Abstract: A greenhouse of an underground heat accumulation system wherein the radiant energy of the sun or wasted thermal energy is accumulated in the soil below the floor of the greenhouse over a prolonged period of time, and spontaneous release of the accumulated energy into the interior of the greenhouse begins in the wintertime due to a time lag of heat transfer through the soil. The release of the accumulated energy lasts throughout the winter.

Abstract: A plastic by-product can be reprocessed by embrittling the plastic by-product at a low temperature, crushing the embrittled by-product to about the same particle size as that of the virgin plastic, adding fine powder of the same or other material to the thus crushed by-product in order that the fine powder is deposited onto the surface of the crushed by-product, and then raising the temperature of the by-product to room temperature. The thus obtained reprocessed material can effectively be utilized as a bulking filler for the virgin plastic or for the other uses.

Abstract: Atactic polypropylene is cooled, disintegrated into granules, mixed with cereal powders such as wheat flour, starch powders, etc. thereby to deposit the cereal powders around the granules, and returned to room temperature thereby to prepare an oil-recovering material. The oil-recovering material is spread onto surfaces of sea water with floating oil or surfaces of land area fouled with oil, such as sand beach, etc. to recover the oil therefrom.