Slow pyrolysis biochar from forestry residue and municipal and farm wastes: characterization and their use in greenhouses as a soil amendment

Biochars from various feedstock’s were produced using a small scale tube furnace and a larger scale muffle furnace via slow pyrolysis as well as a homemade top lit updraft unit. All feedstock’s used to produce bio-char in this work are considered waste streams. Specifically, they included fresh and aged sawdust and bark, sewage sludge, gable (milk carton), chicken manure, various yard wastes and various types of paper products. Production of bio-char and bio-oil from these waste streams has potential to mitigate a large volume of waste while producing valuable by-products.Slow pyrolysis was performed at a heating rate of 20ᴼC/min from a starting temperature of 150ᴼC until the desired high treatment temperature (HTT) was reached. HTT’s started at 300ᴼC and increased by increments of 50ᴼC until a maximum HTT of 550ᴼC was reached. The samples were held constant at the desired HTT for 5 minutes. The biochars from the various feedstock’sand HTT’s were characterized by elemental analysis, gas adsorption capacity (GAC),Brunauer-Emmett-Teller theory surface area, Hg porosity, scanning electron microscope, cation exchange capacity (CEC), pH, and proximate analysis using a TGA. GAC, CEC, pH and percent fixed carbon were typically found to increase with increasing HTT up to a certain critical temperature that consistently fell between 500-600ᴼC. After a critical HTT was reached GAC, CEC and percent fixed carbon started to decrease while pH of the char continued to rise. It was found that the actual yield of fixed carbon did not vary greatly with HTT’s 350ᴼC and above. Two potting experiments in a controlled greenhouse were conducted using char’s from various feedstock’s produced by the larger scale muffle furnace pyrolysis unit as well as the top lit updraft gasifier (TLUD) unit. Lettuce and radish plants were grown to represent a leafy and root, fast growing vegetable. Type of biochar, amount of biochar and HTT of biochar was varied in the growth trials. There was also a heavy metal uptake experiment done, comparing the heavy metal uptake of vegetables grown in raw sewage sludge compared to sewage sludge that was pyrolyzed into char as well as poultry litter biochar and sewage sludge that had been diluted with sawdust