Biochar from microwave pyrolysis of selected feedstocks

This is a brief summary of work carried out by a team of researchers to produce biochar using microwave pyrolysis system developed at Bioenergy, Bioproducts Research Lab (BBRL), at UNB. Various feedstocks such as corn stalk, spruce, maple, switchgrass, and wood pellets were used to produce biochar. A batch type microwave reactor with a frequency of 2.45 GHz and a power generator of 3 kW was used in the pyrolysis experiments. The amount of biochar obtained depends on the microwave pyrolysis conditions and type of feedstock. For corn stalk briquettes, the yield of biochar ranged from 30.9 to 41.1 wt%. The average biochar yield for spruce, maple, and switchgrass was found to be 22.2 wt%, 22.0 wt%, and 24.4 wt% respectively. Please click on the file below for full content of the abstract

Climate impact of diverting residual biomass to cement production

Abstract Co‐firing residual lignocellulosic biomass with fossil fuels is often used to reduce greenhouse gas (GHG) emissions, especially in processes like cement production where fuel costs are critical and residual biomass can be obtained at a low cost. Since plants remove CO2 from the atmosphere, CO2 emissions from biomass combustion are often assumed to have zero global warming potential (GWPbCO2= 0) and do not contribute to climate forcing. However, diverting residual biomass to energy use has recently been shown to increase the atmospheric CO2 load when compared to business‐as‐usual (BAU) practices, resulting in GWPbCO2 values between 0 and 1. A detailed process model for a natural gas‐fired cement plant producing 4200 megagrams of clinker per day was used to calculate the material and energy flows, as well as the lifecycle emissions associated with cement production without and with diverted biomass (supplying 50% of precalciner energy demand) from forestry and landfill sources. Biomass co‐firing reduced natural gas demand in the precalciner of the cement plant by 39% relative to the reference scenario (100% natural gas), but the total demands for thermal, electrical, and diesel (transportation) energy increased by at least 14%. Assuming GWPbCO2 values of zero for biomass combustion, cement's lifecycle GHG intensity changed from the reference (natural gas only) plant by −40, −23, and − 89 kg CO2/Mg clinker for diverted biomass from slash burning, forest floor and landfill biomass, respectively. However, using the calculated GWPbCO2 values for diverted biomass from these same fuel sources, the lifecycle GHG intensities changes were −37, +20 and +28 kg CO2/Mg clinker, respectively. The switch from decreasing to increasing cement plant GHG emissions (i.e., forest floor or landfill feedstocks scenarios) highlights the importance of calculating and using the GWPbCO2 factor when quantifying lifecycle GHG impacts associated with diverting residual biomass to bioenergy use