Since 1 January 2005 it has been mandatory in the Netherlands to specify the source of electricity supplied to consumers and for 2011 CE Delft again determined the Dutch electricity mix. This mix consisted of power generated from natural gas (47%), some of which derived from cogeneration plant (32%), some from pure power stations (15%), coal (15%), nuclear (4%), renewables (31%) and other (2%). The environmental impacts expressed in terms of CO2 emissions and radioactive waste are 300 g CO2/KWh and 0.0001 g nuclear waste/KWh.