Tag Archives: algae

Shortcut converts common cellulose into useable parts.

Synopsis by Wim Thielemans, Sep 23, 2011

Long, J, B Guo, X Li, Y Jiang, F Wang, SC Tsang, L Wang and KMK Yu. 2011. One step catalytic conversion of cellulose to sustainable chemicals utilizing cooperative ionic liquid pairs. Green Chemistry http://dx.doi.org/10.1039/c1gc15597k.

A new one-step process blends a pair of specially selected solvents with cellulose, overcoming a big hurdle in the race to use the plant-based material as a reliable source of chemicals and fuels.

Pairing up a unique blend of specialized chemical solvents with plant cellulose has solved a looming problem for chemists grappling to find an efficient method to break apart naturally abundant cellulose.

The one-step process uses two ionic liquids to break cellulose down into its smaller chemical pieces and convert these pieces into useful chemicals. This is an important feat since cellulose is targeted as an alternative source for the chemicals and fuels currently derived from fossil fuels.

The results show for the first time that combinations of ionic liquids can be very useful in guiding more efficient chemical reactions that create less waste and more product. The findings are interesting because they show it is possible to combine several processing steps just by choosing the correct mixture of solvents.

Cellulose is a major part of plant cells and is the most abundant renewable material on Earth. Every year, plants, algae and some bacteria produce in excess of an estimated 100 billion metric tons. Cellulose is not a food and is a waste product of agriculture.

An enormous research effort is underway to understand how to use cellulose as a starting material for biofuel and chemical production in order to replace crude oil. In this process, cellulose – a long chain of identical chemical units – needs to be separated into the individual units.

The key challenge to convert cellulose into chemicals is its poor solubility – that is, it does not break up easily in liquids. Chemical reactions, though, require close contact between all the parts to work well. In 2002, researchers reported that some ionic liquids were very good at dissolving cellulose.

Ionic liquids are salts – a designation for chemicals made up of both a positively and a negatively charged component– that are liquid at low temperatures, unlike common salts such as table salt. Bulky positive and negative groups that make up the ionic salts hinder their packing into a solid crystal. Thus, they stay liquid to much lower temperatures – even room temperature.

In this work, Chinese researchers used a mixture of two ionic liquids. The first was chosen to dissolve cellulose. The second was chosen because it increases cellulose breakdown into its individual units, and further, into useful chemicals.

Under the right conditions, all the cellulose was broken down. The reaction products were also removed from the ionic liquid mixture by simply adding an insoluble solvent such as methanol or hexane. While there were a variety of different reaction products, up to 48.5 percent of the cellulose could be converted to a single product: 2-(diethoxymethyl)furan. This chemical, in turn, can be easily converted into a variety of other products useful for the chemical and pharmaceutical industries.

The choice of the solvent to extract the reaction products from the ionic liquid also allows researchers to select the reaction products that are recovered.

The ionic liquid mixtures were also reused. No real difference in performance and composition was noticed over 10 repeated reactions.

The researchers chose to dissolve cellulose first followed by a reaction to convert cellulose into smaller, more useful products. However, the results suggest the system is versatile and – depending on which ionic liquids are selected – could be extended to several reactions in a row. Ionic liquids will certainly hold some surprises in the future.

Read more science at Environmental Health News.

 

Chemists convert seaweed to chemicals and fuels.

Kim, B, J Jeong, S Shin, D Lee, S Kim, H-J Yoon and JK Cho.  2011.  Facile single-step conversion of macroalgal polymeric carbohydrates into biofuelsChemSusChem 3:1273-1275.
Synopsis by Evan Beach
Apr 28, 2011

An innovative idea – if adapted to a large scale – could take advantage of an abundant but so far little-used raw material to make biofuels, according to a team of green chemists in Korea. The secret ingredient: seaweed.

Many varieties of seaweeds thrive in the world’s saltwater oceans and seas. Their growth is fueled by carbon dioxide. Unlike most conventional land-based plants, it is possible to produce multiple crops in a year without requiring fertile land and fresh water.

In recent years, microalgae – which are invisible to the naked eye – have been researched and exploited for use as fuels. Mostly ignored in this boom were the macroalgae – the kind you can see with your naked eye and find at the seashore. These seaweeds usually have lower oil content and have not attracted as much attention from chemists and manufacturers.

What they lack in oil, many types of seaweeds make up for in carbohydrates. The red algae species used in the current study is almost 80 percent carbohydrates. These sugars form long chemical chains called agar.

The Korean researchers found two ways to convert the agar into useful products.

In one, they found that agar reacts with an acid catalyst to produce a small molecule known as HMF. HMF is a valuable precursor to a variety of chemicals. To draw an analogy with petroleum refining, HMF would be considered the bio-based equivalent of a petrochemical like toluene that serves as the ultimate starting material for many commercial chemicals. The yield of HMF from the red algae was higher than expected, and this was attributed to unusual simple sugars and linkage patterns in the agar structure.

By adding a different catalyst to agar and introducing a solvent for the reaction, the yield was improved and two different chemical products were formed. Both of these chemicals are well known as biofuels and could be used as building block structures for specialty chemicals as well.

The product yields might be further improved by changing the seaweed growth conditions or even the species. Since the researchers discovered that the agar structure leads to unique reactivity, future work could take advantage of ways to tweak it towards a more favorable composition. Other combinations of catalyst and solvent could be explored as well.

Plastic from algae: How green?

Plastic from algae: How green?

Posted by Evan Beach at May 18, 2010 08:30 AM | Permalink

A story in Discovery News on new algae-based plastic highlights green benefits but misses the challenges.

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An article in Discovery News offers a rare look at how algae can be used to make something other than fuel or animal feed: plastic.

The story would have been more informative if the reporter had discussed the challenges that remain before algae fuels or plastics can become widespread. It is still not clear how algae can be produced sustainably on a large scale.

Reporter Alyssa Danigelis describes a new plastic that can be made with up to 50 percent algae. The company developing it hopes it will be 100 percent algae in a few years. Danigelis draws attention to the major green benefits of this new technology: it uses what would probably be a waste material from biodiesel production, it should not have any impact on the food supply, and further research and development could lead to a compostable material.

The 50 percent algae product also contains polypropylene (PP), a plastic often encountered in everyday life, for example, in microwaveable food containers. Such blends of natural and synthetic materials are not completely biodegradable but they often help to reduce consumption of limited resources.

By using algae left over from fuel extraction, this new plastic supports the idea of a “biorefinery.” The oil, coal and gas industries don’t just produce fuels – they produce the chemical building blocks for everything from industrial solvents to pharmaceuticals, leaving almost nothing to waste. Similarly, biofuel production will be more competitive if all of the raw materials are used productively. Plastic from algae is a step in that direction.

However, water, nutrient and energy demands can be extremely high and these issues are just as serious as whether the technology will compete with food production. Until the science is worked out, the “greenness” of algae – beyond its actual color – is not yet certain.  The story could have made this more clear.