A waste disposal plant comprising: • a combustion chamber, in which waste arranged on at least one combustion grid is burned, • said grid comprising a plurality of moving assemblies that move relative to one another, thereby causing the waste to advance on said grid, • said grid being divided into portions (GE, GC, GF), each comprising at least one of said moving assemblies, • at least one waste feeding assembly, for laying the waste on the grid, • at least one primary air injection assembly, for supplying said air both above and under the grid, • at least one secondary air supply assembly, for supplying said air above the grid, and • a fume recirculation fan assembly, for conveying the combustion fumes towards the upper part of the combustion chamber; said plant further comprising an automatic combustion control system including: • temperature sensors, steam sensors and oxygen sensors arranged in the combustion chamber, from which said control system detects values continuously, and an electronic processing unit, which receives data from said sensors and controls said adjustment assemblies on the basis of the required hourly steam production of the system and of the estimated caloric power of the waste; said processing unit further comprises calculation blocks (C03-01, C03-02, C04, C14); said plant being characterized in that said system further comprises: • a primary air adjustment assembly, which comprises under-grid primary air adjustment assemblies (GREP, RGC, RGF), at least one above-grid or above-vault primary air adjustment assembly (GRAPS), and a primary air preheating adjustment assembly (RGAP), • a secondary air adjustment assembly (GRAS, GAS, GRAS), • a travel adjustment assembly for each grid and a travel adjustment assembly for the waste feeder, and wherein said calculation blocks (C03-01,C03-02, C04, C14) are configured for determining the total quantity of secondary air to be supplied to the grid, which is the sum of the above-vault primary air supplied by the above-grid or above-vault primary air adjustment assembly (GRAPS) and the secondary air supplied by the secondary air adjustment assembly (GRAS); wherein further calculation blocks (C13, C15) are configured to calculating the adjustment parameters of said travel adjustment assembly for each grid and said travel adjustment assembly for the waste feeder; wherein the distribution of the two air currents, i.e. above-vault primary air and secondary air, is entrusted to a splitter which allows, through a first calculation block among said calculation blocks (C03-01, C03-02, C04, C14), to adjust the distribution of the two flows; said first calculation block being configured for calculating the total secondary air flow rate as a difference between a total air flow rate setpoint and an under-grid primary air flow rate, said under-grid primary air flow rate being calculated as the lower one of a setpoint value and a measured value, the total secondary airflow rate being advantageously corrected by means of a manual factor calculated in a correction block as follows: the total secondary air flow rate is further corrected by CO and O2 limit controllers (L01-01, L01-02), through which, if the theoretical value of the total secondary air reaches the minimum limit, any further increase of under-grid primary air will be prevented. • a combustion chamber, in which waste arranged on at least one combustion grid is burned, • said grid comprising a plurality of moving assemblies that move relative to one another, thereby causing the waste to advance on said grid, • said grid being divided into portions (GE, GC, GF), each comprising at least one of said moving assemblies, • at least one waste feeding assembly, for laying the waste on the grid, • at least one primary air injection assembly, for supplying said air both above and under the grid, • at least one secondary air supply assembly, for supplying said air above the grid, and • a fume recirculation fan assembly, for conveying the combustion fumes towards the upper part of the combustion chamber; • temperature sensors, steam sensors and oxygen sensors arranged in the combustion chamber, from which said control system detects values continuously, and • a primary air adjustment assembly, which comprises under-grid primary air adjustment assemblies (GREP, RGC, RGF), at least one above-grid or above-vault primary air adjustment assembly (GRAPS), and a primary air preheating adjustment assembly (RGAP), • a secondary air adjustment assembly (GRAS, GAS, GRAS), • a travel adjustment assembly for each grid and a travel adjustment assembly for the waste feeder, and