Biomass carbonization – a way to increase land fertility
An increasing number of people and entrepreneurs have already thought about and will continue to resolve the issue of restoring the ecological situation not only in a particular region, but completely throughout the world. Over the past decades, somewhere because of the unwillingness to delve into the essence of the interconnection of all natural processes, and somewhere short-sighted activities and the desire to get quick profits, without thinking about the consequences in the future, have led to a deterioration of the environmental situation around the world.
At the moment, huge tracts of agricultural land due to improper crop rotation, oversaturation with chemical fertilizers, pollution of ecosystems with waste, lack of a safe approach to waste disposal, not always favorable weather conditions are completely depleted and are capable of producing a scanty harvest compared to previous years. In addition, most of the world’s soils are not black earth. The issue of healthy eating with ecologically pure products always remains a priority for the survival of mankind and its health, full life and high working capacity.
Therefore, biochar has recently attracted the interest of scientists around the world due to its potential to improve soil fertility and carbon sequestration, and its production is an excellent opportunity for recycling biomass waste. Read our previous article on this topic – “Why Microsoft and Shopify are betting on biochar”
The use of biochar is not a new concept, its use dates back to centuries when it was used to improve the soils of the Amazon, which have retained their fertility to this day. Nowadays, the practice in forestry has been preserved since those times of artificial tanning of certain areas of forest land for obtaining natural fertilization.
At its core, biochar is the same charcoal obtained in the process of biomass pyrolysis and rich in carbon. Pyrolysis is a thermochemical transformation process in which biomass is heated at a high temperature (usually 450-750 ° C) in the absence of oxygen to produce energy products, one of which is biochar (the others are bio oil and synthesis gas). Biochar retains the original structure of the raw material, but has increased porosity. In other words, biochar is the same activated carbon, which is used not only to improve soil fertility, but also to purify water, store energy, reduce emissions of heavy metals, bedding for animals, etc. studying a wide range of biochar applications.
For the manufacture of biochar, or in other words – charcoal, special carbonization devices, charcoal kilns are needed. The process begins with the preparation of raw materials, cleaning them from mechanical impurities (sand, stones, etc.) and chemical, toxic substances (according to the standards of world communities, biochar is considered to be a product that is made from raw materials without toxic impurities). If necessary, the raw material is crushed and then sent along a conveyor to the hopper, from which it enters the carbonization chamber, in which an exothermic reaction occurs at high temperatures, i.e. with the release of thermal energy. This energy can be directed to the preliminary drying of raw materials or to production needs, heating the premises.
The entire carbonization process consists of the following processes: combustion, carbonation and cooling. In turn, the carbonization process has the following stages:
Drying stage: the temperature reaches 160 ° C, the moisture content of the biomass is reduced by evaporation of moisture, no chemical changes occur at this stage.
Initial carbonization: temperature increases to 160-280 ° C. Biomass decomposes, its chemical structure begins to change.
Carbonization: the temperature reaches 300-650 ° C, the biomass decomposes, a large amount of liquid is released, in particular acetic acid, methanol, wood resins, which are processed in a furnace without entering the environment due to the special design of the equipment. In addition, combustible gas (methane, ethane) is also generated in the firebox. Biomass becomes charcoal. 90-99% of carbon passes into a liquid suspension in the form of porous coal grains (C6H2O) with a pore size of 8 to 20 nm. Thus, thanks to the carbonization process, a unique porous product is obtained with an internal pore area of about several football stadiums. Such a structure of the obtained biochar explains its capabilities as a filtering agent, retaining microorganisms and chemical substances inside, and a binding product.
Almost all of the carbon from organic biomass is converted to biochar. The carbonization process in GreenPower charcoal kilns makes it possible to control the non-volatile carbon content in biochar from 70 to 94%.
Raw materials that have passed the stage of carbonization through the channels for raw materials goes further into the stabilization hopper and through the screw conveyor is fed to the unloading.
