Environmental impacts
of cannabis production are of increasing
concern because it is a newly legal and growing industry. Although
a handful of studies have quantified the impacts of indoor production,
very little is known about the impact of outdoor cannabis agriculture.
Outdoor production typically uses little direct energy but can require
significant fertilizer and other inputs due to dissipative losses
via runoff and mineralization. Conversely, fertilizer high in nitrogen
can be counterproductive, as it produces flowers with decreased cannabinoid
content. This study has two aims: (1) To identify reduced-fertilizer
regimes that provide optimal cannabis flower yields with reduced inputs
and (2) to quantify how this shifts greenhouse gas emissions, resource
depletion (fossil and metal), terrestrial acidification, and the eutrophication
potential of outdoor cannabis production. Primary data from a fertilizer
response trial are incorporated into a life-cycle assessment model.
Results show that outdoor cannabis agriculture can be 50 times less
carbon-emitting than indoor production. Dissemination of this knowledge
is of utmost importance for producers, consumers, and government officials
in nations that have either legalized or will legalize cannabis production.