Make your home more ECO

Guest blog by Josef Bares, MTK311 HT19

When I was a child I was always very enthusiastic about ecology and saving our environment, because I grew up in the small village and nature was inherent part of my life since today. Trash sorting, saving water during taking a bath, buying food without plastic packages, planting trees – it could be the way. But when it comes to green energy topic, I wanted to make a smart choice to be self-sufficient and environmental friendly. For those who are interested in “green way” energies and modern possibilities how to make their home more eco, I have few ideas.
In case you come from a village, you are a farmer for a living and grow cereal crops and own forests, nothing is less difficult than make your own pellets or briquettes. It is advantageous in many ways. You can use residues from agricultural crops and sawdust after wood processing, you can use it for gasification or direct combustion and in many countries are pelletizers and biomass boilers supported by government subsidies.
Pellets can be made of many various materials. In home-made conditions we often use agricultural crop residues or wood. It is very firm, natural fuel in cylindrical shape with diameter 16-25 mm and maximum length to 50 mm. Calorific values are moving between 16-18,5 MJ/kg and ash content 0,2- 1,1% for clear wood, 0,7-3% with bark and 3-8% for cereal residues. The water content of biomass should be always less than 13%, otherwise pellets will disintegrate. [1], [2]

Figure 1 Samples of pellets [1]
left – wood without bark, right – rape

Whole process to make pellets out of biomass names pelletization. For pellet production it is very important to have quality homogenous mixture of biomass. Preparation process starts on the field where in case of cereal residues crops are cutted, collected and dried. We cut biomass to optimal size of segments 4 mm, then it is dried on the air or in special drying rooms (this step is the most energy demanding). Final part of preparation is grinding, where we grind biomass to smaller pieces, even to dust. [1]
Next step of pelletization is compaction. Compaction happens in mixing chamber in purpose to get maximally homogenous mixture. When it reaches granulation press, mixture is pressed through the mould at high pressure and temperatus, which makes pellets firm and shiny. It is made more pellets at one time and in case of wood lignin or resin contributes to firmness of one’s piece. [1], [3]

Figure 2 DEMATECH MGL 400 [3]
1 – storage tank, 2 – mixing chamber, 3 – granulation press, 4 – sorter and cooler, 5 – conveyor belt

During granulation temperature hits 120-140 degrees C, therefore we need to cool them, otherwise they would disintegrate or break. After that we pack them into bags, containers or use them in home boilers.
Due to increasing demand for pellets in the world (22,3 million tonnes in 2016 and 9,5% consumption increased from 2015 to 2016 [4]), lower GDP taxes for wooden pellets, prices around 220 EUR/tonne [1], positive influence in the way of combustion and heating, I decided to share this idea with you my friends. Let the pellets be with you.

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