As the third largest fresh vegetable industry in the United States, onions are a staple ingredient in many American households. In fact, onion consumption has risen by an enormous 79% over the last thirty years, and 93% of restaurants in America feature this root vegetable on their menus. However, much less is shared about the environmental impact, and especially the carbon emissions of onions. So we had to ask: What is the carbon footprint of onions?

Onions have a carbon footprint of 0.11 kg (0.25 lb) of CO₂e per pound of produce. This is a very low carbon footprint in comparison to other vegetables, and is largely because onions can be grown locally, have a long shelf life, and often require few resources, such as pesticides, to grow. 

In this article, we’ll walk you through the overall carbon emissions of the life-cycle of onions. From growing and packaging, to transportation and end-of-life practices, you will learn how this vegetable affects the planet and discover some ways to reduce and offset the footprint. 

Here’s How We Assessed the Carbon Footprint of Onions

The carbon footprint is one of the ways we measure the effects of our human-induced global climate change. It primarily focuses on the greenhouse gas (GHG) emissions associated with consumption, but also includes other emissions such as methane (CH4), nitrous oxide, and chlorofluorocarbons, and is generally expressed in carbon dioxide equivalents (CO₂e).

“Carbon footprint: the amount of greenhouse gases and specifically carbon dioxide emitted by something (such as a person’s activities or a product’s manufacture and transport) during a given period”

Merriam Webster

Basically, it is the amount of carbon emitted by you as an individual or an organization providing you with goods and services – including onions:

• This includes GHG emissions from producing the products that we use and foods that we eat (e.g., power plants, factories or farms, and landfills)
• GHG emissions from fuel that we burn directly or indirectly (e.g., logistics and transportation, cooling or heating facilities),
• as well as the GHG emissions attributed to how we consume these products and foods.

To understand the carbon footprint of onions, we must assess its life-cycle and each stage’s sustainability. This life-cycle assessment (LCA) is a method to evaluate the environmental impacts of products and materials.

Here’s the Overall Carbon Footprint of Onions

The overall carbon footprint of onions is 0.11 kg (0.25 lb) of CO₂e per pound of produce, which is very low. For example, onions produce less than half of the carbon emissions of lettuce, and about a tenth of the carbon emissions of cucumber.

So, let’s have a look at each stage of the LCA of onions!

These four stages can be broken down in more detail to understand why the carbon footprint of onions is low in comparison to other vegetables.

What Is the Carbon Footprint of Growing Onions

The carbon footprint of growing onions is 0.05 kg (0.11 lb) of CO₂e per pound of produce, which makes up 42.65% of the overall carbon footprint of this vegetable. This number is low mainly because of their efficient growth times and lack of pesticide use. Negative factors that contribute to this footprint include the use of tractors to plant onion seeds. 

Onions are grown underground, and do not require a great deal of resources. Fewer resources needed in the agricultural process lead to a far smaller carbon footprint. 

Which factors impact the carbon footprint of growing onions?

• How do onions grow: Onion seeds are usually planted by tractors. Onion seedlings, or ‘sets’, are transplanted by hand. The use of tractors is carbon-intensive, but hand-planting is labor-intensive. The onions then grow underground. Underground vegetables generally require fewer resources than vegetables grown above ground in fields or energy-intensive greenhouses.
• What is the growth duration of onions: Onions grown from seed take around four months to mature, whereas onions planted as sets take just under three months to grow. This is a shorter-than-average growing time, similar to that of peppers and potatoes. A longer-than-average growing time increases the carbon footprint, due to the extra resources needed.
• What is the land usage of onions: Onions are a fairly land-efficient crop and on average, 18-40 tonnes of onions are grown per hectare. They have to be carefully spaced at least two inches apart, meaning that they have a lower yield than some other root vegetables. For example, potatoes have a very high yield of 40-70 tonnes per hectare. Land-efficient crops tend to have lower carbon footprints, since less resources are needed.
• What is the water usage of onions: Onions have a relatively high need for water, requiring about an inch of water every week. Because of their shallow root systems, onions are often watered through drip irrigation which requires energy. This contributes to the carbon footprint of this plant.
• What is the pesticide and fertilizer usage of onions: The Environmental Working Group found onions to be the fourth ‘cleanest’ crop, which made it part of their ‘Clean Fifteen’ list of foods that contained the least amount of pesticides. Since pesticide usage produces carbon emissions through manufacturing, transportation, and application to crops, onions have a low carbon footprint at this stage.

In short, the land, water, and pesticides used when growing onions contribute to the overall carbon footprint. However, because onions do not require a lot of these resources, the carbon footprint of growing onions is relatively low. 

What Is the Carbon Footprint of Harvesting, Processing, and Packaging Onions

The carbon footprint of harvesting, processing, and packaging onions is <0.09 kg (<0.2 lb) of CO₂e per pound of produce, which makes up 28.5% of the overall carbon footprint of this plant. Unprocessed and unpackaged onions have a lower carbon footprint, as less resources are required.

