The right answer is solid.
A waste is an object or substance that has been physically or chemically impaired or is no longer usable and / or is intended for disposal or recycling.
These wastes are difficult to eliminate without causing deleterious effects. In Asia-Pacific, 90% of urban solid waste ends up in a wild dump, and it is one of the first sources of diseases. In Mumbai, more than 12 percent of urban solid waste is burned in cities or landfills, polluting the air and soil.