Part 11
Literature Review :
1. Production of Glucose by Enzymatic Hydrolysis from Cellulosic Waste
a) The varieties of available technologies
Since the cellulose is the most abundant renewable resource recently, numerous researches has conducted studies on the process of enzymatic cellulose saccharifaction or known as Enzymatic Hydrolysis of Cellulose. Alexander (1984) stated that cellulose may be converted to ethanol in two discrete steps. The cellulose may be hydrolysed into glucose first using glucose chemically with acid or enzymatically before it is fermented into ethanol. Based on the process of enzymatic hydrolysis, enzymes acts as a catalyst to break down the glycosidic acid bonds of long chain cellulose, starch and fat molecules into smaller, fermentable molecules such as amino acids, fatty acids and simple sugars. T (Demers, Doane, Scott and Pagano, 2009) .
b) Reactions Involved
The hydrolysis of cellulose that carried out enzymatically is reviewed as acid-based processes which uses cellulolytic enzymes as catalyst (Taherzadeh and Karimi, 2007). The conversion of native cellulose into simple sugar will become extremely slow as it is well covered with matrix of lignin and hemicellulos. Thus, pre-treatment of these materials is needed in order to boost the rate of hydrolysis of cellulose (Galbe and Zacchi, 2002). The process of enzymatic hydrolysis is depending on the operating condition. It is best carried out under mild conditions whereas acid hydrolysis requires high temperature and low pH value. By using this method, it is possible to obtain cellulose hydrolysis close to 100% (Ogier et. al., 1999). The optimum residence time and pH might affect each other. Thus, Tengborg et al. (2001) showed the suitable optimal temperature which is 38°C and pH of 4.9 within 144 residence time for cellulose hydrolysed.
Diagram : Representative of Enzymatic Reaction of Starch /Cellulose to Glucose
c) The Researchers or Practitioners that Made this Technology Successful in Their Area
-
The researches or practitioners that made this technology successful in their area
-
Pilot plant (SEKAB) in Sweeden produces 500 litres of ethanol by using wood chips based on both dilute-acid and enzymatic hydrolysis. (www.sekab.com)
-
China Resources Alcohol Corporation (2006), production of ethanol from local corn.
-
Start up of the Abengoa wheat straw to ethanol at Salamca. (2007)
-
Celunol facility in Jennings, Louisiana that produces ethanol from wood and sugarcane bagasse.
-
GreenField Ethanol Inc.,Canada’s largest producers of ethanol. (www.sunopta.com)
d) The Pros and Constraints of the technology
Jin (2010) stated that the process of breaking down cellulose is difficult because it is stable under many chemical conditions and has crystalline structures due to dense packing of cellulose chain. A report by a student from Standford University stated that nearly half of the total cost of manufacturing biofuels from cellulose allocated on enzymatic cellulose hydrolysis where cellulase covered about 15-25% from total cost (Jin, 2011). While, cellulose is consider as an economical alternative source to glucose compared to production of ethanol from starch (Yang, 2007). Compared to the hydrolysis process using dilute acid, as the process occur in much milder process conditions from to (Carbolea, n.d.). One of the disadvantage of enzymatic reactions are ther might be inhibit the cellulase enzyme which are glucose, cellobiose and other components in the aqueous phase (Acton, 2013). Another report by Harmen et al. (2010) obstacle in the existing pre-treatments to produe sugars from lignocellulose which made up of cellulose, hemicellulose and lignin is that insufficient separation of cellulose separation and lignin.
e) The way forward that would help your project
Considering the impact of greenhouse gases on the climate change, an urge for need of new renewable source of energy is rise. Production pf ethanol from lignocellulosic has received much attention in the last decade which produce biofuels from the hydrolysis of cellulose and hemicellulose. To maximize the yield of glucose from the hydrolysis process, pretreatments are needed as no treatment technology can offers 100% coversion of biomass into fermentable sugars (Chatuverdi & Verma, 2013). Another report by Sun and Cheng (2002) list a guidelines of choosing a pretreatment process which are improving the formation of sugars, avoid the degradation or loss of carbohydrate, avoid the formation of by products that inhibitory to subsequent hydrolysis and cost-effective. Therefore, extensive research in this reseach is still require so that a new efficient treatment process is developed or the upgrade of the existing process to give promising, and less costly results.
