In March and April 1992 preliminary test were conducted at Lake Monoun using the
gas lift method as known in the petroleum industry. Initially a pump (or preferably a compressed gas injection) is needed to pull water from the bottom, but as carbon dioxide begins to come out of
solution it creates
buoyancy in the water in the pipes, allowing a self-sustaining process without the need for external energy supply. Due to the fact that the project had little funding and needed to be done by hand, the solution was the use of
high-density polyethylene (HDPE) pipes. The material has a density of 0.961 kg/L which means an almost neutral buoyancy in water. The HDPE plastic is flexible, not brittle, and resistive to chemical and weathering alteration as proven material for natural gas distribution networks. The pipe could be easily soldered electrically in the field from standard segments, and deployed with just the help of rubber boats and floats. With some
ballast, the pipe hangs freely from an anchored raft like a pendulum. Unfortunately, the -rich, oxygen-depleted water from the depth is a challenge for steel fittings:
Corrosion occurred and formed
siderite which removed iron from the steel. In February 2003, a venting pipe was inserted into the lake, in an effort to prevent the disaster from recurring. In the initial
degassing phase, an fountain developed from the water tapped at depth. On the other hand, the deep lake water is rich in
iron(II) ions, which after a while transforms into
limonite. As the lake is a fishing ground for local villagers, the effect of a higher iron intake rate in the upper water layer on fishlife needed consideration before scaling up the degassing rate. In December 2013, the degassing pipe was upgraded with a small solar-power driven rotary pump, since it had lost its self-lift capability due to the bubbling effect in the riser as a significant amount of had been removed from the bottom layers. The new system is able to lift of bottom water to the surface per day. That degassing capability is unfortunately less than the natural inflow of -rich water, therefore two more of these solar pumps are needed to avoid a long-term build up of higher and dangerous levels of in the stratified water levels. ==See also==