Why Compost Coffee Grounds?
What is the impact of composting coffee grounds? When building a composting recipe, do coffee grounds count as food scraps or bulking agent? These are questions we sometimes hear about coffee grounds in a compost pile. Here are some answers:
Coffee Grounds Help With Decomposition
Coffee grounds have a relatively high nitrogen content, similar to vegetable scraps, so they are generally categorized like food scraps for compost recipe building. They help generate heat to speed up the decomposition process.
A recent lab test of Starbucks coffee grounds found that the carbon/nitrogen ratio was about 24:1. The results of that test explained that, “there is more than sufficient nitrogen present in the coffee grounds to provide for the nitrogen demand of the soil microorganisms as they degrade the organic fraction”. Typically, we recommend to our clients that they start their composting process with a 25:1 carbon/nitrogen ratio. So coffee grounds bring a close to ideal carbon-nitrogen ratio right up at the beginning.
They Make Your Compost Safer
Studies from Oregon State’s Composting Program have shown that composting coffee grounds reduces the number of dangerous pathogens and seeds from vegetables and weeds in the compost. This is because the coffee grounds help to maintain a high temperature in the composting process. Coffee grounds also improve the nutritional profile of the compost by improving availabilities of phosphorus, potassium, magnesium and copper.
Obviously, Composting Coffee Grounds Smell Amazing
Even though coffee grounds have a significant nitrogen, grounds also have a significant ability to absorb moisture and control odors. Coffee grounds have had a lot of liquid pressed out of them. The small particle size and texture of coffee grounds is similar to saw dust. Like saw dust, the grounds are capable of absorbing large amounts of water. This makes coffee grounds helpful at absorbing excess moisture and, therefore, preventing odors. Plus, the pleasant smell of the grounds helps to overpower unpleasant odors.
Coffee Grounds Won’t Mess with Your Compost’s pH Balance
We also sometimes hear concerns about the acidity of coffee grounds. Coffee grounds have a pH usually between 6.5 – 6.8, which is slightly acidic but close to neutral. A slightly acidic compost is often actually preferred at the beginning of the compost process. Therefore, we don’t typically expect coffee grounds to throw off the pH of the compost pile.
Coffee Grounds Are Often Free
Since coffee producers typically see coffee grounds as a waste product, coffee grounds are often available for free and make a helpful and versatile amendment to your composting operation.