Saving Waste Like Saving Money: My Encounter with Microbes in the Compost

Then there is the most important part: the dark, rich organic matter. These consist of hundreds of millions of organic molecules, each with its own colour, absorbing and reflecting light. In a mixture of molecules of different colours, no light is reflected, which is why it ultimately appears black. These are not only the material foundation for life; when combined with the inorganic particles in the soil, they create a stable pore structure that stores water and oxygen underground. To improve the soil, one must start by increasing its organic matter.

With this small patch of barren land in my yard, I now had a compelling reason to take composting seriously.

I. Starting Composting with Everyday Waste

In my quest to compost, I have sourced coffee grounds, kept simple piles at home, built composting bins in the field with the non group, and once even went out in the middle of the night to collect a large bag of fallen leaves swept up by street cleaners to fill my bin.

Over the last two years, while living briefly in other places, I have participated in various community composting projects. From traditional farm manure made with livestock waste in villages to professional rotating composters on urban balconies, and composting of different scales and materials in eco-communities and farms, I have seen and learned a great deal from these diverse methods.

Now, I intend to start with my own daily life at home.

Since I started composting, I have been diligently saving organic “waste” as if I were saving money. All the kitchen scraps, leftovers, and fruit given by others that had begun to rot before they could be eaten… I used to feel a sense of guilt or helplessness when faced with these remnants. Now, I view them as wealth, knowing that they will eventually become precious fertiliser for the land.

At home, I use Bokashi composting; every day I add kitchen waste and cover it with EM powder. (Note: EM (Effective Microorganisms) is a microbial activator typically composed of Bacillus, photosynthetic bacteria, lactic acid bacteria, yeast, and actinomycetes, mixed with organic materials like rice bran and fish meal. It inhibits the activity of harmful microbes, particularly pathogens and putrefactive bacteria.)

My great composting helper is an old pair of large scissors; I use them to snip the kitchen waste into smaller pieces as I prep, then pour them into my small Bokashi bucket. Additionally, I use a separate bin to collect used napkins. As a result, various temporary “waste” containers are scattered around the house—a box for coffee grounds, a cup for tea leaves, and peanut shells which I first crush in the food processor. I save coffee grounds with pour-over filters separately and dry them on the balcony, as I find them too bulky for the Bokashi bucket. This approach to composting is perhaps a bit too meticulous, but like cooking in a kitchen, there is no single “correct” or “failed” way; everyone has their own technique.

During the peak of summer, the 15-litre bucket filled up very quickly. I also had to be diligent about draining the compost tea daily; eating a single watermelon could produce one or two litres of liquid. Whenever the Bokashi bucket was full, I would go to a nearby coffee shop to get two bags of coffee grounds, carry them in heaps to the studio courtyard, and use an insulated box for hot composting.

My hot composting bin was converted from a second-hand food insulation box with a capacity of about 60 litres. Since the first batch on May 10th, I have started seven batches over ten months. For each batch, I have kept detailed records of temperature changes and turning schedules. While I struggled to master the conditions for heating up at first, I have now become quite proficient.

Hot composting usually emphasises the carbon-to-nitrogen (C:N) ratio, but my ingredients are typically a 1:1 mix of coffee grounds and Bokashi kitchen waste, plus a bag of napkins, without any “heavy hitters” like fish guts. As long as moisture and oxygen are managed well, the C:N ratio actually becomes the least important factor.

More importantly, I have begun to understand composting from the perspective of the microbes, thinking about what foods are easy for them to digest and what conditions create a comfortable living environment for them.

In hot composting, many different bacteria and fungi are active. Some thrive at mesophilic temperatures (25–45°C), while others are thermophilic (45–70°C). Among the mesophilic bacteria, some produce fluffy white mycelium, while the thermophilic actinomycetes appear as visible speckles of greyish-white. However, the vast majority of these microbes are invisible to the naked eye. They are fervently digesting the food scraps that we humans could not. In this process of digestion, we find one another.

At the very least, the vegetables I’ve planted, fed by this compost, have all grown very robust. For now, my primary goal remains the digestion of the organic remnants of my daily life back into the earth.

Had I not started composting from my daily routine, I probably would never have truly understood that composting, much like tending a jar of kimchi or a sourdough starter, requires consistent daily care. Separating tissues as I go, shredding kitchen waste on the fly—these manual actions have become a natural part of my daily life at home. Some people are horrified by the perceived hassle, but I find joy in it. These habits have also significantly reduced the time I spend taking out the rubbish; now, the actual bin in my house takes a long time to fill up.

