Last year, Vancouver, British Columbia, officially adopted the goal of powering itself entirely with clean energy by 2050.

That’s a bigger deal than it might sound. Plenty of North American cities have committed to getting all their electricity from clean sources within a few decades. But when it comes to decarbonization, electricity is the easy part. (Okay, maybe not easy, but easier.)

Vancouver has resolved to get all its energy, not just electricity, from renewable sources.

The city’s electricity is already 98 percent carbon-free anyway. It comes from hydroelectric dams, via the province’s primary utility, BC Hydro. So the big problems over the next 35 years will be eliminating natural gas for heating and gasoline for transportation, two of the thorniest decarbonization challenges.

Sadhu Johnston helped develop and implement Vancouver’s pathbreaking Greenest City Plan over seven years of work as deputy city manager (during which he also co-authored a book called The Guide to Greening Cities). He was deputy chief of staff to Chicago Mayor Richard Daley — and Chicago’s chief environmental officer, the first such position created in city government in the US — when Vancouver recruited him in 2009. Now, as of earlier this year, he is city manager, overseeing the whole enchilada.

I spoke with him last month on Cortes Island in BC, where our discussion ranged widely over Vancouver’s challenges. I’ve organized it into roughly five sections: heating and buildings, cars and trucks, density, bikes, and larger social challenges. (Definitely read the final section, even if you skip the rest.) I’ve also edited for length and clarity.

David Roberts: You’re aiming to power Vancouver with 100 percent clean energy by 2050. How are you doing so far?

Sadhu Johnston: We’re about 37 to 38 percent renewably powered now in Vancouver, largely because of [clean electricity from] BC Hydro.

From 1990 to 2015, we’ve increased our population by about 30 percent and jobs by about 30 percent and decreased carbon [emissions] by about 15 percent. We’re currently at about 4 tons per person [annual carbon emissions], which is the lowest that we know of in any city in North America..