Chemical products, energy sources, oils, paints, and more from biomass as a raw material many more things than might be thought can be obtained. Aware of this, engineer Mara Gonzlez looked for the most appropriate types of biomass as well as the most suitable processing techniques and technologies for refining them. Her aim was to obtain the most from renewable organic natural resources and thus substitute them for fossil fuels in the future. The PhD thesis was defended at the University of the Basque Country (UPV/EHU) and entitled, Design of bio-refinery processes.
Lignocellulose as raw material
The system for the transformation of the raw material depends on the type of material required to be processed. Thus, Ms Gonzlez first of all decided which type of biomass she would use, opting for lignocellulosic biomass, given its great abundance, variety and availability as well as the low cost of this group of raw materials. This material is composed of hemicellulose, lignin and cellulose, and is the raw material of the paper and pulp industry, amongst others.
The researcher did not make use of all the lignocellulosic materials; she stated that the most useful biomass is that from agricultural, forestry and food industry waste, the very waste that is problematic for the environment and the economy. So making better or full use of them would be highly advantageous.
Organosolv, the best for the first stage of refining
After deciding on the raw material, Ms Gonzlez started the first phase of bio-refinery, undertaking trials using organosolv treatments and caustic soda. Both differ as regards treatment used in the paper industry to obtain cellulose and to overcome certain drawbacks, for example as regards contamination arising from the emissions of liquids and gases.
According to the conclusions of Ms Gonzlez, the organosolv method is the most suitable of the two tested. It recovers the components of biomass or sub-products in an easy and clean manner and, moreover, if ethanol is used as a solvent to carry out the method, the results are even better. Ethanol being a bio-fuel and obtainable from biomass, this solvent required for carrying out the method can be extracted from the very same material to be refined. The caustic soda method, on the other hand, does not wholly meet the aims of bio-refinery: it does not completely and cleanly recover all the sub-products of the biomass, precisely because it requires the energy value of those components to undertake the process.
Clean and applicable products
With the biomass fractionated, in this second stage of refining, Ms Gonzlez tested a number of treatments for the separation and clearing of the sub-products obtained. More concretely, she treated the lignins and the hemicelluloses, seeking to obtain products from them. Both have varied applications. Lignin facilitates the formation of polymers, for example. From hemicelullose simple sugar is obtained, which mediates in obtaining certain products used in plastics.
In this stage of refining, in the case of lignin, Ms Gonzlez carried out ultrafiltration using membranes. The treatment proved to be successful: she obtained contaminant-free fractions of lignin, with high quality properties and suitable thermal behaviour. Also, auto-hydrolysis was applied to the liquid resulting from the separation of the lignin, and thus obtaining simple hemicellulosic sugars.
Steps to the future
The process of refining at a bio-refinery is a complex one. On the one hand, as a first step, Ms Gonzlez proposed the application of methods tested in her thesis to the paper and pulp industry, given that this uses biomass. On the other, she committed to integrated bio-refinery, i.e. she believes that one single bio-refinery should produce various types of products and energy and, to this end, it will need to integrate a variety of processes for the transformation of biomass.
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