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Avocado and onion peels are the new black: natural dyes made with food waste

«Using food waste to produce dyes tackles the sustainability problem from different angles». A conversation with Cara Marie Piazza, Creative Director at CMP Dye House

The production of natural dyes from agro and food waste

With almost 1.3 billion of food produced every year worldwide, the production of natural dyes from agro- and food-waste appears to be a viable solution for consumer health, business, and the environment. «Using food waste to produce natural dyes for the fashion industry tackles the sustainability problem from different angles», explains Cara Marie Piazza, Creative Director at CMP Dye House. «It intersects different industries and creates a logistical system that connects food and fashion production processes». The food-waste dye is nothing new in the history of fashion. Known and used since ancient times, this trend is now witnessing growing popularity, mostly in cities where dye houses can benefit from the high density of restaurants and fast-food chains that provide leftovers to produce dyes. When asked about the production process, Piazza explains, «We always try to work with local restaurants in New York, where we’re based. Restaurants in the city provide us with the food waste we need, such as avocado or onion skins. We have weekly or bi-weekly pickups, and then we can start producing the dyes».

The downsides of natural dyes

While natural dyes have the convenience of being a renewable source and are biodegradable in nature, having a low environmental impact, they are still associated with problems of moderate colorfastness, non-reproducibility of shades, and pollution caused by the use of metallic mordants. To minimize the issues connected with poor color fastness properties, the industry uses different metallic salts that fix the colors on fabrics. Aluminum potassium sulfate, stannous chloride, ferrous sulfate, and copper sulfate are the most common and act as electron donors to form coordination bonds with the dye molecules, assisting in developing the chemical bridge between dye and fiber molecules. «We use Aluminum Potassium sulfate for protein fibers, and Aluminum Acetate and a mix of a light tannin like oak apple tannin or tara powder depending on the dye», states Piazza. The problem with mordants is that they can render the pollution-free intention of natural dyes futile if the chemically contaminated wastewater isn’t disposed of safely. but the dye materials themselves are not pollutants to water. The chemicals mordants can be. Groundwater and river pollution would occur if metallic compounds were used as mordants and not disposed of responsibly. «While our dyes are completely biodegradable», explains Piazza, «we still have to take into consideration the ​​amount of energy used in the process; even if food-waste dyes production is more sustainable than synthetic ones, the water consumption is still an important factor in the equation».

The natural colors of mineral earth pigments and botanical lake pigments, a Cara Marie Piazza workshop with Natalie Stopka

Natural and bio-mordants: viable alternatives to chemical mordants containing metals

These are reported as sustainable and ecologically correct alternatives to metal mordants, providing satisfactory dyeing and solidity properties. Some bio-mordants were proposed as alternatives for aluminum, iron sulfate, copper sulfate, stannous chloride, and potassium dichromate and can be extracted from food waste, such as pomegranate peel, rosemary, and thuja leaves for example. Some foods, like onion skins, contain their own tannins, meaning that little or no fixative is required to dye fabric. Another issue related to mordants and water disposal concerns the pH; pH is crucial when it comes to dyes. Without the right pH levels, the dye might not permanently fix the fiber, compromising results and causing color fading; on the other hand, if the pH of water is too high or too low, the aquatic organisms living within it die. Dye houses must make sure they take care of water used in dye baths before disposal to avoid the risk of releasing water that is potentially dangerous for animals. As Piazza explains, water needs to be neutralized after the process; «we try to neutralize the baths before disposal, to bring them back to a neutral pH. Our garments, dyed with natural dyes, don’t leave microplastics in the water when washed at home. We also try to raise awareness about wash care; we suggest washing the garments by hand, in cold water, and avoiding the sun while air drying. This way, colors do not fade, and garments have a longer life».

Lampoon reporting – Concerning the non-reproducibility matter

Piazza states, «Synthetic dyes are not very stable either, they can change from one collection to another; the phenomenon is more present with natural dyes but we see these changes as an advantage, instead of as a downside». And she continues, «We have to keep in mind that dyes are locally sourced and produced, like wines; they come from different terroirs, we want to normalize colors produced in different places that are, indeed, different». Another thing to take into consideration while working with dyes produced with food waste is the short window of time available to process the raw material and products’ seasonality; «We mainly work with avocado and onion peels, and sometimes with pomegranate, even if this last one is expensive», explains Piazza, when asked about downsides of the process. «Working with natural materials means that we need to be fast and process them before they go bad and start to rot. Since we mainly use avocados and onions, we are not that impacted by seasonality; we try to work with local products, avocados from California, for example». The fashion industry must explore new sources of natural dyes since research in this field is still limited and confined to small-scale production. Instead of adapting food-waste dyes to fast-fashion industry approaches, this trend can encourage a re-thinking of the industry as a whole, questioning if the market demand for such a large-production scale is legit or not, from a sustainable point of view. The food-waste dyes focus on locally sourced dyes beyond cultivation to produce from local waste streams instead.

Cara Marie Piazza 

Creative Director at CMP Dye House, Cara Marie Piazza creates textiles only using natural dyestuffs such as botanicals, plant matter, minerals, non-toxic metals, and food wastes. She works with both designers and artists to realize their Natural dyeing needs as well as creates custom pieces for private clients.

Maria Bellotto

The writer does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article.

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check and buy on Prototipo Store
item collections in limited edition
crafted according to our editorial search

Hemp / made in Italy
Lampoon is working to restore
Hemp production in Italy
as hemp is the one and only
natural vegetal fiber sourceable in the country
for more info, please email us at [email protected]

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