Waste-to-energy project could boost Brazil’s decarbonization goals

Manaus, in the state of Amazonas, is one of the top generators of solid waste among Brazil’s state capitals, with an average of 1 kilogram (2.2 pounds) of garbage per resident every day. According to the Brazilian Association for Waste and the Environment (ABREMA in Portuguese), the waste problem is not exclusive to Amazonas’ most populous city: The state as a whole has one of the highest rates of landfill use, with almost 92% of its cities disposing of their garbage this way. In states like São Paulo and Santa Catarina, that rate is less than 3%.

This practice results in an accumulation of polluting waste that, in addition to creating socioeconomic and logistical problems, contaminates the soil in the Amazon, triggering numerous environmental alerts.

But now, the energy transition may have a solution.

Currently, the same waste that raises experts’ concerns in Amazonas state could become an important ally in the national fight against polluting emissions, thanks to the future operation of the Amazonas Waste Treatment and Processing Center (CTTR in Portuguese). Opened in 2024 but still under construction, Manaus’ CTTR is the state’s first biomethane plant.

The facility will process waste from human activities into biomethane, known as “green gas,” for its high decarbonization potential. This gaseous energy source comes from the decomposition of organic matter. Once collected, the methane is converted into biogas, which is then purified until it reaches its final version. It is estimated to emit up to 2.5 times less CO2 than natural gas.

The project is expected to start operations in 2028, when waste treatment management should be transferred to the new landfill connected to the processing center. Future daily production of green gas is projected at 80,000 cubic meters (2.8 million cubic feet), enough to power 179,000 homes, according to industry representatives. Once fully operational, the center will have the capacity to produce 41 million cubic meters (1.45 billion cubic feet) of biomethane per year.

Biomethane and natural gas have similar molecular structures and are therefore comparable in terms of distribution infrastructure. Hence, the gas produced by the CTTR is strategic for Brazil’s efforts at decarbonization, which remains a challenging goal. “A cubic meter of biomethane reduces 90% of carbon dioxide emissions if it replaces natural gas. This figure could be even higher if the replacement involves diesel. It’s a high-value energy molecule,” says economist Gustavo Soares, a Ph.D. student in Bioenergy at Brazil’s Fluminense Federal University (UFF), in an interview with Mongabay.

Manaus’ initiative could attract global attention in 2025 as discussions on the energy transition intensify in the months prior to COP30, scheduled for this November in Belém, another state capital in northern Brazil. In the wake of the U.N. climate summit, the Amazon region can find ways to combine two important pillars of development — sustainability and energy sovereignty.

However, in order to achieve this goal, environmental debate in global forums must be pluralistic, since “the problem isn’t just the [Amazon] forest,” says ABREMA’s president Pedro Maranhão. “Brazil still has 3,000 [open-air] landfills. Many water sources are contaminated, mostly as a result of improper waste disposal. We need to discuss solid waste treatment and green gas.”

An x-ray of biomethane in the Amazon

Solid waste is the main source of biomethane produced in the state of Amazonas, but not the only one. According to Vinícius Magno, head of energy at Conecthus Institute, Brazil, who leads technological projects to boost sustainable development in Manaus, there are two other alternatives that can efficiently supply the biogas sector.

“Fish entrails are a powerful raw material for biomethane production. They can be considered the second [best input],” the engineer says, adding that the state can benefit from fish farming as it stands out nationally in the sector. According to the Amazonas Institute for Sustainable Agricultural and Forestry Development (IDAM in Portuguese), production of tambaqui (Colossoma Macropomum) — a popular traditional fish in the Amazon — exceeded 17,000 tons in 2024.

The biogas industry has another ally: sugarcane. “Waste from the sugar industry can also be used to produce biomethane and achieve decarbonization,” says Magno. Data from the Brazilian Institute of Geography and Statistics (IBGE in Portuguese) show that the state produced nearly 358,000 tons of sugarcane in 2023 alone. Part of this production structure is located in Presidente Figueiredo, 125 kilometers (77.6 miles) from Manaus, where several alcoholic beverage companies operate. The proximity of this small town to the state capital could facilitate the allocation of sugarcane waste to the CTTR.

