If, however, we opt to add fewer leaves, focussing on starting with the optimal 30 to 33:1 ratio, our moisture will be more than the crucial 60-percent. So, it won’t be long before we get to the optimum 33:1 ratio when things speed up. So, while the 37:1 ratio will delay the speed of our initial composting process, as the microorganisms consume the carbon, releasing carbon dioxide, the nitrogen levels increase. The final compost mix ratio is about 10:1. In the composting process, the carbon is reduced to carbon dioxide, and there is some nitrogen loss too. We were aiming for a minimum of 33 parts of carbon matter for every one part of nitrogen. That caused our C: N ratio to drop to about 37:1. What do you choose when there’s a choice between accepting lower C: N ratios or high moisture content when you compost grass? In our mix above, we added 6.8 pounds of shredded dry leaves to our ten pounds of fresh grass clipping to get the moisture below 60-percent. But as we established, we require double that quantity of leaves to manage moisture levels. So, to get to a 30:1 ratio, for every 10 pounds of grass clippings, you only need 3.5 pounds of dry leaves to end up with a 30:1 mix. Dry leaves have a nitrogen level of 0.75%, and carbon content is 50% carbon (the rest is cellulose and lignin). To capitalize on the high nitrogen levels in grass clipping, we need to mix the clipping into a shredded leaf mass. Managing Carbon/Nitrogen Ratios When You Compost Grass Clippings To increase the surface area available for microorganisms and prevent anaerobic conditions, add relatively finely shredded leaves. Just a point to note here: leaves, like grass clippings, have a flat structure and mat quickly. Next, we’ll consider the effect on the carbon/nitrogen ratio. For now, we’re only considering moisture levels. Therefore, for every 10 pounds of grass clippings, we need to add about seven pounds of leaves. Even if we use dry leaves, their moisture content is still about 35 percent. We need to add dry carbon matter that will absorb (or distribute) the excess 17 percent water. Our aim is to reduce the 77% moisture content in the clippings while retaining fresh clippings’ nitrogen benefits – so drying it out isn’t an option. We’ve established that we need to ensure moisture content below 60% to avoid anaerobic conditions when you compost grass.

Grass clippings