NOVELTY - Preparing products using plant-derived biomass, by subjecting biomass feedstock containing cellulose and lignin to irradiation, sonication, pyrolysis, oxidation and neutralization processes, separating lignin from the biomass feedstock, subjecting lignin separated biomass feedstock to bioreaction to produce ethanol and first waste material, subjecting the first waste material to fermentation to produce methane gas and second waste material, preparing products using ethanol and second waste material and using the methane gas as power fuel for equipments in factories.    USE - The method (M1) is useful for preparing plant-derived biomass based products chosen from (a) methane gas used as power fuel for equipments in factories and heaters for drying the wrapping material and organic fertilizer, (b) ethanol used in combination with synthetic resin for preparing synthetic resin film used for preparing wrapping material which is used for preparing bags for packaging organic fertilizer, and (c) organic fertilizer. The method (M2) and system are useful for preparing fertilizer packaged products (all claimed). The equipments include automation apparatus, an air conditioner and lighting system.    ADVANTAGE - The methods enable effective utilization of waste materials produced during ethanol production, preferably methane gas as power fuel that meets reduced commercial energy supply to the factories when compared to existing use of fossil fuels, and hence production of carbon dioxide is decreased and environmentally-friendly factories can be set up.    DETAILED DESCRIPTION - Method (M1) for preparing products using plant-derived biomass, involves (a) subjecting biomass feedstock containing cellulose and lignin to irradiation, sonication, pyrolysis, oxidation and neutralization processes and separating lignin from the biomass feedstock, (b) subjecting the biomass feedstock from which lignin is separated to bioreaction to produce ethanol and first waste material, (c) subjecting the first waste material to methane fermentation to produce methane gas and second waste material, and (d) preparing products using ethanol and second waste material and using the methane gas as power fuel for equipments in factories. INDEPENDENT CLAIMS are included for the following:    (1) method (M2) for preparing fertilizer packaged products, involves performing the above-mentioned steps (a) and (b), (e) preparing wrapping material using synthetic resin film prepared using the ethanol, (f) preparing packaging bag using the wrapping material, performing the above-mentioned step (c), (g) subjecting the second waste material to bioreaction to produce organic fertilizer, and (h) filling the organic fertilizer inside the packaging filled bags; and    (2) system for preparing the fertilizer packaged products, comprising first processing unit for performing the above-mentioned step (a), second processing unit for performing the above-mentioned step (b), wrapping material preparation unit for producing the wrapping material using the synthetic resin film prepared using the ethanol, packaging bag preparation unit for preparing packaging bags from the wrapping material, third processing unit for performing the above-mentioned step (c), fourth processing unit for performing the above-mentioned step (g), and filling unit for performing the above-mentioned step (h).