.g., oxides of nitrogen, NO

; oxides of sulfur, SO

; particulate matter, PM; and volatile organic compounds, VOC). Energy use across the full fuel cycle is also calculated, to enable comparisons of efficiency and resource use between different fuel chains. The boundaries applied to fuel cycle analyses will have an impact on the environmental effects considered and on the magnitude of these effects.