Biochar is a carbon-rich, fine-grained residue which can be produced either by ancient techniques (such as covering burning biomass with soil and allowing it to smoulder) or state-of-the-art modern biomass pyrolysis processes. Combustion and decomposition of woody biomass and agricultural residues results in the emission of a large amount of carbon dioxide. Biochar can store this CO2 in the soil leading to reduction in GHGs emission and enhancement of soil fertility. Biochar holds the promise to tackle chronic human development issues like hunger and food insecurity, low agricultural productivity and soil depletion, deforestation and biodiversity loss, energy poverty, water pollution, air pollution and climate change. Let us have a close look at some of the most promising applications of biochar.
Use of biochar in animal farming
At present approx. 90% of the biochar used in Europe goes into animal farming. Different to its application to fields, a farmer will notice its effects within a few days. Whether used in feeding, litter or in slurry treatment, a farmer will quickly notice less smell. Used as a feed supplement, the incidence of diarrhoea rapidly decreases, feed intake is improved, allergies disappear, and the animals become calmer.
In Germany, researchers conducted a controlled experiment in a dairy that was experiencing a number of common health problems: reduced performance, movement disorder, fertility disorders, inflammation of the urinary bladder, viscous salivas, and diarrhoea. Animals were fed different combinations of charcoal, sauerkraut juice or humic acids over periods of 4 to 6 weeks.
Experimenters found that oral application of charcoal (from 200 to 400 g/day), sauerkraut juice and humic acids influenced the antibody levels to C. botulinum, indicating reduced gastrointestinal neurotoxin burden. They found that when the feed supplements were ended, antibody levels increased, indicating that regular feeding of charcoal and other supplements had a tonic effect on cow health.
Biochar as soil conditioner
In certain poor soils (mainly in the tropics), positive effects on soil fertility were seen when applying untreated biochar. These include the higher capacity of the soil to store water, aeration of the soil and the release of nutrients through raising the soil’s pH-value. In temperate climates, soils tend to have humus content of over 1.5%, meaning that such effects only play a secondary role.
Indeed, fresh biochar may adsorb nutrients in the soil, causing at least in the short and medium term – a negative effect on plant growth. These are the reasons why in temperate climates biochar should only be used when first loaded with nutrients and when the char surfaces have been activated through microbial oxidation.
The best method of loading nutrients is to co-compost the char. This involves adding 10–30% biochar (by volume) to the biomass to be composted. Co-composting improves both the biochar and the compost. The resulting compost can be used as a highly efficient substitute for peat in potting soil, greenhouses, nurseries and other special cultures.
Because biochar serves as a carrier for plant nutrients, it can produce organic carbon-based fertilizers by mixing biochar with such organic waste as wool, molasses, ash, slurry and pomace. These are at least as efficient as conventional fertilizers, and have the advantage of not having the well-known adverse effects on the ecosystem. Such fertilizers prevent the leaching of nutrients, a negative aspect of conventional fertilizers. The nutrients are available as and when the plants need them. Through the stimulation of microbial symbiosis, the plant takes up the nutrients stored in the porous carbon structure and on its surfaces.
A range of organic chemicals are produced during pyrolysis. Some of these remain stuck to the pores and surfaces of the biochar and may have a role in stimulating a plant’s internal immune system, thereby increasing its resistance to pathogens. The effect on plant defence mechanisms was mainly observed when using low temperature biochars (pyrolysed at 350° to 450°C). This potential use is, however, only just now being developed and still requires a lot of research effort.
Biochar as construction material
The two interesting properties of biochar are its extremely low thermal conductivity and its ability to absorb water up to 6 times its weight. These properties mean that biochar is just the right material for insulating buildings and regulating humidity. In combination with clay, but also with lime and cement mortar, biochar can be added to clay at a ratio of up to 50% and replace sand in lime and cement mortars. This creates indoor plasters with excellent insulation and breathing properties, able to maintain humidity levels in a room at 45–70% in both summer and winter. This in turn prevents not just dry air, which can lead to respiratory disorders and allergies, but also dampness and air condensing on the walls, which can lead to mould developing.
As per study by the Ithaka Institute’s biochar-plaster wine cellar and seminar rooms in the Ithaka Journal. Such biochar-mud plaster adsorbs smells and toxins, a property not just benefiting smokers. Biochar-mud plasters can improve working conditions in libraries, schools, warehouses, factories and agricultural buildings.
Biochar is an efficient adsorber of electromagnetic radiation, meaning that biochar-mud plaster can prevent “electrosmog”. Biochar can also be applied to the outside walls of a building by jet-spray technique mixing it with lime. Applied at thicknesses of up to 20 cm, it is a substitute for Styrofoam insulation. Houses insulated this way become carbon sinks, while at the same time having a more healthy indoor climate. Should such a house be demolished at a later date, the biochar-mud or biochar-lime plaster can be recycled as a valuable compost additive.
Biochar as decontaminant
As a soil additive for soil remediation – for use in particular on former mine-works, military bases and landfill sites.
Soil substrates – Highly adsorbing and effective for plantation soil substrates for use in cleaning wastewater; in particular urban wastewater contaminated by heavy metals.
A barrier preventing pesticides getting into surface water – berms around fields and ponds can be equipped with 30-50 cm deep barriers made of bio-char for filtering out pesticides.
Treating pond and lake water – bio-char is good for adsorbing pesticides and fertilizers, as well as for improving water aeration.
Use of biochar in wastewater treatment – Our Project
The biochar grounded to a particle size of less than 1.5 mm and surface area of 600 – 1000 m2/g. The figure below is the basic representation of production of bio-char for wastewater treatment.
We conducted a study for municipal wastewater which was obtained from a local municipal treatment plant. The municipal wastewater was tested for its physicochemical parameters including pH, chemical oxygen demand (COD), total suspended solids (TSS), total phosphates (TP) and total Kjeldahl nitrogen (TKN) using the APHA (2005) standard methods.
Bio filtration of the municipal wastewater with biochar acting as the bio adsorbent was allowed to take place over a 5 day period noting the changes in the wastewater parameters. The municipal wastewater and the treated effluent physicochemical.
The COD concentration in the municipal wastewater decreased by 90% upon treatment with bio-char. The decrease in the COD was attributed to the enhanced removal of bio contaminants as they were passed through the bio char due to the bio char’s adsorption properties as well as the high surface area of the bio char. An 89% reduction in the TSS was observed as the bio filtration process with bio char increased from one day to five days
The TKN concentration in the wastewater decreased by 64% upon treatment with bio char as a bio filter. The TP in the wastewater decreased by 78% as the bio filtration time with bio char increase. The wastewater pH changed from being alkaline to neutral during the treatment with bio char over the 5 day period
Use in Textiles
In Japan and China bamboo-based bio-chars are already being woven into textiles to gain better thermal and breathing properties and to reduce the development of odours through sweat. The same aim is pursued through the inclusion of bio-char in shoe soles and socks.
Pyrolysis is the thermal decomposition of biomass occurring in the absence of oxygen. It is the fundamental chemical reaction that is the precursor of both the combustion and gasification processes and occurs naturally in the first two seconds. The products of biomass pyrolysis include biochar, bio-oil and gases including methane, hydrogen, carbon monoxide, and carbon dioxide.
