Avoided Greenhouse Gas Emissions From US Pulp and Paper Industry Biomass-Derived Electricity WP-24-05
EXECUTIVE SUMMARY
Although the US pulp and paper sector is the largest contributor to biomass-derived electricity in the US, no life cycle study on the greenhouse gas (GHG) emission characteristics of biomass-derived electricity has been conducted for the sector. The US pulp and paper sector generates 95% of its on-site electricity needs via combined heat and power (CHP). CHP systems, sometimes referred to as cogeneration units, generate both steam and electricity; therefore, it is necessary to allocate the GHG emission impacts, as well as avoided emissions, from this sector via GHG allocation approaches. In this report, all major GHG allocation approaches are reviewed and applied to the US pulp and paper sector to generate allocation fractions for heat and electricity. Fenceline (only considering emissions generated or released by the facility) GHG emission intensities for the US pulp and paper sector, excluding consideration of avoided emissions, ranged from 82 to 316 g CO2e/kWh, depending on the allocation approach used. In a series of studies on the GHG benefits of biomass energy consumption in the US forest products sector, National Council for Air and Stream Improvement, Inc. (NCASI) provided information on the avoided life cycle GHG emission savings from biomass utilization for energy generation in the sector (NCASI 2011; Gaudreault et al. 2012; NCASI 2013 (revised 2014); NCASI 2017). Incorporating avoided emissions and considering GHG allocation approaches to allocate avoided emissions to steam and electricity generation, life cycle GHG emission intensities from industry-generated electricity range from (709) to (2814) g CO2e/kWh for electricity derived from spent liquor solids and range from (482) to (1812) g CO2e/kWh for electricity derived from all other biomass sources. The functions of the kraft recovery system that utilize black liquor, a by-product of the kraft pulping process, not only generate energy but recover pulping chemicals and manage black liquor solids and thus confer additional avoided GHG emissions when alternative use scenarios are considered compared to other biomass sources. Even when a portion of the on-site electricity generation at a pulp and paper mill is derived from supplemental fossil fuels, as is typical for the US pulp and paper sector, the large negative (i.e., avoided) emissions from utilizing biomass residuals more than offset the life cycle GHG emission amounts from the use of fossil fuels, resulting in negative emissions for industry generated-electricity.
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AUTHORED BY
Barry Malmberg, PhD, Principal Research Scientist
Keywords: Greenhouse Gas Emissions, Avoided Greenhouse Gas Emissions, Pulp and Paper, Electricity Generation, Biomass