Using & Repurposing Kitchen Waste: A Complete Guide

By Ellen Rubin

Waste isn’t a waste until we waste it.”
Will.i.am

To live sustainably means purchasing thoughtfully and responsibly, and using what you have to the fullest. In the past, we’ve too easily relied on the garbage can instead of considering how to get the most out of everything. We have created disposable lifestyles that have resulted to too much waste. Instead, be mindful of how you can use items to their fullest.

This includes kitchen waste.

Introduction

A bowl of food waste scraps - Using & Repurposing Kitchen Waste: A Complete Guide

It’s possible to use waste that you would normally throw out to grow new fruits, vegetables, and herbs, or repurpose them to help clean and freshen your home, make beauty products, nourish companion animals, houseplants, or the garden. All the tips and tricks outlined below will save you money, reduce waste, and help you live a more natural lifestyle. Using natural ingredients, instead of chemical-based alternatives that are packaged in plastic, should always be a goal of sustainable living. We should wisely use and reuse what we have and responsibly dispose what we can’t.

Food waste is a huge problem. Some of it is out of our control. It happens in transit or at stores and restaurants. However, 60% of all food waste happens in households. Food production accounts for 26% of global greenhouse emissions, so controlling the use and production of food has a significant impact on climate change. The USDA estimates that 30-40% of the entire food supply is wasted every year. Globally, the UNEP Food Waste Index Report reported that 1.05 billion tons of food was wasted in 2022.

One solution is to reuse, repurpose, or propagate items that we habitually throw in the garbage. The idea of reducing what goes into landfills, while also saving money on new purchases, is one worth pursuing.

Growing New Produce from Waste

I grow plants for many reasons:
to please my eye or to please my soul,
to challenge the elements or to challenge my patience,
for novelty or for nostalgia,
but mostly for the joy in seeing them grow.”
David Hobson

Imagine having to only buy a produce item once, and then using the waste, or a portion of the product, to perpetually grow new produce. This saves the fuel costs associated with production and shipping to the store, and for you to go out and purchase it. It’s also fun and convenient!

Some of the easiest produce to propagate is vegetables that can be started indoors in water. Many can be transplanted outside in soil, and others, particularly herbs, can continue to be grown indoors.

Please note that these are general outlines and if you want to grow your own produce, please look up more exact instructions.

Lettuces, cabbages, and Bok choy can be grown from the core of the head. Simply leave a couple inches of the leaves attached to the base and put the bottom ½” in tepid water that’s changed every few days. The heart retains latent buds that will sprout new leaves. You can either cut these leaves off as needed, or once the roots have grown, plant the entire head in moist soil.

Celery is similar. Cut off the ribs, and put the bottom in a shallow container with tepid water. Leaves will start sprouting from the center core. Next the base begins to rot or the outermost stalks lose their color and dry out. That’s when it needs to be planted in dirt. Celery is multi-functional. You can cut off the stalks for use or let the plant flower and go to seed which can be used as seasoning for dishes such as potato salad. The leaves are useful for salads or flavoring in soups, stews, salsa verde, or pesto.

While these greens start to grow in water, they need to be transplanted to soil to continue growing, unless you are a hydroponic gardener. Vegetables and herbs that can spend all their time growing just in water are considered “vase” plants. All they need are a transparent or translucent vessel so the roots also receive sunlight.

Scallions and leeks, both part of the onion family, are also vase plants. For scallions, keep 3-4” of the stalk attached to the bulb and trim the roots. Place it in 1” of water and give it lots of sun. As they continue to grow, you can clip off tops as needed. If the scallion gets too skinny, you can plant it in soil. Until then, you can keep them handy on a sunny windowsill. Leek bulbs shouldn’t be submerged in water, merely the roots. You can either peel or cut off leaves as it’s growing for use. Like all the other vegetables we’ve talked about, you can plant these in soil if you want.

Garlic bulbs are usually purchased as a clove that you break into individual bulbs. You can choose to plant them like other ornamental bulbs – outside in the fall. If you want to start them indoors, suspend the bulb over water using toothpicks.

To prevent rot, submerge only the very bottom of the bulb. If planted outdoors, the plants should be ready for harvesting in 3-6 months when 2/3 of the leaves are yellow and dry. To keep propagating your garlic, bring your bulbs indoors and let them dry out for a month in a warm, well-ventilated place out of direct sunlight.

You can also eat the green sprout which has a mild flavor. Remember, you shouldn’t use any chemical fertilizers because they’re absorbed by the bulb. Also, organic bulbs/cloves are more likely to sprout.

