Sunday, November 24, 2013

Characteristics of biochar: biological properties

Biochar as a habitat for soil microorganisms

     The pore space of pyrolyzed biomass increases during charring by several thousand folds and is related to charring temperature and feedstock materials. 

     Figure 1. Biochars derived from corncobs (Zea mays L.) produced at incremental pyrolysis temperatures (350–650°C in 100°C intervals) were characterized using elemental analysis, specific surface area, scanning electron microscopy, x-ray diffractometry, and Fourier-transform infrared spectra to estimate the relationship between the physical and chemical properties of biochars and the treatment temperature. Generally, carbonization, aromatization, and specific surface area increased with the elevation of temperatures. 

      Estimates of the resulting surface area of different biochars range from 10 to several hundred square meters per gram (m2 - g–1), which provides a significantly increased surface area for microbial colonization .

Root-biochar-bacteria interaction: 3D projection

Source: Property of Robert Cirino. Bioimaging Center, Delaware Biotechnology Institute, University of Delaware. Using a Zeiss 5LIVE microscope, a 3D projection of a lettuce root (blue), fungal hyphae(blue), and bacteria (green) colonization is visualized. Dyes: Syto 13, Calcofluor white.

     The porous structure of biochar, its high internal surface area and its ability to adsorb soluble organic matter, gases and inorganic nutrients  are likely to provide a highly suitable habitat for microbes to colonize, grow and reproduce, particularly for bacteria, actinomycetes and arbuscular mycorrhizal fungi. Some members of these groups may preferentially colonize biochar surfaces depending upon the physical and chemical characteristics of different biochars.(Figure 2)

Figure 2. The porous structure of biochar invites microbial colonization. Source: (left photo) S. Joseph; (right photo) Yamamoto, in Lehmann and Joseph (2009).

     Depending upon the size of a given pore, different microbes will or will not have access to internal spaces. Several authors have suggested that the biochar pores may act as a refuge site or microhabitat for colonizing microbes, where they are protected from being grazed upon by their natural predators (Saito and Muramoto, 2002; Warnock et al., 2007) or where microbes that are less competitive in the soil environment can become established (Ogawa, 1994).

     The above graphic shows the basic process of how Biochar becomes a safe habitat for micro-organisms and storage of nutrients and moisture, the symbiotic relationship between plants, fungus and micro-organisms, how plants feed this micro-life carbohydrates in return for moisture and nutrients.

1. Biochar applied around a trees root zone or drip line.
2. Plant roots (white) linking up with common stringy soil fungus (pink). The plant carbohydrates produced from photosynthesis are shared with the fungus in return for nutrients and moisture.
3. Fungus linking up with Biochar full of moisture, nutrients and micro-organisms
4. Micro-organisms embedded into the porous structure of Biochar share nutrients with fungus in return for plant produced carbohydrates.

     The pore size variation observed across biochar particles from different feedstocks and pyrolysis conditions is such that the microflora could, indeed, colonize and be protected from grazing, especially in the smaller pores (see Table 1).

Table 1.  Pore diameters in wood and bamboo biochar compared to the ranges in the diameter of various soil microorganisms

     The high porosity of biochar may also allow it to retain more moisture. Pietikäinen et al. (2000) reported that two biochars, one prepared from humus and one from wood, had a higher water-holding capacity (WHC) (2.9mL g–1 dry matter) than activated carbon (1.5mL g–1 dry matter) or pumice (1.0mL g–1 dry matter). An increase in the WHC of biochar may result in an overall increase in the WHC of the soils to which it is added.

     For biochars with a high mineral-ash content, the porosity will continue to increase as the ash is leached out over time; thus, the capacity of the biochar to retain water, provide surfaces for microbes to colonize, and for various elements and compounds to become adsorbed is also likely to increase over time. Smaller pores will attract and retain capillary soil water much longer than larger pores (larger than 10μm to 20μm) in both the biochar and the soil. 

     Water is the universal biological solvent and its presence in biochar pores increases the ‘habitability’ of biochar substantially. 

     Very little is known currently about the functionality of microbial extracellular enzymes interacting with biochar of different compositions. This is an important area for future research.

Tuesday, November 19, 2013


During a field trip organized by the Department of Tropical Agriculture and International Cooperation at NPUST, we visited a bamboo charcoal factory at Hualien County, located in the northern region of Taiwan. In this report I wanted to show the production of bamboo charcoal and the different products they offer.

This bamboo charcoal factory operates in the countryside of Hualien.
Bamboo charcoal is prepared for different purposes and for different products.

Ovens are feed by gas, they count with 4 ovens that operate for 3 days to reach the desired temperature.

Shop and factory owner

Gas is fed by a small compressor that is connected to the gas pipe, fire is started and is introduced to the oven.
Computers control the temperature in the ovens.
After 3 days, the oven can reach a temperature of 1100 C, which is the desirable temperature to produce their charcoal. Once the oven is in that temperature, the computers will stop the fire.