Literature Review :
11. Production of Bioplastics using Anaerobic Digestion
e) The way forward that would help your project
As mentioned by the Bioplastics Magazine (n.d.), high research activity is needed to overcome typical weaknesses of PLA which are low impact strengths and low heat distortion temperature. This also helps to develop tailor-made PLA grades in order to serve special applications. Compostable bioplastics currently available in the market are foremost certified according to the harmonized European standard EN13432 and hence, industrially compostable (European Bioplastics, 2015). More research can be done in this industry as it provides us with a bio based materials that promote our world to apply this green technology..
a) The varieties of available technologies
According to The World Bank (2013) state that an alarming amount of waste is expected when the global solid waste was on pace to increase 70 percet in the year of 2025, rising for more than 3.5 million tonnes per day in 2010 to a more than 6 millions tonnes per day by 2025. As the amount of thrash increases the global cost of dealing with the thrash also increase from $205 billion a year in 2010 to $375 billion by 2025. Hoornweg, Bhada-Tata and Kennedy (2013) also mentioned that as the production of waste increases, it leads to problems as plastics clogs the world’s oceans and rivers, causing flooding in developing-world cities. One of the process that is being use to develop the waste is turning it to wealth. The world is still looking for better solutions to making use of the waste into product such as bioplastics. Science Alert (2014) defines bioplastics as a type of biodegradable material made from organic matter such as vegetable fats and oils or corn and pea starch.
b) Reactions Involved
There are many processes that can be used to produce bioplastics either in lab scale or in massive production. Bubacz and Goldsberry (2014) reported that the non-biodegradable plastics we used today in cheap as it is derived through the polymerization of oil-based products. Production of LA is commonly via chemical synthesis or microbial fermentation, however the bio-product is healthier and more desirable for food, drink and pharmaceutical industries because easily to metabolize by living organism (Bubacz and Goldsberry, 2014). In Figure 1, showed the most common method used today which is condensation polymerization (Polylactic acid, n.d.). PLA tends to have a low to moderate degree of polymerization without additives.
c) The Researchers or Practitioners that Made this Technology Successful in Their Area
There are many researchers or practitioners that made these technologies successful in their local area. Bubacz and Goldsberry (2014) said that the brewing industry tries to maximize their use of by products that is produced to eliminate the need of disposal as well as provides a source of revenue. Brewer’s grain which is the biggest brewing waste provide protein, fiber, and energy which make them desirable in a variety of diet Bubacz and Goldsberry (2014) reported that in Japan, the Akita Research Institute has established a new technology that significantly reduces the cost of polylactic acid, the spent grain derived foundation for the production of biodegradable plastics. Another company that has been established for producing PLA is Corbion Purac. Carbion Purac’s bioplastics is 100 percent made from biobased materials and renewable resources (Carbon Purac, 2013). Carbon Purac has been known worldwide for its lactic acid (LA) derivatives and lecticides and a leading company in functional blends containing enzymes, emulsifiers, minerals and vitamins.
Figure 1. Polymerization of lactic acid through condensation
d) The Pros and Constraints of the technology
The production of bioplastics from PLA has its own benefits. As it is biodegradable, it has multiple end-of-life options which includes recycle and reuse, compost or biodegradable, incinerate or renewable energy recovery, anaerobic digestion and feedstock recovery (Carbion Purac, 2013). Benefits and challenges of bioplastics in anaerobic digestion is that energy production which is compostable waste bags increase the volumes of organic waste for digestion, renewable energy is produced in the form of biogas or heat residual matter and biomass produced remains as compost (Europian Bioplastics, 2015). Another benefits of bioplastics is improvement of C/N ratio which biowaste, especially kitchen waste is often rich in proteins, the C/N ratio being relatively low (<20), leading to high ammonia levels and reduced digestion rates (European Bioplastics, 2015). Many properties of PLA can be customized as it can be manufactured with a wide range of properties as it exists in four different molecular forms (Mehta R et al.). The constraint and challenges are not all certifies bioplastics will degrade to the same extent in the anaerobic digestion step, and it is produce differently in varying technologies (Europian Bioplastics, 2015). Also, the compostable characteristics of bioplastics in an anaerobic digestion and the processability is influence by pre-treatment.
Literature Review :
111. Production of Energy Using Plasma Gasification
a) The varieties of available technologies
Gasification technology has been used for decades as it was introduced a very long time ago in 1850s (Belgiorno, V. et al, 2002). In 1850s, as the development of gasification of coal, most city of London is illuminated by “town gas”. Biomass Energy centre also added that, during the Second World War, small scale gasifiers were used to power internal combustion engine vehicles during fuel shortages. As biomass is quite handled to be begin with, one of the major paths for the conversion of solid biomass into liquid and gaseous fuels, is by thermochemical process such as gasification and pyrolysis (Basu, 2010). El Haggar (2007) defines gasification as a thermal process with a limited amount of oxygen to heat wastes that have a high carbon content to about 1300, while ‘pyrolysis’ is a thermal-chemical decomposition process where waste is heated to a very high temperature (2500) in the absence of oxygen to chemically decompose waste. As gasification converts fossil or non fossil fuels into useful gasses and chemicals, it requires a medium which can be gas or supercritical water (Basu, 2010). While, there is another type of gasification which is plasma gasification or plasma assisted gasification can be used to convert carbon-containing materials to synthetic gas that can be used to generate power and other useful products (Gasification Technologies Council, n.d.).
