A Techno-economic Analysis of Polyhydroxyalkanoate and Hydrogen Production from Syngas Fermentation of Gasified Biomass

Abstract

A techno-economic analysis was conducted to investigate the feasibility of a gasification-based hybrid biorefinery producing both hydrogen gas and polyhydroxyalkanoates (PHA), biodegradable polymer materials that can be an attractive substitute for conventional petrochemical plastics. The biorefinery considered used switchgrass as a feedstock and converted that raw material through thermochemical methods into syngas, a gaseous mixture composed mainly of hydrogen and carbon monoxide. The syngas was then fermented using Rhodospirillum rubrum, a purple non-sulfur bacterium, to produce PHA and to enrich hydrogen in the syngas. Total daily production of the biorefinery was assumed to be 12 Mg of PHA and 50 Mg of hydrogen gas. Grassroots capital for the biorefinery was estimated to be $55 million, with annual operating costs at $6.7 million. With a market value of $2.00/kg assumed for the hydrogen, the cost of producing PHA was determined to be $1.65/kg.

Heterologous Expression of Various PHA Synthase Genes in Rhodospirillum rubrum

“…Cultivations were carried out under heterotrophic and autotrophic conditions as well as in the absence or presence of light 14,15,16,18,42,43 . In most preceding studies, R. rubrum showed slow growth rates leading to long and inefficient cultivations.…”

“…The phototrophic non-sulfur purple bacterium Rhodospirillum rubrum is able to synthesize PHA under heterotrophic and even autotrophic growth with carbon monoxide (CO) and carbon dioxide (CO 2 ) as carbon and energy source 14,15 . Growth of Rhodospirillum rubrum utilizing syngas has already been intensively investigated 14,15,16 . In 2008, a profitable and technically feasible concept for PHA accumulation of R. rubrum based on the utilization of synthesis gas was presented for the first time 16 .…”

“…Growth of Rhodospirillum rubrum utilizing syngas has already been intensively investigated 14,15,16 . In 2008, a profitable and technically feasible concept for PHA accumulation of R. rubrum based on the utilization of synthesis gas was presented for the first time 16 . PHA biosynthesis through syngas fermentation was carried out, and the costs were $ 2 -4 per kg less than in the case of using sugar fermentation and recombinant E. coli strains.…”

“…PHA biosynthesis through syngas fermentation was carried out, and the costs were $ 2 -4 per kg less than in the case of using sugar fermentation and recombinant E. coli strains. Furthermore, H 2 was produced by R. rubrum under these conditions, which is also of great industrial interest 16 . These properties indicate the great biotechnological potential of R. rubrum.…”

Optimal use of hybrid feedstock, switchgrass and shale gas for the simultaneous production of hydrogen and liquid fuels

“…The second is a simple bypass where the composition remains unchanged. Finally, a hybrid membrane/PSA system is proposed to remove hydrogen based on recent results in the literature [33,34].…”