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Sun Feb 12, 2017, 02:09 PM

Nice listing of the putative carbon intensity of biobased chemicals.

It's become increasingly clear to me in recent years that all efforts to address climate change have failed miserably, as we can see by looking at the Mauna Loa carbon dioxide data, at least until the Republicans either destroy the carbon dioxide observatory outright or begin to fudge the data, neither of which will have any bearing whatsoever on the truth itself, other than to obscure it.

Thus, among the many burdens we have placed on all future generations is the likely need they will have, in order to stabilize the climate, for the need to actually remove carbon dioxide - our waste, not theirs necessarily - directly from the atmosphere.

This is an almost impossibly difficult engineering task, although there are many scientists who refuse to give up hope that it is an engineering challenge that can be met. (One of my personal favorites is Christopher Jones's group at Georgia Tech.)

I question it, but I believe that if it is possible at all, biobased chemicals, which theoretically could sequester carbon in an economically viable way inasmuch as the carbon would not be sequestered in the oft imagined waste dumps, but as products, useful products, in particular polymers.

As I catch up on some reading, I came accross an interesting paper in the relatively new, but rich, journal, ACS Sustainable Chemistry and Engineering which gives a very nice table of the carbon intensity of a broad range of biobased chemicals from a number of biological feedstocks.

The paper in question is this: Meta-Analysis of Life Cycle Energy and Greenhouse Gas Emissions for Priority Biobased Chemicals (ACS Sustainable Chem. Eng. 2016, 4, 6443−6454). While the parent paper may be behind a firewall, the "Supplementary Information" which actually contains the data tables on the carbon cost (or benefit) of biobased fuels is not and can be accessed by the general public.

Supporting Information, Meta-Analysis of Life Cycle Energy and Greenhouse Gas Emissions for Priority Biobased Chemicals

If one looks at the table, one will see that many of the chemicals actually release more carbon dioxide than they sequester. While this may seem to make the situation hopeless, it actually need not always be so, since these calculated values assume certain process parameters.

In many cases one of the inputs for processing is heat and currently heat is often provided by the use of dangerous fossil fuels. It is possible however for this heat to be obtained in other ways, notably with the use of high temperature nuclear reactors of types being evaluated all over the world by nuclear engineers. This may offer an avenue to making some of those processes (most notably those involving reformation) that are marginally carbon positive, carbon negative.

Some excerpts of the full paper's text:

Biofuels and biobased chemicals have received significant interest as a potential low-carbon and environmentally sustainable alternative to conventional fossil-based fuels and petrochemicals. As defined by the US Secretary of Agriculture in the Farm and Rural Investment Act of 2002, biobased products are commercial or industrial products that are composed of biological products, renewable agricultural and forestry materials, or intermediate feedstocks, in whole or insignificant parts.1 The annual production of biobased chemicals(excluding fuels) is estimated to be 50 million tons,2 dominated by biobased polymers (55%), oleo chemicals (20%), and fermentation products (18%).3 Commercialization of biobased chemicals is still nascent, and their penetration rate in the global market will be strongly dependent on the development of biorefineries.4 The US Department of Agriculture (USDA)estimates that the global chemicals industry is projected to grow 3−6% annually through 2025, with the biobased chemicals share of that market rising from 2% in 2006 to22% or more by 2025.5

50 million tons is a trivial amount, given that we now irreversibly dump more than 30 billion tons of carbon dioxide into our favorite waste dump, the atmosphere now, and - while we wait like Godot for the solar and wind miracle that never comes - the dumping is rising in volume, not falling. Still, one hopes that we can make progress.

Some other text, later in the paper:

In this study, we reviewed published results for life cycle GHG emissions and energy use for 34 priority biobased chemicals, including those identified by DOE, compared against their fossil-based counterparts. Prior meta-analyses of bioenergy systems showed that there are several factors controlling environmental benefits from GHG emission and energy use, from biomass carbon cycle and soil carbon change to selection of appropriate fossil reference systems, homogeneity of input parameters, and coproduct handling schemes.25,26 The present meta-analysis is conducted for biobased chemicals, focusing on collection and interpretation of existing LCA results with statistical analysis. It does not attempt a harmonization of various cases but rather aims to identify trends across the many feedstocks and processing routes that have been considered, while examining the statistical effects of modeling factors such as coproduct allocation. The main goals of this work are to evaluate a potential renewable chemical standard, to identify gaps in the assessment literature and to synthesize the state of knowledge for net energy and life cycle GHG emissions assessment of biobased chemicals.

Another paper along these lines in the same issue of the same journal that strikes me as interesting is this one: Reductive Catalytic Fractionation of Corn Stover Lignin (ACS Sustainable Chem. Eng. 2016, 4, 6940−6950)

Here's a graphic from the paper's abstract:

The cellulosic ethanol business has failed commercially, and the plants built to make it commercially viable have all failed. These were fermentation systems, inherently batch processes, batch processes, particularly water based batch processes are seldom successful to make commodity chemicals.

But the process here is thermal, and thus quite different, far more amenable to continuous flow.

The stover, irrespective of the failure of the cellulose to ethanol processes, is still carbon captured from the air. Perhaps it's not wise to throw the baby out with the bathwater.

The chemicals shown here in the graphic are hydrogenated ("saturated), but the intermediates (shown in the full text but not shown here) are unsaturated, meaning that they are potential precursors to polymers. What is interesting about these putative polymers (which are not discussed in the paper) is that they are highly functionalized and could in theory be utilized to make resins like commercially important peptide synthesis resins, but more importantly, I think, a whole host of functionalized resins designed to remove dilute and sometimes toxic (or commercially desired) elements from very dilute streams, for example mercury from coal plants now found in all the world's water supplies, or lead, from coal and other sources.

I'd like to think there's still some hope for the future, even in times that seem hopeless.

Esoteric but interesting, I think.

Enjoy the remainder of the weekend.

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Reply Nice listing of the putative carbon intensity of biobased chemicals. (Original post)
NNadir Feb 2017 OP
eppur_se_muova Feb 2017 #1

Response to NNadir (Original post)

Sun Feb 12, 2017, 10:45 PM

1. Very interesting. Kind of wish I were working in this field ...

certainly as opposed to not working at all, which is my present situation.

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