Onions can root in water with about 1/3 of the bulb suspended over a water glass after the bottom has been allowed to dry. It should be transplanted into soil once the roots are 1-2” long.

Lemongrass can be found in your nursery as an ornamental grass that reaches 5 feet. It’s used frequently in Asian cuisine and has a citrusy/ginger flavor. The stem of each stalk has a little bulb at the end. If you don’t see roots on it, peel of dry layers from the outside of the stalk, trim down the stalk, and put it in a jar of water. Within 3-4 weeks, 2” roots should have emerged and new leaves will start to sprout. It can be planted outside to continue growing, though keep in mind this is not a hardy perennial; in much of the world it would be grown as an annual.

Watercress is another green that can be grown on your windowsill as a microgreen, or outdoors as a mature plant. It can be started from a leftover stem being placed in water to root. It’s usually an aquatic plant but you can transfer it to a pot with moist compost. Since this is a shade-loving plant, it doesn’t need a sunny window to thrive.

Some vegetables can be grown from seeds gathered from your produce. Of these, peppers are the easiest because the seeds are ready to plant. Even if they are immature, they will ripen after the pepper has been picked. Merely dry the seeds out on a non-porous surface like a plate for a couple weeks. You can either store them in a dark cool place for planting outside in the right season or start them in plastic pots indoors.

Seeds from beans, peas, and okra can be treated the same as peppers; however, let them dry on the plant if possible.

Tomatoes and cucumbers require a more experienced gardener to prepare the seeds for germination. They rely on the wet method where the seeds are soaked and fermented before they are planted. I’ve never attempted this because it’s more elaborate, but have instead relied on purchasing seeds. There are guides that can walk you through the entire process if you are interested.

Herbs such as basil, cilantro, oregano, parsley, sage, rosemary, thyme, and mint can all be started from cutting in either water or soil. Some can become perennials grown outdoors, others are annuals in colder climates. Many of these can become permanent fixtures on indoor windowsills – available whenever you are cooking. Excess can be made into pesto, infused oils, chopped and frozen in a bit of water or oil in ice cube trays, or dried in the microwave for later use. Propagating and preserving your fresh herbs is a great way to save money, and always have fresh seasonings on hand.

“It’s more than just high-quality food for the family table;
it’s growing the food in a way that does not harm the environment.
That gives me emotional well-being that is important to me.” – Robert Patterson

There are a lot of root vegetables that we eat that can be self-propagated: carrots, parsnips, beets, turnips, potatoes, sweet potatoes, and ginger.

Carrots and beets can be forced to sprout leaves by placing the top few inches in a shallow plate of water. You can use the leaves like you would celery leaves but, in order to grow the root/carrot part, you must plant the tops with leaves in soil.

Potatoes and sweet potatoes sprout roots from the eyes or buds on the potato. Potatoes can be grown directly in the soil. Sweet potatoes can be started by suspending ½ of the potato over water, tapered end down. Roots will appear in about 10 days and shoots will grow from the top. Eventually, if left in only water, the root will rot so it needs to be transplanted into a pot or outside. Sweet potato vines also serve as an attractive decorative plant.

Ginger is the rhizome of the plant. There are eyes or growth buds at the end of the fingers. After washing off the growth-inhibiting spray in warm water you can plant the rhizome a couple of inches below the surface of rich soil and keep it in partial sunlight. It takes about 2 years to flower. When you need, you can cut off part of the rhizome and use it in your cooking. You will find that more rhizomes have sprouted on the original to keep forming new plants.

Mushrooms can be started from your kitchen waste. The stems contain the mycelium from which new mushrooms will emerge. Cut the stems into small pieces to start multiple mushrooms from a single stem. Organic oyster mushrooms are the easiest to start using this method. Mushrooms require specific growing mediums, even if it’s only hamster bedding or shredded cardboard. Under the right conditions, it will take less than a month before your new mushrooms are ready to harvest.

Vegetables are not the only thing that can be propagated from scraps. There are a few fruits that can be started with the seeds or waste of your produce.

Pineapples can be propagated from the leafy part on top. Pick a ripe pineapple with bright, fresh, green leaves in the center and a light brown skin. Remove the top and trim the rind back just leaving an inch of the fruit attached. Trim thin slices from the bottom of the crown until you see root buds (rings of brown dots around the outside base of the stalk).

