Compost your yard waste
Composting your yard waste is a great way ensure you are not needlessly filling up landfills. The problem with putting leaves in a plastic bag is that the since the plastic bag does not decompose, the leaves inside cannot decompose.
The simplest method is to just use the mulch function (no bag) on your lawn mower. The grass clippings will provide a great free fertilizer for your lawn. What could possibly be simpler than doing nothing extra at all? However, if the going gets tough, you will have to use the bag. Rather than filling up a giant lawn bag half-way (or half empty), dump and spread the clippings over your flower bed to prevent weeds from growing around your plants. If there are toxic fertilizers present on the grass, I wouldn’t sprinkle this around the edible plants in your garden.
Of course, if your town picks up your yard waste to be brought to a composting facility, then you should do so. But, if you have room and feel ambitions, you can make your own compost pile of yard waste. Dig a large shallow hole and fill it with some leaves. Lightly cover it with dirt and place some more leaves over that, and sprinkle that with some more dirt. You will be amazed at how many leaves you can fit into such a small hole. If you followed my recommendation of waiting to rake up the leaves, then they should be that much lighter and crumbled. Be sure to mix up the pile every other week or so to ensure there is plenty of oxygen to take place. A year or more later, you should have the finest top soil money can buy.
If you don’t have enough room in your yard (or don’t want to look at the pile of rotting leaves soon to be beautiful, nutrient rich potting soil) but you are uneasy about the fact that you are preventing purely organic matter from returning to the earth, I suppose you could purchase the biodegradable bags instead.