Using the Carbon in Phytoremediation Grasses to Remediate Heavy Metal Brownfields to Make Biofuel.

[NNadir]

Like Joe Biden's search for a woman to be his VP candidate - Kamala Harris is clearly outstanding given the group from which she was selected - he current issue of ACS Sustainable Chemistry & Engineering is an embarrassment of riches, at least for me with my particular set of interests in the future of the world I will leave soon enough. The paper among this rich set that I choose to discuss this morning, as I have a little free time to myself having taken the day off, is this one: Valorization of Phytoremediation Byproduct via Synthesis of Biodiesel from Cockspur Grass (Echinochloa crus-galli) Seed (Sungyup Jung, Minyoung Kim, Hyeran Moon, Young-Kwon Park, Jörg Rinklebe, Chang-Jin Park, and Eilhann E. Kwon, ACS Sustainable Chem. Eng. 2020, 8, 31, 11588–11595)

In terms of full disclosure, about 20 years ago I had a semi-serious interest in going into the biodiesel industry, but thankfully thought better of it. I now understand that biodiesel, like most of the so called "renewable energy" strategies that were supposed to address climate change but didn't, aren't and won't, has proved to be destructive to the environment. One still can't say that freely among my fellow political liberals, but facts are facts and facts matter. The primary reason behind this destructive aspect is connected with land use, in particular the destruction of rain forests to use the land for palm oil plantations; one of the larger drivers of climate change besides the criminal habit of mining dangerous fossil fuels and dumping the waste directly into the atmosphere is land use changes.

But as we address the issue of land use - if we address the issue of land use, we should recognize that there is a considerable amount of land that has been functionally destroyed because of contamination with various industrial by products. Some of these by products are organic molecules, notably halogenated organic molecules like PCB's, PBDE's, PFOS, PFOA...ad infinitim but in other cases they are heavy metals.

An area for remediating contamination of land that has received considerable attention is phytoremediation, which depends on plants that concentrate the contaminants in their biomass, thus removing it from the contaminated areas. This is related to the biomagnification of pollutants, like for instance, the volatile neurotoxic coal waste mercury in seafood, and other foodstuffs. Mercury of course is responsible for the madness of hatters that was captured in Alice in Wonderland. (I often speculate to myself that the intellectual decline we are seeing so well represented by Trump Republicans and many other similar types around the world is not related to the wide distribution of neurotoxic heavy metals, in particular mercury, lead and cadmium.)

Anyway, this cool little paper caught my eye, because my primary environmental focus is process intensification, a contention that there should be no such thing as "waste" at all if future generations are to have even a remote shot at cleaning up the mess we left for them with all our wishful thinking, selfishness and generalized bullshit.

From the introduction to the paper:

Hazardous inorganic/organic matter from diverse anthropogenic activities (e.g., mining, urban development, and manufacturing) causes continuous contamination of soils and nearby streams.(1) As toxic pollutants are slowly accumulated in the environment, people are exposed to harmful substances,(2,3) which could result in adverse health effects.(4) The European Environmental Agency estimates that up to 3 million sites are polluted in Europe and that approximately 250,000 sites would require soil remediation.(5) In the United States, there are more than 1,335 Superfund sites as of February 2020.(6) To remediate contaminated soils, various treatments (i.e., physical, chemical, and biological methods) have been developed,(7) and the choice of a specific technique depends on the types of pollutants present in the soil.(7) Among them, phytoremediation has gained considerable attention as an ecofriendly measure for soil bioremediation considering that it uses plants to extract, sequester, and detoxify pollutants.(8) Although this approach is considered as an environmentally benign process for soil remediation, it produces contaminated plants. Improving the valorization of contaminated biomass from phytoremediation sites(9) would offer a further practical way to conserve natural resources and minimize the environmental impacts by applying the concept of life cycle assessment (LCA).(10)

Biomass collected from phytoremediation sites can be valorized for biofuel production, and this approach also serves as a CO2 mitigation measure.(11) In detail, global energy consumption in 2018 reached to 14 billion tons of oil equivalent,(12) with more than 80% generated from fossil resources.(13) The heavy reliance of energy consumption on fossil resources has become the main contributor of increased atmospheric concentrations of CO2.(14) Nonetheless, substantial efforts have been made over the last few decades to reduce atmospheric CO2 levels.(15,16) Among them, energy production from a carbon neutral resource (i.e., biomass) has been gaining attention because the intrinsic carbon neutralities can balance atmospheric CO2 levels.(17) As biomass is the only carbon-based material among various renewable energies (e.g., photovoltaic, wind, hydroelectricity, tidal, and others), converting biomass into chemicals (including biofuels) based on the concept of biorefinery has also been spotlighted.(18,19)

Very often, far too often for my taste, one sees in the scientific literature the claim that "photovoltaic, wind, hydroelectricity, tidal, and others" are sustainable technologies. They are not. The reason is physics, the extremely low energy to mass ratio of the materials required to make them operative, and the vast amounts of land they are required to consume through destruction, contamination, or simply industrialization. If we are to save the world, in my opinion, these obeisances have to stop.

Anyway...anyway...

It is true that biomass is a potentially sustainable way - even though as practiced now it actually records a higher death toll than Covid-19 - to capture carbon dioxide from the atmosphere, so it is not wise to throw the baby out with the bath water.

