Saving Rubbish Like Money: Meeting Microorganisms in the Compost

And the most vital component of soil – all that dark, black organic matter – contains hundreds of millions of organic molecules, each with its own colour, absorbing and reflecting light. But when molecules of different colours are mixed together, no light is reflected, so the whole appears black. Organic matter is not merely the material foundation for life; when it bonds with inorganic particles in the soil, it also forms a stable pore structure that stores water and oxygen underground. To improve soil, one must begin by increasing its organic matter content.

Having that small, barren patch of soil in the yard gave me a good reason to start composting in earnest.

I. Starting Composting from Everyday Rubbish

For composting, I collected coffee grounds from nearby cafés and stored them at home, built a compost bin in the ground with the “non” group, and even went out once in the middle of the night to collect a huge bag of fallen leaves a street cleaner had swept up, filling the compost bin with them.

Over the past two years, during brief stints elsewhere, I also joined composting efforts in various communities. From farmyard manure piled with animal dung in the countryside, to professional rotating compost bins on city balconies, to composting at different scales and with different materials in ecovillages and farms – I have seen and learned a great deal about the many ways to compost.

Now, I intend to start from everyday life at home.

Ever since I began composting, I have collected all the organic “rubbish” at home as carefully as saving money. Every scrap of kitchen waste, leftover meals, fruit gifted by others that starts going off before it’s finished… Once, I felt a twinge of guilt and helplessness facing these remnants. Now I treat them like treasure, thinking: in the end, all of them will become precious nourishment for the soil.

At home, I do Bokashi composting: I add kitchen scraps each day and sprinkle EM (Effective Microorganisms) powder over them to cover them. (Note: EM is a microbial inoculant preparation, typically based on Bacillus, photosynthetic bacteria, lactic acid bacteria, yeast and actinomycetes, blended with organic materials such as rice bran and fish meal. It suppresses harmful microorganisms, especially the activity of pathogenic bacteria and putrefactive bacteria.)

My trusted composting companion is an old pair of large scissors; while chopping vegetables, I casually snip the kitchen scraps a little finer and tip them into my little Bokashi bucket each day. Used napkins also need to be collected separately in their own bin. The result is that our flat is dotted with various makeshift containers for “rubbish” – a box of coffee grounds, a cup of tea leaves, peanut shells first blitzed in the food processor. Coffee grounds still wrapped in their pour-over filters I collect separately and dry on the balcony – I don’t add them to the Bokashi bucket because they take up too much room. My composting is certainly a touch meticulous, but composting is like cooking: there is no single right way and no failure; everyone’s approach is different.

In the hottest weeks of summer, the little 15-litre bucket filled up fast. Compost leachate also has to be drained every day – eat a watermelon and you’ll collect a litre or two of leachate. Each time the Bokashi bucket fills, I go round to nearby cafés for two bags of coffee grounds, haul them – bundled up in bags large and small – back to the little yard at the studio, and use an insulated box to make hot compost.

My hot compost bin is a converted secondhand insulated food container with a capacity of roughly 60 litres. From the first pile on 10 May, in ten months I have started seven batches. For each bin, I keep detailed records of temperature changes and turning the pile. In the beginning I hadn’t quite mastered the conditions for reaching high temperatures, but now I’m getting the hang of it.

Hot composting calls for attention to the carbon-to-nitrogen ratio, but my mix is usually just roughly a 1:1 balance of coffee grounds and Bokashi kitchen scraps from home, plus a bag of paper towels – no heavy-duty ingredients like fish guts. Once you get the moisture and oxygen right, the carbon-to-nitrogen ratio actually becomes the least important factor.

More importantly, I have begun to understand composting from the microorganisms’ perspective – thinking about what food is easy for them to digest and what conditions make a comfortable living environment.

In hot composting, many different bacteria and fungi are at work. Some thrive in the mesophilic range (25–45 °C), others in the thermophilic range (45–70 °C). Among the mesophilic microorganisms, one species sends out masses of fluffy white hyphae; thermophilic actinomycetes are visible to the eye as scattered speckles of greyish-white. But the vast majority of these microorganisms are invisible to the naked eye. They eagerly digest the food remnants that we humans could not finish. We met each other in digestion.

At the very least, the vegetables I’ve grown, fed on all this compost, are remarkably robust. My primary aim at present is still to return the organic waste generated in my daily life to the soil.

If I hadn’t started composting from my everyday life at home, I doubt I would truly have understood that composting, like tending a jar of pickled vegetables or a sourdough starter, demands daily, sustained care. Separating napkins into their own bin on the side, snipping up kitchen scraps as I go – these small hand movements have become the very fabric of my days at home. Some people look on and exclaim how fussy it all sounds, but I find real pleasure in it. These habits have also saved me an enormous amount of time I would otherwise spend carting the rubbish out; the proper bin at home now stays half-empty for ages.

