What is Biochar
Biochar – that black charcoal like substance discussed so often in recent days for its miraculous effects on soil and compost - is good for more than just your garden. One of the key materials for a sustainable future of the planet, biochar has many other uses that can be integrated into new organic systems for farming, building, clothing, electronics and a whole range of consumer products. Biochar can initiate multiple cascades to optimise and recycle current material, nutrient and energy flows.
It turns out that the stable carbon matrix that biochar is made of has all kinds of interesting properties. This carbon matrix can hold on to things – water, air, metals and organic chemicals. And it also has unique thermal and electrical properties that are still being explored. Finally, the highly porous physical structure of biochar provides habitat for microorganisms. With so many different properties, biochar is bound to have a lot of different uses, but one function that all biochar applications (other than burning it for fuel) share is carbon sequestration. By fixing easily degradable plant carbon into long-lasting charcoal, carbon dioxide is slowly but surely removed from the atmosphere. The biggest drawback to the application of biochar in soil is the cost. Making biochar is either a highly elaborate and capital-intensive technical process or a low-tech, slow and labour-intensive process; both paths are rather expensive. At current prices of $1000 a ton, the $5,000 to amend an acre of cropland with 5 tons of biochar would in most cases exceed the return from that acre. Does it really make sense to work biochar into fields? These economic considerations are not so different from what the natives in the Amazon had to face when they used biochar to improve their soils, and where you will still find plenty of places with over 40 tons of biochar buried into just one acre of soil. Even if no money existed back in those days, it would have made no economic sense to cut down some 80 huge rainforest trees and then use ancient charcoal kilns to make some 40 tons of biochar – just to bury the biochar into one acre of soil. And don’t forget: all this would have been done without any chainsaws or axes and no animals to pull the logs close to the field
The idea of applying dozens of tons of biochar to fields can only come from scholars who, on the basis of the Terra Preta example, have arrived at a false conclusion completely without any practical relevance – i.e. the massive one-time application of biochar. Example of Terra Preta Cultures. The char used back then was probably created in the typical hearths of the natives, in which not just ash but also relatively large amounts of charcoal were produced at relatively low heat. This char, basically a waste product, was then apparently used as a way of preventing infectious diseases. This was done by regularly adding char to faeces and kitchen waste in the large jungle settlements, thus sterilising them. It helps to understand that the indigenous settlements were concentrated along the river branches on high bluffs safe from flooding. That is where the people lived, in densely populated villages, and where most of the Terra Preta is found. Once the organic waste had been stabilised through composting or fermenting it with added char, people discovered that it was an excellent substrate for growing food plants. These methods led to the char being loaded with nutrients and its surfaces achieving greater binding capability through oxidisation, with the consequence that, once worked into the soil, the char was able to fully unfold its function as a nutrient store and humus stabiliser (through the creation of char-clay-humus complexes).
According to investigations carried out by Bruno Glaser and colleagues, the amount of phosphorus in Terra Preta soils compared to natural soils in the immediate vicinity can be up to 500 times higher. Unlike carbon and nitrogen, phosphorus cannot accumulate in the soil through plant growth, but must be added through amendments of excrement, bones and ash. A rough estimate shows that the char-stabilised organic waste of some 500 people must have been worked into every hectare of soil over a period of 1000 years to gain such nutrient content. Accumulating 100 tons of biochar not only took centuries; it also required a “stacking functions” approach.The many uses of biochar. Biochar is much too valuable for it to be just added to soil without using it at least once for other beneficial purposes. Basic uses include: drinking water filtration, sanitation of human and kitchen wastes, and as a composting agent. All of these uses have been documented in many different pre-industrial cultures. In the modern world, the uses multiply: adsorber in functional clothing, insulation in the building industry, as carbon electrodes in super-capacitors for energy storage, food packaging, waste water treatment, air cleaning, silage agent or feed supplement. All those uses could be part of more complex cascades when, after extended up- and down-cycling, biochar can be used in a farmer’s manure slurry pit or in a sewage treatment plant, before being composted and thus finally becoming a soil amendment. Biochar should only be worked into the soil at the end of such “cascades,” keeping in mind that some biochar uses – for cleaning up metal or chemical contamination – would render the biochar unsuitable for agricultural soils and need different recycling pathways.The following list of 55 possible uses of biochar is by no means complete. In fact, it has only just been started. We will initially just comment shortly on a few applications in this list. The Biochar Journal (formerly known as Ithaka Journal) is publishing a series of in-depth articles on many of these uses, highlighting in particular the cascading benefits of biochar in agriculture and livestock farming. Biochar is without doubt one of this century’s most exciting new fields of research, with findings and their practical implementation increasing exponentially from year to year. Nevertheless, however much we enthuse over our field of research and the importance of our findings, it’s the real world that decides about its success.
The cascaded use of biochar in animal farming1. Silage agent, 2. Feed additive/supplement, 3. Litter additive, 4. Slurry treatment, 5. Manure composting, 6. Water treatment in fish farming. At present, some 90% of the biochar used in Europe goes into animal farming. Unlike 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 diarrhea 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 diarrhea. 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. Visit the Ithaka Journal online (http://www.ithaka-journal.net) for in-depth articles on the use of biochar in cattle and poultry farming, as well as many of the other uses described below. Use as a soil conditioner7. Carbon fertilizer, 8. Compost additive, 9. Substitute for peat in potting soil, 10. Plant protection, 11. Compensatory fertilizer for trace elementsIn 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, you 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 it’s surfaces.
The thermal process that produces biochar is called pyrolysis (from the Greek, “pyro,” meaning fire and lysis,” meaning separation). During pyrolysis, the crucial trace elements found in plants (over 50 metals) become part of the carbon structure, thereby preventing them from being leached out while making them available to plants via root exudates and microbial symbiosis. This feature can be used specifically when certain trace elements are missing in a certain regional soil or in soil-free intensive cultures such as “Dutch tomatoes”.
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 defense 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. Use in the building sector12. Insulation, 13. Air decontamination, 14. Decontamination of earth foundations, 15. Humidity regulation, 16. Protection against electromagnetic radiation (“electrosmog”)Two of biochar’s properties 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 mold developing. You can read about 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.Decontamination17. Soil additive for soil remediation – for use in particular on former mine-works, military bases and landfill sites).18. Soil substrates – Highly adsorbing, plantable soil substrates for use in cleaning wastewater; in particular urban wastewater contaminated by heavy metals.19. A barrier preventing pesticides getting into surface water – berms around fields and ponds can be equipped with 30-50 cm deep barriers made of biochar for filtering out pesticides.20. Treating pond and lake water – biochar is good for adsorbing pesticides and fertilizers, as well as for improving water aeration.
