Mainers each year discard about 300,000 gallons of leftover paint that may contain dangerous chemicals, and a lot of it ends up in landfills or incinerators. On Thursday, the Legislature’s Environment and Natural Resources Committee takes up a bill modeled after programs in Oregon and California that creates a paint recycling system. It would create an industry-run program in which unused paint would be collected at drop-off sites at municipal locations and paint stores. Funds collected through paint sales would pay for the system, so consumers, not taxpayers, would support the costs. The bill’s supporters say Mainers spend about $2.4 million in local taxes and fees annually to collect used paint and send it to incinerators or landfills. Oil-based paint is flammable and older paint can contain lead.