Energy

Thermochemical processes

Combustion is the oldest method of obtaining energy from biomass. The old hearths, fireplaces and stoves, have been substituted today by modern and efficient boilers that manage to harness the energy hidden in wood and its derivatives better. If fungi and bacteria prefer damp and proteinic substances, fire feeds better on dry materials that are rich in cellulose. Cellulose is a very resistant, complex molecule made up of long chains of glucose, the most simple sugar. Plants are made up of cellulose, therefore so are wood, leaves, paper and cotton. The various systems to obtain energy from wood can be classified according to the temperature at which combustion occurs and the type of physical and chemical transformation that is obtained. Firstly, it must be said that these systems work with triturated timber. The wood flakes, called chips, can be used as they are or else compressed and compacted into small blocks called pellets. These small wood bricks increase the efficiency of the boilers and make them cleaner. Wood, thus transformed, can be burnt at very high temperatures (around 1000°C) until it is reduced to a mixture of gases, that are instrumental to move turbines and produce electric energy. Burnt at lower temperatures (between 400 and 800°C) wood breaks up into gaseous, liquid and solid substances. The solid component, carbon, can be used again as a combustible, while the liquid part, pyrolytic oil, can power motors or be used as the base for the synthesis of other products.