When it comes to methane emissions, most people think of oil, coal, gas, and livestock. However, according to Louise Parlons Bentata, co-founder and CEO of UK-based startup Bluemethane, one significant source often overlooked is water. “Methane emissions from water are an environmental catastrophe but also a waste of valuable resources that can be turned into clean energy,” she says. Human activities such as rice cultivation, waste streams, and reservoirs emit more than three billion tons of CO2 equivalent per year from methane emissions, but awareness remains alarmingly low.
Founded in 2021 by Parlons Bentata and engineer Nestor Rueda-Vallejo, Bluemethane is part of the fifth cohort of the AgFunder GROW Impact Accelerator. The startup is on a mission to remove methane from various water sources, starting with wastewater treatment in the UK, where utility companies have committed to achieving net-zero status by 2030.
Parlons Bentata explains that methane is produced through the decomposition of organic matter by microbes in water under low oxygen conditions. This phenomenon occurs in environments such as sewers, which are almost entirely anoxic, and rice paddies, where farmers often keep the fields flooded. “At least three billion tons of carbon dioxide equivalent are coming from anthropogenic water bodies like reservoirs, rice paddies, and sewage,” she notes.
Interestingly, the ocean is far less of an issue for methane emissions compared to other water sources. This is because ocean water is constantly moving, and ocean currents dilute and disperse methane over vast areas, preventing it from reaching saturation levels that would allow it to escape into the atmosphere. Additionally, more oxygen is circulated in ocean water, inhibiting the activity of anaerobic microbes that produce methane.
Methane can be released from water in three primary ways: bubbling, diffusion, and degassing. Bubbling occurs in shallow water where methane forms bubbles that rise and burst at the surface. Diffusion happens when the concentration of methane in the water is higher than in the air, causing methane molecules to transfer to the gas phase. Degassing involves a sudden change in pressure that causes dissolved gases to be released rapidly, such as when water passes through a dam wall.
Measuring methane emissions from water bodies presents a significant challenge. While methane emissions in the air can be measured using satellites and drones, these methods are not applicable for water. Bluemethane has recently won a grant to develop a dissolved methane measuring system, which they offer as a paid service. However, the current technology for measuring dissolved methane in complex liquids like sewage streams is still limited.
Various technologies are currently deployed to remove methane from water, including heat, aeration, membrane-based technologies, and vacuum towers. Each of these methods has its limitations. Membranes, for example, can effectively remove almost all methane but require significant energy and clean water to avoid clogging. Vacuum towers are useful for high methane concentrations, such as in Lake Kivu, Rwanda, but are not economically viable for lower concentrations found in the UK.
Bluemethane’s approach focuses on removing the most methane using the least amount of energy. Their technology employs a physical separation method without chemicals or membranes and does not require heating the water. Parlons Bentata likens the process to shaking a bottle of sparkling water: “By shaking it, you speed up the process of the bubbles coming out, and by opening it, you suddenly change the pressure.”
As Bluemethane continues to innovate and push the boundaries of methane capture technology, the potential for turning an environmental catastrophe into a sustainable resource remains promising.