Let the stalk dry out for at least a week, then remove the bottom few layers of leaves to pulling downward. Once it’s dried out, it can be placed in water or planted in soil. Keep it moist for 6-8 weeks, until roots grow when it can be transplanted into a gallon container. Eventually it will need a 5-gallon container. Growing the fruit isn’t a fast process; fragrant pink or red flowers bloom after 3 years and the fruit takes 2-3 years to develop. In the interim it makes a nice houseplant.

Avocados are a popular plant to start from seed, especially as a project for kids. Merely suspend the seed, with the larger bottom end dipping in water an inch or two, until roots grow. Then plant the pit directly in soil. It takes a couple weeks for the pit to crack and a couple more for a tap root to appear. When the stem is 6-7” long, trim it back to 3”. When it re-grows leaves it’s time to plant it in soil. Even if the leaves drop off over winter, don’t worry, this is the plant’s natural dormancy and your plant is still alive.

I’ve planted apple, grapefruit, and lemon seeds and had them grow. However, it would be many years before these reached maturity. It’s still a fun project for children to participate in. Another fun project is to grow pumpkins or beans from seeds.

Using Kitchen Scraps in Your Garden & Home

Kitchen waste can be used for much more than just propagating itself – it has multiple uses in the garden and around the house. Some are obvious, others are lesser known.

The organic gardener does not think of throwing away the garbage.
She knows that she needs the garbage.
She is capable of transforming the garbage into compost,
so that the compost can turn into lettuce, cucumber, radishes, and flowers again…
With the energy of mindfulness, you can look into the garbage and say:
I am not afraid. I am capable of transforming the garbage back into love.” – Nhat Hanh

The most obvious use of scraps is to make compost for your garden. This is a great use of egg shells, fruit and vegetable scraps, newspaper, and garden waste like grass clippings or leaves. Paper towels are another great item to toss in your compost pile, as long as they aren’t greasy.

You want to keep dairy, meat, fish bones, pet waste, anything with pesticides on it, coal and charcoal ash out of your pile, although fireplace ash is ok. There are many, many sources to go to if you want to know the best ways to compost and what the best materials are. There are even countertop and under the sink composters for kitchen waste.

Aside from composting, the most versatile kitchen items to use in your garden and around the house are eggshells, used coffee grounds, banana peels, and orange peels.

Over 100 billion bananas are sold yearly. 30-40% of the weight is in the peel. That means that approximately 36 million tons of banana peel is thrown out every year – most of which ends up in landfills. The peel is rich in potassium, calcium, and magnesium, and also contains sulfur, phosphates, and sodium. Why not repurpose them in one of the following ways?

  • Food: The peel is edible. There are several ways to prepare it including as a bacon substitute. Drinking banana peel tea before bed will help you sleep because it contains tryptophan. You can also dry the peel, then grind it into flour. In addition to the vitamins there is fiber in the peel. You can replace up to 10% of the wheat flour in a recipe with banana flour for more flavorful cookies and cakes.
  • Gardening: Composting is always an option. Chopping the peels helps them decompose faster. They create a great environment for vermicomposting by attracting worms. Banana peels can also be used directly in your garden. Scattering pieces around plants and shrubs encourages flower and fruit production because of the added nutrients. You can also bury small pieces 1-2” below the surface around plants to repel aphids. Insect-eating birds like the peels so you can place some in trees. Be careful that you aren’t attracting rodents like raccoons and squirrels.
  • Pest Control: You can use banana peels, sugar, and apple cider vinegar to create a yellow jacket trap.
  • For houseplants and outdoor plants, you can soak the skins in a closed jar of water for a couple days to create a potassium-rich liquid fertilizer.
  • Health & Beauty: There are a couple ways to use the banana peel for health and beauty purposes. Some believe that it has natural itch relief properties so you can rub a peel on poison ivy or mosquito bites for temporary relief. It is high in Vitamins A, C, B6, and silica, a collagen synthesis. Rubbing it on pores will tighten them and soften skin. It has anti-inflammatory and antibacterial effects on acne so rub affected areas for 10 minutes.
  • Household cleaner applications: Rub peels on your shoes for a high shine instead of relying on chemical-based polishes. Use it for polishing silver by making a paste combining the peel with a bit of water in a blender.

Eggshells are another extremely useful kitchen waste. 7 million metric tons of eggshells are disposed of yearly creating odor pollution in landfills and attracting microbial growth. The EU has even declared them a hazardous waste. The quantity of shells tossed out equals the amount of plastic waste disposed of in oceans every year. Why not productively reuse them?

