Lecture 4 - Organic Waste Treatment
1. Organic Fraction in the Municipal Solid Waste
Organic Waste is the largest fraction of the household Waste. In Germany it was 39,3% in 2017 (study conducted by INFA GmbH, published in UBA 2020, see slide 7 in the ppt element below). In low-, middle and upper-middle income countries it takes up more than half of the waste. Look at the slides below to see some statistics.
Organic Waste in not just a large fraction but also both a possible hazzard as well as a valuable resource. Untreated organic waste can be a breeding ground for insects and attract rodents, which thenagain can transmit diseases in living areas. Spoiled food and improperly dispose feces also lead to for human harmful bacteria in organic waste.
Hence it is important to bring the organic waste to a place, where through proper treatment the health hazard is reduced (e. g. through self-heating in the composting process bacteria are killed-of). Organic Waste that was degraded by microorganismns in aerobic and anerobic processes however, matures into a fine fertilizer for soils which is important to bring back onto the fields as otherwise food security is put into jeopardy and the soil degrades and becomes infertile and also erosive. In a way, it is natures example of how a circular economy should work.
It is however also important where the nutrients are introduced back into the environment. If a large amount of fertilizer is bought out onto the fields in one place and a strong rain follows, the nutrients are washed out and lead to eutriphication in the water-bodies (e. g. rivers). This is of course also the case if all waste is disposed of in form of open dumping as the organic waste degrades and leachate gets uncontrolled into the environment; concentrated in one place. Naturally large amount of food waste would not accumulate in one place as there would be not living being other than the human collecting large amount of residues in one spot.
Also the atmosphere is burdend by improperly disposed of organic waste. In large piles too little oxygen is present, so anerobic degradation takes place, where methane and nitrous oxide are formed, which are stronger greenhouse gases than carbon dioxide which is formed in composting processes. In controlled biogas the production of methane can be utilized to win energy but in open dumpings it is not only harmfull to the climate but also dangerous as it might lead to uncontrolled fires.
Taking everything into account, the proper disposal and treatment of organic waste decides over it being a harmful and hazardous substance or it ensuring food security as a fertilizer and contributing to the green energy mix. This makes it undeniable that learning about organic waste is of utmost important, so let's start by learning about the differnt pathways organic waste can take into the environment.