Have an X style contest that offers patent support, purchase contract grants and cash rewards (say twelve, one million dollar prize/grants). The Winners design the most energy affordable, scalable, device/array system or bio-filter that removes carbon and, secondarily, particulate pollution from urban atmosphere areas.
-Least grid sourced electricity used
-Least Water used.
-Least expensive material construction cost.
-Least maintenance required per month of constant operation.
-Easiest to install in a variety of locations/ climates.
-Does not contribute any net harm or pollution to water and air.
-Fastest to completion of ten functioning units.
-Largest volume per unit of carbon/particulates captured.
-Pollutants to be cache-able on site or with no net transportation cost of new pollution.