Fostering the natural gas supply and providing scientific foundation for reverting the ANP regulation preventing sewage treatment plants and landfills to inject biomethane in the gas grid are some of the project’s goals

Researchers from the Institute of Energy and the Environment (IEE) at the University of São Paulo (USP) are mapping biogas and biomethane production in landfills and sewage treatment plants along with animal and agroindustrial waste treatment plants throughout the State of São Paulo. The project is part of an initiative of the Research Centre for Gas Innovation (RCGI) aiming to propose new ways to make natural gas supply more robust.

Biogas has a concentration of methane (CH4) between 50% and 60%, the other 40% is composed of carbon dioxide (CO2) and a few other elements. It is a fuel gas, which may be used in combustion engines and similar. “Biogas can be used in its raw form, or it may undergo a purification process by which a higher concentration of methane (i.e. more than 80%) without impurities is obtained. This is what is called biomethane. It replaces natural gas with the same characteristics, with the advantage of being a renewable energy source by nature. Besides, it can be injected in the natural gas network, seeing that the natural gas composition is around 80% and 90% methane”, explains Prof. Dr. Suani Teixeira Coelho, who coordinates the project.

Regarding agroindustrial waste, the researchers are especially interested in the biogas produced from vinasse, which is a by-product of ethanol distillation. Vinasse is produced in large quantities: from 8 to 12 litres of vinasse per litre of distilled ethanol. “It is an abundant feedstock and, therefore, in our opinion, an important potential source for biomethane production in the State of São Paulo,” estimates the Prof. Coelho. Currently, the largest share of vinasse is used as nutrient for cultivation (i.e. fertirrigation) in the State of São Paulo.

Prof. Coelho remarks say that the agribusiness sectors, especially the sugar-ethanol sector, are conservative. Hence, she says: “we must show them the real potential: how much it can be yielded, how much natural gas can be replaced by biogas, how much power can be generated, how much diesel can be saved in agricultural machinery when replacing diesel by biogas or biomethane and so on”.

Within a year, the IEE team intends to deliver to producers a map illustrating the State of São Paulo’s potential for biogas and biomethane production. The whole project is predicted to last five years. “We want to know whether they (e.g. potential feedstock) are close to the gas network, how much they can produce and what does this represent to the State’s energy matrix,” Prof. Coelho says. “From this information, we are going to discuss the regulatory framework and the economic perspective: how much does it cost to realize the untapped potential, what are the necessary infrastructure and the adequate regulations, and whether that would be a free market or would be based on tariffs”.

Changes in regulation – Another goal of the project is to attempt a revision from the National Agency of Petroleum, Natural Gas and Biofuels (ANP, the Brazilian acronym) about the regulation that recently banned the injection of biomethane deriving from landfills and sewage treatment plants in the gas grid due to the presence of contaminants, in special siloxanes. This contaminant derives from products such as toothpaste, shaving cream and cosmetics in general, which as present in the waste stream of solid waste and sewage.

“We know how siloxanes can be separated. Our group already studied this, in a joint project with SABESP (i.e. the water and waste management company owned by the State of São Paulo) over fifteen years ago. At that time, it was already possible to separate siloxanes with no difficulties. We want to show that there is no reason for banning the injection of biomethane from landfills and sewage treatment plants in the gas grid,” she states. “There is a huge potential for biomethane from these sources. What is required to be done is specifying quality parameters for producers wanting to inject their biomethane in the gas network.”