1.
Biofuels are fuels in the gaseous or liquid form and can be rapidly regenerated from sources like crops, plants and municipal waste. Existing biofuels are generated from carbohydrates such as sugar and starch (wheat and sugarcane crops). Existing biofuels, such as ethanol, have a lesser energy content (volumetric energy density) relative to conventional hydrocarbon fuels natural gas and petroleum . Furfural and Levulinic acid are molecules that can be obtained from biomass and converted into biofuels. Levulinic acid can be synthesized in greater amounts (>70%) from inedible hexose bio-polymers such as cellulose, which is a polymer of glucose and the most abundant organic compound. Furfural has been obtained industrially for several years from pentose-rich agricultural wastes .
Recently, researchers have employed functional group interconversion, which is modification of certain specific molecules of compounds that contribute to its structure and function, in the production of biofuels. One such biofuel is ethyl valerate obtained from levulinic acid. Another method of production of hydrocarbons involves Dumesic’s strategy mediated through decarboxylation of gamma-valerolactone, which can be synthesized by hydrogenation of levulinic acid .
Yet another, recently developed technique, is Corma’s synthesis, which involves C5 or C6 decomposition products serving as precursor molecules to biofuels . This method produces a C15 hydrocarbon molecule starting from furfural mediated by a C5 molecule called, 2-methylfuran. An important reaction in this process is a trimerization of 2-methylfuran catalyzed by an acid in the presence of water to produce a trimer. Consequently, a hydrogenation reaction is utilized to deoxygenate this trimer and form a C15 hydrocarbon. This molecule acts as a potential bio-diesel compound with benefits over conventional bio-diesels in terms of quality of fuel and sustainability .
ADVANTAGES OF BIOFUELS
Biodiesels are anticipated to be the second most critical biofuel next to ethanol in the next few years. World-wide production of biodiesel is anticipated to approach 24 billion liters by 2017 . Organic chemists envisage a considerable scope related to future development of energy crops and production of advanced and novel biofuels from sources such as industrial or consumer waste, algae etc. . The crucial significance of these first generation conventional biofuels is their convenience of production with established technology. The synthesis of biofuels involves hydrolysis of carbohydrates into sugars that further undergo fermentation to generate alcohol, which is then distilled.
Figure 1: Biosynthesis of Biofuels
NEGATIVE IMPACT OF CONVENTIONAL BIOFUELS
Conventional biofuels produced from carbohydrate containing food crops, like sugarcane and corn, are questionable as they are displacing food crops for land use . Their green value has become debatable, owing to the extensive usage of considerable amounts of energy required by the farming methods utilized for efficient large scale production of biofuels. Organic chemists are, therefore, steering their focus to algae, dead wood and genetically-engineered microorganisms to design second-generation biofuels. Experts are showing interest in employing woody segments of the plants that usually accumulate as waste, such as straw and saw dust .
NEXT GENERATION BIOFUELS
Unlike traditional biofuels, processing of the indigestible parts of plants entails complicated procedures that can break their lignocellulose-based hard structures . This fibrous substance is composed of cellulose, hemicellulose and lignin carbohydrates, which can in principle be hydrolyzed into sugars and then supplied into the predetermined processes to synthesize bioethanol. Fragmentation of cellulose and hemicellulose from the non-fermentable lignin, however, entails steam and a lot of energy. Lignin is at present, burnt to generate heat or electricity .
Biomass-to-liquid (BTL) process is one of the general strategies that can process the lignin and indeed convert the entire wood into fuel. Rapid pyrolysis (heating in the absence of oxygen) of the biomass generates liquid oil, which can then be refined to syngas (synthesis gas, a combination of carbon monoxide and hydrogen), thereby opening avenues for synthesis of products that would usually be obtained from petroleum .
2C(s)+ H2O(g) 2CO(g) + H2(g)
Chemists from Shell participated in developing the process used to convert the syngas into diesel fuel, which is a version of the established Fischer-Tropsch procedure. (The Fischer-Tropsch process, invented by German chemists Franz Fischer and Hans Tropsch in the 1920s, is a catalytic reaction that converts syngas into a range of liquid hydrocarbons similar to petroleum:
nCO(g) + 2 nH2(g) (CH2)n (l) + nH2O(g)
The pilot plant generates 13,500 tons of BTL diesel per year, utilizing wood waste and straw. Choren Industries is of the opinion that with wood waste alone, it can produce 2.5 million tons of fuel every year, similar to the production of 11 traditional petroleum refineries.
Fundamentally different strategies may be developed to find more efficient methods of converting wood and other waste materials into fuels. Globally, chemists in many laboratories are working on enhancing methods and new catalysts for biomass usage. For instance, some researchers from the Max Planck Institute for coal research at Mülheim, Germany, have recently demonstrated that a combination of ionic fluids as solvents and solid acids as catalysts can be used to decompose solid wood to small oligosaccharides, followed by their fermentation .
