Managing the dangers in Lake Kivu - How and why

Lake Kivu is probably the World's largest natural freshwater digester of algae to produce biogas. Its resources in situ may generate power for generations. Extracting gas is essential to avert a future limnic eruption. Undisturbed, the reservoir formed by salinity-based chemoclines, keeps biogenic CH₄ and CO₂ in solution. This is stored in lower strata of the lake.

Gases accumulating ever closer to saturation levels, threaten to cause a future limnic eruption. An eruption as occurred at Lake Nyos in Cameroon in 1986 with 1746 casualties, can result if not prevented. But Lake Kivu has potential and inventory for consequences 1000 times larger.

Based on novel hypotheses on vertical transport and the lake's history, we used multidisciplinary analyses of this situation. One can foresee its outcomes and recognise system constraints.

Therefore, initiating gas extraction enables the vital outcomes; (a) society can enforce extraction methods that ensure prevention of future disasters while, (b) minimizing environmental impact, (c) maximizing useful energy output, and (d) developers pursuing economic projects. The key to safety is management of the chemoclines while producing gas. Achieving safety and production needs the right specification of plant design. For gas production facilities, it is designing to achieve what must be done technically.

After our primary concern for public safety, we examine ways of minimizing any environmental impacts. Changes are caused by natural upwelling of saline meteoric water from lava strata into the deep monimolimnion of nutrient-rich water bodies. Raw gas extracted must be washed with water from the mixolimnion to make the gas fit for use in power-generation and domestic gas.

For maintenance of chemoclines, we discuss how a fraction of the degassed water must be evacuated from the resource strata and re-injected into the mixolimnion to maintain chemoclines. The challenge lies in how to minimize this safety-driven impact on the mixolimnion from toxic effects of H₂S, from CO₂-induced acidity, and oxygen depletion by CH₄ and H₂S.