Legalising Marijuana- Environmental Negatives? –

Recreational Cannabis Legalisation

There are many groups within NZ including the Green Party
that are calling for the legalisation of marijuana for
personal/medicinal use and my question for them is: – How
can they reconcile that stand with the negative
environmental effects from cannabis cultivation?

matter where you sit on its legalization, growing marijuana
affects our environment and that can be in a negative

Growing marijuana indoors requires copious
electricity through the use of high-intensity lamps, air
conditioners, dehumidifiers and much more. In order to grow
it outside, streams become sponges, being sucked dry as seen
in the outdoor grow-ops in California.

What Happens
When Marijuana is legalised:

Illegal marijuana
growers have typically kept their crops indoors to safeguard
themselves against prosecution. Now that marijuana has been
decriminalized in some US states, many will start to
cultivate cannabis outdoors meaning that it will require
more water consumption. A study by the California Department
of Fish and Wildlife in 2015 found that weed cultivation was
excessively diverting water from creeks, which are home to
endangered salmon species.

An estimated 22 litres of
water is needed a day to water marijuana plants, compared to
a wine grape plant, which uses 12 litres.

With any
expansion of an agricultural crop comes the need to
clear-cut more forest and construct road. This increases the
risk of erosion, river diversion, and habitat destruction.
Wild animals are left fending for themselves and possibly
endangering themselves and others.

There is also the
case of pollution with the use of chemicals, which are often
used to kill rodents which may damage the crop. These
chemicals make their way into the sewage system and into our
water supplies. They also make their way into the food
chain, and can pose significant health risks to

Using the State of Colorado in America as
an example, the legalization of cannabis (recreational weed
was approved in a state wide ballot in 2012) has
reinvigorated previously dilapidated industrial areas of
Denver and generated more than $1bn a year in taxable sales.
But the voracious energy consumption of growers is rubbing
up against the city’s ambitions of cutting greenhouse

And with around half of all US states now
allowing cannabis for various uses, hothouse cultivation is
increasingly a concern for governors and mayors promising to
fill a hole in emissions reductions.

Evan Mills, a
senior scientist at the University of California, was one of
the first researchers to quantify how energy hungry the
cannabis industry is, estimating in 2011 that indoor
cannabis cultivation represents 1% of total electricity use
across the US, a figure backed up by a New Frontier study
last year.

Lighting can comprise up to half of a
cannabis grower’s energy use, with the desire to create a
round-the-clock version of natural growing conditions
requiring hugely powerful high pressure sodium (HPS)

As a result, producing just a couple of pounds
of weed can have the same environmental toll as driving
across America seven times.

“The legalization of
recreational or medicinal marijuana in eight states
including California, Florida and Massachusetts, means some
of the nation’s hard-earned progress towards climate
change solutions is on the chopping block as regulators
continue to ignore this industry’s mushrooming carbon

Denver’s electricity use has been
edging up at a rate of more than 1% a year, with nearly half
of that increase due to marijuana-growing facilities, the
city has said. While just a small percentage of Denver’s
electricity is used by cannabis operations, they are far
more energy intensive on a per-square-foot basis than most
other types of businesses. This demand, in turn, drives
fossil fuel use, because Colorado gets the majority of its
energy from coal-fired power plants.

definitely an area of concern,” said Emily Backus,
sustainability advisor for the city. Denver has a goal to
shrink its greenhouse gas emissions 80% by 2050, largely
through boosting renewable energy, improving the efficiency
of buildings and promoting public transit and electric

Denver also signed on to the Paris climate
agreement’s goals with Mayor Michael Hancock decrying the
“serious threat to our economy and way of life” posed by
global warming.

In order to calibrate conditions to
reap multiple harvests a year, growers have to bake the
plants in light while cranking the air conditioning to
ensure rooms stay at a finely balanced temperature. A
dehumidifier is used to prevent mould, carbon dioxide is
pumped in to bolster growth and fans mimic the presence of a
breeze. Irrigation systems are often hoses plugged into the
plants, leading to tubs of water. The goal is healthy,
weighty buds.

All of this uses a lot of energy and
LEDs, despite saving a lot of power, have been deemed by
many growers to be less effective and more expensive than
HPS lights.

The cannabis industry is often pigeonholed
as being very heavy users of resources. LEDs aren’t in
themselves a perfect answer. Because marijuana generally
takes longer to mature under LEDs, it can result in not much
energy being saved.

Marijuana might look and smell
natural, but its ecological footprint is anything but
green. Marijuana is power hungry.

The $3.5bn USA
cannabis industry is one of the nation’s most energy
intensive; often demanding 24-hour indoor lighting rigs,
heating, ventilation and air-conditioning systems at
multiplying grow sites.

As many as 10 states could
legalize recreational marijuana this year, which means the
resultant electricity consumption could cause problems for
public utilities and city officials.

A study by
scientist Evan Mills, with the Lawrence Berkeley National
Laboratory, revealed that legalized indoor marijuana-growing
operations account for 1% of total electricity use in the
US, at a cost of $6bn per year. Annually, such consumption
produces 15m tons of greenhouse gas emissions (CO2), equal
to that of three million average cars.

In 2012,
Colorado became the first state to legalize recreational
marijuana. Two years later, Denver’s 362 marijuana grow
facilities consumed more than 2% of the city’s electricity
usage. State wide facilities are behind roughly half of
Colorado’s new power demands. Electricity represents
roughly 20% of the total cost of a cannabis

In Boulder County during the second quarter
of 2015, a 5,000 square foot indoor cannabis facility was
eating about 29,000 kilowatt hours (kWh) of electricity
monthly. A local household in the county was consuming about

In other states where the recreation market
has taken off, cannabis production is having a similar

According to a report by the Northwest Power
and Conservation Council in Oregon – where recreational
marijuana has been legal since 2014 – an indoor grow
system for only four plants sucks up as much energy as 29

The report also estimated that the
emerging market could warrant the electricity demands of a
small city in the next 20 years.

Skyrocketing energy
levels confirm that the marijuana business is

Grow operations consume $6 billion a year or
enough energy to power 1.7 million American homes. The
industry is not as green as you’d think. Growing consumes
electricity for powerful lamps, CO2 generators, fans and air
conditioning. On a personal scale, it takes as much
electricity to produce one joint-worth of cannabis as
lighting a lightbulb for 25 hours.

In some
cannabis-loving states like California marijuana production
accounted for 3 percent of the state’s entire energy

Evan Mills is a member of the UN
Intergovernmental Panel on Climate Change. “Most key parties
are not yet engaged. California and elsewhere has begun to
address the destructive impacts of unregulated outdoor
cultivation, but have yet to recognize what may be even
greater environmental consequences from the prodigious
amounts of energy used by indoor operations,” said

Outdoor production also has environmental
consequences with deforestation and high levels of water and
pesticide use but outdoor producers will have to abide by
pre-existing environmental laws, just like everyone else. In
effect, that makes indoor production the chief climate
change and energy concern.

As the industry grows, so
will its negative impacts, therefore legalizing marijuana
use should also require the growing industry to power itself

Annual consumption of electricity in the USA
for the purpose of growing marijuana produces 15m tons of
greenhouse gas emissions (CO2), equal to that of three
million average cars.

So we have these groups calling
for legalisation of marijuana on one hand and also calling
for steep reductions in greenhouse gas emissions on the
other. They are quite vocal about blaming agriculture and
the burning of fossil fuels for the country’s GHG
emissions but it seems, taking the USA consumption as an
example of the likely effects from legalisation in NZ, that
logic does not come into their thinking it is just about
self-satisfaction (the nimby style of thinking strikes

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