Front-runners Layla Moran and Kingston and Surbiton MP Sir Ed Davey both have plans to build the economy around it.
Sir Ed says things like retro-fitting home insulation would contribute to that, as would “re-wilding”.
Sir Ed also wants to move to 80% renewable energy by 2030, and guarantee the living wage for people working on green projects.
Mrs Moran has told the Independent she wants the UK to be “not just carbon neutral but carbon negative” and scrap VAT on electric cars.