Process

Krajete® Process is based on the metabolism of methanogenic (= methane producing) Archaea. The energy metabolism and therefore the livelihood of these microorganisms is based on the conversion of carbon dioxide (CO2) and hydrogen (H2) into methane (CH4) and water (H2O). The basic reaction is analogous to the chemical “Sabatier process”, described by Equation 1:

CO2 (g)+4 H2 (g)CH4 (g)+2 H2O (l)
1 mol 4 mol 1 mol 2 mol
1 Nm3 4 Nm3 1 Nm3  
44 tons 8 tons 16 tons 36 tons

“Methanogenesis” or chemical „Sabatier“ Process (catalytic hydrogenation of CO2). Abbreviations “g” and “l” indicate the aggregate state “gas” and “liquid”, respectively.

The central element of Krajete® Process is a continuously stirred tank reactor (CSTR), in which microbes (monoculture) catalyzing the reaction are suspended in an aqueous solution. The methane (CH4) formation within the reactor is achieved by a continuous input of hydrogen (H2) and carbon dioxide (CO2). The feed gas enters the liquid at the bottom of the reactor and is then dispersed by an agitator to get proper dissolution of reacting gases within the liquid phase. While passing the reactor from bottom to top, gases are converted into methane.

One of the key advantages of the biological catalyst is its resistance towards a broad range of feed gas impurities. A variety of industrial exhaust gases has been successfully used for Krajete© Process without purification. The suitability for intermittent production patterns has been intensively tested. Under optimal conditions, the process can go from stand-by to full load within a couple of seconds. The limiting factor is never biology but solely the technical optimization of restart procedures.

Stand-by periods of more than 500 hours have been tested, showing no effect on the productivity after restart. Also several weeks of intermittent operation with frequent changes in load showed no influence on the long-term stability of the process.