After reception at the processing plant, the beet roots are washed, mechanically sliced into thin strips called cossettes, and passed to a machine called a diffuser to extract the sugar content into a water solution, a process known as leaching.

Diffusers are long vessels of many metres in which the beet slices go in one direction while hot water goes in the opposite direction.
The movement may either be caused by a rotating screw or the whole rotating unit, and the water and cossettes move through internal chambers.
The three common designs of diffuser are the horizontal rotating 'RT' (Raffinerie Tirlemontoise, manufacturer), inclined screw 'DDS' (De Danske Sukkerfabrikker), or vertical screw "Tower".
Modern tower extraction plants have a processing capacity of up to 17,000 metric tons (16,700 long tons; 18,700 short tons) per day.
A less-common design uses a moving belt of cossettes, with water pumped onto the top of the belt and poured through.
In all cases, the flow rates of cossettes and water are in the ratio one to two.
Typically, cossettes take about 90 minutes to pass through the diffuser, the water only 45 minutes.
These countercurrent exchange methods extract more sugar from the cossettes using less water than if they merely sat in a hot water tank.
The liquid exiting the diffuser is called raw juice.
The colour of raw juice varies from black to a dark red depending on the amount of oxidation, which is itself dependent on diffuser design.

The used cossettes, or pulp, exit the diffuser at about 95% moisture, but low sucrose content.
Using screw presses, the wet pulp is then pressed down to 75% moisture.
This recovers additional sucrose in the liquid pressed out of the pulp, and reduces the energy needed to dry the pulp.
The pressed pulp is dried and sold as animal feed, while the liquid pressed out of the pulp is combined with the raw juice, or more often introduced into the diffuser at the appropriate point in the countercurrent process.
The final byproduct, vinasse, is used as fertilizer or growth substrate for yeast cultures.

During diffusion, a portion of the sucrose breaks down into invert sugars.
 These can undergo further breakdown into acids.
These breakdown products are not only losses of sucrose, but also have knock-on effects reducing the final output of processed sugar from the factory.
To limit (thermophilic) bacterial action, the feed water may be dosed with formaldehyde and control of the feed water pH is also practised.
Attempts at operating diffusion under alkaline conditions have been made, but the process has proven problematic.
 The improved sucrose extraction in the diffuser is offset by processing problems in the next stages.
After reception at the processing plant, the beet roots are washed, mechanically sliced into thin strips called cossettes, and passed to a machine called a diffuser to extract the sugar content into a water solution, a process known as leaching.
Diffusers are long vessels of many metres in which the beet slices go in one direction while hot water goes in the opposite direction. The movement may either be caused by a rotating screw or the whole rotating unit, and the water and cossettes move through internal chambers. The three common designs of diffuser are the horizontal rotating 'RT' (Raffinerie Tirlemontoise, manufacturer), inclined screw 'DDS' (De Danske Sukkerfabrikker), or vertical screw "Tower". Modern tower extraction plants have a processing capacity of up to 17,000 metric tons (16,700 long tons; 18,700 short tons) per day. A less-common design uses a moving belt of cossettes, with water pumped onto the top of the belt and poured through. In all cases, the flow rates of cossettes and water are in the ratio one to two. Typically, cossettes take about 90 minutes to pass through the diffuser, the water only 45 minutes. These countercurrent exchange methods extract more sugar from the cossettes using less water than if they merely sat in a hot water tank. The liquid exiting the diffuser is called raw juice. The colour of raw juice varies from black to a dark red depending on the amount of oxidation, which is itself dependent on diffuser design.
The used cossettes, or pulp, exit the diffuser at about 95% moisture, but low sucrose content. Using screw presses, the wet pulp is then pressed down to 75% moisture. This recovers additional sucrose in the liquid pressed out of the pulp, and reduces the energy needed to dry the pulp. The pressed pulp is dried and sold as animal feed, while the liquid pressed out of the pulp is combined with the raw juice, or more often introduced into the diffuser at the appropriate point in the countercurrent process. The final byproduct, vinasse, is used as fertilizer or growth substrate for yeast cultures.
During diffusion, a portion of the sucrose breaks down into invert sugars.  These can undergo further breakdown into acids. These breakdown products are not only losses of sucrose, but also have knock-on effects reducing the final output of processed sugar from the factory. To limit (thermophilic) bacterial action, the feed water may be dosed with formaldehyde and control of the feed water pH is also practised. Attempts at operating diffusion under alkaline conditions have been made, but the process has proven problematic.  The improved sucrose extraction in the diffuser is offset by processing problems in the next stages.
Sugar beet