Review on the Extraction Methods of Crude oil from all Generation Biofuels in last few Decades
IOP Conference Series: Materials Science and Engineering
The ever growing demand for the energy fuels, economy of oil, depletion of energy resources and environmental protection are the inevitable challenges required to be solved meticulously in future decades in order to sustain the life of humans and other creatures. Switching to alternate fuels that are renewable, biodegradable, economically and environmentally friendly can quench the minimum thirst of fuel demands, in addition to mitigation of climate changes. At this moment, production of
... s has got prominence. The term biofuels broadly refer to the fuels derived from living matter either animals or plants. Among the competent biofuels, biodiesel is one of the promising alternates for diesel engines. Biodiesel is renewable, environmentally friendly, safe to use with wide applications and biodegradable. Due to which, it has become a major focus of intensive global research and development of alternate energy. The present review has been focused specifically on biodiesel. Concerning to the biodiesel production, the major steps includes lipid extraction followed by esterification/transesterification. For the extraction of lipids, several extraction techniques have been put forward irrespective of the generations and feed stocks used. This review provides theoretical background on the two major extraction methods, mechanical and chemical extraction methods. The practical issues of each extraction method such as efficiency of extraction, extraction time, oil sources and its pros and cons are discussed. It is conceived that congregating information on oil extraction methods may helpful in further research advancements to ease biofuel production. are converted into biodiesel by tranesterification using alcohol with or without a catalyst. Biodiesel is being used as one of the promising alternate fuel sources for diesel engines    . Biodiesel is renewable, environmentally friendly, safe to use, biodegradable and it has become a major focus on intensive global research and development of alternate energy. Although the composition of biofuel is complex, it includes mainly palmitic acid, stearic acid, oleic acid, linoleic acid and other fatty acid esters [5-7]. Generations of Biofuels: Hitherto, an immense research in the exploration and development of alternate biofuel resources with desired qualities has been carried out. Based on the resource type, four generations of energy crops have been categorized as first, second, third and fourth generations. The First Generation biofuels are produced directly from food crops by extracting oils as raw material for biodiesel or bioethanol production through transesterification and fermentation respectively. Bioethanol, fatty acid methyl ester (biodiesel) and pure plant oil are the different types of biofuels currently play a major role at the global level, all belong to the first generation fuels  . Crops such as wheat and sugar are the most widely used feed stocks for bioethanol, while rape seed has been proved a very effective crop for biodiesel. However, first generation biofuels have a number of associated problems. There is a serious debate over their actual efficacy in reducing greenhouse gases (GHG) and CO2 emissions due to the fact that some biofuels can produce negative net energy gains, releasing more carbon in their production than their feedstock's CO2 capturing capacity during their growth. However, the most contentious issue with first generation biofuels is 'fuel vs food'. As the majority of biofuels are produced directly from food crops, the rise in demand for biofuels has led to an increase in the volumes of crops being diverted away from the global food market. This has been blamed for the global increase in food prices over the last few years. This is the foremost reason for the inception of second generation fuels    . Second Generation biofuels have been developed to overcome the limitations of first generation biofuels. They are produced from non-food crops such as wood, organic waste, agriculture waste and specific biomass crops, therefore eliminating the main problem with first generation biofuels. Second generation biofuels are also aimed at being more cost competitive in relation to existing fossil fuel. Life cycle assessment of second-generation biofuels has also indicated that they have increased 'net energy gains' compared to first generation biofuels [10,    Third Generation of biofuels is based on improvements in the production of biomass. It takes advantage of special energy crops such as algae as its energy source. The algae are cultured to act as a low-cost, high-energy and entirely renewable feedstock. It is predicted that algae will have the potential to produce more energy per acre than conventional crops. Algae can also be grown using land and water unsuitable for food production, therefore reducing the strain on already depleting water sources. A further benefit of algae based biofuels is that the fuel can be manufactured into a wide range of fuels such as diesel, petrol and jet fuel. However, scale up of algal systems for biofuel production is not very economical [15, 16] . Fourth Generation Bio-fuels are aimed at not only producing sustainable energy but also a way of capturing and storing CO2. Biomass materials, which have absorbed CO2 while growing, are converted into fuel using the same processes of second generation biofuels. This process differs from second and third generation production in a way that, at all stages of production, the carbon dioxide is captured using processes such as oxy-fuel combustion. The carbon dioxide can then be geo-sequestered by storing it in old oil and gas fields or saline aquifers. This carbon capture makes fourth generation biofuel production carbon negative rather than simply carbon neutral, as it 'locks' away more carbon than it produces. This system not only captures and stores carbon dioxide from the atmosphere but also reduces CO2 emissions by replacing fossil fuels [17, 18] .