During the bamboo to charcoal process the liquid tars are separated and kept in containers for later treatment.
Tars are kept for about six months; they separate the heavier tars from the most soluble ones. The liquids are treated to obtain different products.

Bamboo Charcoal ovens have a chimney that conducts the smoke produced during the process through a pipe and has an exit to an open area. A small fan, placed at the starting point of the pipe, pushes the smoke out.  In order to reduce the smoke produced, gas is adapted to the exit of the chimney which will burn the smoke transforming it in to gas.

Bamboo Charcoal is used in water filtration and has a small demonstration area where electrical conductivity can be tested by the visitors.

I wanted to buy a sample of their product, to use at the lab for different tests, but I found that the price for a kilogram of their product was 1000 NT (30 USD), also was not enough to perform a field test and apply it into soil for plant growth with such a small amount.

I bought a small sample of bamboo biochar to test it at out laboratory, from that small sample we can obtain pH, EC, FTIR, SEM, etc. (Cost 4 USD).

The Bamboo Charcoal Shop offers to the public different products fabricated from bamboo charcoal; among them we can find clothes, disinfectants, repellents, ice cream, pudding, jewelry, etc.

Souvenir shop

Bowls and pots

Clothes made of bamboo charcoal 

Mosquito repellent 

Creams and Shampoo

Tea cups and ornaments

Bamboo charcoal ice-cream 

Bamboo charcoal Jewelry 

60 USD for a necklace 

Bamboo charcoal pudding 

 Trust me...... was really yummyyyyyyy!!!

Monday, November 11, 2013

Polyphenols and biochar

     Polyphenols include several classes of compounds, such as phenols, phenolic acids, flavonoids, anthocyanins, and others, with more complex structures, tannins and lignins. Polyphenols are secondary metabolites produced by plants in response to stress conditions (Bennet and Wallsgrove, 1994), such as infections, large amounts of UV rays or other factors (Popa et al., 2007). 

     Oxidized polyphenols also inhibit growth and development of certain microbial strains. The toxicity mechanism of polyphenols may be explained by the inhibition of hydrolytic enzymes, or by other interactions, such as blocking protein transport, non-specific interactions with carbohydrates, etc. (Popa et al., 2007). Stimulus or inhibition capacity on plant growth and development is closely correlated with the concentration of Polyphenolic compounds used (Anghel, 2001). Polyphenols, a large class of chemicals which  are found in plants, have attracted much attention in the last decades due to their properties and the hope that they will show beneficial health effects, when taken as a dietary input or as complement (Hu, 2007). 

     Phenolic compounds constitute one of the most extensive groups of chemicals in the plant kingdom. It is estimated that more than 8000 compounds have been isolated and described (Ramos, 2007).  

Ingredients are standardized for total polyphenols (1-10%)

Total phenolic content and extraction yield from extracts of jambul peels (Syzygiumcumini) obtained through various methods of extraction. Source:

     In order to test the content of polyphenols in biochar derived from agriculture wastes research has been done, some investigations had found that the combination of charcoal and polyphenols addition have potential to improve the growth and yield of radish. The mixed combination of biochar and polyphenols applied at 1.5 % w/w to compost led to highest root yields (Jordan et al., 2011), in a similar research Niggli and Schmidt (2010) tested biochar applications of biochar in Vineyards and found that grapes from biochar-treated plots had a 10% higher polyphenol content. Together with the much higher amino acid content, this was an indication of a greater aromatic quality of the grapes, which is then passed into the wine.

Comparison between radish treated with and without biochar 
     The formation of root nodules in leguminous plants is initiated by their release of flavonoids, which are polyphenolic signaling compounds (Jain and Nainawatee, 2002). Biochar is highly effective in the sorption of phenolic compounds, including flavonoids (Gundale and DeLuca, 2006). Therefore, high biochar applications may interfere with signal reception and initiation of the legume root infection process.

    Various papers published in the 1960’s point out that polyphenols could inhibit the activity of digestive enzymes and might accelerate nutritional proteins (Bernays, et al., 1989).

Source: 1st International Conference on Food Digestion, Cesena, 19th March 2012.

     Polyphenols have also been acknowledged as regulators of soil processes and mechanisms. It has been proposed that they might inhibit nitrification (Baldwin et al., 1983), decomposition and nutrient recycling (Horner et al., 1988; Kuiters, 1990) as an outcome of the anti-herbivore function that they have.


     Between species, the variation in polyphenol production by plants has been understood as a defense against herbivores (Haslam, 1981; Bernays et al., 1989). Recent evidence proposes that the pools and variations of inorganic and organic soil nutrients can be influenced by polyphenols (Northup et al., 1998; Schimel et al., 1998). In terms of nutrient competition between plants and microbes, these effects may possibly have wide-ranging consequences, also for retention and nutrient cycling in ecosystems. (Hättenschwiler and Vitousek, 2000).