Regional tree die-off events generate large quantities of standing dead wood, raising concern over

catastrophic wildfire and other hazards. Governmental responses to tree die-off have often focused on

incentivizing biomass energy production that utilizes standing dead trees removed for safety concerns.

However, the full distribution of potential woody bioenergy feedstock after tree die-off has not been

evaluated due to the complexities of surveying and precisely measuring large forested areas. In this

paper, we present a novel method for estimating standing dead biomass at a fine spatial resolution

that combines aerial survey data with forest structure maps. Using this method, we quantify biomass

generated by the unprecedented tree die-off that occurred in California following a 4-year drought and

widespread pest outbreaks. The results are used to estimate feasibly recoverable feedstock for energy

production. We find that approximately 95.1 million bone-dry tons (BDT) of dead biomass resulted from

2012–2017 mortality, with a lower bound of 26.2 million BDT. In other words, of the aboveground live

tree biomass in 2012, ~1.3–4.8% died by 2017. Of the standing dead biomass, 29% meets minimum

constraints for potential cost-effective bioenergy feedstock. This proportion drops to as low as 15%

in the most affected areas due to terrain slope, wilderness status, and other factors, highlighting the

need to complement disposal via biomass energy with other strategies to mitigate the risks of the tree

mortality crisis, which is likely to only become more severe over time due to climate change.