Integrating Water Treatment, Biogas and Power Generation

In the realm of alternative fuels, biogas, derived from sources like organic food waste and agricultural residues, has emerged as a pivotal component in companies' decarbonization strategies. Mitsui, in particular, is positioning itself to expand its footprint in the Mexican market leveraging this resource.

Carlos Fuentes, Business Development Executive, Mitsui & Co Infrastructure Solutions, underscores the diverse raw materials for biogas production, ranging from organic food waste and agricultural residues to wastewater treatment plants. The biogas generated, particularly in municipal plants processing organic waste, undergoes anaerobic biodigestion to decompose volatile solids, producing biogas as a byproduct. An additional refinement process, called upgrading, can convert biogas into biomethane, often referred to as renewable natural gas (RNG). Biomethane, possessing the same properties as natural gas, can be employed as fuel or integrated into the gas grid, which is already an established practice in markets like the United States.

The distinction between biogas and RNG lies in their composition, with biogas containing a higher proportion of carbon dioxide, while RNG boasts over 95% methane, subject to regulatory variations across countries.

Biogas typically contains hydrogen sulfide and other contaminants, whereas RNG aligns more closely with the characteristics of natural gas. Technologies for biogas upgrading, such as pressure swing adsorption (PSA), absorption, membrane separation, and cryogenic separation, are advancing, contributing to a reduction in natural gas prices and enhancing viability for end-users. Currently, the average price of RNG stands at US$19/MBtu.

Mitsui's subsidiary, MITInfra, has been active in Mexico for over six decades, primarily focusing on the development of water treatment plants. With a track record of over 102 completed water treatment projects, 40 of which are operational in Mexico, MITInfra integrates power generation facilities through biogas in its largest water treatment projects.

These projects include Atotonilco, treating around 35,000L/s; San Pedro Martir in Queretaro with 750L/s; AguaPrieta with 4,500L/s, and El Ahogado with 2,250L/s.

"Bioenergy, especially in the form of biomethane, aligns with the strategic plans of international organizations like the International Energy Agency (IEA) and is gaining prominence in countries like the United States, where fuel suppliers are mandated to include biomethane in their fuel purchases. These biofuels play a pivotal role in the sustainability strategies of countries and private enterprises in the future", says Fuentes.