A great way to reduce landfill waste by 20-30% is through composting suitable organic materials.
Almost half of solid waste produced in the world is organic or biodegradable, and composting is a proven method for cleanly processing that waste. Compost also has the added benefits of effectively trapping carbon in the soil and then utilizing that carbon as fertilizer to help garden plants grow. Many resources exist to help get started composting at home. For Chicago residents, check out this local resource.