Manaus’ energy supply is based on natural gas produced in Coari, located about 363 km (225 mi) away. The gas goes to the capital through a continual flow pipeline and therefore cannot be stored.

According to Magno, this distribution model poses some risks. “If there’s any kind of interruption in production in Coari, the gas pipeline shuts down, reducing electricity generation. Operations could stop in the Manaus Industrial Complex, which requires natural gas.” The crisis triggered by a potential supply disruption could extend beyond the capital: According to the Agência Amazonas, 2024 saw record consumption of this fossil fuel throughout the state.

Therefore, he says, biomethane production could create a dual solution, combining decarbonization practices with future “energy security reserves.”

According to Magno, energy insecurity is even worse outside of Manaus. The state has 62 municipalities and no standard energy structure. It relies mainly on isolated systems and leaves entire towns without access to transmission lines. The most critical cases are detected in the state’s remote areas — in the north and south. “About 89% of Amazonas’ municipalities are not part of the National Electricity System,” says Magno. Furthermore, most of these cities depend on 121 thermoelectric plants, which are themselves highly dependent on the combustion of fuels such as diesel. To make matters worse, this naturally polluting dynamic is affected during periods of drought.

“When rivers dry up, it’s impossible to supply thermoelectric plants. Many towns are left without electricity. At the same time, [these places] produce waste that, if processed into biomethane, could help decarbonize the sector, in addition to increasing energy reliability in these areas,” he says.

Despite the optimistic outlook, industry representatives offer a pragmatic view. “We’re not going to compete with oil. We [the biomethane sector] are an integral part of the energy transition process. Biomethane is the decarbonization agent for oil-based gas,” says Hugo Nery, president of Marquise Ambiental, the environmental solutions company managing the CTTR.

For Nery, although biomethane is an “excellent alternative,” green gas alone cannot replace fossil fuels.

At least for now.

From waste collection to distribution: The path to green gas

Biomethane production begins with solid waste collection. This material arrives at landfills still as a mix of organic matter with scraps of paper, metal and plastic. The first step is to separate actual organic matter, which is crucial for decontaminating the gas before its distribution. Such “cleaning” is necessary as some of the waste may contain traces of medications, insecticides or other contaminating chemicals.

In the future, the process may be streamlined if the waste arrives at landfills already separated, optimizing time, reducing costs and boosting production.

However, there is a long way to go for that. The volume of biomethane expected by the industry will only become viable in 2031, at least three years after the CTTR begins operating. This is the time required for the company to accumulate a sufficient amount of biogas to be converted into biomethane. Once this stage is completed, the Amazonas Gas Company, or Cigás, is expected to deliver the product to end customers. In 2025, CTTR and Cigás are already discussing the construction of an additional gas pipeline that will include biomethane into the existing distribution network.

Other indirect environmental advances are expected in the process. In addition to the biogas production facility, the Manaus plant will feature a reverse osmosis system, which transforms leachate — a liquid resulting from the decomposition of organic matter — into reused water. “Using nanotechnology, the leachate will be processed into demineralized water, which can be used to clean industrial equipment, for example. The plant is expected to produce approximately 1,000 cubic meters [35,300 cubic feet] of reused water per day,” says Thiago Levy, commercial director of Marquise Ambiental.

What is still needed to start production

Located 40 km (almost 25 mi) from Manaus’ central area, the CTTR occupies 140 hectares (346 acres) previously used by an illegal sand mining group. Given the potential environmental impacts of the activity, the land underwent a forest restoration process before construction began.

The CTTR already holds an environmental license to operate. However, the city government has yet to transfer garbage collection management and waste treatment to the landfill connected to the plant. This is the city’s main landfill, and it reached its maximum capacity in January 2024, after 40 years of operation. Instead of being decommissioned, it was granted a license to operate until 2028.

The press office for Marquise Ambiental, the future manager of the CTTR, reported that “all stages of the process were inspected by technicians from the Amazonas Environmental Protection Institute (IPAAM), with independent reports and opinions issued by the Amazonas State Audit Court attesting to the project’s legality, viability, and environmental safety.”

The press office also stated that, in compliance with Brazil’s Forest Code, a 200-meter (656-feet) distance was established between the plant’s perimeter and Igarapé do Leão, a major watercourse that flows into the Tarumã-Açu River, one of the main tributaries of Rio Negro. This is a sensitive topic as the construction of waste storage facilities near the stream has been reported by authorities in recent years.

