THERE is a need for clarity about how electricity is generated by renewable or non renewable means (“Drax deal a riddle”, Comment, The Press, October 17).

Conventional hydro is totally renewable while coal and gas are totally non renewable.

However the substitution of gas for coal results in a significant reduction in carbon dioxide emissions per unit of power produced.

With respect to pumped power, which is a means of producing hydro power quickly during short periods of peak electricity demand, the associated emissions depend upon what source of power is used to pump the water up to the associated elevated water reservoir.

While the use of largely imported biomass is questionable with respect to emissions there is surely some overall benefit in having a diversified portfolio of energy sources in order to achieve cost effective generation with overall reduction in emissions.

While it is important to increase the proportion of electricity produced from renewable sources we will need to continue with the use of non renewables for some time to come.

David Randon,

Blue Slates Close,

Wheldrake, York