Emissions calculations for Harvested Wood Products and Forest Land

Table of Contents:

• Introduction
• Forest Land
• Harvested Wood Products
• Summary

Introduction

The previous post introduced the International Panel on Climate Change (IPCC) sectors that Canada uses to report greenhouse gas emissions, and estimated Public Electricity and Heat emissions from Statistics Canada data. This post continues that replication effort for the next-largest source of emissions in 2005: Forest Land. As it turns out, Forest Land emissions are tightly coupled to emissions of the Harvested Wood Products sector, so this post looks at both. The material from this post refreshes the IPCC Sectors / Forest Land page, introduces a IPCC Sectors / Harvested Wood Products page, and introduces emissions estimates for both sectors based on data from Canada's National Forestry Database. The estimate is relatively accurate for Harvested Wood Products, and not as accurate for Forest Land. Proper replication of the Forest Land calculation seems difficult. I might come back to it in future, but I expect to need help from someone with domain expertise.

Forest Land

Canada's forests are enormous, and collectively, they exchange a lot of carbon dioxide with the atmosphere and the soil in any given year. Plants in forested land absorb carbon dioxide from the atmosphere to grow (via photosynthesis), and release carbon dioxide to the atmosphere when they die (via e.g. combustion or decay). When forests burn, much of the carbon from the wood is released to the atmosphere, but some is converted to biochar and effectively locked away. When plants decay, microbes break down the wood and release most of the carbon as ${\mathrm{C}\mathrm{O}}_2$, but a fraction of the carbon is converted to stable organic matter called humus that remains in the soil. The long term carbon balance of soil, plant matter, and atmosphere can reach equilibrium in a few hundred years. This equilibrium can recover from disturbances by e.g. fires, insect infestations, and logging. The equilibrium can be indefinitely shifted by e.g. land-use conversion, or environmental changes in temperature, moisture, or atmospheric ${\mathrm{C}\mathrm{O}}_2$ concentration.

Forest carbon accounting is an active area of scientific research, and Canada is an international leader. The Canadian CBM-CFS3 model, and the team that developed it helped define the IPCC guidelines on reporting carbon for forest land. The CBM-CFS3 model is now being replaced with a new model, the Generic Carbon Budget Model, developed within the context of a global open-source collaboration with Australian greenhouse gas experts and the Linux Foundation. Integrating PlanZero with this more-established project is an interesting direction for future work (github issue).

Natural Resources Canada (NRCan) works together with provincial and territorial ministries of natural resources to manage and model Canada's forests for a variety of purposes, including the estimation of direct and indirect greenhouse gas emissions from forests. One artifact of that management is the National Forest Inventory, and for my goal of understanding how Canada's emissions calculations work, it's a great starting point. Canada's emissions in the Forest Land sector are calculated only from so-called Managed Forest.

• Managed Forests: These are forests under direct human influence, including lands managed for timber harvesting, fire protection, or conservation. This covers roughly 226 million hectares (about 65% of Canada's total forest area).
• Unmanaged Forests: Remote northern forests not subject to active human stewardship are generally excluded from the inventory until human activity (like a new road or mine) expands into them.

Harvested Wood Products

Harvested Wood Products represents one of the largest out-flows of carbon from the Forest Land sector. The IPCC accounting guidelines treat Forest Land as a carbon pool with in-flows and out-flows from natural and anthropogenic drivers, and logging is one of the biggest and best-tracked of those drivers. The Harvested Wood Products sector is, itself, also modelled a set of carbon pools, corresponding to volumes of wood used for different purposes, with different lifespans before the carbon they contain returns to the atmosphere. The product categories used in the National Forestry Database are:

• Logs and Bolts for lumber, plywood, veneer and shingles
• Other Industrial Roundwood for poles, pilings, fence posts, shoring timbers
• Fuelwood and Firewood for residential, commercial, or industrial combustion
• Pulpwood for producing paper and cardboard.