Biodiesel, which is currently made on an industrial scale, is composed of "FAME" for Fatty Acid Methyl Esters. All fats are basically triesters (and sometimes diesters or monoesters) of fatty acids, straight carbon chains terminating in a carboxylic acid group, with the trialcohol glycerol. The biodiesel process is to hydrolyze these triesters, and reesterify them with methanol, methanol being a chemical produced in large quantities - on a hundred million ton scale per year - from dangerous natural gas. I believe that methanol, and in particular the symmetric ether made from it, dimethyl ether, DME, is the key to a sustainable future, albeit only if made from the hydrogenation of carbon dioxide not obtained from dangerous natural gas.

More from the authors about their work:

Based on these rationales, this study investigated biodiesel synthesis from a phytoremediation byproduct, for achieving two goals: (1) phytoremediation using a nonedible biomass, available for mass production, and (2) biodiesel production from the contaminated phytoremediation species. In this study, cockspur grass (Echinochloa crus-galli) was used as a model compound. The cockspur grass was chosen because of its rapid proliferation and ability to translocate heavy metal(loid)s from contaminated sites. It is a well-known crop mimicry, that has evolved through artificial selection to resemble features of domestic plants, particularly rice.(24) The grass is a widely distributed nonedible weed, which grows faster than rice.(25) The undesired growth of cockspur grass in a rice paddy can consume a considerable amount of nutrients for rice,(26) suggesting the potential for fast translocation of heavy metal(loids) into the grass. In addition, the cockspur grass seeds can spread and proliferate easily with the production of 40,000 seeds per plant annually.(27,28) Because of these features, the phytoremediation potential of heavy metal(loid)s was tested while monitoring the growth of cockspur grass

Good stuff, I think.

Some pictures from the paper reflecting the results of their study:



The caption:

Figure 1. Absolute amount of heavy metal(loid) uptake by cockspur grass grown in (a) deionized water (DI) and (b) 6 ppm of heavy metal(loid) solution. Each solution was replaced with a fresh one every week.

The caption:

Figure 2. Removal of heavy metals over a three-week period.

For the preparation of biodiesel the grass seeds were thermolyzed, that is, treated with heat in the absence of oxygen. The seeds were heated to temperatures of 900°C at a ramp rate of 10°C in a TGA device (thermogravimetric analytical device). This is not highly scaled chemistry: It is effectively microscale. Nonetheless, if the process were to scale, sustainable heat of 900°C is obtainable from nuclear energy in a carbon neutral setting, with such temperatures allowing for process intensification, allowing for the production of, for example, electricity as a side product.

More pictures:



The caption:

Figure 3. (a) Mass changes of cockspur grass seeds (red) and lipid extracted from the seeds (black) and (b) differential thermogram (DTG)

In my old age I have come to love thermoanalytical chemistry.

The next graphic shows the interesting fact that some of the fatty acids in this plant's seeds are unsaturated acids. This suggests their use to make other important industrial chemicals besides biodiesel.



The caption:

Figure 5. (a) Total FAME yield and (b) relative FAME compositions obtained from transesterification of cockspur grass seeds with silica and methanol.

The caption:

Figure 5. (a) Total FAME yield and (b) relative FAME compositions obtained from transesterification of cockspur grass seeds with silica and methanol.

The authors chose to evaluate alcohols other than methanol for esterifying the fatty acids.

When I thought about biodiesel as a kid, I always thought about mixed alcohol waste streams in lieu of methanol. (These choices can have some problematic issues in diesel engines but are perhaps useful in the displacement of dangerous petroleum based home heating oil with biodiesel. Dangerous home heating oil and dangerous diesel fuel are identical chemically, except for the dyes added to home heating oil to prevent its use for tax avoidance diesel fuel.



The caption:

Figure 6. (a) Total FAAE yield and (b) relative FAAE compositions obtained from transesterification of cockspur grass seeds with different alcohols at 390 °C.

An excerpt from the author's conclusions:

This study examined the feasibility of cockspur grass as a phytoremediation plant species for heavy metal(loid) translocation by a laboratory scale hydroponic experiment. In an aqueous solution containing heavy metal(loid)s, cockspur grass was continuously grown with translocation of the heavy metal(loids) from the aqueous solution into the plant. During cockspur grass growth in the heavy metal(loid) solution, its decomposition was initiated only after 3 weeks of growth. Consequently, the control of a maximum amount of heavy metal uptake by each plant should be considered for the continuous growth of cockspur grass and adsorption of heavy metal(loid)s. Noncatalytic transesterification of cockspur grass seeds was initiated at ?280 °C, and the yield of biodiesel reached up to 98% at 390 °C. Notably, approximately 11.6 wt % of the lipid content in cockspur grass seed was estimated by the TGA test and the Soxhlet extraction test. The biodiesel yield decreased at ?400 °C, and such a trend was ascribed to thermal cracking of biodiesel...

The authors do not much discuss the fate of the metals removed from the soil. Among the other crimes we have committed against all future generations is the depletion of high grade ores of several important elements in the periodic table. It seems to me that much of the world's future energy requirements will thus involve recovery of elements from dilute sources, often the waste piles we so selfishly left. Figures 1 and 2 give a feel for the amount of metals that might be recovered from brownfields.

It's an interesting little paper; I enjoyed thinking about it very much.

I trust you will have a safe and pleasant weekend under the circumstances resulting from the grotesque mismanagement of our safety by the dogma driven fools in the Republican Party. In particular, I hope you will revel in the thought of our superb candidates, Joe and Kamala, in taking the reins and repairing whatever can be repaired after all this willful destruction,.

[BlancheSplanchnik]

1. Saving for later.

I’ll need lots of time— I’m not a graphs person. But I really need some good news about the environment, especially after reading that the orange monster has signed off on opening the Arctic Refuge to drilling 😱😭