I have been working in biofuel research, specializing myself on the concept of biorefinery. I have worked mostly with sugar cane, coffee, orange peel and tree pruning residues and also, with microalgaes. As a result, we don´t only work with biofuels but also with white protein, nanocellulose, and bioplastics, and other residues to value them in PAI+ and GRUBIOC research groups of Autonoma de Occidente University. In this moment, in one of the projects we are working with Entorno Foundation. They have a pilot plant to obtain bioethanol of coffee mucilage with a capacity of 35.000 L/week in batch process. They use this as raw material because these residues are highly polluting for, as approximately one litter of mucilage pollutes 3000 to 5000 L of water. Thus, in the specific case of Colombia they contribute with 12% of DBO5 and 9% of TSS of the overall pollutant load that reaches the Cauca river. But the problem is the low content of soluble sugars, which is why we need to increase it from hydrolysis of insoluble carbohydrates as cellulose and hemicellulose by green technology. Which is a topic that has been little studied. Similar situation concerning the environmental and social impacts we have with sugar cane residues (tops and leaves). For this reason, with the BRISK 2 program in the LNEG (National Laboratory of Energy and Geology, Lisbon, Portugal) and during my visit I found divers tools with the use of Liquids Ionics to rise the content of soluble sugars in the mucilage, and to eliminate the lignin in sugar cane residues. With these objectives in mind I realized the following activities:

  • Sugarcane residues (tops and leaves) were grounded until size particle was less than 0.5 mm with a knife mill
  • Then, the moisture content was determined in coffee and sugarcane residues by drying of this material overnight at 105°C
  • Also, acid chemical hydrolysis in dry sugarcane residues and mucilage coffee was made to
    determine in each one their cellulose, hemicellulose, lignin and ash composition.
  •  My main work was to know the application of Ionic Liquids (IL) in the fractionation (cellulose, hemicellulose, and lignin) and deslignification of sugar cane and mucilage residues. For this purpose, 1-ethyl-3methylimidazolium acetate of Io-li-tec® was used. The complete digestion of biomass was realized at 140°C, for two hours and with 1/20 (S/L) ratio phases. After this time the precipitation of cellulose was begun with 40 mL of NaOH 0.75M and under vigorous agitation for one hour. Later, this solution was vacuum filtrated to separate cellulose of the solution that contained dissolved hemicellulose and lignin. The
    cellulose was washed with plenty of water until getting pH of 7 and dried overnight at 45°C and weighted after. At the same time, this cellulose was chemical and enzymatically hydrolysated to know its purity. The sugars were quantified by HPLC. The supernatant was concentrated by rotaevaporation until 30 mL of volume and then was adjusted the pH to 6,7 with HCL 4M. Ethanol 96% (v/v) was added to this concentrated solution by a factor of three (90 mL) and after it was vigorously mixed thirty minutes. The hemicellulose that precipitated in this step was vacuum filtrated and washed first with 100 mL of ethanol and then with water alone to eliminate salts. This solid was dried overnight at 45°C. To precipitate lignin of residual supernatant, all the ethanol was eliminated by vacuumn evaporation at 40°C and 100 mbar of pressure. Then the pH was reduced to 2 with HCl 4M and the solution was heated for 30 min at 70°C. The lignin was separated by vacuum filtration immediately and washed with acidulate water at pH 2.0 and dried overnight at 45°C. All this procedure was realized by triplicate.
  • Likewise, the cellulose was concentrated with other IL, the imidazole, in sugarcane residues. In this case, at 5 g of dry biomass, imidazole was added at 1/9 (w/w) ratio. The solid mix reacted at 160°C by two hours. After this time was aggregated 90 mL of water and it was
    mixed with all of the biomass at room temperature by one hour. The precipitated solid basically composed for cellulose and lignin, was vacuum filtrated and washed with 135 mL of ethanol 96% to solubilize the imidazole. It was dried at 45°C by 24 hours and its composition was determined by acid chemical hydrolysis. The hemicellulose and lignin of the supernatant was precipitate of the similar form that was explained in numeral four.
  • For the mucilage of coffee, a liquid hydrolysis was done with 1-ethyl-3 methylimidazolium hydrogen sulphate al 99% of Io-li-tec® as ionic liquid. For this, to 4 grams of wet biomass of coffee mucilage, it was added 1,543 g of LI corresponding to 30% of its weight and they were reacted for one and a half hour at 140 ° C. After that, the solution was filtered, and a sample was taken from the supernatant to be analysed by HPLC. The solid corresponding to cellulose and lignin was washed with 100mL of water and dried at 45 ° C overnight.

My stay in the LNEG was very gratifying and I learned new processes with very promising preliminary results. A good chemical characterization of sugarcane and coffee residues was made. Likewise, a good separation of the components of the cell walls of the residues with the IL was achieved and a small work plan was made to continue with the researches in Colombia and with the collaboration of the hosting institution.

For these reasons I would like to thank BRISK 2 for the excellent opportunity they gave me to learn about new green techniques to treat lignocellulosic biomasses under the concept of biorefinery. I also appreciate all the collaboration of Doctor Rafal Lukasik, his kindness to receive me and give me all the scientific support and resources so that my stay would be very productive. Also to all his staff, specially to Johana Bernardo and Pedro for their patience and teachings, as well as Belina Ribeiro for her support in the HPLC analysis and Maria do Céu Penedo for her assistance in the laboratory. Thanks also to all my colleagues in K2 LNEG laboratories.