NOVELTY - Forced ventilation composting system comprises a composting reactor, an air jacket, a static gas collecting cover, an ammonia sampling port, a nitrous oxide sampling port, a temperature and humidity inspecting device, a humidity sensor, a temperature sensor, a time relay, an air pressure pump, a flow meter, an air chamber, a first measuring point and a second measuring point. A perforated plate is divided to an upper composting reactor and a lower air chamber. The outer side of composting reactor is provided with air jacket. The upper part of composting reactor is set with an exhaust port.    USE - The system is useful for preserving nitrogen and phosphorus in livestock and poultry compost and reducing greenhouse gas nitrous oxide emission (claimed).    ADVANTAGE - The method improves the metal ion content in the industrial wastes; achieves nitrogen preservation and phosphorus fixation effect, and thus it improves the quality of the compost product; is environmental-friendly; and promotes the utilization of resources of livestock and poultry compost.    DETAILED DESCRIPTION - Forced ventilation composting system comprises a composting reactor, an air jacket, a static gas collecting cover, an ammonia sampling port, a nitrous oxide sampling port, a temperature and humidity inspecting device, a humidity sensor, a temperature sensor, a time relay, an air pressure pump, a flow meter, an air chamber, a first measuring point and a second measuring point. A perforated plate of a container is divided into an upper composting reactor and a lower air chamber. The outer side of the composting reactor is provided with the air jacket. The upper part of the composting reactor is provided with an exhaust port. The composting reactor is provided with the first measuring point, second measuring point and humidity sensor. The temperature sensor of a temperature controller is provided with the first measuring point and second measuring point. The temperature and humidity inspecting device is connected to the humidity sensor by a wire. The upper surface of the composting reactor is equipped with the static gas collecting cover. The static gas collecting cover is provided with the ammonia sampling port and nitrous oxide sampling port. The lower part of one side of the perforated plate of the air chamber is set with a ventilation pipe. The ventilation pipe of the flow meter is connected to an air booster pump. A control switch of the air booster pump is connected to the time relay by wire. An INDEPENDENT CLAIM is also included for preserving nitrogen and phosphorus in livestock and poultry compost and reducing greenhouse gas nitrous oxide emission, comprising (i) adjusting the mass ratio of carbon element with nitrogen element in the livestock and poultry compost by adding a conditioning agent, and adding conditioning agent to the livestock and poultry compost until the moisture content is 55-65 wt.%; (ii) carrying out modification treatment of metal salt-rich industrial wastes, and synchronously composting the uniformly mixed material in a material conveying system conveyed to the stored nitrogen and phosphorus in livestock and poultry compost, and the greenhouse gas nitrous oxide emission is composting reactor of the forced ventilation composting system, stacking on the upper part of the composting reactor provided with temperature sensor and humidity sensor, and placing the humidity sensor on the compost pile; (iii) monitoring the changes in temperature and humidity of the compost pile occurring during the entire composting process by using the temperature and humidity inspecting device, and controlling the forced ventilation time during the composting process; (iv) carrying out ventilation process of the compost pile by controlling the opening and closing of the air booster pump provided with the perforated plate; (v) passing nitrous oxide and ammonia produced during the composting process from top of the composting reactor by the exhaust port, and collecting nitrous oxide and ammonia samplings from the static gas collecting cover which is tightly installed on the composting reactor; and (vi) adding modified metal salt-rich industrial waste to the livestock and poultry compost, where the metal salts is of magnesium, iron, aluminum and calcium ions whose total amount added is 15-30% the total nitrogen quantity (mol) in the livestock and poultry compost.