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Dirty Energy & Fuel

'Woody' Biomass Breakthrough: Fungus is the Key

The resurgent interest in alternative fuels has propelled interest in using biomass “feedstocks” as an energy source for liquid fuel and bio-electricity generation. But bio-fuel (and other ‘commodity chemicals’) derived from ‘woody’ biomass faces one big technical challenge: how to separate the useful constituents of cellulose-based biomass (i.e., its six-carbon, sugar building blocks) from the not so useful ones (such as lignin and hemicellulose)?

In the past, attempts have been made to do this separation by applying acid/base compounds to the biomass, or even adding microbes to digest the tough proteins–with less than satisfying results. Now, however, research by Ray et al, has shown promising results, and the key is a well-known variety of fungus.

Before woody (or cellulose) biomass can be ‘depolymerized’ and converted into fuel, constituents like lignin (a tough protein) have to be separated from the cellulose. Recent research has shown that two types of brown rot fungus are able to do this with significantly greater efficiency.

The two types of brown-rot fungi used by Ray et al are the Coniophora puteana and Postia placenta varieties, and their research showed that a 3 to 4 week treatment of the biomass (sapwood from pine trees in this case) “significant;y enhances the release of sugars (the actual fuel source) by cellulose enzymes.” *

Control experiments conducted to achieve similar, bioconversion results with other fungi proved far less successful. This research seems to be a successful proof of principle that brown rot may be the key to efficient biomass processing that researchers have been searching for over the past few decades.

That said,  while biomass/bioenergy is an attractive alternative to burning (and extracting) fossil fuels, all such feedstocks  release CO2 when burned. Different biomass feedstocks generate more or less carbon, but some sources of biomass are unsustainable, such as corn grown for ethanol fuel. Further, the (non-industrial) burning of biomass in the developing world–especially ‘woody’ biomass derived from forests/woodlands–is the source of black soot aerosols which are a major contributor to atmospheric warming.

This carbon can be captured, but designing processing plants to do this will add to their cost, and then, all this captured carbon has to be ‘sequestered’ somewhere, which also adds to the cost.

A forest is far more useful–in terms of ‘ecosystem services’–as a carbon sink, than as a fuel source. Also, biomass conversion to electricity (bioelectricity) is significantly more efficient than its conversion to liquid fuel (see my older, ecolocalizer article: ISO Efficient Bioenergy: Ethanol vs. Bioelectricity)

* Quoted from the Editors’ Choice news blurb in the 28 May, 2010 edition of Science (author JSY). The actual research results were published in the March 2010 edition of the journal of Biomass Bioenergy.

Image: biomass-bioconversion Pilot Plant (College Station, Texas)




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