After cooling and screening for at the exit, fine-grained coal is also formed, which can be pressed into pellets or briquettes for barbecue using the Briquetting Line.
Various products are obtained during the carbonization of biomass. Temperature is the most important indicator in this process. Heating leads to the disintegration of complex biomolecules, as a result of which new substances are formed: various gases and solid fuels. If the temperature exceeds 400 ° C, then the solid fraction is charcoal, which is almost 100% carbon. And if the temperature is in the range of 200-300 ° C, then the solid fraction is a heat-treated mass, and the process itself is called “torrefaction”, read our next article on this topic.
The gaseous products formed during carbonization can be partially condensed into liquid pyrolysis oil, which is used in further production or can become a transport fuel. Non-condensable gases contain mainly carbon dioxide, carbon monoxide, methane, hydrogen. These gases and pyrolysis oil can be used as fuel.
The high temperature also increases the calorific value of the fuel. The calorific value of charcoal may even exceed the calorific value of coal, since charcoal contains less ash. The calorific value of heat-treated wood (torrificate) is, as a rule, slightly higher than that of untreated wood, since the moisture content is much lower compared to the raw material, which increases the energy density.
As a raw material for the production of biochar, various organic biomass can be used: agricultural waste, including corn, rice husks, etc., shells of various nuts and seeds of fruit trees, firewood, waste from logging, wood processing and paper production,
So pyrolysis may be the most economical way to generate electricity from biomaterial.
Benefits of biochar.
Biochar is used in agriculture to increase the fertility of dry, depleted soils containing a small amount of humus. The porosity of biochar contributes to a significantly better retention of nutrients and water in the soil. Numerous field experiments and trials have confirmed its effectiveness in stimulating the growth of agricultural crops even with little watering, which is especially important in arid regions and with a changing climate. Also, it is the porous structure of biochar that improves soil biology and its fertility, retaining nutrients for a long time and preventing them from washing out, which makes it possible to reduce the amount of fertilizers applied to the soil. In addition, biochar binds CO2 in the soil for a long time and thereby reduces greenhouse gas emissions into the atmosphere. Biochar contains no toxic substances and heavy metals.
The main properties of biochar:
- In recent years, more and more attention is paid to biochar, as it is a promising fertilizer that can stop the process of soil degradation and prevent a number of global economic and environmental problems.
- Thanks to the active ions contained in biochar-fertilizers, carbon does not evaporate into the environment, but remains in the soil for a long time, easily absorbed by the roots of plants. Thus, the amount of greenhouse gases in the atmosphere decreases, and at the same time, the threat of the greenhouse effect and global warming decreases.
- Improving the fertility of soils with high yields in the near future will provide a solution to the problem of hunger in developing countries, with the subsequent formation of their economies.
- The use of an environmentally friendly means for soil restoration contributes to the removal from the soil of aggressive chemicals that were previously introduced (herbicides, pesticides, other pesticides), which affect not only the earth, but also threaten human health.
- The porosity of biochar ensures the retention of nutrients and moisture in the soil, which are transport routes for mycorrhiza, i.e. mycelium, which increases productivity, provides oxygen access to plant roots and air circulation.
- Improves the composition of infertile soils (alumina, sandy loam and sandy soils).
- Retains and maintains nutrients and essential trace elements in the soil, eliminates the problem of their leaching.
These specific characteristics determine the variety of ways to use biochar. Its use in the agricultural industry is gaining new momentum every year. More and more agricultural entrepreneurs are turning their attention to soil restoration, looking for safe solutions to increase yields.
The biochar market has experienced significant growth due to factors such as the wider use of biochar in power generation, agriculture, forestry and others. The growing demand for various products in organic farming is one of the main factors influencing the growth of the biochar market. It is also expected that the growing use of biochar in water treatment will be another important growth driver driven by demand for wastewater treatment plants around the world.