Reader Mailbag: Thoughts on Grass Clippings in Compost
A reader writes, "Granger, you're a freakin' genius. Cast some knowledge down from the mountain on me. [Here's my question:] I've actually been adding grass clippings as browns...I pile them up in the back yard, let them dry out of a few weeks and then add them. They are all brown and dry by them...do you think that is bad? Also, I worry that grass clippings lead to increased weeds in my garden plot...any thoughts?
I have done a lot of research into composting and how it all works. Extension services have produced some really informative pages on how to get started. Cornell, in particular, has a great page on the science of composting. Understanding how compost forms is a good way to work through problems.
Here's what I think. The phrase, "browns and greens," is kind of misleading. Color, while a good rule of thumb, isn't determinative. Coffee grounds are a green, for example, and one of the best greens out there. So, the color of your grass shouldn't matter. What is important is its carbon to nitrogen ratio. Fresh grass typically has a C:N of between 10:1 and 20:1. (I've seen varying figures reported) It seems that anything below 30:1, which is the ideal C:N ratio for compost, is a "green," while anything above is a "brown." I think of browns and greens this way: if it burns, it's probably a brown.
Now, so what "color" is dead grass that's perhaps a few weeks old? That's hard to say. I suspect that perhaps some of the nitrogen has been extracted while it sat and that if added to a pile it wouldn't heat it up like fresh clippings would. That's just a guess, but I don't know if it'd really serve the purpose of a brown. It might. I just don't know. (I'd love to know how it works for you)
Regardless, I don't think it's a bad practice. If the end result is compost, then don't sweat it. Alternatively, you could add it to the pile right away and mix in some super browns like sawdust. I got a giant bucket of sawdust and it was a breeze to work in. But, then again, you might be producing more grass than you can compost at once. I tend to leave my clippings on the lawn. After a week, they've either broken down or been whisked away with the wind, scattered to the four corners of my neighborhood.
For the second part of your question, you might get seeds in your compost. This is a genuine problem. However, if you hot compost the high temperatures should deactivate the seeds, alleviating any problems there. Cold composting, done over a year or more, might accomplish the same thing, but I'm not too certain on this point. In the end, I think the benefits of using aged and mature compost outweigh the risks of stray seeds.
As an aside, I scored some major grass today. A lawn service crew that was working on my neighbor's yard gladly filled up a giant bin of grass clippings for me. My pile keeps getting hotter by the day. Fascinating stuff.
I have done a lot of research into composting and how it all works. Extension services have produced some really informative pages on how to get started. Cornell, in particular, has a great page on the science of composting. Understanding how compost forms is a good way to work through problems.
Here's what I think. The phrase, "browns and greens," is kind of misleading. Color, while a good rule of thumb, isn't determinative. Coffee grounds are a green, for example, and one of the best greens out there. So, the color of your grass shouldn't matter. What is important is its carbon to nitrogen ratio. Fresh grass typically has a C:N of between 10:1 and 20:1. (I've seen varying figures reported) It seems that anything below 30:1, which is the ideal C:N ratio for compost, is a "green," while anything above is a "brown." I think of browns and greens this way: if it burns, it's probably a brown.
Now, so what "color" is dead grass that's perhaps a few weeks old? That's hard to say. I suspect that perhaps some of the nitrogen has been extracted while it sat and that if added to a pile it wouldn't heat it up like fresh clippings would. That's just a guess, but I don't know if it'd really serve the purpose of a brown. It might. I just don't know. (I'd love to know how it works for you)
Regardless, I don't think it's a bad practice. If the end result is compost, then don't sweat it. Alternatively, you could add it to the pile right away and mix in some super browns like sawdust. I got a giant bucket of sawdust and it was a breeze to work in. But, then again, you might be producing more grass than you can compost at once. I tend to leave my clippings on the lawn. After a week, they've either broken down or been whisked away with the wind, scattered to the four corners of my neighborhood.
For the second part of your question, you might get seeds in your compost. This is a genuine problem. However, if you hot compost the high temperatures should deactivate the seeds, alleviating any problems there. Cold composting, done over a year or more, might accomplish the same thing, but I'm not too certain on this point. In the end, I think the benefits of using aged and mature compost outweigh the risks of stray seeds.
As an aside, I scored some major grass today. A lawn service crew that was working on my neighbor's yard gladly filled up a giant bin of grass clippings for me. My pile keeps getting hotter by the day. Fascinating stuff.
3 comments:
Thank you sir. Most informative.
Also...I reccomend using brown paper bags from the grocery store as "brown" material in your compost pile. I really helps to cut down on those wasteful and annoying plastic bags of which I have thousands stuffed into a box in my garage.
Yeah, I agree. Brown paper bags do work well. Paper towels seems to work well, too, so long as I rip them up enough. What I'm really impressed with is the "compostability" of shredded paper. I have a cross-cut shredder that I shred bills and things with. It makes nice sized shreds that seem to dissapear really quickly.
Post a Comment