12 September 2021

Let’s talk about you and me(thane)

Here on the farm in Cornwall we have three large composting bays where we compost absolutely every single bit of green waste we make, together with the cardboard flower boxes we receive from our suppliers. As mentioned in James’s previous post about The Three Ws (weeds, water and waste) the decomposition of that organic matter decreases its volume to about 5% of its original size. This means you can fit 57 cubic metres of green waste in to a 9 cubic metre composting bay. This means that over the process of its decomposition it condenses to around a 6th of its original volume. Mind blown. Since we’ve been in Cornwall we’ve filled five of those bays, totalling 285 cubic metres of green waste. In London, that would have been the equivalent of about 130 commercial bin loads of green waste. This is waste that had to go in to a big bin, get loaded in to a bigger truck, get driven around London… you get the point. It’s also waste we had to pay for!

Not only does this now create wonderfully nutrient-rich compost for us to use on our farm, it also turns waste in to something really valuable for us as well as helping us reduce our greenhouse emissions.

There’s an unfortunate and counter-intuitive truth with all of our organic waste. Chucking something like a bunch of flowers in the bin doesn’t feel like a big deal for the environment, because it breaks down right? Well, yes, but as illustrated by this useful post here, greenhouse gas emissions actually increase when organic matter is buried in landfill, because without air, the decomposing process produces methane. Methane is a greenhouse gas, meaning its presence in the atmosphere contributes to the earth’s temperature and climate system. Although methane comes from natural sources (we all know about cows passing wind) it’s also emitted from anthropogenic sources, or human-related sources and over the last two centuries, the methane concentration in the atmosphere has more than doubled, making it the second most abundant anthropogenic greenhouse gas, with carbon dioxide in first place. However, methane is able to absorb far more heat than CO2, making it 25% more powerful than CO2 at trapping heat in the atmosphere, with a global warming potential 84 times greater than CO2 in a 20 year time frame.

Despite being more potent than carbon dioxide, methane is less persistent. Co2 has a longer-lasting effect on the environment but methane certainly sets the pace for the speed at which our climate is warming up, with its concentration in the atmosphere increasing faster now than at any time since the 80s, accounting for 25% of global emissions. This is why efforts to reduce methane would have almost immediate benefits to the climate.

Of all the sources of methane emissions, waste accounts for 16% of the total, so keeping green waste out of landfill certainly would have significant results. As with anything of this nature, it’s not about a few people doing it perfectly but about many people doing what they can.