Novel Technologies
While several scientists are directing their efforts on recycling agricultural waste and wood, others are aiming to generate fuel from scratch. A method being recently developed is industrial production of fuel using microorganisms only in the presence of carbon dioxide and sunlight .
Geneticist Craig Venter, who pioneered the shotgun-sequencing of microbial genomes in the 1990s, initialized the idea of creating microorganisms which could be modified towards the production of fuels . The main premise behind this concept is that the metabolic cycles of such organisms could be designed and optimized to the degree that they would produce only desirable end-products and no waste. While these concepts are tempting and seem lucrative, there are possibilities of ethical dilemmas over scientists generating new, unnatural life forms and possible ramifications if these are released into the environment.
Another approach is being used by some scientists to address the benefits of engineering specific biomolecules, typically enzymes, to degrade lignin. For instance, a Cambridge, Massachusetts, based company has engineered maize plants that produce an enzyme, which digests cellulose . Their strategy is to render this enzyme switchable so that the plant does not destroy itself, while it grows in the field, but can be programmed to degrade its own cellulose post harvesting. One promising approach followed by Agrivida is a temperature change. By manipulating the plant to produce a cellulose-degrading enzyme from heat-resistant (thermophilic) organisms, which are activated at temperatures around 60ºC, the company can turn on cellulose decomposition merely by heating the biomass to this temperature.
The surge in genomic information of many different organisms provides other options for efficient conversion of biomass to fuels. For example, the genomes of the microorganisms digesting cellulose in the stomachs of ruminants could generate novel enzymes that would aid in this process . Additionally, the information and knowledge pertaining plant genomes could assist in identification of plants that are not yet utilized in agriculture and would be best relevant for domestication and utilization as biofuel feedstock. While the conventional domestication of agricultural crops took ages, the knowledge of modern genomics should help scientists to obtain suitable new varieties in the next few years.
Another school of thought asks why should we develop new organisms when we have algae? The US Department of Energy (DoE) had funded research into the production of biofuels from algae as part of the Aquatic Species Program from 1978-96, but shifted resources to corn ethanol when it appeared that algal fuels would cost more to exploit. Rising oil prices in 2007-08 have stimulated a renewed interest in the algal alternative.
ECOFRIENDLY FUELS EXTRACTED FROM GREEN ALGAE
The biggest advantage of algae over conventional biofuels, is that they do not displace food crops for land use . They can be cultivated in purpose built reactors, in ponds constructed on desert land, and also fenced-in sections of coastal waters. Also, much of their biomass comprises lipid membrane, which can undergo transesterification to biodiesel, producing a residue that will be enriched in protein, carbohydrate and water, which can be utilized as animal feed or fermented to alcohol.
The company Solix Biofuels, founded in 2006, has been designing reactors for the growth of microalgae . They employ enclosed recycling of carbon dioxide emissions from power stations. On the contrary, PetroSun BioFuels, a subsidiary of the oil company PetroSun, has begun cultivating algae in open saltwater ponds encompassing 1100 acres in Rio Hondo, Texas. In its purpose-built refinery on site, which was established in April 2008, PetroSun’s goal is to produce 4.4 million gallons (16.7 million liters) of algal oil every year, some of which will be utilized to produce jet fuel.
Other companies, including Chevron and Shell, declared new collaborative projects investigating the potential generation of biofuels from algae in 2007 and 2008. Shell has initiated an exploratory project in collaboration with HR Biopetroleum that already cultivates algae in ponds on the coast of Hawaii . In October 2008, the Carbon Trust (UK) declared the 'algae biofuels challenge', a program which will contribute to a grant of upto £26 million to develop technology and infrastructures to render algal biofuels viable.
It is still ambiguous whether any of these attempts and collaborations will generate substantial fuels used at gas stations, as this industry could be challenged by unanticipated hurdles from politics and competitive markets. Nevertheless, with oil prices soaring high and increasing awareness of the climate crisis both among politicians and the general public, there is a dire need for the advent of second-generation biofuels.
2.
Several components are added to food for the following reasons :
Color Additives
Color additives are pigments or dyes that when added to a food substance, has the ability to impart color. Color additives are added to food to compensate for the loss of color in food items due to exposure to light, temperature extremes, humidity and storage conditions . 2) they may be added to enhance the natural variations in color 3) and to add color to colorless food items
Artificial colors are preferred over natural colors, owing to their reasonable cost. Processing of resources to obtain natural colors entails more time and cost compared to mass-production of synthetic dyes. Also synthetic colors have a much longer shelf life than natural colors .