Mongabay contacted the city of Manaus’ government to understand what is needed to sign the contract transferring waste treatment to the CTTR Amazonas landfill. It also asked whether the contract granting the city the right to manage the waste will be kept until 2028 or whether the deadlines could be changed to sped up the start of biomethane production.

IPAAM was questioned about the risks, if any, posed by CTTR construction works to the stream’s water quality. At the time of publishing this article in Portuguese, the institute and the city had not responded to questions emailed by Mongabay.

Marquise Ambiental, for its part, is relying on its experience in the industry to move the project forward. The company participated in the creation of GNR Fortaleza, the first biomethane plant in Brazil’s northern and northeastern regions. After seven years of operation, the unit located in the state capital of Ceará is responsible for 31.6% of the biomethane produced in Brazil and supplies 15% of all gas consumed in the state. Production uses solid waste from Fortaleza and Caucaia.

A favorable scenario for expanding production, but with challenges

According to the dynamic panel of biomethane producers of the Brazilian National Agency for Petroleum, Natural Gas and Biofuels (ANP), the country produced 81.5 million cubic meters (2.88 billion cubic feet) of biogas in 2024. According to economist Gustavo Soares, the numbers seem encouraging, especially considering the country’s vast biodiversity and solid agricultural base — the surplus of which can “feed” this structure.

Ethanol, solid waste and agricultural industries are among the largest potential suppliers of raw materials for biomethane production. In the medium term, in order for the biogas infrastructure to benefit from this waste supply, investment in logistics and infrastructure will be essential to overcome challenges, Soares says. “Animal manure also has great potential [for use by the biomethane industry], considering Brazil’s large cattle population. The animals, however, are on pastures, which creates economic and biological challenges.” According to Brazilian Institute of Geography and Statistics (IBGE in Portuguese), the country has nearly 239 million head of cattle.

Soares says he believes that initiatives to encourage biofuels will be crucial for the sector’s expansion. Among them is RenovaBio. Created in 2017, this program is based on international climate commitments to reduce polluting gases and requires fuel distribution companies to purchase Decarbonization Credits (CBIOs), which correspond to one ton of carbon not emitted into the atmosphere.

Another initiative that can potentially boost biofuels is the Fuel of the Future program, which promotes the transition to cleaner, renewable energy sources. Under this program, fuel distributors must purchase enough biomethane annually to decarbonize their energy portfolio by approximately 1% — under a target that seeks to incorporate 10% of green gases into the natural gas available in the Brazilian market.

“The goal is to decarbonize the fossil fuel sector and focus on the environmental characteristics of biomethane. Large [polluting gas] emitters such as the chemical and steel industries, as well as aluminum [producing] companies, will be required to meet decarbonization targets. Biomethane is an excellent alternative,” Soares says.

Energy efficiency can maximize biomethane gains

The adoption of renewable energies is an important step toward reducing emissions worldwide. Felipe Barcellos, a biomethane expert at the Institute of Energy and the Environment (IEMA in Portuguese), goes further and says that this trend can be boosted if combined with energy efficiency.

In short, “energy efficiency” means producing more with fewer resources: for example, lighting the same number of rooms in a house with fewer light bulbs, consuming less electricity.

For Barcellos, this could be the key to optimization. “It’s important that both the plants seeking to produce biomethane and the electronic devices that will use this energy have efficient models, consuming less biomethane [overall]. This is the best of all worlds: combining biomethane, renewable energy and energy efficiency.”

He says that these practices promote a culture of conscious consumption and, in the long term, can reduce the small emissions that are part of the natural biomethane cycle. “Biomethane is a green gas that is CO2-neutral. However, like all burned gas, it emits other polluting gases in small amounts. With energy efficiency, this impact can also be reduced.”

*Mongabay visited the CTTR Amazonas facilities at the invitation of the Brazilian Waste and Environment Association (ABREMA).

Banner image: A bird perches on debris looking for food in Brazil. Image courtesy of AP Photo/Andre Penner.

This article was first published here in Portuguese on Jul. 23, 2025.

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Xavier Bartaburu Editor

Roberto Cataldo
Translator

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