Shells are 1/3 pure calcium. They also have trace amounts of magnesium, sodium, potassium, iron, zinc, and copper. To use them, wash out the shell and remove the membrane. Then sterilize them by either baking in a 250° oven for 20 minutes, or putting them in the microwave for 4-5 minutes on high. Some people recommend putting shells in a container of water for the microwaving process. I’ve done it without the water. Since the shells are slow to decompose, you will probably want to smash them up or even pulverize using a blender or mortar and pestle. Now they are ready to use.

  • Nutritional supplement: The high calcium content in eggshells makes it a great nutritional supplement for birds and chickens. It also aids in the bird’s digestion.
  • Gardening: The nutrients help plants grow by balancing soil pH; their alkaline structure helps neutralize acidic soil. Their texture enhances soil aeration and improves water flow. The surface area of the shell binds nutrients from other decaying organic matter and prevents them from leaching from the soil into the groundwater. Calcium is key to creating strong plant cell walls. Vegetables like peppers, broccoli, spinach, eggplants, and tomatoes do better when crushed shells are added to the planting holes or around the plants themselves. 4-5 crushed egg shells can be used per plant for fertilizing. For a quick boost, make a liquid fertilizer by soaking shells in cooling boiled water overnight. The strained liquid can be used up to once a week.
  • The calcium boost of eggshells also helps with earthworm reproduction and growth.
  • While many sources recommend using crushed eggshells as a slug and snail deterrent, the thick slime coating on the pests is usually sufficient to protects them from harm. If you don’t have a major problem and want to try this method, you need a crushed shell ring ¼” thick and 2” wide that you keep refreshed. The shells may also work to deter neighborhood cats from digging.
  • There are a lot of sources that recommend using half shells as a seed starter. You would need to crush the shell before planting the cup because it’s too sturdy for delicate roots to break through. You are better off using the egg carton for this. Once the rooted seeds are ready to plant, merely cut the carton apart and plant the entire section. The carton will quickly decompose and add brown matter to the soil.

Coffee grounds is another abundant kitchen waste that can be used in a variety of ways. Just be sure that you use only used grounds. If you aren’t a coffee drinker, but want to try one of the tips listed below, many coffee shops save their spent grounds and give them away for free. After all, there is 15 million tons of spent coffee grounds generated every year (2019 statistic).

Coffee grounds are a source of potassium, phosphorus, magnesium, and especially nitrogen. It’s both the chemical composition and the texture of coffee grounds that are useful in the garden and around the house.

  • Gardening: Vegetables like (not tomatoes) cucumbers, onions, lettuce, and corn; fruits such as blueberries and raspberries; and flowering plants like roses, gardenias, hydrangeas, and azaleas all like acidic soils. You can use the coffee grounds as a top dressing on the soil, mix it in the top layer, or make a tea by letting 2 cups of grounds soak in 5 gallons of water overnight. If you have a mulch layer that gets smelly, then just lightly rake it into the soil. Strangely enough, the caffeine in the coffee can slow down, or even stunt, plant growth so don’t use more than a ½” of grounds per 4” of soil. The coffee feeds microbes which will help improve soil drainage, is a good food for worms and vermicomposting, and helps prevent fungal infections. It’s also a suitable medium for cultivating mushrooms. If you aren’t using your coffee grounds in your garden, you may be able to donate them to a community garden and keep them out of landfills.
  • Deodorizing: Even though it can get smelly decomposing in the garden, the chemical composition of coffee grounds is a natural deodorizer for us in the refrigerator, your trash can, or the pantry. They also work as a scrub to help remove the smell of onions and garlic from your hands.
  • Pest deterrent: The fragrance and texture are a deterrence to pests such as ants, mosquitoes, beetles, fruit flies, and cockroaches. Both smell and texture discourage slugs, cats, rabbits, and squirrels. You can also use it as a flea repellant on pets. Sprinkle grounds on your dog’s coat during bath time, then rinse thoroughly. Be careful because it’s harmful if your pets consume it.
  • Cleaning agent: Coffee grounds are a natural cleaning agent that can be used several different ways. Rubbing the grounds on scratches in dark woods will lessen them. You can use them as a non-toxic alternative to harsh chemicals to clean stubborn stains on pots, pans, utensils, grills, and sinks. They may possibly stain light-colored, porous surfaces. Cleaning up the ash in a fireplace is difficult because the light-weight ash will fly up. Add coffee grounds on top of them to keep the ashes contained then compost them both.
  • Beauty: Using grounds as a body scrub exfoliates and improves blood circulation. You can use it by itself or incorporate it into a soap. If you want to make your own scrubs, most recipes include water, coconut oil, salt, and coffee grounds. You can also use it as part of your hair care routine. There are some claims that it increases blood flow to the scalp and encourages hair growth. Regardless, it will exfoliate your scalp and reduce the buildup of hair products. Keep in mind that it may enrich dark hair tones.
  • Household Decor: The grounds can be incorporated into candles to add a comforting fragrance. It can also be used as a natural dye for fabrics. These may fade over repeated washings but they start out as tan to rich brown.
  • Winter Gripping Agent: The parks department in Krakow, Poland has been experimenting with using coffee grounds instead of sand or salt to help with icy walks. The coffee doesn’t necessarily melt the ice, but provides traction without hurting the environment or your pet’s paws. In spring, when the grounds and snow melt into the surrounding landscaping, it acts as a nutrient.
  • Cooking: Coffee grounds can be used as a meat tenderizer and marinade. After re-brewing the grounds and letting them cool, place the marinade and meat in the fridge for up to 24 hours.

