Wednesday, July 16, 2014

Slash-and-char

     Slash-and-char is an alternative to slash-and-burn that has a lesser effect on the environment. It is the practice of charring the biomass resulting from the slashing, instead of burning it as in the slash-and-burn practice. The resulting residue matter charcoal and biochar improves the soil.

    In that context, charcoal can be made by numerous and varied methods, from the simplest (an earth cover on the pile of wood, with strategically placed vents) to the most sophisticated (a modern plant that recuperates and recycles strictly all exhaust gases). (See also: biomass, explaining some of these methods and advantages.)

Slash-and-char offers considerable benefits to the environment when compared to slash-and-burn.

    It results in the creation of biochar, which can then be mixed with biomass such as crop residues, food waste, manure and / or other, and buried in the soil to bring about the formation of terra preta. Terra preta is one of the richest soils on the planet - and the only one known to regenerate itself, although precisely how this happens is hotly debated within the scientific community.

    It moreover sequesters considerable quantities of carbon in the safest and most beneficial fashion, as opposite to the negative effects of the slash-and-burn. Switching to slash-and-char can sequester up to 50% of the carbon in a highly stable form. The nascent carbon trading market that sponsors CO2 sequestration projects, could therefore help supplement the farmers' income while supporting a decrease in the pace of deforestation and the development of a more sustainable agriculture.




Figure adapted from Lehmann – Biochar sequestration in terrestrial ecosystems, supra note 11 at 407 (“If this woody aboveground biomass were converted into biochar by means of simple kiln techniques and applied to soil, more than 50% of this C would be sequestered in a highly stable form.”) and from Steiner, Christoph. 2007. Slash and char as alternative to slash and burn - Soil charcoal amendments maintain soil fertility and establish a carbon sink.


References
Biochar Sequestration In Terrestrial Ecosystems – A Review, by Johannes Lehmann (2006) – supra note 11 at 407 (“If this woody above ground biomass were converted into biochar by means of simple kiln techniques and applied to soil, more than 50% of this C would be sequestered in a highly stable form.”)

Steiner, Christoph. 2007. Slash and char as alternative to slash and burn - Soil charcoal amendments maintain soil fertility and establish a carbon sink. Dissertation, Faculty of Biology, Chemistry and Geosciences, University of Bayreuth, Germany, Bayreuth.

Tuesday, July 15, 2014

Influence of biochar in seed germination and growth rate (part 2)

Introduction
Application of biochar as soil amendment:
     Detailed studies of ancient Amazonian Terra Petra soils have revealed that anthropogenic original black carbon with a high aromatic content has been stabilized, in part, due to interactions with minerals, micro-organisms and soil organic matter (Brodowski et al. 2005; Liang et al. 2010).

    The adsorption of soil materials to black carbon protects black carbon from oxidation and decomposition (Nguyen et al. 2008). This implies the mineral attachment to biochar is important in the stabilization process. Interactions and reactions happened immediately on application of biochar to soil, especially at its surface. 

   The biochar surface proper ties play an important role in these interactions and reactions, and the fresh biochar surface properties are controlled by the pyrolysis conditions applied and feed stocks used. Investigations on the mechanisms of mineral incorporation with biochar are useful in order to reveal the interactions / aggregation of biochar and soil materials, in particular factors of soil affecting biochar stability

Raw Material
    Oil palm fiber, coconut fiber, Cryptomeria japonica and eucalyptus woods were obtained from China Steel Company (Taiwan). The samples were washed with distilled water several times to remove dust and impurities and then dried at 105°C for 24 h to remove any surface moisture and then weighted previous pyrolysis process.

Experimental Procedure
   The pyrolysis experiments were performed on 0.973 kg of dried Eucalyptus, 0.556 kg of dried Cedar, 1.438 kg oil palm fiber and on 0.514 kg of Coconut Fiber, in a small scale stainless steel tubular reactor with a sweep gas (butane gas) connection. The reactor was heated externally by a single gas stove like. The system can be run up to a maximum temperature of 350°C. A K-type thermocouple (TES 1310) was used to check accurately the temperature inside and outside the reactor. 

    The temperature of the reactor was increased until it reached the desirable temperature of 300 to 350°C. The sample was kept at this temperature for 30 to 60 min under a flow gas and the unit was then left to cool down to room temperature. After pyrolysis, the bio-char was removed from inside the reactor and weighed. The product’s yield was calculated using the following equation, where Wf and Wo are the dry weight (kg) of produced bio-char or bio-oil and dry weight (kg) of precursor (palm shell) as a feed for process, respectively.

    Previous authors (Brown et al. 2006; Chan and Xu, 2009; Hammes et al.) have confirmed that the different nature of biochars product are typically influenced by wide range factors including different types of materials being used or feedstock quality and also different charring condition.


