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Gasification and biodigester technologies are the most promising for large-scale implementation, as shown in study results
Every year, millions of tons of agricultural, forest, and urban organic waste are generated in Latin America and the Caribbean. Although several studies performed in recent decades indicate that this trash, instead of being dumped into the environment, can be transformed into alternative energy sources, fertilizers, and other by-products through biochemical and thermochemical technologies, this possibility is not yet fully explored in the region. The article The state-of-the-art of organic waste to energy in Latin America and the Caribbean: Challenges and opportunities points out the technical complexity of technologies, combined with the high cost of investments for implementing them, as well as the lack of research and public policies focusing on this area, which prevents the issue from moving forward in these countries.
The study is the result of a doctoral research program being carried out by Mexican civil engineer Rodolfo Daniel Silva Martínez at the Institute of Energy and Environment of the University of São Paulo (IEE-USP), within the scope of the FAPESP Shell Research Center for Gas Innovation (RCGI). Under the guidance of researcher Alessandro Sanches Pereira, he is investigating the feasibility of implementing anaerobic digestion technology in small to large-scale biodigesters in Latin America and the Caribbean. “The first step of the study was to specifically attempt to understand the current situation of biochemical and thermochemical technologies for the treatment of organic waste in the region,” Martínez explains.
To lay out this scenario, Martínez, his doctoral program adviser, and other researchers from institutions in Colombia, Sweden, and Germany gathered more than 21,000 academic studies on the subject written between 2000 and 2019. In the selection process, 199 of them became the bibliography for the article. “These technologies have been implemented in Latin America and the Caribbean especially over the last four decades, but experiences vary significantly from country to country, given the complexity and socioeconomic inequality of the region,” he reports. “Argentina, Brazil, Chile, and Mexico are leading the way: laws have changed, and governments now understand the advantages of adequately treating organic waste, which is aligned with circular economy logic and involves economic, social, and environmental benefits. Nevertheless, there remains much to be done in the entire region, including these four countries.”
Combustion is the predominant solution – As the article points out, combustion is the thermochemical technology most-used, today, in the region, due to its low financial cost. Some 67% of the sugar mills in Guatemala and 100% of those located in Honduras, for example, take advantage of sugarcane bagasse via incineration, as the process is also called. Generally speaking, the electrical power obtained from burning waste supplies the mill’s own demand. However, the alternative is not restricted to the sugarcane industry. In countries like the Dominican Republic and Cuba, the study reports that such waste materials as rice husks or coffee pods are used, as well as scrap wood. “However, if this is not done properly, combustion has a huge impact on the environment, due to the emission of greenhouse gases into the atmosphere, especially carbon dioxide, in addition to such possible pollutants as dioxins and furans,” Martínez notes.
The researcher states that there are other thermochemical technologies that cause less of an impact on the environment. One of them is pyrolysis, which is a high-temperature process performed without oxygen, generating bio-oil that can be transformed, for instance, into fuel to replace petroleum products or serve as a raw material for the chemical industry, like producing pharmaceuticals and cosmetics. Another example of this type of technology is gasification, which can cause transformation through various thermochemical reactions on solid wastes with biodiesel, hydrogen, heat, or methanol. “However, both gasification and pyrolysis are expensive technologies that must be imported from Europe and the United States. Ideally, they should be developed here, instead of buying them, but there is a lack of technical knowledge. So, that’s why we need to invest in research.”
Tropicalization of technology – In the article, Martínez proposes that gasification could be a promising technology to be implemented in Latin America and the Caribbean. “However, before a large-scale implementation in the region, the problem of the possible impacts of such pollutants as nitrogen oxides or halogens must be resolved,” he alerts. According to the researcher, the most viable option would be anaerobic digesters, which is a type of biochemical treatment by which organic material that has been decomposed by microbial action generates biogas. “The first small-scale biodigesters were installed in the region, especially in the early 1970s, and in the following decade most countries had developed experiments with this technology because of the low investment and maintenance costs,” Martínez states.
He reminds that biochemical technologies, as in the case of biodigesters, fermentation, and capturing gas from landfills, are more natural and consume very little electricity, but they are not suitable to all situations. “Biochemical treatments would take years to process wood scraps, for example. In this case, it is best to take advantage of thermochemical technologies, while keeping in mind the characteristics of each location,” he adds.
Martinez observes that interest in large-scale biodigesters has been gaining space in the region’s countries, in recent years, despite the high implementation and maintenance cost and their technical complexity. Among the examples is the first large-scale dry biomethanation unit to treat the organic fraction of urban solid waste in Latin America, inaugurated in 2018. The project was the fruit of a partnership between the Minas Gerais company Methanum Energia & Resíduos, the Federal University of Minas Gerais, and the Transshipment Station of the Companhia Municipal de Limpeza Urbana (COMLURB), of the city of Rio de Janeiro.
The technology used is called extra-dry methanation and it produces fertilizers and biogas from solid wastes. Except for some imported equipment used in the plant, almost everything was developed and manufactured in Brazil: constructive, process and control engineering; and the materials. “In Brazil, we have what we call the ‘tropicalization of technology”, which is the adaptation of European technologies to our local context, which produces better results and gives incentive to the country’s industries,” Martínez says.
For that reason, despite the challenges, the researcher looks with optimism on the perspectives for the region. “We are on the right track. There are now many collaborative networks where Latin American and Caribbean researchers share experience and knowledge,” he says. “However, for this to be implemented, the countries need public policies focusing on this issue.”
The article The state-of-the-art of organic waste to energy in Latin America and the Caribbean: Challenges and opportunities can be read at https://www.rcgi.poli.usp.br/wp-content/uploads/2020/08/1-s2.0-S0960148120305887-main.pdf?x48325.