Almost anything organic can be composted. That's why I have a plastic bucket sitting on my kitchen counter to capture orange rinds, banana peels, egg shells, wilted lettuce, and all the other typical household refuse from breakfasts and dinners. When the bucket is full we dump it on the compost pile. As you might guess, it fills faster in the summer when we eat more fresh produce from the garden, grocery store, or farmers market, but that isn't the limit.
Composting can take place throughout the year. Though temperatures below 40 degrees will put the microorganisms responsible for decomposing to sleep, you can still put your organic collection on your pile. Mixed with leaves and other garden material from fall cleanup it's ready for the micro critters to eat when spring temperatures warm them up. With lots of work and attention you can keep your compost pile warm enough to maintain decomposition throughout the winter, but most of us don't want to take that effort when it's cold outside.
I try to keep the composting spirit alive through the cold months by maintaining the habit of putting scraps in the bucket and traipsing through the snow to dump it on the pile when it's full. During the colder months it may take two or three days to fill our bucket; we just don't eat as many fresh vegetables. I do know that it will contain some items that we use regularly: cucumber skins, lettuce heels, coffee grounds, my tea, banana peels.
Imagine my chagrin when I began to notice that the bucket was remaining nearly empty for days. Upon investigating I noticed an obvious absence of the morning coffee filter and grounds. It didn't take long to find the misplaced organics as I fished through the trash can beneath the sink. Oh, the horror of it.
It's true that composting and gardening are more important to me than to other members of my household. I know they humor me when I spend as much time as I do in the gardens. I do what I can to educate them about simple gardening activities, particularly composting. And I assume they understand it and have a similar sense of environmental awareness. But you know what happens when you "assume" that others will act a certain way.
Are coffee grounds in the trash truely a crime? Of course not. But imagine if all the coffee filters and grounds in your city, or state, or country were placed in a compost pile. Millions of pounds of coffee could become millions of pounds of compost. Starbucks gives their used grounds away for free because they know gardeners everywhere can benefit from them.
Now think about all of the banana peels and orange rinds and vegetable leftovers that get dumped in trashcans beneath kitchen sinks. Multiply the amount of organic material you dump by the millions of households that do the same and we're talking about a serious issue. San Francisco has a mandatory recycling and composting ordinance that is trying to reach zero waste by the year 2020. That's an amazing goal by a major U.S. city.
For now you can play a small yet important role in protecting our environment by composting waste that would otherwise find it's way into landfills or waterways. Be aware of materials that can be recycled naturally. Throw a bucket of kitchen scraps on a compost pile. And above all, don't discard those coffee grounds.