It was also because I started growing vegetables a few years ago that I began reading about the ethics of care and ecofeminism. While academic discourse uses theory to interpret the world, the body responds to life through concrete action. When Tronto and Fischer wrote about the ethics of care in 1990, they proposed that care is “a species activity that encompasses everything we do to maintain, continue, and repair our ‘world’ so that we can live in it more fully. This world includes our bodies, ourselves, and our environment, which we attempt to weave into a complex, life-sustaining web.” In the process of caring, we invest emotion and form an emotional bond with the cared-for. Yet, care is often regarded as a form of domestic reproduction rather than production, and is therefore undervalued.

But tending the land is the most fundamental form of production. In the chapter “Soil Time” of *Matters of Care*, Belcasa writes: “Coming to know the life within the soil through seeing and touching also reveals the forging of a connection with the soil’s dark other-world through intimacy and care.” Composting is the same; with hands immersed in humus, intimately touching and turning it—this is both the digestion of remnants and the production of nutrients for the land.

Looking after high-temperature compost is not actually easy. In the height of summer, amidst 40-degree heat, tipping out Bokashi compost with its fermented sour smell and mixing it evenly by hand with coffee grounds is probably not something everyone would be willing to do.

At first, I found it a bit difficult to start, but after spending a long time with it, I began to adapt to the smell of the compost. I don’t find the fermented scent of Bokashi compost foul; rather, the scent that emerges after the high-temperature phase is a complex, fertile fragrance, carrying a sense of the earth’s solidity and warmth.

Once the temperature of the compost has dropped slightly, I turn the pile with my bare hands, crushing any remaining large chunks as I go. By this point, most of the kitchen waste has been transformed; only a few things, like corn cobs or pomelo peels, still retain their shape, but they can be easily squeezed open or torn apart by hand. This step isn’t strictly necessary; I think I simply enjoy the tactile sensation of them in my hands.

After turning the pile, the scent of the compost lingers on my hands, black organic matter lodges in the creases of my nails, and traces of it remain on my clothes. Through this process, I have slowly become familiar with the habits of thermophilic microbes. There is no absolute ratio; one can only frequently observe the temperature and humidity, then turn and adjust the pile. Perhaps because I turn the pile so often, creating high temperatures together with the microbes, my hands have gradually become attuned to the conditions required for that heat. It is a very subtle perception, akin to mastering a skilled craft. In this intimate relationship of care, the microbes in the compost are also changing and influencing my own body.

A while ago, I took a bin of compost to an exhibition by the non collective; the kitchen waste accumulated at home had turned into loose, fragrant humus. We spread it across the klee klee & friends shop at Columbia Circle in Shanghai, inviting visitors to turn it by hand and use their sense of touch to feel this microbe-digested compost. During the exhibition, we also organised a composting workshop to teach everyone how to do high-temperature composting.

Another designer friend, Houzi, who lives nearby, also got a bucket. Thus, we began exchanging materials for fertiliser. A while ago, when I started a new bin of compost, she brought over her Bokashi bucket. Before she left, I asked her to take a bag of matured compost back to fertilise the potted blueberries at her home.

However, this time, there was an issue with the liner in Houzi’s bucket, and the liquid wasn’t draining properly. The result of the fermentation was a slimy, stinking mixture of solids and liquids.

That is the nature of composting; if the liquid fertiliser isn’t drained in time, it produces a stench that would put many people off. But this isn’t necessarily a failure, as these organic materials will eventually become nutrients for the soil. I mixed the mess she brought with coffee grounds, paper towels, and sawdust, adjusted it to the right humidity, and put it all into the compost bin. A few days later, the temperature of the compost rose to 65 degrees again, and the smell transformed into that of active decomposition.

I also have a friend in Shanghai who recently moved into a studio with a yard, and she too was persuaded by me to dive into composting. Of the two rose bushes in her garden, the one regularly fed with Bokashi liquid fertiliser is now visibly growing and flowering more vigorously.

Composting has opened up a bodily connection from eating to planting; it feels like a very concrete physical practice, even on this extremely limited patch of land within the city. The practice of composting has also led me to re-examine the source of our food, the land beneath it, and the process of production. For those of us in the city, how can we eat better, and how can we plant better?

In the studio yard, the dark compost blends into the reddish-brown clay. Slowly, the soil begins to loosen, the colour changes, and moisture no longer drains away so rapidly. Last summer, loofah, okra, chillies, and dragon fruit grew lushly in the ground (the tomatoes didn’t survive the Hangzhou heat), and in autumn, I planted cauliflower and peas.

I dilute the liquid fertiliser from the Bokashi compost with water for application, while the output from the high-temperature matured compost is scattered directly onto the surface. When sowing peas in autumn, I discovered that the areas where compost had been mixed in during the summer loosened with a gentle dig, whereas the areas without compost remained as hard as rammed earth bricks.

Right now, possessing a large bin of sieved compost, I feel incredibly wealthy, and my heart is full of 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.