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Friday, February 26, 2021

ISO Efficient Bioenergy: Ethanol Verses Bioelectricity

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With the fluctuating price of oil, a finite resource, and concerns over CO2 emissions, many energy companies and developers have turned to utilizing biomass as alternative fuel (biofuel)

This trend is actually taking two pathways: using biomass to convert to ethanol to power automobiles (which has been around for awhile now), and, converting biomass to electricity to power electric (or hybrid) vehicles (a more recent alternative). The question of which path is most efficient, sustainable, and less carbon-intensive is a vitally important one in terms of this nation’s “energy future”.

In one past study (e.g., Hedegaard, et al, 2008), analysis showed greater fuel displacement and GHG offsets via biomass for electricity, verses for ethanol production. But until recently, no one had actually quantified the main factors involved in both pathways, and compared them.

But this past May, scientists J. E. Campbell, D. B. Lobett and C. B. Field, reported the results of their quantification approach and “life-cycle assessment”. In a report published in Science (May 22, 2209), the authors describe the methodological tools and models they used for their biomass usage comparisons.

The researchers compared bioelectricity to ethanol with respect to two factors: total transportation kilometers, and GHG offsets per unit area of biofuel cropland.

Further, they apply these variables to various automobile types (small, mid-size, full size, compact, sedan, SUVs, etc.). A “meta model” called EBAMM (Energy and Resources Group Biofuel Analysis Meta Model) was implemented to consider different usages covering a range of biomass stocks (”feedstocks”) and energy conversion technologies (including both corn and cellulose for ethanol production). The assessment also included variables such as the total input (energy) needed to grow the feedstock and then convert it to either bioelectricity or ethanol.

And the result of all this quantification? According to the authors: “Bioelectricity outperformed ethanol across a range feedstock, conversion technologies, and vehicle classes.” They also showed an average of 81% more transportation kilometers and 108 % more GHG offsets (per unit area of cropland used) for bioelectric vehicles (BEVs), verses ethanol powered vehicles (ICV; internal combustion vehicles).

This is significant research and promises to have a major impact on our national alternative (and renewable) energy future. The quantity of land available for growing biofuel crops is obviously limited. When one considers additionally crop conversion’s impact on food prices and greenhouse gas emissions, this limitation is all the more strict. When looking at transportation efficiency and carbon off-sets together, it becomes clear that maximum efficiency of land use is paramount to achieving both goals (clean, fuel efficient transportation, and climate change mitigation through CO2 reduction).

In this life cycle assessment, there is a clear winner. And questions remain: can we now use this new data to choose the wiser (more efficient) path? Or, will entrenched interests (and established energy infrastructure) mandate some compromise–a third path? And there are other biofuel sources out there–green algae for one, which has the distinct advantage of directly absorbing CO2 and being a dual food/fuel sources. However, like all biomass fuels, burning algae produces CO2. The question for any biomass usage is how much carbon dioxide does it give off verses another? The advantage to using biomass is that it is a renewable resource (some types, like corn, are less sustainable). But ultimately, biomass can only reduce CO2 with respect to fossil fuels; they still generate GHGs.

A broader approach to securing our energy future includes a diversified, energy “portfolio” of biomass, wind, solar, geothermal, hydrogen, possibly nuclear, wave/tidal power, and even, still, some oil/gasoline (hydrogen boosting of IC engines is becoming more common).

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