Florbela Carvalheiro: Biomass Fractionation Processes for the Biorefineries
Florbela Carvalheiro, who is a researcher at Bioenergy Unit of LNEG, presented following the Modern Concepts for Biomass Deconstruction under Biorefineries. She started with some historical examples from Portugal where wood gas was used for tractors and transport vehicles in the 1920s. Later in 1979 in Brazil the first car was moved by ethanol. Today the development of biofuels directs the aviation sector. Meanwhile the sector hasn’t reached all parts of life the bioeconomy is starting through.
Then Ms Carvalheiro talked about biomass composition, which consists of cellulose, hemicellulose, lignin and extractives and when thinking about refining biomass one needs to get the separated biomass fractions. When using lignocellulosic material as biorefinery feedstock the material first has to run through a pretreatment. There the aims are selective fractionation and recovery of all fractions in order to get value from all biomass components by their selective conversion to products. At the same time environmental and economic performance as well as the properties/value of the products obtained shall be improved and the requirements of downstream processes shall be optimised. The limitations of the fractionation are achievable selectivity, high use of energy and/or chemicals and high process costs. Ms Carvalheiro then gave an overview about the main pretreatment options which include physical, chemical, physico-chemical and biological processes. She showed in detail some of the processes like extrusion as physical process and acid hydrolysis, alkaline and organosolv processes as example for chemical treatment. Following Solid (Super) Acids, inorganic salts and Ionic Liquids (ILs) were shown as examples of novel-chemical processes. Physico-chemical processes were presented with hydrothermal processes mainly including liquid hot water (autohydrolysis) treatments and uncatalysed steam explosion. Supercritical fluids (SCF) were presented as an example of novel physico-chemical processes. Examples of biorefineries (commercial or demo scale) using some of the processes presented before were also shown.
Ms Carvalheiro concluded her presentation with the statements that there is no single method that can fulfil all the requirements for the effective biomass fractionation. The use of combined/sequential processes targeting different fractions, i.e. the separate recovery of hemicellulose and lignin, may be advantageous. Furthermore novel processes (e.g. based on ILs) can also be effective, as they may be able to convey the two goals in a single process.
When expecting, that pretreatment can provide low costs, low energy demand and low levels of (non-hazard) catalysts, to be highly selective, allowing for multireaction processes in a one-pot stage and furthermost consolidated (bio)processing, Ms Carvalheiro stated that research for solutions is on the way yet some progresses still need to be made.