segunda-feira, 10 de março de 2014

I BWChE - 2G BIOETHANOL: THE TREASURE BEHIND THE TRASH

Have you ever thought about the power hidden in unused part of plants?  For example the sugarcane bagasse used for generate heat for the ethanol production process. What would be your reaction, dear BetaEQ reader, if I told you that it's possible to generate more ethanol using the compounds in sugarcane bagasse? Yeah, it's possible and nowardays many scientists are doing a lot of researchs on this area, in Brazil and around the world. Keep reading to know more about the thing that can revolutionize the biofuels field, called: "2nd (and 3rd) Genaration Ethanol". 

Ethanol and Bioethanol

Ethanol or ethyl alcohol (C2H5OH) is a clear colourless liquid, it is biodegradable, low in toxicity and causes little environmental pollution if spilt. Ethanol burns to produce carbon dioxide and water. Ethanol is a high octane fuel and has replaced lead as an octane enhancer in petrol.  The principle fuel used as a petrol substitute for road transport vehicles is bioethanol.It is mainly produced by the sugar fermentation process, although it can also be manufactured by the chemical process of reacting ethylene with steam.
The main sources of sugar required to produce ethanol come from fuel or energy crops. These crops are grown specifically for energy use and include corn, sugarcane, maize and wheat crops, waste straw, sawdust, reed canary grass, cord grasses, jerusalem artichoke, myscanthus and sorghum plants.

Second Generation Fuels: What is it? 

Second generation biofuel technologies have been developed because first generation biofuels manufacture has important limitations. First generation biofuel processes are useful, but limited: there is a threshold above which they cannot produce enough biofuel without threatening food supplies and biodiversity. They are not cost competitive with existing fossil fuels such as oil, and some of them produce only limited greenhouse gas emissions savings. When taking emissions from production and transport into account, life-cycle emissions from first-generation biofuels frequently exceed those of traditional fossil fuels.Second generation biofuels can help solve these problems and can supply a larger proportion of our fuel supply sustainably, affordably, and with greater environmental benefits. The goal of second generation biofuel processes is to extend the amount of biofuel that can be produced sustainably by using biomass comprised of the residual non-food parts of current crops, such as them stems, leaves and husks that are left behind once the food crop has been extracted, as well as other crops that are not used for food purposes, they are produced from cellulose, hemicellulose or lignin.  

Meet the Plants Components: An Introduction 

Cellulose: Cellulose is a major component of wood. It is a long chain of linked sugar molecules that gives wood its remarkable strength. It is the main component of plant cell walls, and the basic building block for many textiles and for paper, for example. 



Hemicellulose:  Is any of several heteropolymers (matrix polysaccharides), such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength. It is easily hydrolyzed by dilute acid or base as well as myriad hemicellulase enzymes. 



Lignin:  Is a complex polymer of aromatic alcohols known as monolignols, substance THAT binding the cells, fibres and vessels which constitute wood and the lignified elements of plants, as in straw. After cellulose, it is the most abundant renewable carbon source on Earth. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum,meaning wood. 



The Max-Planck Institut and the Researches 

Chemists at the Max Planck Institut für Kohlenforschung in Mülheim an der Ruhr have found an efficient way of making the components of the biopolymer lignin easier to use. Lignin stabilises plant cells and contains organic compounds, which are valuable to the chemicals industry for the production of biofuels, for example. The compounds in lignin are, however, difficult to access. The chemists in Mülheim can now chemically convert these building blocks so that they are more readily available.

The first step in reaching the treasure in lignin: Wood chips are ground down in a ball mill and mixed with sulphuric acid. The acid splits the biopolymer into its individual components. Thanks to a new approach discovered by the Mülheim-based chemists, these can also be processed more effectively.
Lignin could be a source for such materials. Lignin is a biopolymer, stored by trees and shrubs in their cell walls. It penetrates the cellulose fibres of wood cells, making them rigid – and woody. The highly cross-linked chain molecules constitute 20 to 30 percent of the dry mass of woody plants; their building blocks could be useful in the chemicals industry, for example when refining biofuels or as starting materials for plastics.

Brazilian researcher leads a team and strengthens the search for best solutions

“We have known about the potential of lignin for a very long time,” explains Roberto Rinaldi, Max Planck Research Group Leader at the Mülheim-based Institute. Up until now, however, the treasure in the wood could not be extracted – at least not in a cost-effective way.  While chemists have been able to break down the tightly cross-linked chain molecules in lignin into smaller units using an acid at high temperatures, the result has been an unruly mixture of countless compounds containing oxygen, which are difficult to separate. Brazilian researcher Rinaldi and his Group have now helped to solve this problem. The chemists have found a relatively simple way of cleaving lignin and simultaneously removing as much oxygen as possible from these compounds. The remaining compounds are primarily hydrocarbons, mostly arenes, which are aromatic compounds that are easier to sort.

“We can combine the reactions because we allow two catalysts to interact,” explains Roberto Rinaldi. Catalysts are chemical tools, which initiate or accelerate reactions but remain chemically unchanged themselves at the end of the reaction. The catalysts used by Rinaldi are not particularly exotic: one of them is Raney nickel, a powder containing mainly porous nickel that hydrogenates organic molecules; zeolites, porous aluminosilicate minerals that extract water from an intermediary product of the chemical ‘triple jump’, are also used. “These are not newly invented catalysts,” says Rinaldi. “We are just approaching the problem of making lignin usable with new methods.”

The combined process needs less energy

Up until now, high temperatures of up to 500 degrees Celsius and pressures of 200 bar (200 times atmospheric pressure) have been necessary to fragment the lignin structure. In contrast, the combined process used by the researchers in Mülheim takes place in relatively mild conditions – at around 150 degrees and at pressures of less than 40 bar – and therefore requires less energy. “Building the apparatus needed for the reactions should not be a complicated procedure”, says Rinaldi.

Become interested? Send me an email to 2g.biofuels@gmail.com to receive files and articles explaining more about this subject. I hope you've enjoyed the text. 

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