Biochars



(Note: Due to biomass availability we used Cryptomeria japonica for the continuation of the experiment) 



Cryptomeria

Scientific name: Cryptomeria japonica
     Cryptomeria is a monotypic genus of conifer in the cypress family Cupressaceae, formerly belonging to the family Taxodiaceae. It includes only one species, Cryptomeria japonica. It is endemic to Japan, where it is known as Sugi.  The tree is often called Japanese cedar in English, though the tree is not related to the true cedars (Cedrus).
Rank: Species

Energy-dispersive X-ray spectroscopy and scanning electron microscope 
    Recent studies suggest that the types and rates of interactions (e.g., adsorption–desorption, precipitation–dissolution, redox reactions) that take place in the soil depend on the following factors: (i) feedstock composition, in particular the total percentage and specific composition of the mineral fraction (especially Fe, Mn, Na and Ca); (ii) pyrolysis process conditions; (iii) biochar particle size; and (iv) soil properties and local environmental conditions. (C.H. Chia et al.  (2012)).


Scanning Electron Microscopy (SEM) . Biochar production (material characterization).  

Fig. 1- Biochar production (raw material characterization) SEM



Fig.2- Biochar production (193 ⁰C)



Fig.3- Biochar production (250 ⁰C)



Fig.4- Biochar production (316 ⁰C)



    There is an increasing awareness of the importance of understanding the chemistry of biochar to optimize its role as a soil additive. The addition of SEM–EDX provides a comprehensive picture of the organic and inorganic chemistry on a biochar.  In figure 1, the formation of particle size is showed, from raw material to the highest temperature applied to obtain biochar. Is observed how porosity is developed, higher temperatures – the porosity increases, giving as a result better water holding capacity.

    In the following, the results of the energy-dispersive X-ray spectroscopy are presented, it can be observed how the different elements are formed in the materials depending on the pyrolysis temperatures. Some elements are not present in biochar with higher temperatures. Following are the graphs and figures of these data.



Energy Dispersive X-Ray Analysis (EDX)






Energy Dispersive X-Ray Analysis (EDX)





Biochar time and yield after pyrolization of Cryptomeria japonica (syn. Cupressus japonica L.f.) 




Characterization of materials



Electrical conductivity




    From the figures above, we can observe that depending on the temperatures applied the properties of the biochar changes, pH increased from 4.79 to 8.01 going from acid to alkaline. EC reached its higher point at 316 ⁰C. CEC showed the highest level in biochar 250°C.  Volatile matter decreased with higher temperatures and water holding capacity increased as biochar temperatures increased.


X-RAY

These figures show the formations of cellulose, carbon 60 and Graphite are observed in the different temperatures applied to the raw material after analyzing samples by X-ray.



FTIR
    Infrared spectroscopy and is a common technique for investigating chemical functionality in biochar materials. Previous studies where FTIR has been used to characterize biochars have focused on the changes in the biochar’s functional groups as a function of pyrolysing temperature. 


     A combination of reflectance FTIR imaging and SEM–EDX imaging is very effective for characterizing the spatial distribution of organic and elemental chemistry on biochar particles. In this analysis of biochar the FTIR was used specifically to determine the functional groups present for  each temperature and biomass,  especially carbons and aromatics.


Atomic absorption spectroscopy (AAS)
     Presence of heavy metals was determined by atomic absorption which determines the presence of metals in liquid samples. It also measures the concentrations of metals in the samples. Important elements (Lead, cooper and strontium) were evaluated. 


The results showed that as the temperature of biochar increased, the content of these elements decreased.





Biochar germination - net house




Net house pot germination

a) Biochar and soil weighted, b) Biochar and soil added to germination pots, c) 4th day of germination, d) 7th day of germination, e) Last day of germination (harvesting), f) Plants been prepared for shoot measures. 


Germination percentage taken during 14 days 

Percentages and averages of germination results. Biochar produced at 250 °C showed better germination percentage. 


Measures taken after harvest
Plant morphology measures. Biochar produced at 319 °C showed higher averages in shoot length and biochar 250 °C resulted with the highest biomass weight.



Biochar germinations petry dish

1- Measure pH and EC of biochar in water at 1: 5 (w/v) ratios.
2- Ground finely a subsample of biochar and determine total carbon and nitrogen contents were dry combustion analysis using an elementar analyzer.
3- Sieve all biochars using a 4 mm sieve before use for soilless Petri dish bioassay.
4- Particle size fraction (using a stack of sieves)
5- Soil-less Petri dish bioassay for corn and rice (Experiment)

Materials
Biochars: - Cedar

45 petri dishes
675 corn seeds
45 filter papers
Distilled water 20 mL/per dish)
Incubate  at 25℃ (in a dark place) for 72 H.





Characterization of materials


Volatil matter



Water holding capacity



Germination results
Petri dish germination
Germination for the 3 different temperatures of biochar using 5 different quantities. 




Percentages and averages of germination results. Biochar produced at 250 °C showed higher averages in number of seeds germinated and root length.










References:

Brodowskia S, Amelung W, Haumaier L, Abetz C, Zech W (2005) Morphological and chemical properties of black carbon in physical soil fractions as revealed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Geoderma 128: 116-129

C.H. Chia et al. / Vibrational Spectroscopy 62 (2012) 248– 257

Liang B, Lehmann J, Sohi SP, Thies JE, O’Niell B, Trujillo L, Gaunt J, Solomon D, Grossman J, Neves EG, Luizão FJ (2010) Black carbon affects the cycling of nonblack carbon in soil. Organic Geochemistry 41: 206-213

Nguyen BT, Lehmann J, Kinyangi J, Smernik R, Riha SJ, Engelhard MH (2008) Long-term black carbon dynamics in cultivated soil, Biogeochemistry 89:295–308