Tag Archives: food waste

Solar and wind energy storage via food waste and carbon nanotubes

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Scientists are researching devices other than batteries for wind and solar energy storage according to an Oct. 27, 2016 news item on Nanowerk,

Saving up excess solar and wind energy for times when the sun is down or the air is still requires a storage device. Batteries get the most attention as a promising solution although pumped hydroelectric storage is currently used most often. Now researchers reporting in ACS’ Journal of Physical Chemistry C are advancing another potential approach using sugar alcohols — an abundant waste product of the food industry — mixed with carbon nanotubes.

An Oct. 26, 2016 American Chemical Society (ACS) news release, which originated the news item, expands on the theme,

Electricity generation from renewables has grown steadily over recent years, and the U.S. Energy Information Administration (EIA) expects this rise to continue. To keep up with this expansion, use of battery and flywheel energy storage has increased in the past five years, according to the EIA. These technologies take advantage of chemical and mechanical energy. But storing energy as heat is another feasible option. Some scientists have been exploring sugar alcohols as a possible material for making thermal storage work, but this direction has some limitations. Huaichen Zhang, Silvia V. Nedea and colleagues wanted to investigate how mixing carbon nanotubes with sugar alcohols might affect their energy storage properties.

The researchers analyzed what happened when carbon nanotubes of varying sizes were mixed with two types of sugar alcohols — erythritol and xylitol, both naturally occurring compounds in foods. Their findings showed that with one exception, heat transfer within a mixture decreased as the nanotube diameter decreased. They also found that in general, higher density combinations led to better heat transfer. The researchers say these new insights could assist in the future design of sugar alcohol-based energy storage systems.

Here’s a link to and a citation for the paper,

Nanoscale Heat Transfer in Carbon Nanotubes – Sugar Alcohol Composite as Heat Storage Materials
by Huaichen Zhang, Camilo C. M. Rindt, David M. J. Smeulders, and Silvia V. Nedea. J. Phys. Chem. C, 2016, 120 (38), pp 21915–21924 DOI: 10.1021/acs.jpcc.6b05466 Publication Date (Web): August 30, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Light emitting diodes (LEDs) from food and beverage waste

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It’s exciting to think that with emerging technologies we’ll be able to make use of waste products rather than sending them off to fill up garbage dumps. An Oct. 13, 2015 news item on Nanowerk highlights some research where food and beverage waste products could be used to produce light emitting diodes (LEDs),

Most Christmas lights, DVD players, televisions and flashlights have one thing in common: they’re made with light emitting diodes (LEDs). LEDs are widely used for a variety of applications and have been a popular, more efficient alternative to fluorescent and incandescent bulbs for the past few decades. Two University of Utah researchers have now found a way to create LEDs from food and beverage waste. In addition to utilizing food and beverage waste that would otherwise decompose and be of no use, this development can also reduce potentially harmful waste from LEDs generally made from toxic elements.

An Oct. 13, 2015 University of Utah news release, which originated the news item, describes some of the issues with our current LEDs and how the researchers went about synthesizing the waste for reuse,

LEDs can be produced by using quantum dots, or tiny crystals that have luminescent properties, to produce light. Quantum dots (QDs) can be made with numerous materials, some of which are rare and expensive to synthesize, and even potentially harmful to dispose of. Some research over the past 10 years has focused on using carbon dots (CDs), or simply QDs made of carbon, to create LEDs instead.

Compared to other types of quantum dots, CDs have lower toxicity and better biocompatibility, meaning they can be used in a broader variety of applications.

U Metallurgical Engineering Research Assistant Professor Prashant Sarswat and Professor Michael Free, over the past year and a half, have successfully turned food waste such as discarded pieces of tortilla into CDs, and subsequently, LEDs.

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From bread to bulb

To synthesize waste into CDs, Sarswat and Free employed a solvothermal synthesis, or one in which the waste was placed into a solvent under pressure and high temperature until CDs were formed. In this experiment, the researchers used soft drinks and pieces of bread and tortilla.

The food and beverage waste were each placed in a solvent and heated both directly and indirectly for anywhere from 30 to 90 minutes.

After successfully finding traces of CDs from the synthesis, Sarswat and Free proceeded to illuminate the CDs to monitor their formation and color.

The pair also employed four other tests, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, Raman and AFM [atomic force microscopy] imaging to determine the CDs’ various optical and material properties.

“Synthesizing and characterizing CDs derived from waste is a very challenging task. We essentially have to determine the size of dots which are only 20 nanometers or smaller in diameter, so we have to run multiple tests to be sure CDs are present and to determine what optical properties they possess,” said Sarswat.

