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Coffee drinkers are causing a problem. What to do with the millions of tons of used coffee grounds that are created every year?

To date scientists have found numerous ways to make use of the smelly, damp, brown waste, discovering that they can be used as a fertiliser feedstock, that they can be mixed into animal feed, or can be used as an energy source for biofuels.

Recently adding to this list, chemists found out that in a powder form they could be used as a way to remove heavy metal ions (such as lead or mercury) from water.

Whilst this last method has a very practical goal in making water safer for human consumption, it also had an impractical side, in that an additional process was needed to separate the powder from the purified water. That problem has also now been solved, as a team from the Italian Institute of Technology in Genoa, has discovered a way to use the coffee grounds in a filter that greatly simplifies the process.

The researchers have published their results in the journal ACS Sustainable Chemistry & Engineering, where they describe the filter as a, “…bioelastomeric foam composed of 60 wt % of spent coffee powder and 40 wt % of silicone elastomer [that] uses the sugar leaching technique.” The findings continue to explain how the foam was, “…successful in the removal of Pb²⁺ and Hg²⁺ ions from water. [Whilst] The capability of the bioelastomeric foams to interact with Pb²⁺ and Hg²⁺ is not affected by the presence of other metal ions in water as tests in real wastewater demonstrate. [Furthermore] The fabricated foams can be used for the continuous filtration and removal of metal ions from water, demonstrating their versatility, in contrast to the sole coffee powder utilized so far, opening the way for the reutilization and valorization of this particular waste.”

The foam filter made with used coffee grounds removes heavy metal ions like lead and mercury from contaminated water.

As the online journal Science Daily reports, the results are very promising, as it states that, “In still water, the foam removed up to 99 percent of lead and mercury ions from water over 30 hours. [Whilst] In a more practical test in which lead-contaminated water flowed through the foam, it scrubbed the water of up to 67 percent of the lead ions.”

But the journal continues by highlighting the most important part of the filter system, when it states that, “Because the coffee is immobilized, it is easy to handle and discard after use without any additional steps.”

Whilst the discovery has yet to undergo a full peer review, and so is some way off being applied industrially, the idea that coffee grounds are not simply for landfill may take away some of the bitter taste from your next cup. In fact, it is great to know that in the future, drinking coffee will improve your drinking water.

In recent weeks, actually in recent decades, the biofuel industry has come under pressure to prove that it is economically viable. Headlines such as “Biofuels ‘Irrational and worse than fossil fuels’” (BBC April 2013) and “Greens reconsider biofuels mandate” (Bloomberg July 2016) have come in a rush of negative stories as the biofuel industry strives to prove its value.

But a new wave of thinking is to turn the bulk waste of plant matter, lignin, (from the stalks, stems and dry, woody pulp from many crops) into a useful chemical feedstock.

Up until now the only way to get any value from this waste product was to burn it for heat or electricity production, but now a research team from Sandia National Laboratories has found a possible route to breaking open lignin so that it can be utilised for its chemical properties.

The study began as a way to make biofuels a more realistic solution to replace fossil fuels, but has since turned into a potential route for cheaper chemicals production. The researchers started by examining the biofuels business model, and realised that in many cases it simply wasn’t viable. Growing corn to produce ethanol is a highly technical and expensive process that uses a lot of land and requires months of growing to produce a product that, for the most part, will simply be burned.

The team then looked at the fossil fuel industry, and saw many similarities in its structure to the biofuel industry. Crude oil production is a highly technical and expensive process given that is extracted from miles underground (or even under oceans), it is expensive to refine and then often needs to be shipped (across continents) to its market, simply to be burned. The business model only really becomes effective once the specialty chemicals industry has extracted the useful feedstock from crude.

As the study’s principal investigator Seema Singh outlined, when she said, “Gasoline is a low-value, high-volume product. This is balanced by the high-value chemicals derived from about 6-10 percent of every barrel of oil.” Her team realised, that what the biofuels industry needs is a way to add value to its business model, and turning crop waste products into a chemical feedstock would definitely achieve that.

The discovery began with chemists wondering how to access the chemical properties of lignin, and as often happens, they found inspiration from nature. As Singh says, “We know that over a long period of time fungus and bacteria do eventually break down lignin. If we can understand this process, we can use what nature already knows for biofuel and chemical production from lignin.”

As the online journal Science Daily reports, “Since bacteria are easier to engineer for industrial production of desired chemicals, the researchers focused on bacteria. The best candidate was Sphingobium, or SYK-6, found in the lignin-rich waste stream from wood pulp production.

SYK-6 was extremely intriguing because it only feeds on lignin. Microbes generally live off sugar, which is much easier to break down and extract energy from. Imagine a choice between eating a corn kernel or a corn husk.”

Using a method called metabolic flux analysis, the team was able to follow the route of carbon from the feedstock, and find out how SYK-6 metabolises lignin. In doing so, “The Sandia team’s paper reports the method used to decipher the metabolic pathway of SYK-6.”

