Do not leave the clippings in the bags, they will become a slimy gooey mess. Mix the clippings into your other compost ingredients such that they add the heat without forming mats of grass. This would work much better if you would shred your ingredients before adding to the pile. Be sure to also keep enough moisture for the micro organisms to breakdown your vegetative matter. Al

What is bad about a "slimy gooey mess"? This is a serious question. Other than aesthetics (which I don't care about at all) is there something bad about letting the clippings heat up in the bag?

I know shredding and turning would make a nicer, hotter pile, but I'm lazy and won't do it that way. So it's a cold pile I'm dealing with.

Very little of my gardens are veggies, mostly ornamental. I'm not worried so much about not being organic, but worried about introducing diseases or weeds or bugs and killing a $30 peony or stand of blue spruces...

Will heating in the bag help kill bad things, or do I have to quit picking up other peoples stuff?

What is bad about a "slimy gooey mess"? I'd like to know the serious answer to this question as well...there are many times that I get bagged clippings, and for one reason or another do not get them put out in a timely manner..and I too have the results of it, stinky clippings still in a bag...what can be done to salvage this ooey gooey mess? is it still ok to toss in?

From the "not-so-scientific" pool of composters- the slimey, gooey mess is merely a matter of how much you want to deal with it. Yeah, I'm sure there is something to be said for the bacterial disgusting-ness that is going on in there that would warrant a 20-minute stint on "60 Minutes," but it would seem to me that even a cold-composting process (which I mainly do) will eliminate the nastiness of this mess.

I also take other people's OM discards, and toss into my pile. While I rarely get into the amount of heat that IS generated in my cold-composting efforts, I do GET a good amount of heat, I turn occasionally (maybe a total of 5-6 times from April to October), and I get compost. Anything that was a slimey, gooey mess has usually reduced itself over the course of the composting process and the occasional turning, and I get compost.

I rarely concern myself with the detrimental health-aspects of composting & exposure to bacteria. I've seen worse stuff cleaning out my fridge.

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The problem you will have is that the grass in the bag is decomposing anaerobically. Hot composting is an aerobic process utilizing aerobic bacteria not anaerobic bacteria. The majority of the beneficial soil-dwelling bacteria are aerobic bacteria. So before adding the "composted" grass clipping to your garden they will have to sit for some time exposed to oxygen to destroy the anaerobic bacteria and become repopulated with aerobic bacteria. This is also the reason that soil should be added to the compost pile - as an inoculant.

So why not just do it aerobically to begin with?

This may go against your lazy nature but I would spread the grass out in the sun to dry during the week between collections. This will preserve most of the nitrogen content of the grass which is really the value of the product. Then store the dry grass in the garbage bags for addition to your compost pile along with leaves and other refractory material. You will have to make sure that the grass is suffciently dry before storing. The danger is aerobic composting will start in the bags and set the grass on fire. This is not a great danger because of the closed environment of the plastic bags but you should be aware of the possibility.

Anaerobic bacteria aren't bad, they just smell that way.

Anaerobes are not very beneficial from a gardening perspective, but they're not harmful either.

From a composting perspective, anaerobic bacteria leave less volume when digesting material than aerobic bacteria. So if you want to maximize your compost volume, then you want to minimize the smell and stink of anaerobic activity whenever you can.

On the other hand, anaerobic bacteria can play a positive role in waste disposal by decomposing material and minimizing the volume of the remains.

I have had large piles of grass clippings sit next to the compost bins for weeks because I haven't been able to get to them to mix them in with other stuff. I have just then lifted the slimy mess and put it into the bin, or even on new beds. Not as pleasant as nice finished crumbly compost, but I figured it was OM and didn't want to waste it.

Here is my experience of letting wet grass clippings sit in black plastic bags in the sun in hot weather.

They get Hot! and so does the bag so be careful lifting them up to dump, It was hot enough to burn once! They also get stinky and slimy and perhaps breed some anaerobic bacteria. I wouldn't worry too much about all that if you don't mind the stink and slime then it isn't such a big deal.

Heating in a bag might help some to kill weed seeds but I wouldn't expect it to do anything about fertilizers, pesticides, or herbicides. If you are worried about chemicals the gather grass clippings at your own risk. I don't use much chemicals personally but I am still willing to collect grass clippings for my compost.

If you have been composting mainly with leaves before, you might be suprised to see how hot grass clippings can make a pile get. A big glob of wet grass clippings might not make really pleasant compost so I do my best to spread it out before covering with a layer of leaves or other carbon material.

Just so you know, the strong smell is a sign that the nitrogen is escaping so it is good to mix with carbon material is the pile as soon as you can or you loose a little of the benefit of the grass clippings. If the smell starts to get like the bottom of a samp or pond muck, that is a sign that things have gotten anaerobic and you want to avoid that when you can. Experiment a bit and see how it goes.

Composting doesn't need to be very complex. If it is not heating up, it needs more nitrogen or moisture needs adjusting. If it is smelly, it either needs more carbon or it is too wet. Starters, inoculants, soil, tumbling, and turning are not required. Only time and a mix of materials.

Good luck with it.

I'm also from the school of "the science of composting can be intimidating". I mainly cold compost, but with a decent mix of the right stuff I can get some occasional heat and manage to turn out one large, very good looking, very good smelling batch each gardening season.

My grass cuttings stay on the lawn, but I do get fresh clippings from our city compost site - when I drop off brush or an overload of weeds I don't want in my compost, I'll fill up a couple of bags with grass clippings someone else just dumped off. They do go bad fast, but if you have no aversion to working with them in that state, no harm, no foul.

My only problem this time of year is having to start a new pile since I haven't finished distributing my ready batch yet. I am accummulating an over abundance of greens and will have to layer the new pile with shredded newspapers until the trees drop their leaves. Guess the only thing I'd do with the grass clippings - whether they're fresh or tending toward slime - is churn them up for a while so they don't clod up. Then it all just kind of works on its own.

Thanks for the responses. So now we've heard the bad and not-so-bad about slimy smelly grass clippings. Back to my other question, will letting these things cook in the bag by the sun help kill any of the bad things I might be bringing home?

I think I answered that in my long post but here it is again.
Cooking in the bag in the sun could help against weed seeds if it gets hot enough. As to other bad things, I'm not sure about fungus diseases or bacterial diseases. I also don't know that the heat in the bag will do anything to chemicals like pesticides or herbicides. Much of the benefit of the compost is from the microbes and only partially from the heat.

Don't worry about the clippings no matter what state of decomp you find them in. Perfectly OK. They may have been cut and bagged on Monday and set on the curb Thursday. They will smell nasty, feel slimy, but that isn't a problem. If you are concerned about weed seed, look at the lawn behind the bags when you pick them up from the curb. If the lawn is weedy, you may get weed seeds. I have never seen anyone bag grass clippings that has a weedy lawn. Just doesn't go together--compulsive neatnik bags grass but lets the lawn go to weed--doesn't happen very often. What you will get is chemical from all the weed killer Mr. Neatnik uses. You can often smell it when you open the bag. Deal with that carefully.