After two weeks of municipal strikes, the wheelie bins lining the roads are starting to bulge . . . and smell. There’s one plus to this, however. Since the surplus of refuse is literally lifting the lids of the bins, I’ve been able to get an easy look at what people are throwing away. To a large extent, they are throwing away greens. And there’s nothing green about that.
One of the most dangerous myths about the environment is that it is better to send something biodegradable to a landfill than something that will last a hundred years, like a plastic bottle. Quite frankly, that’s a load of garbage.
The last thing you want to happen in a landfill is biodegradation. Deep in a landfill, in the absence of oxygen, bacteria break down plant material into methane. This gas is 21 times more potent as a greenhouse gas than carbon dioxide. If garden waste is composted or left to decompose in the garden, it will give off some carbon dioxide, but not more than it absorbed when it was growing. So sending plants to the landfill is at least 21 times worse for the atmosphere than composting them.
Grass clippings are the worst, since they decompose much faster than, say, twigs. It is impossible to precisely calculate these things, because of the many variables in landfills, but a reasonable estimate based on a thorough scientific report, is that 1 kg of garden waste in a landfill will give off 77 grams of methane. This means that a full, standard black refuse bag (750mm x 950mm) containing 14 kg of grass clippings will give off as much greenhouse gasses as burning 9.5 litres of petrol by driving nearly 100 kilometres. Recycling the equivalent quantity of plastic—the same bag filled with 3 kgs of empty PET plastic bottles—would save less than a sixth as much greenhouse gases as composting that bag full of grass.
Our lawn space is considerably smaller than many suburban gardens. But my gardener says that in the summer, he mows about two bags worth of clippings twice a week. So in some months, our grass clippings would be causing as much damage to the atmosphere as the electricity consumed by our house, if we were throwing these clippings out with the garbage.
But we don’t. I don’t have much energy for composting, so just a fraction of the clippings go into a somewhat neglected compost pile, which nonetheless manages to produce some good compost in time. The rest is stored in reusable large woven polypropylene bags until we have a carload. Then I haul them a couple of kilometres to the nearest Pikitup garden refuse transfer site, so the municipality can compost for me. It’s a small inconvenience to keep my grass truly green.