Greenhouses may seem sustainable since you can grow plants that are not native to your region, cutting down on food miles.
However, greenhouses are not as green as you might expect because they require a lot of energy and can still cause pollution due to pesticide use.
Here’s everything you need to know about the environmental impact of greenhouses.
1. What Are Greenhouses Made Of?
The panels of a greenhouse are usually made from glass, but others can be made from plastic.
The structure will likely be supported by metal and timber, for example, metal plates holding the glass panels together and wooden pillars inside.
Greenhouses are often covered in plastic sheets or fiberglass sheets to protect plants from unpredictable weather or UV rays from the sun.
2. Is the Production of Greenhouses Eco-Friendly?
Generally, the production of greenhouses is not particularly sustainable.
Firstly, many materials used to build greenhouses are non-renewable, such as plastic and metal.
Although sand appears to be in abundance, that does not mean that glass is considered a renewable resource.
It can take hundreds or thousands of years, for rocks and shells to break down into new sand, which is why it’s not technically renewable from a human time scale.
Although wood is renewable, trees can take decades to mature, so they are not easy to replenish if the wood is being harvested irresponsibly.
Plus, many of these materials are not sourced sustainably; plastic and metal are sourced via mining.
Mining can physically degrade the environment due to deforestation, construction of the mine site, soil erosion, and soil instability.
However, many greenhouses are made from recycled materials, which is a step in the right direction; recycling uses less energy and resources than producing new materials.
The biggest environmental concern when it comes to greenhouses is energy use to regulate the temperature or provide lighting.
Most energy worldwide is from nonrenewable sources like fossil fuels, with only 30% coming from renewables.
So, high energy use is unsustainable and contributes to climate change unless it comes from renewable sources.
Greenhouses are actually one of the biggest energy users in the agricultural industry.
3. Is Growing Plants in Greenhouses Eco-Friendly?
When it comes to sustainability, there are pros and cons when it comes to growing plants in greenhouses.
As mentioned earlier, greenhouses are very energy-intensive, which is not eco-friendly.
Most of this energy is required to maintain the indoor environment and run the mechanical systems and evapotranspiration.
On the other hand, greenhouses reduce food miles, which is the distance food travels before reaching customers.
As you can create the perfect environment to grow plants or food that normally cannot grow in your area, you rely less on importing goods from abroad.
Research found that relying on domestically grown food alone can reduce food mile emissions by 0.27 GtCO2e and emissions from production in general by 0.11 GtCO2e.
However, the high energy use is still concerning.
For example, in the Netherlands, greenhouses make up 80% of the energy use from agriculture.
Greenhouses have a long lifespan if they’re high quality and are maintained well.
It’s possible to keep the same greenhouse for up to 40 years, so there is not a regular demand to harness energy and resources to replace greenhouses.
Greenhouses can prevent the need for deforestation as excess land does not need to be cleared for growing food or certain plants.
Although you might not think it, since greenhouses are secluded from the surrounding environment, many farmers still use pesticides in their greenhouses.
Pesticides, insecticides, and herbicides are harmful to pollinators such as bees.
Run-off from pesticides can also spread pollution and harm plants and animals.
Research has found that pesticides from greenhouses can enter the surrounding environment.
There have been moves to make greenhouses more sustainable, for example, using thicker glass to reduce energy use from heat or adding solar panels.
Research found that making their roofs curved and using photovoltaic cells to convert sunlight into energy reduced the need for external energy sources.
Up to 98% of the energy needed to run the greenhouse was from the cells.
Greenhouses can also contribute to waste.
Many greenhouses are covered in removable plastic sheets to protect crops from sudden temperature changes or shield them from UV rays.
These sheets can also be made from fiberglass. So, these are also nonrenewable.
They also do not have as long of a lifespan as the greenhouse itself, so they will need to be replaced a few times within the greenhouse’s lifespan.
Their exact lifespan varies depending on the quality and materials, but generally, they seem to last between four to ten years if cared for properly.
If they are not secured, they can contribute to plastic pollution by being displaced during storms.
They also need to be disposed of properly at the end of their lifespan to prevent them from contributing to pollution or breaking into microplastics.
Some may be recyclable but are too large for a home recycling bin, so they will have to be sent to a specific facility.
In the environment, animals and fish can consume microplastics which negatively impacts their health as their stomachs are full of non-food items, so they have less room for food.
Humans can also consume microplastics from eating animals and fish.
In humans, microplastics may negatively impact immune health or cause inflammation.
There have been moves to make biodegradable greenhouse sheets.
This is a step in the right direction, as bioplastics are often made from plant-based sources, which are renewable.
However, some biodegradable plastics are only biodegradable in certain conditions or do not break down as much or as quickly as customers might expect, so bioplastics are not always a perfect solution.
4. Do Greenhouses Produce Greenhouse Gasses?
Greenhouses indirectly produce greenhouse gasses.
As the world continues to rely on fossil fuels, and greenhouses are big energy users, they can contribute to greenhouse gas emissions.
So it’s best to power heaters, coolers, and lights with renewable electricity if possible.
However, it’s not always feasible to place solar panels on small greenhouses as they may block out too much sunlight, so it’s only really an option with large greenhouses that can afford to lose some space for plants.
5. Are Greenhouses Recyclable?
Many types of plastic are recyclable, while some types of wood are also recyclable.
Greenhouses are much too big to go in a home recycling bin, and the facilities this waste gets sent to will not have the means to process them anyway.
Instead, greenhouses need to be deconstructed and sent to specific recycling facilities.