Tuesday, July 20, 2010

First "Artificial Cell" May Provide Souce of Algal Fuel.

In the latest issue of "Chemistry World" is a report describing "the first synthetic cell". What has in fact been done is to insert a chemically synthesised genome into a bacterial cell. The M.mycoides genome contains over a million letters of genetic code and current DNA-technology can string-together perhaps a few thousand units in one go. The team led by Dan Gibson and Craig Venter have exploited the ability of yeast to join together small pieces of DNA using enzymes.

Grown in a Petri-dish the synthetic bacterium looks almost identical to the natural version and can similarly self-replicate. For the development of tailor-made life, it is necessary to understand what each gene codes for. The longer-run might be that genomes could be designed, but achieving that is some way off. It is more probable that a simple artificial genome could be created that has the essential properties of a living organism.

This could permit other gene-circuits being introduced for example to produce biofuels or fine-chemicals. Dr Venter's company, Synthetic Genomics, intends to use the cell synthesis technology to produce modified algae cells from which to make biofuel. The aim is to make a complete algal genome from which "superproductive organisms" could be derived.

It is possible that the designer method can overcome some of the drawbacks involved with making fuel from algae, namely robustness and competitiveness of particular strains over other organisms, enhanced growth rate and yields of algal oil. The method might be the key to the widescale production of fuel from algae, which is thought to be the better option over making it from land-based crops such as soya and corn, since the yields are much greater and there is no competition with food-crop production, and provide a real alternative to a globalised world that is utterly dependent on supplies of imported crude oil.

Algae also offer the potential of aiding in the curbing of CO2 emissions from power stations and cement factories, and in cleaning nitrates and phosphates from agricultural runoff water and effluent from sewage plants, while simultaneously furnishing useful fuels such as biodiesel and ethanol according to how the algae are processed.

Related Reading.
"The first synthetic cell,"By Hayley Birch, Chemistry World, July 2010, 29.

Sunday, July 11, 2010

Nanomaterials are Prey to EU Ministers.

In his 2002 novel, "Prey", the late Michael Crichton advanced a fictional scenario in which nanoparticles escaped from a lab and formed swarms in the desert with the drive and ability to kill humans and other animals whom they could use as feeding-templates on which bacteria could grow to replicate more of their kind. While such a scenario does appear alarmist and unlikely in reality, there remains nonetheless a sense of disquiet over the safety of nanomaterials, and their potential toxicity should they be released into the environment.

In 2008, manufacturers of skin "care-products" decided to avoid them in their formulations and now EU ministers have decided that nanosilver particles (also used e.g. in washing machines and in shoes to get rid of nasty smells) and multiwalled carbon nanotubes should be banned in electronic and electrical products. Members of the EU Environment Committee made this call during their vote on possible amendments to the "Restriction of Hazardous Substances Directive".

In addition, the Committee has recommended that all electrical and electronic products (including fast-computers and solar cells) that contained "nanomaterials of any nature" should be so labelled as containing them. Hence an onus would be on manufacturers to provide safety hazard information on any nanomaterials that their products may contain.

This appears quite tricky for example given the putative application where carbon nanotubes could be used as "synthetic nerves" in limb prosthetics, by acting as template around which neural tissue might grow. As introduced into the human body directly, any potential toxicity might prove rather difficult.

My awareness of the toxicity of carbon nanotubes is that the jury is out. I know of one study of them designed to search for the formation of free-radicals (toxic, short-lived molecules derived from oxygen) which seemed to indicate that the nanotubes actually soaked-up these species, leaving less of them than would be the case in their absence. That said, there are other studies that support a toxic role for carbon nanotubes. Since silver nanoparticles act in cleaning biological stains and smells by producing hydroxyl and other oxygen radicals, which are toxic in vivo, then if they were ingested the consequences could be dire.

The vote on the proposals is due in October, as reported in the July 2010 edition of Chemistry World, published by The Royal Society of Chemistry.

Friday, July 02, 2010

14% Efficiency for Thin-Film Solar Cells, but Where will the Indium Come From?.

One principal advantage of thin-film solar cells is that they use far less (maybe 1/100th the amount) of the semiconductor materials that are required to fabricate first-generation solar cells. The disadvantage is that compared with typical efficiencies of 15% for conventional solar cells, a practical efficiency of around 8% is more normal for thin-film cells.

Thin-film technologies offer the further prospect that the cells can be printed onto various flexible materials using a kind of ink-jet method, which offers numerous prospects for photo-voltaic devices in the future, beyond the simple scheme of roof-based solar panels. They are also more resistant to ionising radiation and should serve better in satellites which are in orbit above the Earth's atmosphere and hence more exposed to damage by cosmic radiation during their working lifetime of perhaps a few decades.

However, the solar-energy company MiaSolé recently reported that an efficiency of 13.8% had been achieved from thin-film panels of practical dimensions (1 m^2), rather than a much smaller lab-scale test (1). This unprecedented value has been corroborated by the DoE National Energy Laboratory (NREL).

At nearly 14%, the efficiency of the thin-film panels which are made from copper, indium, gallium and selenium (CIGS), is close to that of silicon, albeit being much cheaper to produce.
The world player in thin-film solar technologies is First Solar which makes its panels from cadmium and tellurium (Cad-Tel). While there have been steady gains in the efficiency of these, there is a practical limit of not much more than 10%, though 11.2% was reported recently (1).

While improvements in the CIGS panel efficiencies can be expected, there is the matter of accessing the materials themselves, from which they are made, most immediately indium. There are no significant ores of indium which is principally a by-product of zinc production, although roughly it is three-times as abundant (0.25 ppm) in the Earth's crust as silver (0.075 ppm). Indium is leached from slag and dust of zinc production and the metal further purified by electrolysis.

It has been estimated on the basis of the amount of indium in zinc ore stocks, there is a world reserve base of 6,000 tonnes. Given current consumption of the metal, this is sufficient for only 13 years and less than that if CIGS technology takes-off. It has been concluded therefore that in the future less than 1% of solar pv will be in the form of CIGS thin-film cells.

This prognosis is challenged by the Indium Corporation, who are the world's greatest producer of Indium, and assert that though the adaptation of more efficient recovery methods and from other ores, including tin, copper and other polymetallic deposits in hand with an expansion of mining operations, the supply of indium will prove sustainable (2).

Recycling of indium along with other rare metals (3) will also prove pivotal. It is nonetheless to be expected that there may be a supply-demand gap for indium, with a substantial escalation in its price, at least over the immediate term which is likely to impact on the inauguration of the thin-film CIGS cell industry. A rise in the price of indium is forecast as emerging CIGS and more established and steady LED and LCD markets compete for it, leading to a plan to stockpile the metal in the expectation of realising greater profits from it in the future (4).

Related Reading.

(1) http://blogs.forbes.com/energysource/2010/06/10/a-new-record-for-thin-film-solar/
(2) http://www.answers.com/topic/indium#cite_note-USGSCS2007-10
(3) http://blogs.forbes.com/energysource/2010/03/24/recycling-scrap-rare-metals-vital-to-future-technologies/
(4) http://seekingalpha.com/article/95798-smg-s-55-million-ipo-plan-stockpile-indium