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Recycling and thermovaluation, part of the sustainable management urban solid waste model

For years authorities have imposed public bidding for collection, sweeping and cleaning system (CSL); another for final disposition (FD) and even another for hospital waste; consciously or unconsciously ignoring, potentially recycling material management (RMM). Regarding exploitation, even the legislation transgresses the technical concepts and has thus has divided into two groups: exploitable and non-exploitable home urban solid waste (USW) 1 as if it were technically different from exploiting them separately.

According to the said decree, exploitable material is RMM which is gathered and marketed by human recyclers which has some rejection waste which ends up at the Bogotá Doña Juana Landfill (DJLF). Technically waste deemed as “non-exploitable” is exactly the opposite: waste usable by employing biological processes, such as composting and thermal processes such as gasification, plasma, or thermovaluation.
 

Read more: The opportunity for wind energy in Colombia.


Ordinary waste includes grass and tree trimmings, that has a separate collection fleet and should not be taken to the DJLF, but submitted to biological treatment along with other biological waste such as waste from farmers markets and home kitchen waste, previously classified without cooked waste, so the end product is organic fertilizer.
 

According to the same decree, non-usable waste along with voluminous waste, and rejected recycling waste is ideal for thermal exploitation using thermovaluation to generate energy.
 

These three components, RMM, plant waste composting, and thermovaluation for the remaining ordinary waste is the alternate technology that would solve the DJLF issue and that is a real change to the current waste model.
 

We would pass from a burial waste model to a comprehensive management model where only the inert waste from the thermovaluation plants would be buried.


The developed world has progressed in this direction with  Zero Waste programs, as shown in the following chart for the case of Europe.

As may be seen, as a country achieves greater development, landfill technology is minimized (in red) and RMM, composting technology (in green) and thermovaluation (in yellow) are maximized.


Read more:  A mistaken technology, the issue with the Doña Juana landfill.
 

For countries such as Germany, Belgium, Switzerland, Denmark, and the Netherlands, waste burial has been reduced to 1%. These landfills are also less environmentally impacting than the DJLF as they only harbor inert waste-treatment residue, without the production of leachate or methane gas, the greatest glasshouse gas contaminant (21 times more contaminating than carbon dioxide).
 

For Denmark, for instance, 54% of the waste is treated with thermovaluation, 44 % with compositing, and recycling and close to 1% in landfills. The European average in 2014 was 44% for composting, and recycling, 27% for thermovaluation, and still 28% in landfills, demonstrating that the process is gradual and that the mentioned technologies are not incompatible but complementary.
 

Lastly, the right part of the chart shows the situation of Bogotá, with figures still maintained to date: 15% recycling and 85% in landfills and the change for 2024 with thermovaluation plant: 11% landfill and 61% of the waste produced for thermovaluation and an increase in composting and recycling of 27%.
 

If possible, Bogotá would pass to a situation similar to Croatia (83 and 17%), in front of Finland (17, 50, and 33%), and only surpassed by eight European countries.
 

It is noticeable than in 2015, the world had 1,914 thermovaluation plants: 1,350 in Japan, 480 in Europe, and 84 in the United States, with a significant increase of 16 plants built in the last 10 years.
 

Thermovaluation


There are doubts in the country on the feasibility of thermovaluation in Colombia as some people criticize the production of CO2. Although it should be accepted that all technologies leave a carbon footprint, it is essential to focus on analyzing thermovaluation. This technology is essentially a thermoelectric plant which instead of consuming fossil fuel it would use USW, a less expensive fuel, which is currently disposed of and causing great environmental and health impact, as the DJLF.
 

This fuel change would avoid the need of extractive mining for fossil fuel; reason enough to justify its implementation.

The plants designed and proposed by Veolia for México City in 2017 has an installed capacity of 110 MW, with 4,500 tons/day of waste; similar data from feasibility studies for Bogotá. A Universidad Nacional de Colombia (UNal) 1982 & 1984 research project entitled “Study of a Thermal Plant for Bogotá using waste collected in the city” resulted in a plant with an installed capacity of 150 MW, with 6,000 tons/day of USW.

 

Read more: Reactor for leachate treatment, a solution for landfills (in Spanish).

 

In summary, there are several factors that make implementing thermovaluation as a viable and undeferrable option for Bogotá, among others:

  • The lack of appropriate land plots, without agricultural purposes, such as the DJLF, to implement landfills,
  • The opportunity presented by this project to be located in urban areas such as those in cities like Tokyo, London, Helsinki, and Barcelona, among others,
  • The capability of this technology to not generate liquid waste –leachates–, or noxious gases such as methane gas,
  • Treatment time in hours compared to hundreds of years of decomposition in landfills,
  • Easy and convenient marketing of the main product, clean energy, and
  • The possibility of establishing several units in different areas of the city, reducing collection fleet lengthy trips, and therefore pollution.
     

As a conclusion, a USW sustainable management model different from the current burial model would simultaneously include:

  1. RMM recycling,
  2. Plant-sourced composting correctly separated at the source,
  3. Thermovaluation for the remaining ordinary waste and for the recycling and composting plant reject portion, and
  4. Final disposition or landfill to bury only inert waste–ash–from thermovaluation plants.


This requires investment in infrastructure including the plants, land, classifying stations that comply with environmental and sanitary regulations; collection fleets for every type of material: MPR, ordinary plant, and home compacting waste, all of them with different collection frequencies.


Without a doubt, it is indispensable to have the political will to embark on such a model based on recycling, utilization of waste, and the volition to minimize waste sent to landfills. Therefore, it is very strange that this was not explicitly expressed in the City Development Plan approved by the City Council on May 31 of 2020.

 


1 Decreto 1077 de mayo de 2015 del Ministerio de Vivienda, Ciudad y Territorio, “Por medio del cual se expide el Decreto Único Reglamentario del Sector Vivienda, Ciudad y Territorio” http://www.minvivienda.gov.co/NormativaInstitucional/1077%20-%202015.pdf

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