Ethtec ProcessEthtec Process
Ethanol is being increasingly used worldwide as a renewable liquid fuel for transport. It is used either neat or in blends with petroleum fuels. However conventional ethanol production relies on the sugar and starch content of food crops, and requires the specific planting of these crops for ethanol.
By contrast, Ethtec can convert low-value material, often deemed "waste", into ethanol without the need to utilise primary agricultural sugar or starch resources. It utilises the so-called second-generation or "lignocellulosic" ethanol technology. Lignocellulosics are fibrous biomass materials such as wood, sugarcane bagasse, grain crop stubbles, cotton stubble and grasses.
If commercialised, Ethtec's technology could provide low-greenhouse impact liquid fuel demand through ethanol produced from lignocellulosic biomass, without interfering with food production or causing land or other environmental degradation.
Ethtec has successfully proven its patented second-generation ethanol technology in the laboratory. A scaled pilot plant is now under construction in New South Wales, Australia (see Pilot Plant) to test commercial production feasibility with a range of feedstocks such as wood and sugar cane harvest residue.
The Ethtec plant will comprise a series of four independent but linked technologies operating in a continuous process, and featuring water and acid recovery and recycling loops (see Fig. 1).
Figure 1 Ethtec process diagram showing ethanol production steps and materials recovery/recycling loops.
- Hydrolysis:
Concentrated sulfuric acid treatment of lignocellulosic feedstock to produce sugars using a twin screw extruder and tube reactor; - Lignin separation and acid recovery:
Separation of the lignin and acid from the sugars, recovery/recycling of the acid for further use in the hydrolysis step, and recovery of the lignin for combustion via cogeneration to produce energy; - Fermentation:
Simultaneous fermentation of two types of sugars (pentose and hexose) to ethanol using newly developed micro-organisms; and - Ethanol recovery:
Recovery of ethanol from the fermentation broth by induced phase separation using potassium carbonate, and recycling of the water back to earlier phases.
The pilot plant is designed to convert approximately two tonnes per day of waste lignocellulosic material into ethanol. The plant will demonstrate and enable further development of the technology for commercialisation.