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Emitted Methane as Feedstock for Bio-manufacturing – improving the Earth’s climate in small bites

Posted on February 20th, 2017 by in New Materials & Applications

Sina - methane

(Source: The Business Journals, www.bizjournals.com)

 

There are good reasons for the burning flares in refineries, chemical and natural gas processing plants and oil wells.  From a distance it looks like a tall chimney with a red flame atop.  The primary function of the flares is to act as safety devices.  When there is overpressure (unplanned) in any of the hundreds of refinery vessels or pipes, vented gas is sent to the flare where it burns out.  This has been a longstanding practice in refineries to reduce the risk of explosions.  Another function of the flares is to burn the excess methane produced during various operations.  Examples include methane produced during cracking and pyrolysis of crude oil as well as that separated during fractionation in distillation columns.

There are other sources of methane outside of refineries and factories.  Every city, small and large, has facilities to treat the waste produced by its population.  Waste treatment processes generate methane.  Live stock farming is the source of one quarter of man-made methane emissions.  Due to the swamp-like environment of rice fields, this crop generates 10% of human methane emissions. The human sources add up to 64% of total methane emission to the atmosphere; the balance of 36% is emitted by natural sources. By far the largest source (one third) of human contribution originates from the production and use of fossil fuels including petroleum.

Plenty of methane is generated by natural and anthropogenic (man made) processes.  Methane has a global warming potential (GWP) of 86.  This means the heat trapping impact of methane is eighty six times worse than that of carbon dioxide (GWP=1).  Atmospheric life of methane is 12 years.  Methane uses include as fuel, feed for the production of synthesis gas (CO + H2) and chloromethanes in large quantities.  There are few applications for the relatively small quantities of methane that is produced in scattered locations around the US and other countries.

Professor Ramon Gonzales, at the Rice University, has proposed a new technology to convert methane to useful products, in a January 2017 publication.  The paper was published online in Science Daily on January 9, 2017 and was also summarized in the concurrent print version of the Science. (Source: J. M. Clomburg, A. M. Crumbley, R. Gonzalez, ScienceDaily www.sciencedaily.com/releases/2017/01/170109113803.htm, 9 January 2017).

The paper discusses methane as a feedstock for biological processes to make intermediate chemicals and solvents.  Gonzales says that among their findings the most surprising was that waste methane burned off in 2014 alone could have been transformed, via bio-manufacturing, into seven important organic chemicals — methanol, ethylene, propylene, butadiene, xylene, benzene and toluene   The amounts were sufficient to meet 100 % of the industry’s requirements for that year.

The proposal by Gonzales et al states: “In contrast to current chemical manufacturing methods, characteristics inherent to bioconversion processes—such as the ability to operate at mild temperatures and pressures and achieve high carbon- and energy-conversion efficiencies in single-unit operations—result in more streamlined and less technologically complex processes. These characteristics enable flexible, smaller-scale, and capital expenditure–efficient operations that can both support and benefit from a large number of facilities, according to the economies of unit number model.”

As a supportive argument they cite the decrease in the entry-level capital cost of corn-grain ethanol facilities.  Those operations are the most widely developed examples of a bioconversion process.   Capital expenditure has substantially decreased as the number of plants has increased since 1995.  Consequently rapid, small-scale, and widespread deployment has netted over a 10-fold increase in U.S. ethanol production in the last two decades.

Significant progress in metabolic engineering, synthetic biology, genomics, and industrial process design has driven industrial bio-manufacturing close to broad adoption. There has been emphasis on single-carbon feed stocks, such as methane or CO2 that currently remain unused to the detriment of the environment.  Those advances would allow applications where large-scale chemical manufacturing is infeasible or too costly.  A schematic of the conversion process proposed by Gonzales et al can be seen below:

Sina methane 2

(Ref: J. M. Clomburg, A. M. Crumbley, R. Gonzalez, ScienceDaily www.sciencedaily.com/releases/2017/01/170109113803.htm, 9 Jan 2017)

The significance of methane as feedstock of bio-processing is illustrated in a 2015 report titled: Industrialization of Biology: A Roadmap to Accelerate the Advanced Manufacturing of Chemicals, published by the US The National Academies of Sciences, Engineering, and Medicine (Source: THE National Academies Press, Washington, D.C., www.nap.edu).  It states, to achieve parity between the biosynthesis and traditional chemical synthesis a number of candidate processes are being pursued in the industrial production of chemicals.

The present feedstock for biomanufacturing chemicals is fermentable sugars from starch. The starch, in turn, derives from grains such as corn. The continued expansion of biomanufacturing chemicals will require additional feedstock from nongrain sources.  Cellulosic biomass holds great promise as a feedstock pending resolution of technical barriers.  A great deal of attention is focused on different forms of biomass to address the challenges associated with using recalcitrant cellulosic material in industrial biotechnology. There is also much development activity in the facilitation of the use of syngas, methane, and carbon dioxide for manufacturing.

The high point of the Gonzales et al’s proposal is its focus on the profitability of small bioprocessing plants.  Markets are far more powerfully driven by the prospects of profits than by any government regulations.  Contribution to a reduction in environmental emissions provides a favorable secondary incentive to the industry.  There is hardly a company that would not love to convert environmental waste streams into value-added products profitably.  Governments can contribute most effectively by investing in institutions jointly formed with the industry to drive technological developments.  Partnership and investment by the industry has a better chance, than other alternatives, of keeping research and development focused on commercially viable goals.


 

All opinions shared in this post are the author’s own.

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