Composting in our homes and yards is essentially a simulation of the biological decomposition processes that take place naturally in the wild. “In these processes, bacteria, fungi, molds, protozoa, actinomycetes, and other saprophytic organisms feed upon decaying organic materials initially, while in the later stages of decomposition mites, millipedes, centipedes, springtails, beetles and earthworms further breakdown and enrich the composting materials. The organisms will vary in the pile due to temperature conditions, but the goal in composting is to create the most favorable environment possible for the desired organisms.” 1
I started composting in the suburbs of Chicago two decades ago primarily to reduce carbon pollution (methane emissions from landfills), lower my carbon footprint,2 support soil microbiota, but also to provide organic fertilizer for our gardens. I moved to Washington DC nearly four years ago and among the first things I did after settling into my apartment was to set up aerobic indoor composting. After years of composting organic kitchen and yard waste outdoors in two 3ftx3ftx4ft bins to which even the neighbors made contributions, I was challenged with finding an approach that would work successfully in my small studio apartment.
Apartment-scale composting does not lend itself to supporting the larger arthropods and annelids that are a part of the yard bin compost ecosystems.3 Being a vegetarian and cooking nearly all my meals at home, I generate a lot of kitchen scraps which need to be broken down quickly, without having to dwell on getting the optimal proportions of “greens” (nitrogen sources) and “browns” (carbon sources) in the mixture to establish a composting equilibrium.4 After researching various approaches, I decided on a simple setup5 with red wiggler worms purchased from a local garden center.
I bought a small metal bin from a neighbor’s moving sale, lined it with sturdy plastic or jute bags (rice bag, soil or mulch bags) in which I made slits for drainage. I layered shredded newspaper at the bottom of the bag, tossed in used coffee grounds, vegetable peelings, and fruit rinds and then, per instructions, introduced the wigglers (to my dismay, I found only a few alive when I opened the package). I made sure the pile was aerated and moist but after a couple of weeks, I discovered that none of these worms were alive in the pile. Not to be dissuaded, I dug up a couple of earthworms from a friend’s garden and introduced them into the pile only to find a few days later that they too had perished, having crawled out of the bin. After these setbacks, I was determined to work out an approach of my own – one that did not require the introduction of any extraneous worms. Bacteria and fungi are ubiquitous and make their presence felt in the kitchen in food spoilage (moldy bread, rotting fruit, spoiling of milk) as well as in food creation (fermenting milk to produce yogurt, fermenting rice-lentil batter for South Indian savory delicacies, Korean Kimchi, etc.). So I decided to let the microbes around me decompose my kitchen scraps. I covered the small compost bin to retain humidity and left it in a warm place. Because of the tiny living space, speed is of the essence when it comes to processing the daily waste. I tear up chunks of peels/rinds into smaller pieces, crush shells of peanuts and pistachios, etc. before putting them into the bin. I avoid putting in walnut shells, stone seeds of nectarines, etc. as they take months to decompose. I also wipe dishes after cooking and the dinner plates after eating with paper napkins and toss them into the pile – this reduces the amount of soap and water needed to wash these utensils. I do add any leftover oils or soured milk to the pile, but after first soaking them into newspaper, drying them out a little, and then shredding them up into the bin. I occasionally mix in shredded newspaper to mop up the excess moisture that is released from the decomposition. I do not use material from our office paper shredder as I found it to contain shredded credit cards, envelopes with plastic windows and plastic lined papers. Wax/parchment paper that I use to wrap my lunch in seems to decompose readily. I stir the pile with my hand once a week or so to aerate it.
With this setup, the pile began to get warm and seemed to be reducing in volume albeit slowly. One summer day, I brought a handful of soil from my friend’s garden (which had no macro invertebrates that I could see) and added it to the bin. Later in autumn, I added a handful of leaves and acorns of willow oaks gathered from the sidewalk on my walk back from work. Soon the pile was steaming hot, releasing an earthy fragrance similar to that of soil after the first rains. Composting was finally going on in earnest and I did not look back! Once the bag in the bin was full, I tied it up loosely and allowed the digestion to be completed in the bag. The results were absolutely impressive – within 2 months of filling up a bag, I had a dark, fine crumbly mix of rich compost which I could use as a top dressing for my indoor plants or extract its nutrients into water to feed the plants.
I use a scoop of the finished compost as a starter culture of the organisms in a new batch. I continue this process now in my new apartment where I have switched to composting in larger plastic planting pots. As these pots do not get recycled, local garden centers, nurseries, and landscapers doing street plantings are willing to give them away for free. As a side note there is a lot of high-rise construction going on here which per the District mandate must include greening/landscaping.
I was thrilled to notice recently that the compost pile is teeming with macro organisms (oribatids and other soil mites) in addition to the unseen microbes. It is a delight to watch these mites scurrying about among the scraps.
- Earth-Kind Landscaping. Chapter 1: The Decomposition Process. Texas A & M AgriLife Extension. https://aggie-horticulture.tamu.edu/earthkind/landscape/dont-bag-it/chapter-1-the-decomposition-process/
- Composting At Home. EPA. https://www.epa.gov/recycle/composting-home
- T. D. Schowalter, 2016. “Decomposition and Pedogenesis” in “Decomposition of Organic Matter”, Insect Ecology (Fourth Edition). https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/decomposition-of-organic-matter.
“Decomposition of organic matter is the most essential microbial process occurring in soil.”
“Decomposition of organic matter involves four component processes: photo-oxidation, leaching, comminution, and mineralization. Arthropods are key factors influencing comminution and mineralization.”
- Composting: Balancing Your Greens and Brows. Cornell Waste Management Institute. http://cwmi.css.cornell.edu/balancing.pdf
- How to Make a Compost Pile in a Small Apartment. Apr 12, 2014. Forbes. https://www.forbes.com/sites/rent/2014/04/12/how-to-make-a-compost-pile-in-a-small-apartment/#3429056a30f4
Nutrition and Your Health: 2015–2020 Dietary Guidelines for Americans https://health.gov/dietaryguidelines/2015/guidelines/
- R. Barrett. October/November 2017. Compost: Your Trash, Nature’s Treasure! American Chemical Society. https://www.acs.org/content/acs/en/education/resources/highschool/chemmatters/past-issues/2017-2018/october2017/composting-your-trash-natures-treasure.html