Abstract: At least one part of a road surface is covered by a photocatalyst layer containing a photocatalyst such as titanium dioxide, etc. to purify pollutants in exhaust gases emitted from vehicles by photocatalytic reaction of the photocatalyst. Pollutant-originating matters as retained on the photocatalyst layer are washed away by rain water or sprinkled water. In one embodiment of the invention, road 12 is a road provided with a dewaterable pavement and rain water passes through surface layer 18 during raining, flows over and along base layer 16 and is discharged. In surface layer 18, numerous aggregates of small particle sizes 1802 are projected from the entire surface of concrete layer 1804. Titanium dioxide layer 20 is formed by injecting or spraying a mixture comprising titanium dioxide, cement, a filler and water onto the entire surface of surface layer 18 thinly and is water-permeable.

Abstract: At least one part of a road surface is covered by a photocatalyst layer containing a photocatalyst such as titanium dioxide, etc. to purify pollutants in exhaust gases emitted from vehicles by photocatalytic reaction of the photocatalyst. Pollutant-originating matters as retained on the photocatalyst layer are washed away by rain water or sprinkled water. In one embodiment of the invention, road 12 is a road provided with a dewaterable pavement and rain water passes through surface layer 18 during raining, flows over and along base layer 16 and is discharged. In surface layer 18, numerous aggregates of small particle sizes 1802 are projected from the entire surface of concrete layer 1804. Titanium dioxide layer 20 is formed by injecting or spraying a mixture comprising titanium dioxide, cement, a filler and water onto the entire surface of surface layer 18 thinly and is water-permeable.

Abstract: Sewage sludge or an agricultural or fish waste material is subjected to pretreatment in the form of wet mill treatment and then is subjected to anaerobic digestion.