What happens to biodegradable materials in a landfill?

The short and sassy answer is: (1) bad things, or (2) nothing. As you read above, there is no oxygen or light present inside a landfill, so materials don’t break down the way they would under normal conditions. Consider a disposable fork made out of a plant-based bioplastic (maybe made from corn starch or wheat). While it might biodegrade in the presence of oxygen, it might never break down at all inside a landfill, or as it slowly breaks down, it will emit methane, as discussed above. The same is true of paper products, which are biodegradable but which break down much more slowly than normal under landfill conditions, emitting methane as they do.

I know this is disheartening to read, especially when alternatives like bioplastic disposables present the hope for a better solution. As with all things, my best suggestion is to apply the five “R”s principle: if you have worked through the “Refuse,” “Reduce,” and “Reuse” steps and find yourself facing an unavoidable disposable product situation, look for a certified (by BPI or CMA in the US) compostable option. After the product has been used, be sure to close the loop by composting properly; most compostable disposable products and packaging require an industrial compost facility. If you don’t have access to one, just put the items in the garbage (bioplastics are generally not recyclable and can contaminate recycling batches) and comfort yourself with the knowledge that at least they were made out of a renewable resource.