For comparison, a human hair is around 75,000 nanometers in diameter.

The various tests Sarswat and Free ran first measured the size of the CDs, which correlates with the intensity of the dots’ color and brightness. The tests then determined which carbon source produced the best CDs. For example, sucrose and D-fructose dissolved in soft drinks were found to be the most effective sources for production of CDs.

An environmentally sustainable alternative

Currently, one of the most common sources of QDs is cadmium selenide, a compound comprised of a two toxic elements. The ability to create QDs in the form of CDs from food and beverage waste would eliminate the need for concern over toxic waste, as the food and beverages themselves are not toxic.

“QDs derived from food and beverage waste are not based on common toxic elements such as cadmium and selenium, which makes their processing and disposal more environmentally friendly than it is for most other QDs.  In addition, the use of food and beverage waste as the starting material for QDs allows for reduced waste and cost to produce a useful material,” said Free.

In addition to being toxic when broken down, cadmium selenide is also expensive—one website listed a price of $529 for 25 ml of the compound.

“With food and beverage waste that are already there, our starting material is much less expensive. In fact, it’s essentially free,” said Sarswat.

According to a report from the US Department of Agriculture, roughly 31% of food produced in 2014 was not available for human consumption. To be able to use this waste for creating LEDs which are widely used in a number of technologies would be an environmentally sustainable approach.

Looking forward, Sarswat and Free hope to continue studying the LEDs produced from food and beverage waste for stability and long term performance.

“The ultimate goal is to do this on a mass scale and to use these LEDs in everyday devices. To successfully make use of waste that already exists, that’s the end goal,” said Sarswat.

Finally, the CDs were suspended in epoxy resins, heated and hardened to solidify the CDs for practical use in LEDs.

The researchers have made an image of the luminescent carbon dots available,

PHOTO CREDIT: Prashant Sarswat The luminescence of carbon dots can be seen when irradiated with UV light.

PHOTO CREDIT: Prashant Sarswat The luminescence of carbon dots can be seen when irradiated with UV light.

Here’s a link to and a citation for the paper,

Light emitting diodes based on carbon dots derived from food, beverage, and combustion wastes by Prashant K. Sarswat and Michael L. Free. Phys. Chem. Chem. Phys., 2015,17, 27642-27652 DOI: 10.1039/C5CP04782J First published online 01 Oct 2015

This paper appears to be behind a paywall. One final note, despite the paper’s title there doesn’t seem to be any mention of combustion waste in the news release which is a bit puzzling.

PlasCarb: producing graphene and renewable hydrogen from food waster

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I have two tidbits about PlasCarb the first being an announcement of its existence and the second an announcement of its recently published research. A Jan. 13, 2015 news item on Nanowerk describes the PlasCarb project (Note: A link has been removed),

The Centre for Process Innovation (CPI) is leading a European collaborative project that aims to transform food waste into a sustainable source of significant economic added value, namely graphene and renewable hydrogen.

The project titled PlasCarb will transform biogas generated by the anaerobic digestion of food waste using an innovative low energy microwave plasma process to split biogas (methane and carbon dioxide) into high value graphitic carbon and renewable hydrogen.

A Jan. 13, 2015 CPI press release, which originated the news item, describes the project and its organization in greater detail,

CPI  as the coordinator of the project is responsible for the technical aspects in the separation of biogas into methane and carbon dioxide, and separating of the graphitic carbon produced from the renewable hydrogen. The infrastructure at CPI allows for the microwave plasma process to be trialled and optimised at pilot production scale, with a future technology roadmap devised for commercial scale manufacturing.

Graphene is one of the most interesting inventions of modern times. Stronger than steel, yet light, the material conducts electricity and heat. It has been used for a wide variety of applications, from strengthening tennis rackets, spray on radiators, to building semiconductors, electric circuits and solar cells.

The sustainable creation of graphene and renewable hydrogen from food waste in provides a sustainable method towards dealing with food waste problem that the European Union faces. It is estimated that 90 million tonnes of food is wasted each year, a figure which could rise to approximately 126 million tonnes by 2020. In the UK alone, food waste equates to a financial loss to business of at least £5 billion per year.

Dr Keith Robson, Director of Formulation and Flexible Manufacturing at CPI said, “PlasCarb will provide an innovative solution to the problems associated with food waste, which is one of the biggest challenges that the European Union faces in the strive towards a low carbon economy.  The project will not only seek to reduce food waste but also use new technological methods to turn it into renewable energy resources which themselves are of economic value, and all within a sustainable manner.”

PlasCarb will utilise quality research and specialist industrial process engineering to optimise the quality and economic value of the Graphene and hydrogen, further enhancing the sustainability of the process life cycle.

