# Reevaluating carbon storage and emissions in California’s harvested wood products: implications for alternative waste parameters

## TL;DR

This study improves estimates of carbon storage and emissions from wood and paper products in California landfills by refining waste parameters.

## Contribution

The research introduces updated product-level decay and storage parameters to reduce uncertainty in carbon accounting for landfilled wood and paper.

## Key findings

- Updating waste parameters increased cumulative carbon storage in landfills by 11.77 MMT CO2Eq and reduced emissions by 11.18 MMT CO2Eq from 1953 to 2020.
- Wood products stored significantly more carbon (164.07 MMT CO2Eq) compared to paper (31.41 MMT CO2Eq) over the same period.
- Product-level analysis revealed similar annual carbon emissions for wood and paper products, but higher annual storage for wood.

## Abstract

Harvested wood and paper products can store large amounts of carbon long-term but also contribute to carbon emissions once discarded. Currently, several tools are used for inventory and reporting carbon in wood and paper products in the U.S. Carbon in wood and paper is tracked from initial manufacturing, through its lifetime, and final fate (e.g., dumps, landfills, incinerated, or recycled). Once discarded into landfills, a portion of wood and paper is assumed permanently stored; however, carbon storage of specific products can vary widely which influences carbon storage and emissions estimates. Using historical California harvest data and state-level inventory model, HWP-C vR, this research built model capacity for expanding and refining waste parameters, such as product-level decay half-lives and proportions of permanent carbon storage to reduce waste parameter uncertainty. By updating the proportion of carbon permanently stored in landfilled wood and paper products and by adding product-specific discard pathways, carbon in solid waste disposal sites cumulatively increased moderately by about 11.77 MMT CO2Eq and emissions decreased by about 11.18 MMT CO2Eq in California from 1953 to 2020. Updated parameters furthermore made it possible to compare product-level carbon storage and emissions within landfills such as newspaper, office paper, coated paper, cardboard, plywood, and lumber. The cumulative wood product categories resulted in similar amounts of carbon compared with paper products – 28.21 MMT CO2Eq (0.415 MMT CO2Eq annually) and 27.39 MMT CO2Eq (0.403 MMT CO2Eq annually) respectively; however, the carbon storage of wood products was much higher than paper, with 164.07 MMT CO2Eq (2.413 MMT CO2Eq annually) stored compared with 31.41 MMT CO2Eq (0.462 MMT CO2Eq annually) respectively. These carbon emissions and storage estimates illustrate the value in understanding carbon dynamics at the product-level particularly when considering climate impacts from landfill emissions even after product disposal.

The online version contains supplementary material available at 10.1186/s13021-026-00407-7.