Is it a problem?
It certainly can be. It depends what you decide to do with it. Green waste is an overall term that covers, not only grass clippings, but leaves, branches, bushes – the “droppings” from the things in your yard. If you prune a bush, trim a tree, pull weeds, mow the grass – the result of all this weekend warrior work is green waste. Storms, also, with their attendant strong winds, cause havoc and leave a mess in the back yard. (Sometimes in the local streets as well.) That is green waste.
What do we do with it?
It is not a good idea to be sending green waste to the local dump. Our towns and cities have to deal with a lot of stuff that has been dumped. Dumps (landfills) are limited in size. Sending a lot of green waste (obviously this includes the larger components, the thick branches, tree trunks, the invasive bamboo that no-one wants in their garden any more) takes up a lot of space. It is certainly not sensible to put things in landfill if they can be otherwise dealt with.
How does methane come into the story?
Methane is a potent gas. We can (tongue in cheek) blame the cows and other farm animals for the production of methane, however green waste is definitely a potential problem as well. When green waste goes into landfill, it is compacted, covered, which removes oxygen, and decomposition without oxygen produces methane. Bacteria go to work, increasing methane generation. Methane may be up to 25 times more potent than carbon dioxide.
As well as methane, green waste decomposition can produce “leachate”. This allows rainwater to soak into the landfill, permeating the spaces and draining away decomposing matter, that is chemicals and organic matter, toxins and pollutants. If this gets to the creeks and rivers, and drinking water is polluted, there could be health issues to deal with. So without doubt the answer is, don’t put green waste in landfill.
At the top of the list would be recycling and composting. Recycling converts green waste to other products (you must have seen the rough hewn, country style tables and chairs that some clever artisans are able to create) and means less green waste in the rubbish dump. Composting breaks down the waste items and turns it into something that can be incorporated in your garden to improve the soil. The waste is decomposed in the open air, and not deprived of the necessary oxygen in the process.
Maybe the best option?
Ask professionals to deal with the green waste you have accumulated. There are green waste removal companies who will make sure your waste is not just dumped in landfill, but will make sure it is recycled or composted. They come to your place, pick up the pile of green rubbish, and take it away to be dealt with in accordance with best practice.