The present invention provides a biomass dryer/burner having an air cleaning apparatus adapted to accept emissions from the biomass dryer/burner and to convert said emissions to clean air to meet government emission standards. The biomass dryer/burner unit includes a dryer adapted to dry biomass, such as demolition waste or cut trees. The biomass dryer/burner unit optionally including a burner adapted to burn biomass. The biomass dryer/burner further producing emissions requiring cleaning before exhausting to the atmosphere. The air cleaning apparatus including a spray scrubber fluidly connected to the biomass dryer/burner adapted to moisten emissions, a recirculation tank in fluid communication with a collection tank, and the recirculation tank further having a sensor adapted to measure contaminant levels contained within the recirculation air filtration system. The sensor contained within the recirculation tank measures levels of carbon monoxide. If the air contained within the recirculation air filtration system measures above a predetermined contaminant level, then the air contained within the recirculation air filtration system is directed back into the spray scrubber. If the air contained within the recirculation air filtration system is below a predetermined level, then the air is exhausted into the atmosphere.