Graphitic carbon has been identified as one of Europe’s economically critical raw materials and of strategic performance in the development of future emerging technologies. The global market for graphite, either mined or synthetic is worth over €10 billion per annum. Hydrogen is already used in significant quantities by industry and recognised with great potential as a future transport fuel for a low carbon economy. The ability to produce renewable hydrogen also has added benefits as currently 95% of hydrogen is produced from fossil fuels. Moreover, it is currently projected that increasing demand of raw materials from fossil sources will lead to price volatility, accelerated environmental degradation and rising political tensions over resource access.

Therefore, the latter stages of the project will be dedicated to the market uptake of the PlasCarb process and the output products, through the development of an economically sustainable business strategy, a financial risk assessment of the project results and a flexible financial model that is able to act as a primary screen of economic viability. Based on this, an economic analysis of the process will be determined. Through the development of a decentralised business model for widespread trans-European implementation, the valorisation of food waste will have the potential to be undertaken for the benefit of local economies and employment. More specifically, three interrelated post project exploitation markets have been defined: food waste management, high value graphite and RH2 sales.

PlasCarb is a 3-year collaborative project, co-funded under the European Union’s Seventh Framework Programme (FP7) and will further reinforce Europe’s leading position in environmental technologies and innovation in high value Carbon. The consortium is composed of eight partners led by CPI from five European countries, whose complimentary research and industrial expertise will enable the required results to be successfully delivered. The project partners are; The Centre for Process Innovation (UK), GasPlas AS (NO), CNRS (FR), Fraunhofer IBP (DE), Uvasol Ltd (UK), GAP Waste Management (UK), Geonardo Ltd. (HU), Abalonyx AS (NO).

You can find PlasCarb here.

The second announcement can be found in a PlasCarb Jan. 14, 2015 press release announcing the publication of research on heterostructures of graphene ribbons,

Few materials have received as much attention from the scientific world or have raised so many hopes with a view to their potential deployment in new applications as graphene has. This is largely due to its superlative properties: it is the thinnest material in existence, almost transparent, the strongest, the stiffest and at the same time the most strechable, the best thermal conductor, the one with the highest intrinsic charge carrier mobility, plus many more fascinating features. Specifically, its electronic properties can vary enormously through its confinement inside nanostructured systems, for example. That is why ribbons or rows of graphene with nanometric widths are emerging as tremendously interesting electronic components. On the other hand, due to the great variability of electronic properties upon minimal changes in the structure of these nanoribbons, exact control on an atomic level is an indispensable requirement to make the most of all their potential.

The lithographic techniques used in conventional nanotechnology do not yet have such resolution and precision. In the year 2010, however, a way was found to synthesise nanoribbons with atomic precision by means of the so-called molecular self-assembly. Molecules designed for this purpose are deposited onto a surface in such a way that they react with each other and give rise to perfectly specified graphene nanoribbons by means of a highly reproducible process and without any other external mediation than heating to the required temperature. In 2013 a team of scientists from the University of Berkeley and the Centre for Materials Physics (CFM), a mixed CSIC (Spanish National Research Council) and UPV/EHU (University of the Basque Country) centre, extended this very concept to new molecules that were forming wider graphene nanoribbons and therefore with new electronic properties. This same group has now managed to go a step further by creating, through this self-assembly, heterostructures that blend segments of graphene nanoribbons of two different widths.

The forming of heterostructures with different materials has been a concept widely used in electronic engineering and has enabled huge advances to be made in conventional electronics. “We have now managed for the first time to form heterostructures of graphene nanoribbons modulating their width on a molecular level with atomic precision. What is more, their subsequent characterisation by means of scanning tunnelling microscopy and spectroscopy, complemented with first principles theoretical calculations, has shown that it gives rise to a system with very interesting electronic properties which include, for example, the creation of what are known as quantum wells,” pointed out the scientist Dimas de Oteyza, who has participated in this project. This work, the results of which are being published this very week in the journal Nature Nanotechnology, therefore constitutes a significant success towards the desired deployment of graphene in commercial electronic applications.

Here’s a link to and a citation for the paper,

Molecular bandgap engineering of bottom-up synthesized graphene nanoribbon heterojunctions by Yen-Chia Chen, Ting Cao, Chen Chen, Zahra Pedramrazi, Danny Haberer, Dimas G. de Oteyza, Felix R. Fischer, Steven G. Louie, & Michael F. Crommie. Nature Nanotechnology (2015) doi:10.1038/nnano.2014.307 Published online 12 January 2015

This article is behind a paywall but there is a free preview available via ReadCube access.