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Potential of biochar in Canadian Oil Sand reclamation

Researchers from the University of Udine have recently published the following paper: Fellet et. al. (2011) Application of biochar on mine tailings: Effects and perspectives for land reclamation.  Chemosphere 83, 1262-1267.   The paper is an important contribution to the biochar in reclamation space and describes the interaction of four different rates of a single biochar applied to mine tailings associated with historic lead and zinc extraction.  Having reviewed and reduced the data presented in the paper, I do have a couple of general thoughts around the data set.  My caveat to this interpretation is that I was looking for broader trends rather than statistical significance and used the mean values presented in the paper.  Additionally, most of the data was presented in graphical rather than tabular form, so the data I used obviously has a degree of error associated with it.  However, even with this in mind, the data provides some salient points:  

·         Water Holding Capacity: Linear regression with r² = 1.00.  This was observed in a clay texture class (3% sand, 14% silt, 83% clay) which is interesting as it challenges the opinion that biochar is most effective in coarse grained materials.   

·         pH:  pH increased from 8.1-10.2 when applied to the soil.  This needs to be considered when applying to alkaline soil.  However, if the intent of biochar is for increased water holding capacity in semi-arid and arid conditions, then this may override any impact on plant growth associated with increased pH. The weathering effect of biochar in these soils over time may also play an important role in these systems, and the increased pH may only be a temporary consideration.  However, pre-washing could be required prior to application if a negative and long-term effect on plant growth is observed.

·         Electrical Conductivity:  As for Water Holding Capacity, a linear increase was observed with increased biochar (r² = 1.00).  Again the effect on saline/sodic soils needs to be considered and pre-washing may be required.  Long term leaching effects should also be considered.

·         Cation Exchange Capacity:  When all four values are used, the data again shows a linear correlation.  The data presented in this paper indicates a reduced CEC when 1% biochar was incorporated into the tailings compared with no char addition to the mine tailings.  Original data shows no statistical difference between 0% and 1%, so when I use data for the tailings with char addition the correlation coefficient becomes  r² = 1.00.

·         Metals:  Bar charts presented by Fellet et al. (2011) would suggest that for certain metals, biochar reduces leaching (when using TCLP extraction methods).  When presented as scattergrams with log concentrations, the effect appears negligible, with the possible exception of Al.  Even then I’m not getting too excited.  These results may be a function of the pH effect described above.  A similar experiment with metal loaded soils in the near neutral to acidic range will provide a useful comparison.    Based on this data set, my conclusion is that in alkaline soils and mine tailings, biochar is ineffective in metal stabilization, despite the increase in CEC which thoeretically should increase metal adsorption.

I also have a PDF version of this review that includes the graphs I used for this interpretation.  If you would like a copy, please email me at andrewharley@ascensionsoil.com.  

Researchers with the USDA’s Agricultural Research Service (ARS) installed infrared heaters in experimental wheat fields at the agency’s Arid-Land Agricultural Research Center in Maricopa, Ariz., to simulate growing conditions expected by 2050.  As expected, the heaters accelerated growth, increased soil temperatures, reduced soil moisture, induced mild water stress on the crops and had a nominal effect on photosynthesis. 

While the research was conducted to identify adjustments to planting schedules, the decreased water content in soils with increased heat is going to have other ecosystem effects, other than simply plant yield.  Dr Swetnam of the University of Arizona http://web.me.com/twswetnam/Pyrodendrochronology/Home.html presented gave a thought provoking presentation at the Forests at Risk symposium in Aspen, CO last week http://www.fortheforest.org/page_82. Based on tree-ring data going back 2,000 years, there have been two severe drought periods in the southwest.  Regardless of the cause, we need to be looking at innovative ways to handle drought conditions within the southwest. 

ASC and partners are looking at biochar for improved water holding capacity in reclamation sites in the Intermountain West, and the same approach may be useful for agricultural areas as well. 

Abstract

Soil amendments can immobilize metals in soils, reducing the risks of metal exposure and associated impacts to flora, fauna and human health. In this study, soil amendments were compared, based on “closed system” water extracts, for reducing metal mobility in metal-contaminated soil from the Broken Hill mining center, Australia. Phosphate fertilizer (bovine bone meal, superphosphate, triple superphosphate, potassium orthophosphate) and pine bark (Pinus radiata) were applied to two soils (BH1, BH2) contaminated with mining waste. Both soils had near neutral to alkaline pH values, were sulfide- or sulfate-rich, and contained metal and metalloid at concentrations that pose high environmental risks (e.g., Pb = 1.25 wt% and 0.55 wt%, Zn = 0.71 wt% and 0.47 wt% for BH1 and BH2, respectively). The addition of fertilizers and/or pine bark to both soil types increased water extractable metals and metalloids concentrations (As, Cd, Cu, Fe, Mn, Pb, Sb, Zn) compared with nonamended soils. One or more of the elements As, Cd, Cu, Mn, Pb, and Zn increased significantly in extracts of a range of different soil+pine bark and soil+fertilizer+pine bark tests in response to increased pine bark doses. By contrast, Fe and Sb concentrations in extracts did not change significantly with pine bark addition. Solution pH was decreased by phosphate fertilizers (except for bovine bone meal) and pine bark, and pine bark enhanced dissolved organic carbon. At least in the short term, the application of phosphate fertilizers and pine bark proved to be an ineffective method for controlling metal and metalloid mobility in soils that contain admixtures of polymetallic, polymineralic mine wastes.

Thesis by Villarreal Manzo, Luis Alberto, Ph.D., The University of Arizona, 2009, 253 pages; AAT 3350468

Copy can be ordered at link

Biochar incorporation in soils has the potential to remove carbon from the atmosphere and to improve soil quality. This research focused on evaluation of the benefit of biochar incorporation in an Arizona soil. Different concentrations of biochar (charcoal from mesquite biomass-derived black carbon) were added to soil in greenhouse experiments. Seven common or potential Southern Arizona crops (alfalfa, wheat, cotton, grain and sweet sorghum, barley and switch grass) were evaluated in the greenhouse experiment. In this experiment; increased biochar concentration treatments produced greater height and biomass production in alfalfa. Sorghum biomass production also increased with biochar concentration. There were no significant differences in biomass production in wheat and barley with increased biochar concentration. Switch grass biomass production had a significant negative correlation with increased biochar concentration. Sweet sorghum biomass production was evaluated in a field experiment conducted at the University of Arizona Red Rock Agricultural Center. A relatively small amount of biochar was incorporated in the top 20 cm of soil in one treatment and soil only was the other treatment: there were no significant differences in yield.

Water characteristic curves and bulk densities were measured for biochar/soil mixes. The FASE model was used to simulate evapotranspiration and crop yield for the field sorghum experiment and for several crops grown in the Valsequillo Irrigation District, Puebla, Mexico with measured soil parameters. The model predicted no significant increase in sorghum yield for the level of biochar incorporated in the soil. An increase in yield was predicted for Valsequillo crops.

Abstract (Summary)

I’ve just downloaded the app to my EVO - very cool

Here is a radio report for the work we are doing using biocahr for the reclamation of an abandoned mine land in the Aspen Mining District of Colorado