Story written by Alaina Hickey, Nick Zaremba, Amanda Campbell & Laura Markley

On Friday, February 23^rd, a group of EMPOWER students led the class with a presentation focused on the existence of methane in Lake Kivu, continuing the discussion from the previous week on the geological processes controlling the evolution of the East African Rift and the Great Lakes of East Africa. These two student-led discussions were scheduled in preparation for an EMPOWER field course that will be taking place in Rwanda on Lake Kivu in June, which will focus on scientific issues pertaining to water resources and power generation in Rwanda. Professor Chris Junium, an organic geochemist who will also be taking part in the field course, joined the class to aid in the discussion on the complex biogeochemical cycling and water column chemistry of the lake.

Lake Kivu is located on the border of Rwanda and the Democratic Republic of the Congo and lies along the Albertine Rift, the western branch of the East African Rift. The lake is estimated to hold 55 billion cubic meters of methane (CH₄) and 250 billion cubic meters of carbon dioxide (CO₂), which are normally held at depth due to the meromictic nature of the lake. Similar to Fayetteville Green Lake, Lake Kivu is a meromictic lake, meaning that it does not normally overturn. As long as the lake remains stratified, the methane and carbon dioxide are not released into the atmosphere. However, this lake, along with Cameroonian Lake Nyos and Lake Monoun, are three known lakes to undergo limnic eruptions. Limnic eruptions are rare natural disaster cases in which the dissolved carbon dioxide and/or methane suddenly erupts from deep waters, forming a gas cloud that can asphyxiate wildlife and human populations. Methane and carbon dioxide are expected to reach saturated levels in the lake in 50 to 200 years, which poses a gas eruption threat to more than two million people along its shores. Geologic evidence in the lake’s surrounding region suggests mass biological extinctions have taken place in the past, which is likely a result of outgassing events triggered by volcanic activity. Understanding the unique geologic and chemical processes of the lake can help predict and potentially prevent future catastrophes.

In an effort to control methane levels in the lake, ContourGlobal, a U.S. based energy company, acquired project funding in 2011 to begin a large-scale methane extraction project, which now operates through a local Rwandan entity named KivuWatt. This is the only gas/water extraction project operating in the world. An offshore platform is used to extract, separate, and clean the gasses obtained from the deep waters before pumping purified methane through an underwater pipeline to on-shore gas engines. This exploitation of methane aids in maintaining permanent stratification of the lake and mitigating the dangers associated with the release of CH₄ and CO₂. The project also provides an environment-friendly and sustainable source of power generation, decreases the country’s use of diesel to generate electricity, and reduces electricity costs for consumers. Extraction is reported as cost-effective and relatively simple – once the gas-rich water is pumped to the surface, the dissolved gases (CO₂ and CH₄) begin to bubble out as water pressure decreases. This project is expected to increase Rwanda’s energy generation capability by as much as 20 times, and will enable Rwanda to sell electricity to neighboring African countries.