Scum can be used to compost and fertilize the soil for growing vegetables. By collecting scum from sources like kitchen grease, hair, and soap residue, it can be mixed with other organic materials like leaves and grass clippings to create nutrient-rich compost. This compost can then be used in the garden to improve soil quality and provide essential nutrients for vegetables to grow. It's important to properly balance the ingredients in the compost pile and regularly turn it to ensure proper decomposition. Using scum in composting is an environmentally friendly way to recycle waste and create healthier gardens.