Thermovaluation is thermal exploitation of waste avoiding environmental issues such as landslides
The 1984 research project entitled, “Study of a Thermal Plant for Bogotá using waste collected in the city”, allowed several UNal engineering students opted for the mechanical engineering degree, although the suggestion was ignored, the authorities decided to change to open dumps, garbage burning or disposal in water bodies for landfills to reduce the environmental impact.
The DJLF is a lot of land located south of Bogotá where daily approximately 6,413 or 192,390 tons/month are buried and receiving approximately 704 garbage trucks a day from Bogotá and some other eastern towns of the province of Cundinamarca like Cáqueza, Choachí, Chipaque, Fosca, Gutiérrez, Ubaque, and Une.
This waste is piled up in levels –a disposal combination per area and terraces due to the wavy terrain– that according to the latest licenses granted approved optimizing the land, meaning that as the capacity has been reached, the authorities approved disposing of waste in areas which had been previously closed with the purpose of not extending the wasteland and impacting more neighbors, by increasing height instead of area.
The license granted by the Regional Autonomous Corporation (CAR, for its Spanish acronym) allowed operating zone III until 2008, and then with some modifications it was extended to 2014, time in which another modification to the license was granted and extended to march 31 of 2022.
These licenses were granted to the Bogotá Public Utility Special Management Unit (UAESP, for its Spanish acronym). Later (in 2018) the CAR licensing authority was changed to the National Agency for Environmental Licensing (ANLA, for its Spanish acronym) and the license grantee was also changed to Centro de Gerenciamiento de Residuos Doña Juana S.A. ESP (CGR).
Leachates are the resulting liquids of the percolating process which carries a great number of compounds present of the solid it passes through. The DJLF has a treatment plan that processes all the liquids (21.3 L/sec on average) produced by the landfill with a quality that only complies with 60% of the parameters established by the environmental authority–the DBO5%, (aluminum, cobalt-chrome, boron, and iron among others surpass the parameters established by the Colombian regulations).
Also, there is a set of control equipment to monitor gas pressure, and clinometers to measure waste mass movements and the so-called “electronic noses” to monitor aggressive smells, produced gas, leachates, and waste decomposition, among other equipment, which are not enough to warrant a correct operation of the landfill.
The landfill is managed by a set of three main contracts, a residue management contract, a biogas treatment contract, and a consultancy contract.
The landfill technology implies a complex engineering task and rigorous regarding complying with the technical parameters and regulations included in the Environmental Impact Study the concessionaire carried out for the approval of the environmental license.
In the case of the DJLF, these conditions are more critical due to the nature of the terrain and that its exploitation is in an optimization stage, implying depositing fresh land over “old” waste, which carries different settlement rates, leachate production and gas production that make the operation even more dangerous.
These situations will become more frequent due to climate change that produces contraction and expansion of the waste mass; with ill-timed weather changes, localized rainfall increases leachate production and the likelihood of landslides of the waste mountain which is currently at 90m measured between the natural ground the and waste hill.
On the other hand, the waste exploitation technology progresses as the priorities change to a zero garbage model which is not burying untreated waste, leading to the disappearance of the currently known landfills and to the implementation of technologies to minimize waste production, reusing and recycling waste, leaving a very small portion of the waste.
Based on 1979 data, UNal concluded that waste has an inferior caloric value of 1,821 KCAL/kg (7.62 MJ/kg/). By using thermal plant technology (thermovaluation), the current 6,000 tons/day of waste in Bogotá would need three generation plants, each one with 50 Mw capacity. In other words, the waste in Bogotá has a potential energy capacity of 150 Mw.
As a reference, the street lighting system in Bogotá currently has an installed capacity of 40 Mw. What the city would have avoided in environmental, social, economic, and health issues, among others if instead of implementing a landfill, the authorities would have used that study, they would be producing energy as an alternative electricity source.
Back in 2012, Bogotá implemented a program named “Zero garbage” and carried out several studies to choose a technology, reaching the same result of the UNal study.
The best option for the city was to implement thermovaluation plants, in other words, thermal power plants using urban waste (non-recycled garbage) as fuel. Technologies such as gasification, pyrolysis, and plasma gasification were dismissed, among other reasons for being more robust and mature, needing more capital expense, operational expense, and risk.
Once thermovaluation is defined as the technology of choice –which the world has at least 2,000 TVPs– they began feasibility studies with the following results:
With this they finished the first stage of the study and recommended starting a second stage and registering it with the Mining Energy Planning Unit (UPME, for its Spanish acronym), carry out an Environmental Impact Assessment for requesting approval to the environmental authority and the detailed engineering of the infrastructure to implement.
The arrow shows that these types of plants require air supply from the unloading area to the combustion chamber to avoid foul odors during operation and use air for combustion.
Despite the established in the environmental license of not amplifying the DJLF, the UAESP carried out a consulting contract for optimizing old DJLF waste sites for:
This would provide an acceptance waste capacity of 91,580.000 at a maximum height of 3,015 meters above sea level and 37 years of operation (from 2024 to 2061.) The current DJLF operator offered UAESP designing the definitive designs for the DJLF optimization project with the respective environmental licensing processing.
Regardless of who does the project, it carries a great geotechnical risk with environmental and health consequences, as it would imply depositing waste over already closed waste disposal sites and which have already had landslides, besides continuing with obsolete technology. This would be returning to the “Zero Garbage” model and ignoring the OECD (which Colombian is now part) suggestions for a sustainable city, and eternalizing the vulnerability of the city for having just one final disposal site with the dire consequences to the city if it fails.
Some of the benefits of thermovaluation (TVP) over landfill (LF) technology are:
The maturity of the TVP technology regarding emission and odor control has allowed placing them in urban areas, for instance in Porto(Portugal) is 1.4 miles from the airport, the same as in London and Barcelona, just to name a couple.
Concerning the current DJLF operator (CGR), they have shown a total lack of commitment to the contract, showing 11 non-fulfillment actions s regarding the DJLF and were penalized monetarily and ordered to carry out the civil work to correct the non-fulfillment. CGR has also not complied with the sanctions established in court orders or the ANLA actions
This shows that not only the DJLF technology was mistaken and that authorities should have implemented another solid waste disposal technology, but that the current operator is operationally and technically unfit to run the LF and the city and its inhabitants will suffer the consequences.
There is still something more concerning and that is that the current Mayor of Bogotá did not consider of any importance to include it in the Development Plan presented to the Bogotá City Council just last week and not including this in the budget for the city, like finishing the study of 2014 and beginning construction of several thermovaluation plants to start operating in 2025.
Consejo Editorial: Fredy Chaparro Sanabria Director Unimedios, Nelly Mendivelso Rodríguez Oficina de Prensa, Liseth Sayago Cortes Oficina de Realización Audiovisual, Carlos Raigoso Camelo, Oficina de Producción Radiofónica, Ramiro Chacón Martinez Oficina de Proyectos Estratégicos.
Editora: Liliana Matos
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