Mid-ocean ridges, subduction zones and underwater volcanoes are huge generators of methane and carbon dioxide which enters the seawater and forms a hot plume. These vents are like subsea forest fires, the ‘smoke’ from which rises until it reaches a level where it dissipates in surface waters and subsequently enters the atmosphere.

The STEP RHV concept is to capture the hot rich plume just above its source, leaving the vent biota untouched, and allow the bubble stream to rise within a gas-lift chamber. This consists of a vertical pipe containing bubble-breaking vanes designed to rupture the tough hydrate coat which forms around the gas pockets and ensure maximum gas/water mixing. The outside of the chamber carries heat-exchange fins to promote cooling of the hot plume by natural heat exchange with the ocean. By the time the gas reaches the top of the chamber it has either dissolved or formed hydrate crystals. Due to the reduced density of the gas/water column, the internal pressure is considerably higher than the surrounding ocean. This is the ‘Gas-Lift’ effect.

This excess pressure is used to transport the mixture sideways and downwards to arrive some kilometres away from the vent zone at a seabed location of relative inactivity (there are many such ‘backwaters’ in the deep ocean). During this transit, further cooling takes place and heavy mineral inclusions are formed to ensure that the hydrate is negatively buoyant by the time the mixture is released. In this manner the vent gases can be locked up for much longer periods (thousands of years rather than tens) before they emerge as part of the natural carbon cycle. In particular the hydrate crystals are relatively stable on the ocean bottom. In this way we can take maximum advantage of the time delay built into the Global Thermostat. Of course, this is not a long-term solution; but that is what STEP is all about.

• An average machine redistributes 0.3km3 of gas-rich water per year containing 12 million tons of Methane and other vent gases.
• This prevents the release of 33 million tons of CO2 per year.
• 900 such Machines would offset anthropogenic emissions of CO2
• The associated Heat Sequestration per machine is 23 Gigawatts continuous, equivalent to 4 Central Power Stations.
• There are an estimated 3 million subsea volcanoes and 20,000 kms of subduction zone.

• Building such machines would be viable for the existing offshore industry
• Having been put in place, the machines are automatic
• The machine would be cleaned, adjusted and relocated annually.

• The RHV is totally wave-powered using renewable energy.
• The displaced methane would be sequestered for many years

• Such projects could be financed by a Carbon Tax; ideally through a "World Carbon Bank"
• Governments could buy in to such schemes; it's jobs for their industry and a way to be seen to be doing something!

• Development costs are estimated at $50 million
• Field Survey would cost approx €100 million
• A working prototype would cost approx €40 million
• India could subsequently build a full-size machine for the same price
• Assuming a methane bounty of only €5 per ton, machine pays for itself in 9 months