Can i compost without a compost bin and just digging into the ground?

Yes! You can dig a traditional composting trench and fill it with your food scraps. You should weekly turn it with a pitchfork to ensure sufficient air flow to break down the materials. Alternately, you can also compost in trenches with worms without having to turn it (as the worms aerate it themselves). You can do this through the winter as well, though you'll need a larger trench, and you'll need to add plenty of manure to keep the trench warm enough for the worms (manure gets warm as it breaks down).