Preliminary laboratory production and characterization of biochars from lignocellulosic municipal waste

Converting lignocellulosic municipal waste to biochar represents a carbon sequestration mechanism and a production route that diverts potentially useful feedstocks from landfills. In this preliminary investigation, slow pyrolysis to 480 °C was used to produce biochars from 18 different wastes which were characterized by proximate analysis to determine ash, volatile matter and fixed carbon content. Desirable soil amendment properties such as cation exchange and gas adsorption capacities and pH were also measured. Pristine wood and several closely related products exhibited low ash and high fixed carbon content while paper and cardboard products were found to have higher ash and volatile matter content. Cation exchange capacity (CEC) values were comparable to activated carbon (AC) and within a similar range for most feedstock biochars, with grass and cardboard biochars having the highest CEC. All biochars were found to have similar gas adsorption capacities (GAC) that were lower than AC while newsprint biochar had a GAC twice as high as other samples. All biochars showed neutral to slightly alkaline pH values. In general, lignocellulosic municipal waste biochars exhibited a diverse range of potentially beneficial properties and should be further investigated as prospective soil amendments.