You can gasify many materials besides plastic (garbage/waste stream). Filter out metals, brick, rock, glass first. Perhaps site near existing landfills in order to balance the ingest stream between ongoing waste and the waste mine. I have heard the phrase that the landfills of today are the mines of tomorrow, but I think they're more like Superfund sites, all to require remediation in the future at some point (hence the importance of projects that can reasonably degrade these materials into inert byproducts).

https://netl.doe.gov/research/coal/energy-systems/gasificati...