It is also because I started growing vegetables a few years ago that I began reading about ethics of care and ecofeminism. Academic discourse uses theory to interpret the world; the body responds to life through concrete action. Writing on the ethics of care in 1990, Tronto and Fisher proposed that care is ‘a species activity that includes everything we do to maintain, continue, and repair our “world” so that we can live in it as well as possible. That world includes our bodies, ourselves, and our environment, all of which we seek to interweave in a complex, life-sustaining web.’ In the process of caring, we invest emotion and form affective bonds with the cared-for. Yet care is often dismissed as a form of reproduction confined to the domestic sphere rather than genuine production, and for that reason it goes unvalued.

Yet tending the land is the most fundamental form of production. Bellacasa, in the chapter “Soil Time” in Matters of Care, writes: ‘Knowing the life in soil through looking and touching also shows how we forge connections, through intimacy and care, with soil’s dark otherworld.’ Composting is no different – hands steeped in humus, touching and turning intimately within it – digesting what remains, yet also producing nourishment for the land.

Caring for a hot compost pile isn’t exactly easy. In summer, under the 40 °C heat, tipping out the Bokashi compost with its tang of fermented sourness and then mixing it through the coffee grounds by hand – not something everyone would readily choose to do.

In the beginning, I found it a little hard to know where to start, but through long familiarity I’ve grown used to the smell of compost. I don’t find the fermented aroma of Bokashi unpleasant at all, and the scent that transforms things once the heat has passed is a complex, fertile fragrance carrying the solid warmth of the earth itself.

Once the heat in the compost has dropped a little, I turn the pile with my bare hands, breaking up any larger pieces as I go. By this stage most of the kitchen scraps have transformed; a few things like corn cobs and pomelo peel still hold their shape, but they can already be crushed or torn apart by hand. Really, this step isn’t necessary – I simply enjoy the way they feel in my hands.

After turning the pile, the smell of compost lingers on my skin, dark organic matter lodges under my fingernails, and the traces of it mark my clothes. And it is through this process that I’ve slowly come to know the habits of thermophilic microorganisms. There is no absolute formula; you simply observe the temperature and moisture often, turn the pile again, and adjust. Perhaps because I turn the pile so frequently, creating heat alongside the microorganisms within, my hands have gradually developed a feel for the conditions that sustain high temperatures. It is a very subtle sensitivity, like taking up a skilled craft for the first time. In this intimate relationship of care, the microorganisms in the compost are also changing and shaping my body.

Not long ago, I brought a bin of compost to an exhibition by the “non” collective. The kitchen scraps I had accumulated at home had become loose, sweet-smelling humus. We spread it out inside the klee klee & friends shop at Shangsheng Xinsuo, inviting visitors to turn it over with their own hands, to feel these composted materials through the sense of touch. During the exhibition we also hosted a composting workshop, guiding everyone through making hot compost together.

Another friend, a designer called Monkey who lives nearby, also got a bucket. So we exchange materials for compost. A while ago, I started a new compost batch and she brought her Bokashi bucket over. On her way out, I asked her to take home a bag of fully matured compost to feed the potted blueberry bush back at her place.

This time, however, the drainage layer in Monkey’s bucket had a problem and the leachate couldn’t drain properly. What fermentation had produced was a slimy, foul-smelling mixture of solids and liquids.

This is the nature of composting: if you don’t drain the compost leachate promptly, it produces a stench that puts many people off. But it can’t really be called a failure either – these organic materials will still become nourishment for the soil in the end. I mixed what she’d brought with coffee grounds, paper towels and wood shavings, adjusted the moisture to the right level and put it all into the compost bin. A few days later, the temperature in the pile had climbed back to 65 °C, and the smell had transformed into the scent of active digestion.

Another friend who lives in Shanghai recently moved into a studio with a yard, and I’ve got her into composting too. Of the two roses in her yard now, the one regularly fed with Bokashi compost leachate is clearly growing and flowering more vigorously than the other.

Composting has opened up a bodily connection from eating to sowing – a remarkably tangible form of bodily practice, even if it unfolds on this tiny, extremely limited patch of land in the city. And the practice of composting has also made me re-examine the origins of food – the soil beneath it and the process of its production. For those of us in the city, how can we eat better, and how can we sow better?

In the studio yard, dark compost is mixed into the reddish-brown clay. Slowly, the soil begins to loosen, its colour shifts, and moisture no longer drains away so quickly. Last summer, luffa, okra, chillies and granadillas grew luxuriantly in the ground (the tomatoes couldn’t survive Hangzhou’s extreme heat); in autumn, cauliflower and peas were sown.

I apply Bokashi compost leachate diluted with water, while the output of the hot compost, once fully matured, is spread directly on the surface as fertiliser. When sowing peas in autumn, I discovered that where compost had been mixed into the soil over summer, it loosened with just a light dig – while where no compost had been spread, the ground was still as hard as a rammed-earth brick.

Right now, sitting on a big bin of sifted compost, I feel immensely rich, my heart brimming with anticipation for spring.

[2] Tronto, Joan C. 1998. “An Ethic of Care.” Generations: Journal of the American Society on Aging, vol. 22, no. 3, pp. 15–20.

[3] Bellacasa, María Puig. 2017. Matters of Care: Speculative Ethics in More than Human Worlds. Minneapolis: University of Minnesota Press.