You're chopping carrots for dinner when you reach for the compost bin, sweeping the tops and ends into it without a second thought. A moment later you're juicing a lemon and tossing away the rind. That crusty loaf of sourdough on the counter? It's been there over a week, and it's off to the trash.

We've all done it. In the rush of cooking, food scraps tend to fall into two categories: compostable or disposable.

But many of these so-called scraps are culinary building blocks in disguise.

In today's food landscape, where prices are high, waste is widespread, and sustainability is more urgent than ever, it pays to rethink what we throw away. An estimated 30 to 40 percent of the U.S. food supply is wasted each year, contributing to both landfill waste and greenhouse-gas emissions. Yet plenty of food scraps that we treat as trash could be tomorrow's secret ingredients.

Saving scraps can also help you ­become more resourceful in the kitchen, explains environmental activist Bea Johnson, author of Zero Waste Home. "For me, it's about creativity, but the cost savings are a reward for anyone."

Whether you're trying to stretch your budget, reduce waste, or flex your creative muscles, these tips can help you look at your kitchen scraps in a whole new light.

CITRUS PEELS

"My favorite wasted scraps are citrus peels for zest," says Auset Shridevi, the executive chef for the website Eating Love. Shridevi likes to use a Microplane, an ultrasharp hand grater that yields fine, flavorful zest - "perfect for just about any baked good or cream frosting."

Shridevi uses citrus zest in savory cooking, too. "For something savory, lemon or lime zest with garlic, fresh herbs, and avocado oil makes a great rub for marinating chicken or fish," she explains. Or mix orange zest with sugar to adorn the rim of a favorite beverage.

You can dry your citrus zest or use it fresh, or try this simple method to make citrus salt:

• Zest your citrus.
• Spread the zest on a baking sheet. Dry it at the lowest oven setting, or leave it at room temperature until it's dry and brittle.
• Mix about 1 tablespoon dried zest with ¼ cup sea salt.

Use citrus salt on roasted veggies or grilled fish, or as a rim for a summer mocktail. (Try it with our Pink Grapefruit Margarita at "Summer Mocktails.")

VEGGIE PEELS AND ROOTS

Many peels and root ends left over after chopping vegetables can become a flavorful stock.

Johnson likes to collect veggie peels and roots in a jar and store them in the freezer for an easy, scalable stock method. "When the jar is full, throw the scraps into a pot, cover them with water, bring to a boil, simmer for 15 minutes, then strain."

Shridevi recommends cooking your stock over low heat to preserve delicate flavors. "Avoid bittering veggies like broccoli, cabbage, or collard greens," she advises.

Your homemade stock can become the base for soups or sauces, adding depth while sidestepping food waste. (Try it in our Kale, White Bean, and Fennel Soup.)

You can also use the stock for cooking grains or legumes. Refrigerate your stock for up to five days, or freeze it in portions for several months.

STEMS AND CORES

Stems from broccoli, kale, and collards tend to end up in the compost pile, but these commonly neglected bits are nutritious and edible.

"Vegetable stems do not need to be discarded," Johnson says. "I chop them and add them to the dish instead. Chopping or peeling stems can make them easier to handle."

For example, you can peel thick broccoli stems and slice them into matchsticks for stir-fry, or chop collard stems small and use them in soups or sautés with herbs and garlic.

Because they're tougher, these stems may take a few extra minutes to fully cook, but they'll reward you with texture and flavor that you'd otherwise miss out on.

EGGSHELLS AND COFFEE GROUNDS

Before discarding your coffee grounds or eggshells after breakfast, consider giving them a second life in your garden.

Eggshells and coffee grounds are rich in nutrients that support strong plant growth. Crushed eggshells add calcium to the soil, which helps prevent blossom-end rot in tomatoes and peppers; coffee grounds provide nitrogen to boost leafy greens and herbs.

To prepare these food scraps for the garden, follow these steps:

• Rinse the eggshells and let them dry before crushing them.
• Let the coffee grounds air-dry to prevent mold.
• Sprinkle directly into the soil or mix into your compost for an easy, eco-friendly fertilizer that keeps your garden thriving.

Sometimes your scraps just won't work in cooking, and that's OK. If all else fails, many of these scraps make ideal compost matter.

If you're able to compost your scraps, the most convenient place to collect them is in a designated countertop compost container. Keeping a large outdoor compost bin, meanwhile, is an affordable and efficient way to transform your kitchen scraps into gardener's gold. (Try our simple six-step method to start composting at "How to Start Composting.")

You can also try keeping your compost in the freezer, which can eliminate bugs and odors - a great solution for those without much counter or yard space, or for people who want to save scraps over time before taking them to a community drop-off site.