Onions are often sold loose, which is part of the reason why they have a lower carbon footprint than vegetables which are frequently packaged in plastic, such as salad mix. However, the processing stages and machine-harvesting of this crop contribute to the carbon emissions of this stage. 

Which factors impact the carbon footprint of harvesting, processing, and packaging onions?

• How are onions harvested: Onion harvesting is a very intricate process, which usually takes place overnight to prevent sunburnt onions! They are either harvested by hand, or machine. Machine harvesting and tractor use have negative impacts on soil health and release a lot of carbon emissions, increasing the carbon footprint of onions. 
• How are onions processed: Onions have to cure in the field for 1-2 days before going on to be processed. Processed onions are a major part of the food industry, with onion paste, onion powder, and onion oil used as common flavorings. As well as this, onions are sold ready-chopped, pickled, or in frozen dishes, such as onion rings. Around 15-18% of onions are processed. This processing requires a lot of electricity and resources, increasing the carbon footprint. However, these processed products could lead to less waste, due to extended shelf-life.
• How are onions packaged: Onion packaging differs from store to store, but many onions are sold loose. Sometimes they are packaged in mesh bags, or polyethylene bags which increase the carbon footprint of this stage. Opting for loose onions is a way to lower your personal carbon footprint. 

In short, onions that are unprocessed and sold loose have a lower carbon footprint than those packaged in plastic or sold pre-processed. 

What Is the Carbon Footprint of Transporting of Onions

The carbon footprint of transporting onions is <0.05 kg (<0.1 lb) of CO₂e per pound of produce which amounts to 28.84% of the overall carbon footprint. This is a relatively low carbon footprint because onions can be grown in many states, making it easier to buy local produce. Produce grown in other countries will have a much larger transportation footprint.

Onions grown locally produce far fewer food miles from transportation, making locally-grown onions better for the environment.

Which factors impact the carbon footprint of transporting onions?

• Where are onions grown: Onions are easy to grow across many states, and are commonly found in areas where potatoes are grown. The leading states for onion production are Washington, Idaho, Oregon, California, and Texas. Onions are grown commercially in over 20 states, which means that locally-grown onions can be relatively simple to find. This reduces food miles and means that the carbon footprint of this stage is low.
• How are onions transported: Onions are transported either by road, rail, air, or ship. Like most fresh produce, they require constant refrigeration during transportation. Unfortunately, refrigerated vehicles can emit up to 29 times more potentially carcinogenic particulate matter and six times more nitrogen oxides than far larger, modern diesel truck engines. If onions are bought from local farms, the carbon footprint is decreased.

In short, the carbon footprint of transporting onions depends on where they are grown. Luckily, due to the widespread nature of onion farming, it is often possible to purchase locally grown onions to reduce the carbon footprint. 

What Is the Carbon Footprint of the End-of-Life of Onions

The carbon footprint of the end-of-life of onions is largely impacted by the amount of food and packaging wasted. Around 43,000 tonnes of avoidable onion waste is discarded every year. However, since onions are often sold loose, there is less plastic waste with this vegetable.

Onions have a long shelf-life and often are sold without packaging, meaning that the end-of-life of onions should have a relatively low carbon footprint. However, onion waste still often ends up in landfill, increasing the carbon footprint of this stage.

Which factors impact the carbon footprint of the end-of-life of onions?

• How are onions disposed of: 43,000 tonnes of avoidable onion waste is discarded every year. Onions are completely compostable but often end up in landfill, which is a big problem for the environment. Unfortunately, 20% of onions are wasted before they even reach shelves, due to aesthetic imperfections. The resources used to grow these crops just to discard them are enormous, and negatively impact the carbon footprint of onions. To reduce this waste, the demand for ‘wonky fruit’ has been rising. 
• How is the packaging of onions disposed of: Since onions are often sold loose, there is little waste, which is a big factor in the low carbon footprint of onions. On the other hand, processed onions are often sold in plastic packaging, which creates a higher carbon footprint. Many of the polyethylene bags used for packaging are recyclable, as long as the polyethylene is not bonded with other plastics. This is because polyethylene is generally only recycled to make like-for-like products. However, a lot of plastic that we recycle ends up on the other side of the world, causing a threat to developing countries. So, it is much more sustainable to buy loose produce. 

In short, buying unpackaged onions, and storing them properly, leads to far less waste. Being conscious of the way you dispose of onion waste will reduce your carbon footprint.

How Does the Carbon Footprint of Onions Compare to Other Types of Food

Onions have a very low carbon footprint compared to other vegetables. Additionally, vegetables tend to produce far fewer carbon emissions than other types of food, making onions a highly sustainable choice!

Let’s see how onions compare with other vegetables.

