How to Make Soap Using Food Waste

Today, I want to share with you how you can incorporate food waste into your soaps. We know that food waste is a major problem, accounting for an estimated 1.3 billion of food wasted globally each year.

What food waste can I use to make soap?

For this blog I chose three types of food waste: used coffee grounds, used tea leaves or flowers, orange peel and oat milk pulp. All of these ingredients will add exfoliating properties to your soap bars while preventing them being dumped in the bin.

Food Waste | How to make soap using food waste | Bottega Zero Waste

Choosing Oils for Soap Using Food Waste

The bulk of my recipe is formed by olive oil, which I had previously infused in some bay laurel leaves. The leaves had fallen in my garden in my summer house in Italy. I didn't want them to go to waste!

The olive oil is then followed by coconut oil, which I normally buy in bulk and keep in this big jar.

Next, I have added sunflower oil for it's silkiness in soap making. I also chose to include it in this recipe because it's one of those oils that gets thrown away often as it's widely used for frying. You can even reuse sunflower oil you've already used for frying! If there are bits of food in it, just make you filter them out first.

Want to understand more about Soap Making?


Handling Lye Safely

Sodium hydroxide is the ingredient that will transform the oils into soap. If you are new to soap making, make sure you download my tools and lye safety checklist. It will walk you through the security measures with handling lye.

How to Make Soap with Food Waste

You will need:

Our essential and mandatory safety tools are made up by gloves, googles and if you can, a mask or respirator.

For tools we will need:

  • Four soap moulds
  • Four beakers to divide the soap batter and mix in the different food waste items
  • A stick blender
  • A spoon
  • A spatula.

Download the recipe card and ingredients list for soap using food waste here.

Soap with Food Waste Recipe

1. We will begin by weighing our sodium hydroxide and our water in two separate beakers. Never use an aluminum beaker, and make sure that the beaker you add the water to is heat safe pyrex or stainless steel.

2. With our googles and gloves on we add the lye into the water. Never do the opposite because it will cause an extreme heat reaction that could make the lye erupt out of the container.

3. Mix until the lye is dissolved and set aside, away from pets and children. Allow it to cool down to about 110°F/36°C. For this you will need a thermometer, you can use a laser or a candy/meat thermometer.

Make the lye solution | How to make soap using food waste | Bottega Zero Waste

4. In the meantime, we will weigh our oils and prepare our food waste. We will use used coffee grounds, used finely ground tea leaves, used oat milk pulp and used lavender tea buds. Make sure all of these ingredients are fully dry before incorporating them into your soap.

5. Once the lye and oils have cooled down to about 110°F/36°C, we can begin adding the lye to the oils. First, mix with a spatula or a tablespoon. Then we will use a stick blend to reach a state called trace.

Trace | How to make soap using food waste | Bottega Zero Waste

Trace is when the lye water and oils have fully mixed together to reach a light custard consistency. When we let the soap drip on top of the surface, we see a faint trail.

6. At this stage, we can incorporate our additives (e.g. food waste). Simply add the waste to the beaker and mix with a teaspoon or spatula.

Note: For the sake of this blog, I have split the batter in four to show you how to add different additives this video. However, if you are a beginner I don't recommend doing this. The soap will become hard very quickly and may solidify before you can pour it. I recommend doing one type of additive at a time.

Adding food waste | How to make soap using food waste | Bottega Zero Waste

7. After, add the essential oils. I chose eucalyptus for the coffee soap, patchouli & bergamot for the oat milk soap, lavender for the lavender buds soap and grapefruit for the oat pulp soap. I cannot tell you how good my whole house smelled after this!

8. Depending on how thick or thin your trace is, you might need to stick blend each soap a couple of extra seconds before pouring the soap into the mould.

9. Then, I suggest covering the soap with a piece of cardboard, making sure not to touch the soap surface or the carboard will get stuck to the soap.

The carboard will insulate the soap and keep it warm, promoting what we call "gel phase" which makes the soap harden faster. You can also add a blanket or a few pieces of cloths on top of it.

Cover with cardboard | How to make soap using food waste | Bottega Zero Waste

10. After 24 hours we are ready to unmould the soaps! Gently pull them out of the mould. They might be a little sticky, but that's normal.

11. We need to give them time to "cure", as at this point they cannot be used. The lye water will need to evaporate so that the soap is not caustic anymore. To cure, just place it on a shelf in a dry room and turn every once in a while.

After 4-6 weeks cure time, it will be gentle and usable! I truly believe that making your own bath & beauty products with fewer ingredients is the most effective way to reduce waste.

Food waste soap | How to make soap using food waste | Bottega Zero Waste

I hope you enjoyed that recipe, make sure to tag me in your food waste soap creations on Instagram @bottegazerowaste! I'd love to know, what food waste would you turn into soap?

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