How to Compost Paper and Cardboard
Updated: Oct 28, 2020
Home composting is the most convenient and environmentally-friendly way people can deal with their organic kitchen waste; garden waste and any of those natural, unprocessed materials (like wood, cellulose fibres, wool and compostable packaging) which break down naturally over time into nutrient-rich humus without producing greenhouse gases or leaving any toxic chemicals behind.
And while it may seem peculiar to dispose of eco-friendly packaging (like paper, paperboard, fibreboard and corrugated cardboard boxes) into compost heaps rather than into recycling bins, composting is the best and most agrestal way to dispose of them. After all, these types of compostable packaging are made from all-natural materials and composting is Mother Nature's way of decomposing organic waste.
Not that as a compostable packaging manufacturer we're poo-pooing recycling; far from it. We know that recycling has many benefits for the planet and, when you get right down to it, all of our paper and cardboard products are made in part from recycled materials and they too can be recycled as well as composted. However, recycling is not a zero waste endeavour and the eco-benefits of this type of waste management aren't as grand as we'd like to imagine. Turning post-consumer paper into saleable products is not a clean operation and the environmental advantages of recycling vary widely between waste management facilities based on how technologically sophisticated they are. For instance, did you know that while recycling can save the 10-litres of water needed to produce every brand new sheet of A4 paper, recycling facilities actually use more fossil fuels to operate than paper mills, not to mention that the paper recycling process creates an inky, potentially hazardous sludge which presents an incredibly tough disposal challenge.
Composting on the other hand is a completely clean disposal process, one which helps to produce nutrient-rich humus; a natural fertiliser which every plant and agricultural crop needs to grow healthy and strong. And while recycling can help save energy, resources and raw materials and helps to produce more paper, composting creates the organic mulch the world needs to grow more trees and crops - and that form of sustainability, to us at least, is more important than producing more paper.
To gardeners, compost is considered "black gold" because of the many benefits it has for horticulture and agriculture. Compost is therefore invaluable.
Not only that, but paper-based products are incredibly useful materials to put into compost heaps. They help to preserve the air flow necessary to run an efficient compost pile; they help to soak up excess moisture (which prevents the compost from becoming compacted) and, being rich in carbon, they're a handy ingredient to use to balance out the nitrogen levels of 'green' compostable materials such as grass clippings, food waste and animal manure.
So, the better alternative - the cleaner, more planet-friendly and more beneficial option to placing paper-based materials in landfills and recycling plants - is to compost them. After all, paper-based products are natural, so should be dealt with naturally.
But how do you go about composting eco-friendly packaging like paper and cardboard effectively in a home compost heap or compost bin?
How to Add Cardboard and Paper to Compost
What types of cardboard and paper can you compost?
Across the composting community, you'll find two opposing views on the types of cardboard and paper you can and shouldn't compost. One view is that all paper-based products; including glossy, waxed and printed paper or card can be placed in compost heaps. The conflicting view is that these materials should not be composted.
In the past, there'd be good reason to say that these types of packaging shouldn't be composted because for many years, the inks, glues and glosses cardboard manufacturers used to use weren't water-based and therefore weren't eco-friendly. Rather, they were petroleum-based and contained metallic pigments. Therefore, it is true that for a long time, glossy cardboard and printed newspapers, if composted, could pose a risk of leaking harmful chemicals back into the earth.
However, due to the volatile economics of oil (which compelled paper and printing manufacturers to opt for more affordable and Earth-conscious paints, fixatives and epoxies), the types of paper-based packaging available nowadays should be fine to compost. That's because most of the contemporary inks, glues and glosses available now are water-based and are made from organic materials such as vegetable oil, soybean and kaolin (a form of clay), meaning they break down naturally, just like the paper and cardboard itself. Be that as it may, it is still possible that some manufacturers and printers continue to use petroleum-based ingredients in their products to this day, particularly if they want to achieve an opalescent or particularly lustrous sheen.
Therefore, whether you choose to compost or recycle glossy and waxed cardboard and printed paper is entirely up to you. Without contacting the manufacturers directly to find out what their paints, fixatives and epoxies contain, you may think it's better to be safe than sorry and opt to recycle these forms of packaging instead, only choosing to compost Kraft paper and cardboard boxes as these are, in terms of toxicity, very clean; they contain no glues, no bleach and usually no inks.
Whichever kinds of paper-based materials you choose to compost, how do you ensure that these materials get broken down effectively in your home compost bin?
How to Prepare Cardboard and Paper for Composting
🍂 If the paper or card you're planning to compost has cellophane, acrylic or silicone-based sticky tape or labels on it, then these need to be removed as they won't degrade with the rest of the compost. Forgetting to remove sticky tapes, labels and any other types of plastic or foil liners will only result in compost contamination from micro-plastics, greenhouse gases and toxic chemicals. Not the kinds of things you want ending up in your compost heap, in your garden's soil, in local waterways or in the atmosphere.
🍂 It's recommended (though not necessary), to break down any large pieces of paper and cardboard into smaller pieces prior to being placed in your compost heap. By shredding or tearing cardboard into smaller fragments, you'll not only help speed up their decomposition process (because a larger surface area has been created for the microbes to work across), you'll also ensures that clumps of composted materials won't form which is important as you don't want any air pockets in the compost from being blocked as this can compromise the oxygen integrity of your compost pile.
Not only will a compromised compost pile be unable to supply the micro-organisms with the oxygen they need to break down the organic matter, the core temperature of the compost heap won't be maintained, meaning the entire decomposition process will slow down or will stop entirely.
