Article written by Sara Silva, from the No Footprint Nomads project.
What is composting?
Composting is the controlled decomposition process of organic matter by microorganisms in the presence of oxygen – organic waste is “eaten" by bacteria and fungi that use oxygen. In fact, the presence of oxygen (air) during the process is very important for the success of composting, as will be seen below.
The result is compost, an organic fertilizer rich in nutrients and with a pleasant smell, nothing like the pile of waste that originated it. (1)
The science behind it
Composting is nothing more than an imitation of the natural process of decomposition of organic matter that takes place in nature and that forms the first layer of soil – humus.
During the composting process, there are several groups of microorganisms that develop: bacteria are the pioneers and feed on simpler compounds; fungi and actinobacteria (a “mutant", half fungus and half bacteria) break down the most difficult to digest materials and colonize the compound when the temperature drops; finally, more complex organisms appear and protect plants from diseases when compost is used as an additive.
The process is aerobic, that is, it needs oxygen. In the presence of this element, composting is faster, produces higher temperatures, and does not cause unpleasant odors. The high temperatures eliminate disease-causing microorganisms, making the compound safe for use in food production. (1)
In short, composting requires:
oxygen – adequate aeration must be ensured for the aerobic process to take place; (1)
water – about 40 to 65% water so that chemical reactions can occur and microorganisms can survive; (1)
carbon-nitrogen balance – carbon and nitrogen are two of the nutrients needed to feed microorganisms. The balance between them is important for the success of composting. Carbon is an energy source for microorganisms and absorbs excess moisture. Carbon sources include dry leaves, branches, newspapers, or cardboard. Sources of nitrogen include vegetables and fruits, coffee grounds, or tea leaves. (2)
What to compost? (3)
Vegetable and fruit scraps and peels
Tea leaves and bags (if the bag is made of paper and not plastic)
Coffee grounds and filters
Cardboard and paper
Leftover cooked food without fat (ex: white rice)
What you should not use to compost? (3)
Fats and oils
Meat and fish bones
Meat and fish leftovers
Cigarette ashes and butts
Composting is an economical and natural solution to the problem of organic waste. Instead of being taken to a landfill, where it causes a nauseating smell and environmental problems, composted waste returns nutrients to the earth. (4)
The advantages do not end here:
when done correctly, composting produces a safe and natural fertilizer that can be used instead of chemical ones;
provides resistance to pests and diseases, improves the water and nutrient retention capacity of the soil, and reduces the pollution caused by chemical fertilizers;
reduces the volume of organic waste and the cost of collecting it. (4)
How to begin?
Lipor’s website offers a number of resources to help you start your composting project (in Portuguese). Numerous resources can be found in English. For example, here.
1. Graves, R. E., & Hattemer, G. M. (2010). Chapter 2 – Composting. In Part 637 Environmental Engineering National Engineering Handbook. Forth Worth, Texas: National Production Services. Retrieved September 9, 2020, from https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=28910.wba
2. Sherman, R. (2017, April 7). Backyard Composting of Yard, Garden, and Food Discards. Retrieved September 09, 2020, from https://content.ces.ncsu.edu/backyard-composting-of-yard-garden-and-food-discards
3. Flyer Horta da Formiga Compostagem. (n.d.). Retrieved September 09, 2020,from https://www.lipor.pt/fotos/gca/flyer_horta_formiga_compostagem_13340292435e4bdc5017413.pdf
4. O Portal de Ambiente e Sustentabilidade. (2011, May 9). Retrieved September 09, 2020, from http://www.planetazul.pt/edicoes1/planetazul/desenvArtigo.aspx?aini=20165