Chemistry of artificial food colors
Food coloring molecules are ionic substances, since they possess negative and positive ions, which are bound together by ionic bonds . When one of these substances dissolves in water, the ions that form the solid substance are expelled into the solution, wherein they interact with the polar water molecules, which contain partially negative and partially positive charges. Another significant characteristic of food colors is that they retain their color, when dissolved in water, owing to the absorption of certain wavelengths of light and permit other colors to pass through giving rise to the colors that we perceive. Food-coloring substances particularly possess long bands of alternating single and double bonds, that cause excitation of electrons in these molecules at relatively low energy. The energy utilized for an electron to transition from excited state to the ground state is equivalent to the energy of visible light. This is the reason the food-coloring molecules have the capacity to absorb light from the visible spectrum.
Negative impact of Food Colorings
Several scientific reports have demonstrated that food colors cause attention deficit hyperactivity disorder (ADHD) and allergic reactions in children . Red color added to many food items like strawberry flavored yogurt and cranberry juice has been derived from the blood of certain insects. The blood of these insects contain a deep-red dye called carminic acid and may cause adverse effects such as allergic reactions or anaphylactic shock.
Figure 2: Chemical Structure of Carminic Acid
3.
Plastics are a group of synthetic or natural materials, that may be imparted a shape when soft and then hardened to sustain its assigned shape . Plastics are polymers, which are substances comprising repeating units. Synthetic polymers include polyethenes used in plastic bags. The length of the chains and the arrays render the polymers lightweight, yet strong and flexible. These characteristics have made synthetic polymers useful, and since we have learned to produce and modify them, polymers have become an integral part of our routine lives.
In 1969, scientist John Wesley Hyatt, reacted cellulose, obtained from cotton fibers with camphor and discovered plastic, in an attempt to find a substitute for ivory . Thus, manmade substances could replace natural substances such as horns and ivory from animals. This discovery helped in protection of environment.
There are two main categories of plastics :
Thermoplastics: These are softened using heat and then molded using injection or vacuum or blow molded. Examples: acrylic, polystyrene, polypropylene, PVC and polythene.
Thermosets: These are produced using a heat process. But once they are fixed (like concrete) and cannot modify their shape by reheating. Examples; melamine (kitchen worktops), polyester and epoxy resins, Bakelite (black saucepan handles).
Composite plastics are produced using combinations of materials to augment the properties. For example, glass fiber is amalgamated with polyester resin to create GRP, which is a material used in fishing rods and boats.
Polythene is the basic example of a linear polymer.
Figure 3: Structure of Polythene
Plastics play a significant role in our lives, with their versatile uses. They have numerous uses such as packaging, transportation, construction, agriculture, health care, entertainment and sports industry .
CONCERNS ABOUT PLASTICS
Although, invention of plastics was revolutionary and they played an important role in human life, in the post war years, there was a drastic change in the public perceptions of plastic . While so many plastics are disposable, it persists in the environment. Although, the industry began recycling plastics, as a part of waste-management programs, recycling of plastics has been imperfect and most of the plastics accumulate in the landfills or in the environment.
Yet another serious concern over plastics has been the potential danger to human health . These concerns stem from the use of additives like bisphenol A (BPA) and a family of chemicals called phthalates that are incorporated into the plastics during the manufacturing procedures, rendering them more durable, flexible and transparent. Some researchers express their concerns about the evidence that these chemicals may release from these plastics into food, water and eventually enter human bodies. In large concentrations, these additives have been shown to be carcinogenic and impair the endocrine system. There is a serious dilemma among the scientific community about the negative impact of these chemicals on children and the potential passage and accumulation in the forthcoming generations.
Works Cited
Chemical Heritage Foundation. n.d. http://www.chemheritage.org/discover/online-resources/conflicts-in-chemistry/the-case-of-plastics/all-history-of-plastics.aspx. 14 March 2016.
fda.gov. November 2004. http://www.fda.gov/Food/IngredientsPackagingLabeling/FoodAdditivesIngredients/ucm094211.htm#qafortified. 13 March 2016.
Higson, A. Royal Society of Chemisry. n.d. http://www.rsc.org/Membership/Networking/InterestGroups/OrganicDivision/organic-chemistry-case-studies/organic-chemistry-biofuels.asp. 13 March 2016.
Rohrig, B. acg.org. October 2015. 13 March 2016.
Royal Society of Chemistry. Biofuels: the next generation . n.d. http://www.rsc.org/Education/EiC/issues/2009May/Biofuelsthenextgeneration.asp. 13 March 2016.
the.warren.org. n.d. http://www.the-warren.org/GCSERevision/resistantmaterials/plastics.html. 13 March 2016.
