Definition, Calculation and Comparison of the “Biomass Utilization Efficiency (BUE)” of Various Bio-based Chemicals, Polymers and Fuels

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DatePublished - Nov 2015
Number of pages26
Publishernova Institute
Original languageEnglish

Abstract

This paper defi nes, introduces and applies a new term, the “Biomass
Utilization Effi ciency (BUE)”. This is a new and relatively simple
approach to evaluate and compare different bio-based chemicals, materials and fuels based on the input-biomass, the used conversion
process and the end product. A BUE analysis can answer the following
questions: How effi ciently is biomass utilized? What share of the
biomass is ending up in the fi nal product?
To summarise the role of the Biomass utilization effi ciency (BUE) in
the context of existing methods, it is obvious that this new metric has
an emphasis on the best combination of biomass feedstock, process and
bio-based product that is absent from existing calculations routinely
used by research and process chemists and engineers. At present, waste
minimisation during a manufacturing process is addressed through
the choice of methods and optimisation of conditions. However, it
is now clear that inherent waste, produced by aerobic fermentation
for example, is easily overlooked when it concerns the conversion of
biomass into chemical intermediates or fuels.
Biomass utilization effi ciency (BUE) helps create awareness
about alternative approaches for producing bio-based products. The
difference in material effi ciency between direct acetic acid production
(anaerobic fermentation) and ethanol oxidation is clear (BUEH = 90%
compared to 60%). The same also applies to other examples covered
in this paper. As demand for renewable resources rises, the effi ciency
of (bio)-chemical transformations will come under greater scrutiny. We
anticipate the relevance and importance of insightful BUE calculations
will increase as the bio-based chemical industry adapts to growing
economic and material competition for resources.
Finally, this paper shows that it is important to use the right molecule
with the right process in the right application. Molecules that have low oxygen content are more suitable for energetic purposes whereas
molecules with higher oxygen content (and additional functional
groups) are more suitable to create material with specific chemical
properties. This oxygen-associated “functionality of biomass can
reduce the steps of making a chemical and in that way reduce also the
energy needs for the final molecule production” (Diels 2015). To put
it differently, the use of oxygenated biomass only makes sense for biobased
material uses. The only exception might be octane enhancers of
the combustion process but those additives can also be grouped under
the umbrella of material use of biomass.
Even though they were not a part of the scope of this paper, phenolic
lignins should also be very suitable to create materials under the points
we just mentioned above. Special cases are molecules such as succinic
acid, which capture CO2 in their molecular formula. Here, one has the
additional, ecological benefit of reducing a greenhouse gas. Moreover,
the formula we apply does not take into account that the CO2 created
by e.g. making ethanol from biomass could possibly be used to also
make value added products like e.g. methane in a biorefinery approach.
In some cases a full environmental assessment shows different
results. The BUE method does not take into account the energy use
and environmental impacts related to bio-feedstock supply.

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