Photo: making compost in the Dignan Street Community Garden.
In a month’s time, I’ll be flying to San Francisco to start the Fulbright Wallace residency at Headlands Art Center. As the work I’ll be making there focuses on our relationship to the earth, my aim is that the residency and what it produces sits lightly on the planet. Living in Aotearoa means the flight itself will be the largest producer of CO2 emissions. So I decided to attempt to offset my flight by making compost in our home and community garden.
I researched the CO2 emissions caused by my flight and how much I could offset that by making compost. The results varied massively. So my carbon footprint calculations aren’t going to stand up to any sort of scientific scrutiny. That said, I’m still interested in keeping track of this. Allowing some creative license, here are my initial calculations.
I spearheaded an initiative for our community garden to receive food scraps from our local Countdown supermarket every week, diverting it from landfill. With this and other materials, I’ve made 12 cubic meters of raw compost, with the support of the other community gardeners.
Over time, that reduced by 75% to 3 cubic metres of finished compost. Depending on the moisture content, this equates to approximately 3 tonnes of rich compost, full of microbes.
Plants use photosynthesis to convert sunlight into sugars. After the sun sets, these sugars are drawn down the plants’ roots and into the soil as exudates. Spreading compost on plants increases the amount of microbes . These are attracted to the exudates, increase the CO2 that the plant takes out of the atmosphere and lock that carbon up in the soil. One study in America calculated that for every tonne of compost spread around plants, 0.24 tonnes of CO2 is drawn into the soil. By these calculations, my 3 tonnes have given me a credit of 0.72 tonnes of CO2.
In addition, by diverting the food scraps to the compost, we save the CO2 they would have emitted in landfill. According to one American study, every tonne of food scraps reduces the amount of CO2 emissions by 0.46 tonnes. Roughly a third of my 3 tonnes of compost were food scraps, taking my CO2 credit up to 1.18 tonnes.
I chose to use www.chooseclimate.org to calculate what my two flights are really costing the environment. Their calculation was 2.332 tonnes CO2. This means I still have 1.152 tonnes of CO2 to offset. I plan to do this with more compost creation which I hope to continue during the residency. I’ll also be looking into other ways I can keep my footprint light while I’m there.
I have to admit that these figures can in no way measure the absolute joy, peace and sense of interconnection with all life that comes from making compost, growing food in it, eating the produce and putting the scraps into the compost. That’s my real motivation.