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Canada's black carbon inventory - 2017 edition

1. Introduction

Black carbon (BC) is a short-lived, small aerosol (or airborne) particle linked to both climate warming and adverse health effects. Black carbon emissions have recently become a focus of attention due to their effects on the near-term warming of the atmosphere and on human health. Reducing black carbon emissions is of particular interest in polar regions, such as the Arctic, which are especially sensitive to the effects of black carbon. When black carbon particles settle on snow and ice, they darken the surface and enhance absorption of solar radiation, thus increasing the rate of melting.

The Paris Agreement lays out a collective goal to limit global average temperature rise to well below 2 °C above pre-industrial levels, and to pursue efforts to limit that increase to below 1.5 °C. This will require taking action on long-lived GHGs such as carbon dioxide and short-lived climate forcers such as methane, hydrofluorocarbons and black carbon. The Pan-Canadian Framework on Clean Growth and Climate Change was released in 2016, which recognized the importance to near-term climate and health benefits of reducing emissions of short-lived climate forcers.

The Arctic Council was one of the first fora to recognize the importance of taking action to address short-lived climate forcers and pollutants, such as black carbon, methane and ground-level ozone. During Canada’s chairmanship (2013–2015), the Council promoted actions to achieve enhanced reductions of black carbon and methane emissions. A key component of these actions is the voluntary reporting by Arctic states of their black carbon emissions to the United Nations Economic Commission for Europe (UNECE). At the 2015 meeting of Arctic Council ministers, Canada, along with other Arctic states, renewed its commitment to take action to reduce black carbon emissions. As part of this commitment, Canada will continue to improve the quality and transparency of information related to black carbon emissions and to publish national black carbon inventories.

This document describes Canada’s third annual inventory of anthropogenic black carbon emissions, covering years 2013, 2014 and 2015. All emissions reported in this inventory are from anthropogenic (human) sources. Natural sources of black carbon such as wildfires are not included.

1.1 Background on black carbon emission quantification

Black carbon is an aerosol (airborne particle) emitted from combustion processes in the form of very fine particulate matter. Black carbon is not emitted on its own, but as a component of particulate matter less than or equal to 2.5 micrometres in diameter (PM2.5), along with other components, such as organic carbon (OC) and inorganic compounds such as sulfates.

Two important assumptions underlie the present inventory: black carbon is predominantly emitted in PM2.5; and only PM2.5 emissions resulting from combustion contain significant amounts of black carbon. Therefore, the basis for the black carbon inventory is the PM2.5 emitted from combustion processes, multiplied by black carbon ratios specific to each type of source. Although important in some cases, PM2.5 emissions from non-combustion sources, such as dust raised by traffic on paved and unpaved roads or by wind and machinery on open fields or mine sites, are not considered sources of black carbon.

Black carbon emissions are grouped in the same categories as those used in Canada’s Air Pollutant Emission Inventory (APEI); these categories are described in Annex A to the present document.

The dataset that breaks down the PM2.5 emitted from a particular source (e.g. diesel engine emissions) into its different components, including black carbon and organic carbon, is known as a speciation profile. Most speciation profiles contain a fraction for elemental carbon; these fractions are commonly used as a surrogate to quantify black carbon emissions. The current inventory primarily relies on the United States Environmental Protection Agency’s (U.S. EPA) SPECIATE database (EPA 2014) to calculate black carbon emissions from compiled combustion PM2.5 emissions. Several BC/PM2.5 ratios are specific to the combustion processes or technologies (e.g. appliance types for residential wood combustion), to the fuel type (e.g. diesel, gasoline, natural gas) or to the application (e.g. natural gas use for electrical power generation). Annex B lists all ratios used in this inventory.

Industrial PM2.5 emissions originate from both combustion and non-combustion sources; however, only PM2.5 emissions resulting from combustion contain significant amounts of black carbon. Where readily available, the PM2.5 emissions data from combustion were used in conjunction with BC/ PM2.5 fractions to estimate black carbon emissions (Table 2-2). Separating combustion from non-combustion sources of PM2.5 remains a challenge in some cases due to a lack of data on activities (i.e. quantity of fuel burned) and on non-combustion sources (e.g. rock dust at a mine). In those cases, combustion and non-combustion PM2.5 are separated based on the judgement of experts with knowledge of industrial processes.

The estimates in this inventory are based on the best available information at the time of compilation. Estimates of PM2.5 emissions are consistent with those reported in the 2017 Air Pollutant Emission Inventory. Please refer to the APEI Report (Environment and Climate Change Canada 2017) for a description of estimation methods for PM2.5. The present document will describe how black carbon emissions were estimated from PM2.5 emissions.

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