How Does the Carbon Footprint of Onions Compare to Other Types of Vegetables

In comparison to other vegetables, the carbon footprint of onions is very low. For example, cucumbers produce nearly 10 times the carbon emissions of onions. Salad vegetables need more resources to grow, making their carbon footprint far higher than root vegetables.

So, onions are one of the vegetables with the lowest carbon footprint. But how do they compare to other types of food?

How Does the Carbon Footprint of Onions Compare to Other Types of Food in General

Root vegetables have a very low carbon footprint in comparison to other types of food. They produce around 31 times fewer greenhouse gas emissions than beef. 

When it comes to greenhouse gas emissions (GHG), foods are often compared in terms of emissions per 1,000 kilocalories (as opposed to their weight in lbs or kg).

Additionally, since onions are low in calories, a far greater amount of produce is needed to equal 1,000 kilocalories.

• To eat 1,000 kilocalories, you would need to consume 25 servings, which is around 10 large onions or 88 ounces.
• In comparison to beef you would only need 4.6 servings to eat 1,000 kilocalories, or 16 ounces.
• Comparatively, vegetables can have a high carbon footprint per kilocalorie, but are enormously less calorific than animal-based food.
• More calorific plant-based foods, such as pulses and nuts, have a miniscule carbon footprint in comparison to animal-based proteins. A single portion of beef amounts to around five and a half portions of onions, in terms of calories.
• This means that per portion, you will be consuming fewer calories, and so the carbon footprint will not be as large as this graph suggests.

Even though the carbon emissions for onions are low in comparison to other types of food, try to be mindful of the ways you can lessen your environmental impact when you purchase them.

How Can You Reduce and Offset Your Personal Carbon Footprint

All of the food you eat will have some form of carbon footprint, even when you buy foods with low CO₂e, such as onions. However, there are ways to offset and reduce your personal carbon footprint. 

There are a few easy techniques to buy more eco-friendly onions, and you can also find ways to offset the carbon footprint after your purchase.

How Can You Reduce Your Carbon Footprint When Shopping for Onions

When shopping for onions, consider these ways to lessen your impact on the environment:

1. Shop locally and seasonally: Onions are in prime season from summer to fall. Buying from local farms reduces the carbon emissions produced and makes it a much more sustainable choice. If you are near a local, small-scale farm, which harvests by hand, your purchase will be even better for the environment.
2. Choose organic: Organic onions produce a much lower carbon footprint than non-organic vegetables, due to the lack of pesticide production, distribution, and the overall higher health of soil for crops, insects, and animals.
3. Buy plastic-free: Avoid pre-processed and packaged onions, and instead opt for whole, loose produce. This will decrease the overall carbon footprint of your purchase massively.
4. Store your onions correctly: Onions can actually last for up to a year in the correct storage conditions, but moisture and light can lead to premature spoilage. Store them in a cool dark place, and freeze chopped onions to lead to a longer shelf-life, and less food waste. To create even less waste, you could even use the skin of onions to create your own onion powder, or make a natural dye.

Taking these actions are a great way to lessen your own carbon footprint, but there are also ways to offset the impact of consuming onions as well.

How Can You Offset Your Personal Carbon Footprint

Carbon offsets are reductions in carbon emissions that are used to compensate for carbon emissions occurring elsewhere – for example for the carbon emissions that are associated with onions. They are measured in tons of CO₂ equivalents and are bought and sold through international brokers, online retailers, and trading platforms on what is known as the global carbon offset market. 

“Carbon Offset: a way for a company or person to reduce the level of carbon dioxide for which they are responsible by paying money to a company that works to reduce the total amount produced in the world, for example by planting trees”

Oxford Dictionary

In terms of onions – and indeed all food types – there will always be a carbon footprint, because of the resources it takes to get your food from farms to the place where you’ll eventually eat them. And while there are ways to reduce your carbon footprint when shopping for onions, carbon offsets would be a way to reduce your CO₂e emissions all the way down to net zero (or even to become climate positive).

However, when you purchase carbon offsets, it’s important that they actually make a difference in offsetting (aka reducing) total carbon emissions. To achieve that, the following are key criteria:

• Carbon offset projects have to be effective (different projects have different effectiveness rates)
• Carbon offset projects have to be additional
• Carbon offset projects have to be permanent
• The claims from carbon offset projects have to be verifiable

To find the best carbon offsets for you personally, check out our full guide on the best carbon offsets for individuals, where you’ll also learn more about how these carbon offset projects work, what their respective offsetting costs are, and what your best way would be to offset your own carbon emissions.

Final Thoughts

Onions have a very low carbon footprint when compared with other vegetables and an even lower carbon footprint when compared with other foods. However, you can try to reduce your carbon footprint even further by eating organic, reducing food and plastic waste, and purchasing local, seasonal produce. When you do enjoy onions, think about whether you can offset the carbon emissions created, to make this healthy vegetable a more sustainable option!

Stay impactful,

Sources

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