How to Shred Cardboard for Compost
There's no "best way" to make paper-based products and compostable packaging smaller for composting; whether you shred, cut or tear, the results will be the same. However, shredding card and cardboard boxes by hand can be a tough job, especially for those with medical conditions like arthritis or carpal tunnel syndrome. Which is why many people opt to use an electric shredder to shred their cardboard into thin strips prior to placing it into their compost heap. Scissors, box cutters and gardening sheers can also be used. Alternatively, soaking the cardboard in water for a few days will make it much easier to tear or cut.
Soaking cardboard in water dotted with a tiny amount of washing up liquid will make the card easier to cut, tear or shred. It will also help speed up the cardboard's decomposition process. For a truly eco-friendly alternative, fresh urine makes for a good accelerator too!
The Best Ways to Compost Cardboard and Paper
There are two ways in which you can compost cardboard and paper. The method you choose will depend entirely on how quickly you want to create nutrient-rich fertiliser and whether you have a lifestyle which gives you (a) the time to shred and/or soak the cardboard first and (b) the time to maintain your compost heap.
Method 1 - "Shred and Spread" - The Hands On Technique For Natural Fertiliser in a Jiffy
🍂 Start your compost pile or compost bin with a 4-inch layer of soaked and/or shredded cardboard and paper. Place these alongside other high-carbon materials (which in composting circles are known as "browns"); such as dead leaves, ash or straw.
🍂 Sprinkle with water to make these "brown" materials damp. This will help create the right environment and conditions the microbes and fungi need to degrade the waste. By keeping the pile moist like a wrung-out sponge, you'll also be discouraging rodents from nesting in your compost.
🍂 Next, add a 4-inch layer of nitrogen-rich materials (such as fresh grass clippings, kitchen waste and animal manure) on top of the "browns". In composting circles, these materials high in nitrogen are nicknamed "Greens".
🍂 Keep making layers like this - brown, green, brown, green - until you're on your last layer of "greens". After that, it's time to add a 2-inch layer of soil to the compost.
🍂 After five days, aerate the start of your compost heap by turning over the pile with a pitchfork; maneuvering the outside layers into the centre. By doing this, you'll not only prevent matting (which can slow down the decomposition process), you'll also be introducing more oxygen into the pile which provides both a rich, oxygenated atmosphere for the micro-organisms to live and thrive, it also helps regulate the core temperature of your compost heap. This is essential to do because if your compost pile exceeds 65°C, the helpful bacteria will die and the compost you've made just becomes a pile of worthless rubbish. After the initial aeration, aerating can be done every 7 - 14 days.
🍂 While aerating your compost pile for the first time, if your compost is starting to look and feel dry, dampen it until it becomes soft again. You can do so by using a watering can filled with rain water or by moistening with a hose. Rain water is preferred to tap water as it is pH neutral and contains fewer traces of chemicals like chlorine and fluoride which can impact the quality of your fertiliser. After dampening your compost heap for the first time, it's important to check every 3 - 7 days.
Your compost pile should contain 40 to 60 per cent water; the easiest way to check that your compost heap is damp enough is to put on a pair of gloves, pick up a handful of compost and squeeze it. If water gushes out, it's too wet (so you will need to add more "brown"materials) and if you can't squeeze out any water, the pile is too dry and therefore you need to water it.
🍂 Once aerated and moist, continue adding layers of brown materials, green materials and soil whenever the ingredients become available or until you start running out of space in your compost bin. Then you can start on your next one!
It's important to note that a good balance of both "green" and "brown" materials is maintained while composting as the micro-organisms which produce the fertiliser function best when this balance is spot on. Aim for 25 - 50 per cent "green" materials with the remainder being made up of "brown" ingredients. It's also essential to avoid any one material dominating the heap, especially grass clippings as these can become a slimy, smelly mess.
Method 2 - The Lasagna Way (A Slower Process which Requires Little Effort)
🍂 Start your compost pile or compost bin by laying down sheets of cardboard and paper; wet them (using a spray bottle or watering can is handy) and cover with a 2-inch layer of soil.
🍂 Build up just as you would with the "shred and spread" method - on top of the soil cover with alternating layers of "green" materials, "brown" materials and earth whenever they become available.
With this method, there is no need to worry about having to aerate your compost pile and the only time you need to dampen the compost by hand is when you add layers of paper or cardboard to the mix.
Please note that while the following video demonstrates how to use the lasagna method to fill a raised bed, the same approach can be applied to compost heaps and compost bins.
How Long Does it Take to Compost Cardboard and Paper?
All paper products contain an organic polymer called lignin. Lignins are what give the cells of wood their high levels of rigidity and their resilience to rot. Which means that the more lignins left in a paper-based product, the longer it will take to decompose. During the process of manufacturing office paper and corrugated cardboard, most of the lignins in the wood pulp are removed, however about five percent remain in computer paper, 10 per cent remain in card and about 30 per cent are left in newspaper.
For that reason, computer or office paper - especially if it's shredded - is perfect for using in the 'shred and spread' method as homemade fertiliser can typically be created within six to eight months (although, if you'd like to make top-notch, high-quality fertiliser, you should wait for at least two years for the compost to become fully mature).
The lasagna method on the other hand takes a lot longer - typically between one and two years - because the cardboard and newspaper used in this type of sheet mulching both contain a greater amount of lignins, therefore making this type of composting a slow operation.
Many green-fingered compost enthusiasts who want to create organic fertiliser quickly avoid composting with newspaper. That's because newspapers contain at least 30 per cent of their organic polymers, meaning periodicals and magazines take much longer to decompose naturally, hence why a lot of gardening aficionados choose to recycle them rather than compost them.
It's important to note, however, that the speed of which compost can be created is based on several factors including; the size of the compost pile or bin, how often it's aerated, the ratio of materials used, and the weather, etc. So, the length of time it will take you to create organic fertiliser will be completely different to how long it will take your neighbours.