DESCRIZIONE
A method of treating biomass material, which can achieve volume reduction or carbonization of biomass material can be achieved at extremely low cost, is disclosed. The method of treating biomass material to achieve volume reduction or carbonization of one type or more of biomass material which is selected among food scraps, livestock excreta, agricultural waste products, marine waste products and forest waste products in a pressurizable and heatable container, includes: placing the biomass material in the container; setting an initial condition of the container after placing the biomass material, the initial condition including all of (a) an atmosphere in the container having oxygen, (b) a temperature range in the container being equal to or greater than 55 degree Celsius and equal to or less than 80 degree Celsius, (c) a pressure range in the container being equal to or greater than atmospheric pressure and equal to or less than 15 atmospheric pressure and (d) carbon monoxide concentration being equal to or greater than 100 ppm; increasing temperature of the biomass material over 80 degree Celsius under the initial condition; setting a continuation condition after initiating increase in the temperature of the biomass to over 80 degree Celsius under the initial condition, the continuation condition including (i) the atmosphere in the container having oxygen, (ii) the pressure range in the container being equal to or greater than atmospheric pressure and equal to or less than 15 atmospheric pressure and (iii) a carbon monoxide concentration in the container being equal to or greater than 100 ppm; and maintaining the continuation condition, in order to spontaneously increase temperature of the biomass material over at least 150 degree Celsius, and achieve volume reduction or carbonization of the biomass material.