If you don't have a garden (ie live in an apartment etc), is there any benefit (reduced methane?) to composting food scraps before throwing the soil in the trash/landfill?
Not my area of expertise here, but I would think that doing so would help by reducing the overall volume of your waste. As food breaks down into soil, it packs tighter and reduces its overall volume. I assume that garbage trucks are limited by the volume that they can carry, not the weight, so reducing your waste volume should help reduce your overall carbon footprint by marginally reducing the number of vehicle-trips that it takes to collect your waste.
That being said, I would have to think that reducing the amount of waste that you create in the first place will have a bigger impact than reducing the volume of a given mass of waste.