The researchers published their results in the scientific journal Proceedings of the National Academy of Science, where they explained the rationale behind their study as follows;

“In this study we combined the unique approaches of both chemical engineering and biology to gain a deeper understanding of the metabolism of a soil bacterium, Sphingobium sp. SYK-6, that enables it to survive on lignin-derived monomers and oligomers. Understanding the central metabolism of SYK-6 will enable researchers to redesign the metabolic pathways of Sphingobium sp. SYK-6 more effectively to provide a renewable route for the production of products currently sourced from petrochemicals.”

Sandia National Laboratories researchers Arul Varman, left, and Seema Singh.

However, this discovery is an unfinished story, as Patti Koning makes clear when she explains on the Sandia National Laboratory website how Singh and her team are already working on ways to genetically engineer SYK-6, in order to “…stop its metabolic process at a point when platform chemicals can be extracted from the lignin.” She also points out that, “Another path would be to splice the genes responsible for the important desired metabolic process in SYK-6 onto a strong industrial host like E. coli to create a chassis for desired fuels and chemicals. Platform chemicals, which can be used to derive valuable chemicals like muconic acid and adipic acid, are the goal.”

Ultimately the discovery opens a path that may turn plant waste into a chemical feedstock that could produce high-value products.

“Lignin is an untapped resource,” said Singh. “But as a basis for high-value chemicals, it is of immense value. Those high-value chemicals can be the basis for polyurethane, nylon, and other bioplastics. Decoding SYK-6 metabolic pathway is providing a roadmap for lignin valorization.”

While the science for industrial chemical production from lignin may still be a long way off, it is an amazing breakthrough to have found a way to turn waste plant matter into chemical feedstock. Given the impact that the chemical industry has on modern lives, how different would the world be if high-value chemicals were produced from the wheat stalks grown in Africa, or the corn husks of Peru?

Photo credit: Pacific Northwest National Laboratory

Photo credit: Dino Vournas

Main credit: Mike Belliveau

Polymer manufacturers and designers are naturally interested in how elastic their polymers are, but up to now they have not had a way to accurately predict how stretchy or rigid new polymer designs will be. This is because, whilst a theoretical level of elasticity is calculable, the flaws and defects that are found in real world polymeric molecular chains are an unknown factor that prevents a precise formula being created.

That is until now, for a research team from MiT have created a method to calculate how elastic a new polymer will be; a key discovery that polymer engineers have been trying to make for more than a century. As Jeremiah Johnson, a Professor of Chemistry at MiT and a key player in the research explained, “This is the first time anyone has developed a predictive theory of elasticity in a polymer network, which is something that many have said over the years was impossible to do.”

Previous calculations to predict how flexible a polymer would be were very theoretical, as they did not compute how many of the molecular chains were defective. In theory all of the molecular chains in a polymer bind with another chain, however some of them inevitably bind with themselves to create ‘floppy loops’ that weaken the material.

Seeing that this was the root of a problem, Johnson and his colleague Bradley Olson, an Associate Professor of Chemical Engineering at MiT, came up with a way of measuring the number of defects in a polymer.

A discovery the online journal Phys.Org reports the discovery as follows;

“The researchers designed polymer chains that incorporate at a specific location a chemical bond that can be broken using hydrolysis. Once the polymers link to form a gel, the researchers cleave the bonds and measure the quantity of different types of degradation products.” Developing this research further, the team have made a breakthrough as, “By comparing that measurement with what would be seen in a defect-free material, they can figure out how much of the polymer has formed loops.”

The result is a formula for predicting a polymer’s elasticity. As Anne Trafton explains on the MiT website, “First, they calculated how a single defect would alter the elasticity. This number can then be multiplied by the total number of defects measured, which yields the overall impact on elasticity.”

You can watch the video of MiT’s explanation of the discovery here.

Olsen described the process himself, when he said, “We do one complicated calculation for each type of defect to calculate how it perturbs the structure of the network under deformation, and then we add up all of those to get an adjusted elasticity.”

The process has already been tested out on numerous materials and has held true, proving it to be a far more accurate predictor than the previous methods (known as the affine network theory and the phantom network model), neither of which factored defects into their calculations.

Now the team has published their results in the peer review journal, Science, where the research team reported how, “The results led to a real elastic network theory (RENT) that describes how loop defects affect bulk elasticity. Given knowledge of the loop fractions, RENT provides predictions of the shear elastic modulus.”

The research is already being hailed as a massive step forward in our understanding of polymer dynamics and will be a massive boon to both polymer manufacturers and designers. Something that Sanat Kumar, professor of chemical engineering at Columbia University, who was not part of the research, agreed with when he said, “They have taken an age-old problem and done very clear experiments and developed a very nice theory that moves the field up a whole quantum leap.”

But the researchers have not yet finished their work, as they plan to expand their predictive process to cover other materials, with Olsen stating that, “I think within a few years you’ll see it broaden rapidly to cover more and more types of networks.”

Meanwhile the Phys.org website explains how the researchers, “are also interested in exploring other features of polymers that affect their elasticity and strength, including a property known as entanglement, which occurs when polymer chains are wound around each other like Christmas tree lights without chemically binding to each other.”

But for now polymer traders and plastic producers are looking forward to the improved products that it is hoped will be developed now that much of the guesswork of polymer design has been removed.

As Trafton explains, “This theory could make it much easier for scientists to design materials with a specific elasticity, which is currently more of a trial-and-error process.”

Photo credit: Jose-Luis Olivares/MIT