Wednesday, February 27, 2013

Methane's Real Potential: Plastics

Methane has been getting a good run these days due to it being the energy ingredient in a little-known resource we call "natural gas".....

Yet, while the gas boom has been a silver lining in the cloud of the US economic recovery, it comes with a price: methane is not going to help the effort to curb greenhouse gases.  In fact, it has 21 times the heat retention properties as carbon, so hurting it seems more likely.

This chart shows the many sources of methane by-product
Unfortunately, in every case, the gas is too contaminated
for energy use.
Scientists have been trying for, really, centuries, to harness energy from biogas produced in landfills and waste management plants.  After all, what better resource to use for human energy consumption than what humans inevitably "emit" anyway?  So why haven't we done so already?  Biogas produced out of plants and landfills are mixed with too many "dirty" compounds that render it useless.  Since it costs too much to clean up, most facilities burn it off instead.

That's where Craig Criddle, professor of civil and environmental engineering at Stanford University, comes in.  Criddle has a different idea for methane; while its energy seems near impossible to draw on a cost-efficient scale, turning it into plastic is very doable.

Groundwater bacteria munching on methane.
Why?  Because microbial organisms called methanotrophs do it for us.  Criddle and his staff cultivated these specific types of bacteria and developed a technique whereby feeding them lots and lots of methane enables them to produce a large amount of polymer compound called polyhydroxybutyrate (PHB for short).  Not only do the methanotrophs produce up to 60 times their body mass in PHB, but their metabolism completely rids the PHB of any kind of contamination.

While it's not going to solve energy issues, this method makes a solid argument that methane, not petroleum, should be looked at as the chief source of our plastic products.  Criddle himself gives an economic reason:

“From a business standpoint, it makes far more sense to use methane as a polymer feedstock than to burn it for power production...PHB sells for $3 to $4 a kilogram on today’s market, while methane burned for electricity production would return from 40 to 80 cents a kilo.”  - Craig Criddle to Glen Martin, Stanford Engineering

In addition, converting methane to a polymer sequesters all the carbon that would usually and eventually make its way into the atmosphere under our current petroleum-based process.  Thus using methane-based polymers are not only cheaper, but have a direct effect on greenhouse gas emittance, as well.

Seems like a pipe-dream?  Not at all.  Stanford alum Molly Morse, PhD, is the CEO of Mango Materials, which has just recently been permitted to operate a PHB production facility at a wastewater plant in the Redwood City area of San Francisco County.  If all goes well, methane-based polymers could be a commercial product- and a welcomed innovation- within a few years.

Donal Thoms-Cappello is a freelance writer for Rotor Clip Company.

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