Ask HN: How can we capture car exhaust better?

Conventional wisdom says it's not worth it for two reasons: Compressing the exhaust would require on onboard device that would be heavy and it + the weight of the captured exhaust would burn more gas than it'd save What's the state of the art of these devices? Is it reasonably possible to innovate to a smaller device? Second, what do you do with all that compressed exhaust? Could we repurpose the gas station infrastructure so that every time you get gas, you drop off liquid emissions? Maybe you have trucks that come around and pull it out of cars in parking lots like seamless for emission drop pickup?