User:Max005/Microbial electrolysis cells

A Microbial Electrolysis Cells (MEC) is the next step in Microbial Fuel Cells which uses bacteria to generate hydrogen. By coaxing the common bacteria with acetic acid it was possible to generate a 91 percent yield in hydrogen. Nearly all of the hydrogen converted was usable hydrogen gas which one day could lead bacterial hydrogen production on a large scale.

Microbial Electrolysis Cells
MEC systems are based on a number of components.

Microorganisms - they are attached to the cathode. To what extent they they affect the function of the MEC is not        clear nor is it clear to what extent the operation of an MEC is affected by the inoculum core.

Materials - The anode material in a MFC can be the same as an MEC. The materials are carbon cloth carbon paper, graphite felt, graphite granules or graphite brushes. Platinum is used as a catalyst to reduce the overpotential required to drive the hydrogen production. The high cost of platinum is making research into biocathodes a good alternative. Other materials issues include membranes (although some MECs are membraneless), and tubing and gas collection systems.

Generating Hydrogen
The way it works is that the bacteria consume the acetic acid and release electrons and protons creating up to 0.3 volts. When more than 0.2 volts are added from an outside source, hydrogen gas bubbles up from the liquid. Hydrogen productions has reached a up to 3.12 m3H2/m3d with an energy input of 0.8 volts. There is a range of hydrogen production depending on what organic substances are used. Lactic and acetic acid achieve 82% efficiency while while unpretreated cellulose is 63% and 64% for glucose.

Water hydrolysis which also produces hydrogen is only 60 to 70 percent efficient. MEC system creates 144% more available energy than the electrical energy used to produce it.

Calculations Overall hydrogen recovery was calculated as RH2 = CERCat. The Coulombic efficiency is CE=(nCE/nth), where nth is the moles of hydrogen that could be theoretically produced and nCE = CP/(2F) is the moles of hydrogen that could be produced from the measured current, CP is the total Coulombs calculated by integrating the current over time, F is Faraday’s constant, and 2 is the moles of electrons per mole of hydrogen. The cathodic hydrogen recovery was calculated as RCat = nH2/nCE, where nH2 is the total moles of hydrogen produced. Hydrogen yield (YH2) was calculated as YH2 = nH2 /ns, where ns is substrate removal calculated on the basis of chemical oxygen demand (22).

Uses
MEC produced hydrogen can be used as fertilizer manufacture. With very large farms or farm cooperatives could produce hydrogen from wood chips and then through a common process, use the nitrogen in the air to produce ammonia or nitric acid. Both of these are used directly as fertilizer or the ammonia could be used to make ammonium nitrate, sulfate or phosphate.

"We drive a lot of vehicles on natural gas already. Natural gas is essentially methane," says Logan. "Methane burns fairly cleanly, but if we add hydrogen, it burns even more cleanly and works fine in existing natural gas combustion vehicles."

History
It was invented and patented by Dr René Alexander Rozendal. Bruce Logan showing that you can use microbes to create electricity with the Microbial fuel cells went a step further. Working with colleagues in Penn State he was able to come up with a way to alter the design and use a small jolt of electricity to create hydrogen.