A cellulose hydrolysis method including a step comprising: contacting a fermentation medium comprising paper sludge as carbon source with cellulase obtained on site from cellulase bacteria, until the mean glucose monomer number of cellulose molecules in the fermentation medium is decreased to a range between 5 and 500; wherein the method further comprises the step prior to the step: X) bacteria production comprising the sequential steps of: a) cultivation of cellulolytic bacteria from deep frozen stock into nutrient agar plates or Luria Broth plates, and incubating them at a temperature within the range between 30°C and 40°C for a first duration within the range between 1 day and 3 days, b) inoculation of a fermentation starter culture in liquid form with three or more colonies taken from said plates, c) incubation of the fermentation starter culture at a temperature within the range between about 30°C and about 40°C for a duration within the range between about 1 day and about 4 days, d) incubation of a production culture for a period within the range between 36 hours and 72 hours, started by mixing fermentation starter culture in an amount within the range between 1 wt.% and 10 wt.% with respect to the total weight of the production culture; biomass is harvested upon the end of the step (d) as a fluid product, by application of centrifuge corresponding to an acceleration on the production culture within a range between 29000 m/s 2 and 80000 m/s 2; optionally followed by drying of the biomass under air circulation at a temperature within the range between 40°C and 50°C until solid matter ratio in the biomass reaches to at least 90 wt% to obtain a solid product; and the step comprises a hydrolysis step taking place in an aqueous mixture prepared by mixing paper sludge with a solid content within the range between 25 wt.% and 40 wt.%, with the following further ingredients added onto the paper sludge, amounts of the further ingredients being given per ton of the paper sludge: - 5 kg to 10 kg of corn steep liquor, or 12.5 kg to 25 kg of beet molasses, or 2.5 kg to 5 kg of yeast extract, or 5 kg to 10 kg of beer yeast waste, or a mixture thereof; - 50 g to 250 g of MgSO 4; - 100 g to 200 g of the solid product, or 25 liters to 50 liters of the fluid product; further wherein said aqueous mixture is aerated at a temperature between 30°C and 40°C for a period between 24 hours and 72 hours, whilst maintaining the water content of the aqueous mixture. X) bacteria production comprising the sequential steps of: a) cultivation of cellulolytic bacteria from deep frozen stock into nutrient agar plates or Luria Broth plates, and incubating them at a temperature within the range between 30°C and 40°C for a first duration within the range between 1 day and 3 days, b) inoculation of a fermentation starter culture in liquid form with three or more colonies taken from said plates, c) incubation of the fermentation starter culture at a temperature within the range between about 30°C and about 40°C for a duration within the range between about 1 day and about 4 days, d) incubation of a production culture for a period within the range between 36 hours and 72 hours, started by mixing fermentation starter culture in an amount within the range between 1 wt.% and 10 wt.% with respect to the total weight of the production culture; biomass is harvested upon the end of the step (d) as a fluid product, by application of centrifuge corresponding to an acceleration on the production culture within a range between 29000 m/s 2 and 80000 m/s 2; optionally followed by drying of the biomass under air circulation at a temperature within the range between 40°C and 50°C until solid matter ratio in the biomass reaches to at least 90 wt% to obtain a solid product; and a) cultivation of cellulolytic bacteria from deep frozen stock into nutrient agar plates or Luria Broth plates, and incubating them at a temperature within the range between 30°C and 40°C for a first duration within the range between 1 day and 3 days, b) inoculation of a fermentation starter culture in liquid form with three or more colonies taken from said plates, c) incubation of the fermentation starter culture at a temperature within the range between about 30°C and about 40°C for a duration within the range between about 1 day and about 4 days, d) incubation of a production culture for a period within the range between 36 hours and 72 hours, started by mixing fermentation starter culture in an amount within the range between 1 wt.% and 10 wt.% with respect to the total weight of the production culture; the step comprises a hydrolysis step taking place in an aqueous mixture prepared by mixing paper sludge with a solid content within the range between 25 wt.% and 40 wt.%, with the following further ingredients added onto the paper sludge, amounts of the further ingredients being given per ton of the paper sludge: - 5 kg to 10 kg of corn steep liquor, or 12.5 kg to 25 kg of beet molasses, or 2.5 kg to 5 kg of yeast extract, or 5 kg to 10 kg of beer yeast waste, or a mixture thereof; - 50 g to 250 g of MgSO 4; - 100 g to 200 g of the solid product, or 25 liters to 50 liters of the fluid product; further wherein said aqueous mixture is aerated at a temperature between 30°C and 40°C for a period between 24 hours and 72 hours, whilst maintaining the water content of the aqueous mixture. - 5 kg to 10 kg of corn steep liquor, or 12.5 kg to 25 kg of beet molasses, or 2.5 kg to 5 kg of yeast extract, or 5 kg to 10 kg of beer yeast waste, or a mixture thereof; - 50 g to 250 g of MgSO 4; - 100 g to 200 g of the solid product, or 25 liters to 50 liters of the fluid product;