Can Tomato Sauce Be Composted (Composter’s Guide)

Composting is wonderful because it reduces waste and creates rich, nourishing foods for plants. So many things can be composted, including fruit, vegetables, cardboard, expired herbs and spices, crushed eggshells, cooked pasta, oats, coffee grounds, etc. But what about tomato sauce? Can it be added to your compost pile?

Tomato sauce can be composted, but large quantities can be bad for your compost due to its slight acidity. However, if you have one or two expired bottles of tomato sauce, you can add them to your compost pile as it adds moisture, which is vital for the composting process.

If you are hesitant to compost your expired tomato sauce or pasta sauce, you’ve come to the right place. This article will discuss whether tomato sauce can be composted and how to compost tomato sauce properly.

Can You Add Tomato Sauce to a Compost Pile?

Food and other organic waste have unique properties that contribute to compost quality. Tomato sauce is high in moisture but lacks physical structure. 

Tomatoes and pickled food products can harm your compost pile because their high acidity can kill the good bacteria that are necessary to break down the organic material. However, the acidity levels in tomato sauce are stabilized with sugar and other additives. 

The moisture in the tomato sauce is beneficial for a compost pile because if there isn’t enough moisture present, it will either fail to work or take a very long time for the process to complete. If you add tomato sauce to your compost pile, ensure that you have enough bulking agents such as yard waste or sawdust to add structure to the mix and absorb the excess moisture. 

Food waste produces a bad odor (mainly ammonia and leachate). Therefore, it is important to keep your compost pile well aerated to prevent foul smells and to remain aerobic and free of standing water. You can reduce leachate through sufficient high carbon bulking agents and aeration. 

Although it is not uncommon to have leachate and odor production, there are ways to make it less unpleasant. You can also capture leachate and reapply it to the compost.

Composter’s Guide: How to Add Tomato Sauce to Compost

Tomato sauce (also known as ketchup) is an excellent additive for a compost pile, mainly for its odor suppression properties. After about 5 to 10 days, a compost pile’s pH level rises to seven and releases an unbearably strong ammonium smell. This is called the thermophilic stage, where the pile loses a significant amount of moisture.

This is where tomato sauce comes in handy. Even though tomatoes are acidic, adding an appropriate amount of the sauce to the pile will help reduce the pH below 7, ultimately suppressing ammonium emission. 

Ideally, a compost pile should be +/- 60% on a wet basis to add dry ingredients and materials such as leaves. Ketchup can easily make up a big part of the moisture required for composting. However, it also provides carbon you need to consider for the CN ratio, which should be about 25-30:1 to avoid high acidity and ensure healthy composting.

Let’s start at the beginning. After building or buying a compost bin or box, get all your materials ready for layering, including the tomato sauce. The perfect ratio for a compost pile is 40% nitrogen (green materials) and 60% carbon (brown material).

60% Carbon materials can include;

  • Straw
  • Hay
  • Untreated sawdust
  • Cornstalks
  • Sod
  • Chopped corncobs
  • Small twigs

40% Nitrogen materials can include;

  • Vegetable & fruit waste
  • Garden debris
  • Fertilizers
  • Grass clippings
  • Manure 

Start to layer everything you want to compost in the designated composting area but avoid adding ingredients such as;

  • Diseased plants – can transfer bacterial or fungal issues to your compost which could contaminate your garden.
  • Meat – produces a bad odor and attracts rodents.
  • Milk & milk products – produce a bad odor and attract rodents
  • Cooking oils – upsets the moisture balance of the compost pile and attracts animals and insects.
  • Bread products – attracts pests.
  • Rice – when raw, it can attract insects and rodents, and when cooked, it can breed dangerous bacteria.
  • Colored & glossy paper – The foils from the ink do not break down and will cause your compost to contain chemicals.
  • Human & animal waste – produces a bad odor and can create a health risk
  • Walnuts – contain juglone which is toxic to some plants
  • Tomatoes & tomato plants – the high acidity levels in tomatoes can kill the good bacteria necessary for breaking down organic materials.

You should layer greens and browns in your composting unit like lasagna to ensure that the food is completely covered as it breaks down;

  • Layer One – Add one layer of the carbon materials (brown), followed by a slight mist of water and a bit of tomato sauce.
  • Layer Two – Add one layer of nitrogen materials (green), another slight water mist, and some more tomato sauce.
  • Layer Three – Add a layer of topsoil (no insecticide-treated soil or sterile potting soil), followed by another light misting and tomato sauce.
  • Repeat the layers until there are no materials left.

How to Maintain Your Tomato Sauce Compost Pile

Looking after your compost pile is relatively straightforward. The important thing is to turn the pile once a week or when the temperature falls below 110 °F (43 °C) to ensure that the new or outer materials get a chance to be in the center of the pile where the most heat is. 

This is where the organic materials break down the fastest. When you have more materials you want to add to the pile, add them in the layers with the mist and tomato sauce in between like you did when you started the pile. Turn the new materials into the pile immediately using a garden fork. 

If you have added many carbon materials, give the pile a misting and add more tomato sauce to keep the moisture level at the correct percentage.

Can You Add Tomato Pasta Sauce to a Compost Pile?

A tomato pasta sauce can be composted, depending on the other ingredients in the sauce. However, since tomatoes are slightly acidic, adding large amounts of them to your compost pile can be bad. 

However, when we say large amounts, we refer to a restaurant with lots of leftover pasta sauce or a tomato business getting rid of all their old stock. So it will not be a problem if you add the little bit leftover from last night’s dinner. 

Can Tomato Plants Be Composted?

Since it is possible to compost tomato sauce, it begs whether you can compost the tomato plant as well? Some gardeners are all for composting tomato plants and have done so with satisfying results, whereas others are more reluctant to add them to their compost piles. 

There are a few things to consider before you chick the last of the season’s tomato plant onto a compost pile, including;

Unsuccessful breakdown. Placing large tomato plants to compost could become problematic should the pile not be managed properly. You could end up with unsightly compost containing large pieces of tomato plants that did not decompose successfully.

The process did not kill all the seeds. composting may not necessarily kill all the tomato seeds that remained in the plant and could result in tomato plants growing in your garden where you don’t want them.

Potential Spreading Of Diseases. Unfortunately, compost can spread diseases that can harm or potentially kill the plants you add the compost to. Diseases like bacterial canker and fusarium are die-hard diseases that often get transferred by tomato plants.


There is no right or wrong answer in this case because adding tomato sauce to compost works for some, while others tell you to avoid it altogether. The key here is moderation and monitoring the pH, moisture, and temperature to keep the compost from going bad.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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