Orange peels work as a pest deterrent. Mosquitoes don’t like the smell so you can either scatter the peels, put strips in repelling devices, or even rub the peels directly on your skin. Cats, aphids, and ants also don’t like the smell so you can either sprinkle shredded or grated peels around plants, or even shallowly bury them.

Orange peels have potassium, nitrogen, calcium, magnesium, and D-limonene. If you want to use them for cooking, you can make marmalade, candy the peels, zest and freeze it for later use, sprinkle it on yogurt or oatmeal, use dried peels to favor teas, or put some in a jar of sugar or salt to infuse it with a citrus flavor. Infused jars will last for a couple weeks.

Combining peels with vinegar and letting it steep for a couple weeks to extract the oils and fragrance will create a natural cleaner. The rind contains vitamin C and antioxidants. Dry and powder it for use in skincare products to exfoliate and brighten the skin.

Cooking water is another item we routinely waste by pouring it down the sink. When you’ve cooked pasta, boiled eggs, or steamed/boiled vegetables, the water becomes infused with various nutrients such as nitrogen, potassium, calcium, or magnesium. Merely let the water cool down and use it to water either houseplants or garden vegetables. Not only are feeding your plants, but you are saving water.

Tea leaves contain nitrogen, tannic acid, and other minerals. Add the leaves (minus bag) to your compost pile or directly to the soil. Keep in mind that it will make the soil more acidic. Other compost candidates are paper towels, onion peels, vegetable scraps, or ground-up unsalted walnut and peanut shells. The shells also make a decent mulch because they take a while to decompose, aid soil aeration and drainage, all while adding a boost to organic matter.

Other waste-saving strategies include: putting your vegetable bits, poultry and meat bones, and shrimp shells in a bag in the freezer until you have enough to make a stock. Things like watermelon rinds can be either pickled or put into the compost pile.

Remember to use the leaves of beets, carrots, celery, and radishes. They make a tasty sauté or young leaves work well in salads. You can also make an insect/animal deterrent spray from water steeped with spicy peppers, garlic, onion, or anything else that would repel insects, deer, and rabbits.

If you keep an open mind, almost everything used in the kitchen can be used fully or repurposed.

The first rule of sustainability is to align with natural forces, or at least not try to defy them.”
Paul Hawken

There are a few kitchen products that are very useful in other areas of your home even if they aren’t waste products. Instead, they are handy to keep as natural and inexpensive alternatives to more toxic products. These include baking soda, vinegar, and cinnamon.

Baking soda and vinegar are great products for everything including cleaning, laundry, health, and beauty applications. Just exploring their uses is an entire book in itself.

Cinnamon is very helpful in gardening. It’s a fungicide so it can help seedlings avoid diseases that attach either before or after germination, heal plant wounds, prevent damping-off disease on cuttings, and gets rid of slime mold and rust which are soil-borne diseases. It also works as a rooting hormone, deters ants, flying bugs like mosquitoes, and furry pests such as rabbits, squirrels, and other rodents. You can either sprinkle the powder or make a spray by letting it steep in warm water overnight.

Final Thoughts…

The environment and the economy are really both two sides of the same coin.
If we cannot sustain the environment, we cannot sustain ourselves.” – Wangari Maathai

If the definition of sustainability is to support a process continuously over time and balance economic, environmental, and social aspects of human activity, then the epitome of that is to mindfully use what we have to the fullest. This includes using our waste to either propagate new plants and/or sustain our gardens and homes that doesn’t unnecessarily add to landfills.