13th May

Fuel Cells

The first meeting is with Rubén Camargo about fuel cells. The university started to look at fuel cells for possible environmental developments, but they are now also applied in the medical field.

A fuel cell is composed by two solutions, one anodic, the other one cathodic, separated by a membrane. It works exactly like a normal battery, but the cathode is fed by the oxygen, and the anode by the fuel. The fuel used to be hydrogen, but the hydrogen being a very little dense gas at normal temperature, it is not easy to bring it to the anode. So the investigations are now about ethanol as fuel, since it is liquid and much easier to carry. It does not even imply to change the materials: the same polymere electrolyte membrane is used. Other universities in Colombia are also working on this concept, in Medellín, Bucaramanga, and Bogotá.

In fact, ethanol can also be burnt, to produce heat, which can be transformed into electricity. The efficiency of the burning the ethanol cannot be higher than 40% (due to the limit of the Carnot cycle), and with the best real reactor, it reaches 32%. On the contrary, using the ethanol in a fuel cell has a theoric efficiency of 90%, and in practise, values of more than 50% can be reached.

A fuel cell is very small: it is a few millimetres thick, and for one square centimetre of cell, the voltage produced is of 0.6V, and the current of microamperes. It is not much, but you can add these cells in serie and in parallel, in order to obtain usual values of tension and intensity. As the cells do not heat, there is no risk of such stacking.

Paper making

Our second meeting is with the professor Jorge Borrero. He used to teach biology many years ago, then he worked in two industrial plants, one of them producing sugar, and then a paper mill. Afterwards, he entered the Universidad del Valle, where he completed his master in Chemical Engineering, and currently he is making his doctorate. Now, he is working in a revolutionary process of fabricating paper. Let’s start with a few generalities about this industry:

The paper is produced from the wood. The tree wood is mainly composed of fibres, cellulose and hemicellulose, united together by the matrix, called lignin. To make paper, one needs to dissolve this lignin and remove it, because it gives a dark colour to the paper, then the fibres are brought to a paper making machine where they are organised in a direction, thus forming paper. One of the most used process in the world in the Kraft cooking, which consists in the dissolution with sodium hydroxide (NaOH) and sodium sulphite.

Every year, in the world, 1.6 billions of tons of wood are cut to produce 356 million tons of paper. The most commonly used trees for the paper industry in Colombia are the eucalyptus and the pine tree, since these trees grow very fast under the tropics (7 and 15 years respectively). They possess a big trunk, few branches of small size. One of the problems of these plantations is that the trees do not allow other vegetal species to grow under, due to the distance between each tree, related to the light availability under. In the plantations where the trees are very close one to the other, and form a roof, not enough light reaches the ground and so nearly nothing can grow, because without light, a plant cannot grow.

Another important effect observed by the Colombian Society of Ecology, the eucalyptus extract iron and aluminium salts from the soil, salts that come back to the soil when the trees are decomposed by micro-organisms. As a consequence, the soil becomes more acid. A proof that the lack of light is not the single cause for the fact that nothing grows below pine trees and eucalyptus: no seeds germinate below these trees although they do not need light to do so.

Therefore, it is like a monoculture, which absorbs everything from the soil very fast, and does not prevent the erosion (with the few branches and leaves, there is nothing to protect the ground from the raindrops). Thus, even with trees being replaced, the paper industry is already not sustainable.

The idea of Jorge has been to replace the trees with the residues of the most cultivated crops in Colombia: banana, rice, palm oil tree, sugar cane ! It is estimated that, considering only in sugar cane, at least 250 000 hectares are planted in the department of Valle del Cauca, and similar or even greater surfaces are used for other products like the banana (in the Uraba region, in Antioquia department), the rice (Huila department, !). It is reckoned that at least some 350 000 hectares are used in the rest of the country by the panalera industry (the sugar from the sugar cane, is lightly processed to obtain a sugar loaf, which can be dissolved in water to make agua panela, or used to cook).

For each hectare harvested, the residues are produced in high quantity, reaching 40 to 60 tons per hectare. Just imagine the quantity of raw material we have here! In addition, most of the residues are currently burnt directly in open air in situ, despite the interdiction set by the authorities (because it generates pollution), or they are left on the floor, to get buried, so that this material is reincorporated in the soil, thanks to the action of the microbiology (it is an anaerobic process generating methane, a greenhouse gas 21 times more powerful than CO2).

The residues to be used are triturated, and the tips are removed (because they absorb too much chemicals and don’t produce paper).

The process is the following one: the residues are removed from the crop, then they are placed into a reactor, which contains a mixture of solvents and Moore salt in good proportions. The Moore salt is a component rich in micronutrients, that is to say, it can be used eventually as a fertilizer.

The big difference is that the crops residues only need some 20 minutes inside the reactor (meaning a reduction of the energy needs). At the end of the digestion, the products inside the reactor are pasta of fibres, which will be used for the paper, and a mixture generally called black liquor, composed of dissolved lignin, Moore salt and the solvents. This liquor can be used as fuel thanks to its high calorific power, and the final ashes can serve as fertilizer thanks to the characteristics of their components.

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The quality of the paper achieved with this process is the same as the paper coming from “normal” trees. Jorge already has his process patented in Colombia via PTC, and he is in negotiations in USA and Brazil to protect his invention. And despite the deliberate lack of advertisement, Jorge is often contacted by paper industry companies in order to work exclusively with them. He has rapprochements with some multinationals, with whom he has reach important agreements, which is necessary due to the high costs of the investigation.

It is estimated that this process, with the availability of the raw material, the low price of this raw material, the short reaction time and the need of less water and chemicals, will reduce drastically the production cost of the paper (by 37%). As a conclusion, Jorge is happy that with this invention, independently of the economic aspects, he will bring his contribution to the protection of the planet, since the trees are among the most essential treasures of our Earth.