Twenty topics about biochar production, quantitative analysis and applications were presented during the “Black Carbon and Biochar for Soil Fertility and Carbon Sequestration” session at the ACS meeting in Denver, CO, United States on Aug 29, 2011. These sessions were part of the division of the environmental chemistry meetings that examines how chemistry can be used to monitor, measure, and mediate environmental issues caused by humans and by natural causes.
The presentations about biochar quantification focused on the need to record data for all of the variables involved in its production (pyrolysis temperature, heating rate, particle size and feedstock) and tools and techniques for quantifying the resulting chars. Bill Cooper of Florida State University discussed the use of Dopant Assisted - APPI (Atmospheric pressure photoionization) to reveal the specific molecular structure of the various chars and displayed the results in a van Krevelen diagram. Colleen Rostad of the USDA presented information gained from water extracts of chars that were analyzed with ESI-MS (electrospray ionization and Mass Spectrometry). Isabel Lima from the SRRC-USDA-ARS also reported proximate analysis of sugarcane bagasse. These quantitative methods confirmed the work of previous researchers; high temperature chars have more hydroxyl groups, are more aromatic, have a higher surface area, elute more Nitrogen and result in more ash and a higher pH. There was a lively discussion about ASTM test methods for proximate and ultimate analysis, which were originally designed to understand biomass substrates as fuels and the need to develop standards for chars that will be applied to soils.
The work of Katherine Keske and Greta Lohman of Colorado State University was presented. Their study focuses on a regional approach to understand the greenhouse gas (GHG) emissions of different types of gasifiers, and pyrolysis systems. Their analysis suggests that modern gasifiers and pyrolysis systems with energy capture of waste heat can have a net negative effect on GHG emissions as long as the feedstock is being transported less than 25 miles. Catherine Stewart of USDA-ARS discussed the need for long term data regarding GHG emissions, because the current data is quite variable. She referred to a paper by Kurt Spokas (2009) that suggested that variations in soil type, pyrolysis temperature, and feedstock can push a system from positive to negative and vice versa. While N20 emissions seem to reduce by the application of biochar, CH4 emissions from soils where biochar has been applied seem to be more dependent on local variables. Francesca Cotrufo of Colorado State University reported on the use of carbon isotopes to test carbon emissions and sequestration in greenhouse and lab tests. Her work suggests that adding biochar to soils increases the CO2 emissions above the background rate, but that it appears to be coming from the biochar – not the native SOM, and the net result appears to be carbon sequestration in those particular tests.
Biochar’s affect on soil fertility was another common topic. Francisco Calderon of USDA ARS reported on the use of DRIFTS FTIR (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) to understand what portion of SOM (soil organic matter) is decomposing in field samples. His work with mollisols in the Great Plains is focused on using biochar as an alternative to wheat-fallow rotations, and he is gathering data about biochar erosion relative to slope. Gerard Cornelissen spoke about his work in Zambia, Malaysia and Indonesia. Subsistence farmers in Zambia are starting to use biochar made from corn stover. Because so little char is available, it is placed directly in a planting basin prior to seed planting. On poor, acidic, sandy soils these farmers are seeing yield increases up to 400%. On better soils, the yield difference is smaller.
There were also several presentations about biochar and activated chars as a mediator of contaminants. Kyoung Ro of USDA ARS showed information about activated biochar as a filter for ammonia gas. The ammonia can be leached from the biochar filter cartridges by soaking in water for 24 hours and the effluent may be useful as a fertilizer. Tom Potter of USDA SEWRL discussed herbicide sorption in ultisols of the southeastern U.S. coastal plain under conventional and conservation tillage systems. Seok-Young Oh presented work on biochar-mediated reductive transformation of nitro herbicides and other residues. Joshua P Kearns presented information about biochar as a low cost absorbent to remove pesticide residues from drinking water in developing countries. Minori Uchimiya explained biochar characteristics and functions as a heavy metal sorbent in soil with special attention to the role of surface ligands. Christopher D Petlz, of the Rocky Mountain Biochar Initiative, presented results from experiments using biochar for soil remediation on abandoned mine lands and tailing piles in the San Juan Mountains, CO. Isabel Lima discussed the heavy metal adsorption capacity of biomass and animal-manure derived biochars, and showed data that suggested that acid oxidation is best for chars made from wood, and steam activation is better for poultry litter chars. Paul M White, Jr. presented data on the use of sugarcane bagasse and pine wood biochar effects on aerobic soil dissipation of metribuzin and pendimethalin. He also reported on a phenomenon of reduced weedy amaranth germination in fields where biochar had been applied.
This report was submitted by Carolyn Hoagland, an NSF IGERT fellow and Ph.D. student in the department of soil and crop science at Colorado State University.