Within our REVALUO system, after sorting and classifying, all organic waste goes through a Hydrolysis process to extract all possible sugars. These sugars can be inside the MSW as free sugars, they can be in the form of starch that originates in food scraps, they can also be in the form of cellulose present in packaging, disposable diapers, and small pieces of paper and cardboard.
Once the sugars are obtained, we are able to produce BioEthanol.
BioEthanol production from agricultural and municipal solid waste (MSW)
The diagram shows the basic process that can be used for different types of biomasses. Each biomass requires a different process for pre-treatment, treatment and a specific process for the treatment of sugars depending on the desired end product. The water is either separated at the end of the process as distilled water or it is fed back into the process or bottled and sold as distilled water for other industrial uses. The surplus produced in the form of vinasse is incorporated into the next REVALUO process, Thermolysis.
Materials that can be recycled with REVALUO
Urban solid waste biomass.
Forest residue biomass: bark, roots, fine branches, pruning of urban trees.
Agricultural waste biomass: rice husk, rice straw, maize, sorghum, pruning, etc.
Food residue biomass: olive and grape pomace, fruit industry residues (cider, vinegar, oil, nutshells), etc.
Schematic diagram of solid waste management
1 – Pretreatment of waste
– Sterilisation and washing of waste with superheated water to remove free sugars and initial treatment of starches.
– The resulting waste contains all the original material, including small pieces of plastic and other materials.
2 – Hydrolysis of starch
– Use of 2 different enzymes (amylases) at specific temperatures and pH to convert starch to sugars in a process lasting up to 36 hours.
3 – Cellulose Hydrolysis
– At the end of the starch Hydrolysis process, the temperature is reduced, and the pH is adjusted to add the enzyme (cellulase) that will convert the cellulose into glucose.
– Simultaneously with the cellulose Hydrolysis, we start the fermentation of sugars already available in the stream.
4- Sugar fermentation
– The cellulose Hydrolysis phase and simultaneous fermentation lasts up to 48 hours
5- Solids separation
– Separation and washing of the remaining solids in the waste stream using a screw dewaterer or a press filter, depending on the destination of the solids. Normally the solids will be sent to the following process, Thermolysis, with a reduction in mass of up to 30% and 50% in volume due to the increase in the apparent density of the material.
6 – Distillation of the liquid stream
– The liquid stream passes through a distillation column to obtain BioEthanol at a concentration level of 92% (96° GL).
– At the bottom of the column we will have an aqueous stream rich in matter, but without Ethanol, called vinasse.
– The BioEthanol stream goes to the dehydration system.
7- Vinasse concentration and evaporation
– Vinasse goes through a triple effect evaporator to recover the previously used water and obtain a sludge with a solids content of around 18%.
That sludge will be sent to the next process of the REVALUO waste management system, Thermolysis.
8- Ethanol dehydration
– Ethanol produced in the distillation column is sent to a zeolite column. There its concentration will rise from 92% to 99,5% and its specifications will be suitable for blends in gasoline.