During my work trips to Latin America and the Caribbean as an Environmental Specialist for the Bank, I discuss the importance of safeguards and sustainability with our clients and stakeholders. In that context I try to encourage innovative solutions to protect the environment, solutions that go beyond the minimum requirements.
After working in solid waste management projects for more than 10 years (mostly landfills) and visiting a composting site in Argentina a few weeks ago, which has implemented an innovative solution of transforming sludge from a waste water operation to compost, I once again found myself asking the question: why don’t we do more composting? Is it because we are afraid of the smell? Is it because we are too lazy to separate organic waste from the rest? Is it because we don’t know enough about composting? I decided it was time for me to answer those questions. So I did some research on the science of composting, the different composting technologies and the composting process and bought myself a compost bin and a tumbler composter. This is what I learned…
First I had to understand what composting is and the science behind it. Composting is defined as a controlled decomposition following the natural breakdown process of organic residues. It transforms raw organic waste materials into biologically stable substances that are really beneficial to the quality of soil. The composting process goes through two main phases once adequate conditions are in place (i.e. having the right amount of raw material):
- The Active phase (duration: several weeks) – In this phase temperatures increase (up to 150°F) and microorganisms called thermophiles that thrive in high temperatures, start working on breaking down the raw material, killing pathogens (bacteria, viruses or other microorganisms that cause disease) and weed seeds with the help of aeration (oxygen); and
- The Curing phase (duration: one month to a year) – In this phase the temperature goes down to around 100°F where mesophilic microorganisms continue decomposing the organic materials with less need for oxygen until you get to a biologically stable substance. Some of the key parameters to monitor during the process are moisture, pH, oxygen, organic acids and Carbon:Nitrogen (C:N) ratio.
Surprisingly, there are many composting technologies; those include windrow composting, passively aerated windrows, forced aerated windrows, in-vessel composting and bin composting, all terms I wasn’t familiar with until today. Windrow composting is the production of compost by piling organic matter or biodegradable waste, in small and porous long rows (windrows), which can be turned over to increase the amounts of air in the piles. This method is suited to producing large volumes of compost. Passively aerated windrows include perforated pipes placed at the base of each windrow to promote a flow of air through the raw material. Forced aerated windrows are similar to passively aerated windrows piles, but blowers are installed at the ends of perforated pipes or air ducts to speed up the process. In-vessel composting uses an enclosed equipment to achieve maximum control of temperature, oxygen and moisture. Finally bin composting is similar to in-vessel composting but is smaller and less expensive.
To determine which technology fits better your needs you can look at criteria such as investment (i.e. cost), maintenance, space needed, and time it takes to have the final compost and labor needs (see figure). For example if low cost is the most important factor, you have enough space and you have enough labor then windrow composting is the best solution. If you do not have a lot of space, but do have the funds and need to have the compost ready fast then in-vessel composting is the best solution. But for you and me, bin composting is probably the way to go at home…
So, after understanding the process and the technology I now felt more comfortable to try it myself! I bought myself an indoor compost bin and a tumbler composter for around US$125 on Amazon (see here and here respectively) and started composting a few weeks ago. Based on my experience in those few weeks I can tell you that it is easy to do, it doesn’t smell bad and it is better for the environment. In addition my plants love it!