As part of efforts to reduce carbon emissions in the iron and steel industry, which are especially pertinent in Canada due to rising carbon taxes, Canadian producers have been investigating the effects of replacing coal used in pulverized coal injection with biochar. Although there has been research into the economic value and effect on net life cycle emissions of using the biochar product itself, there are no comprehensive techno-economic analyses which investigate the value and potential uses of the by-products of biomass pyrolysis. These by-products include volatile organic compounds, known collectively as tar or bio-oil, and light gases, which are mainly hydrogen, carbon monoxide, carbon dioxide, and methane. Since only 20-30% of the mass of pyrolyzed biomass is actually converted to char, with the rest converted to the by-products, [1] usage of these by-products is likely the key to increasing the value of biochar to a degree that makes up for the market price of biochar currently being several times that of pulverized coal.
This project aims to create a model and realistic case study for determining the overall value of various uses of the by-products of biochar production, which interested parties can refer to in order to augment their analyses of the projected value of solid biochar as a replacement for pulverized coal or other uses. Due to the large scale and potential market of iron and steel producers, that industry is the primary focus of these analyses.
One of the simpler uses is to combust the products for heat, directly offsetting natural gas usage. Methodology for designing a process system to utilize these by-products for heat production for the purpose of offsetting natural gas, as well as challenges involved in designing this system are discussed, along with an economic analysis of the costed system, including life-cycle carbon dioxide emissions and net present value projections based on current and projected carbon taxes.
[1] E. Amini, M. S. Safdari, J. T. DeYoung, D. R. Weise, and T. H. Fletcher, “Characterization of pyrolysis products from slow pyrolysis of live and dead vegetation native to the southern United States,” Fuel, vol. 235, no. June 2018, pp. 1475–1491, 2019.