b) Reactions Involved
Nowadays, the gasification of fossil fuels is more common than of non-fossil fuels like biomass for production of synthetic gas. Basically, the plasma gasification which is a multi stage process converts the low qualtity feed stocks such as coals, oil sands and municipal waste into more valuable outputs (AlterNRG, 2009, Dodge, n.d.). Dodge (n.d.) explained that in the first stage in order to process the feed stock uniform and dry, valuable recyclables have to be sorted out. If a biomasss is heated under a restricted oxygen supply, it is first pyrolyzed and then decomposed into condensable and non-condensable gas. The second step is gasification, where extreme heat from the plasma torches is applied inside a sealed, air-controlled reactor (Dodge, n.d.). Plasma gasification is then vaporize the feed stocks into components parts such as hydrogen and carbon monoxide(AlterNRG, 2009). The vaporized stream of elements is called the synthesis gas or syngas (AlterNRG, 2009). Basu (2010) reported that the producer gas reaction, which produce syngas is endothermic gasification reaction and the equation is as follows :
Source : Biomass Gasification and Pyrolysis : Practical Design and Approach by Prabir Basu
The third stage, which is gas clean up and recovery, syngas is then clean up by remove the environmentally destructive elements such as sulphur oxide, nitrous oxide and even carbon dioxide(AlterNRG, 2009, Dodge n.d.). Later, it can be process into variety of valuable commodity such as hydrogen, diesel fuels or gasoline(AlterNRG, 2009). The syngas can also be used directly as fuel to produce heat, steam and electricity(AlterNRG, 2009). Generally, the gasification of biomass involves in removal of oxygen from the fuel to increase its energy density (Basu,2010). For example, a typical of biomass has about 40-60% oxygen by weight, but as it converts to useful gas, it contains small percentage of oxygen as oxygen is removed by either dehydration or decarboxylation (Basu, 2010).
c) The Researchers or Practitioners that Made this Technology Successful in Their Area
There are many researchers or practitioners that made these technologies successful in their local area. Bubacz and Goldsberry (2014) said that the brewing industry tries to maximize their use of by products that is produced to eliminate the need of disposal as well as provides a source of revenue. Brewer’s grain which is the biggest brewing waste provide protein, fiber, and energy which make them desirable in a variety of diet Bubacz and Goldsberry (2014) reported that in Japan, the Akita Research Institute has established a new technology that significantly reduces the cost of polylactic acid, the spent grain derived foundation for the production of biodegradable plastics. Another company that has been established for producing PLA is Corbion Purac. Carbion Purac’s bioplastics is 100 percent made from biobased materials and renewable resources (Carbon Purac, 2013). Carbon Purac has been known worldwide for its lactic acid (LA) derivatives and lecticides and a leading company in functional blends containing enzymes, emulsifiers, minerals and vitamins.
d) The Pros and Constraints of the technology
According to Biomass Energy Centre (BEC) (n.d.), gasification technology is widely being used as it is being applied in heating water in central heating, district heating or process heating applications. Other than that, gasification is use as a part of systems producing electricity or motive force and transport using an internal combustion engine (BEC, N.D.). The Gasification Technology Council (GTC) (n.d.) stated that there are more than 272 operating gasification plants worldwide with 686 gasifiers. To date, China has the largest number of gasification plants, while the thirty three gasification plants are located in the United States (GTC, n.d.). Waste Management World (n.d.) stated that according to Air Products which the facility is under construction at New Energy and Technology Business Park near Billingham, will be the first of its in UK and in the world (Messenger, n.d.). Messenger (n.d.) also reported that the plant expected to divert up to 350000 tonnes of non-recyclable waste from landfill per year to meet the UK’s waste diversion target. The company also mention that gasification technology provided by AlfterNRG, which is Westinghouse advanced gasification technology has the potential to generate a wider range of useful products, including heat, hydrogen, chemicals and fuels (Messenger, n.d.). From the historical timeline, in the late 1990s, America’s Westinghouse Corporation, the first pilot-scale plasma gasification projects were build in Japan to convert municipal solid waste, sewage sludge and auto shredder residue energy (Dodge,n.d.). There are many more companies and researches conducted since then as the emergence of this technology. Historically, it has been used to refine coal and biomass into variety of liquid fuels, gases and chemical and in the earlier 19th century it started to develop into modern coal plants as well as municipal light and power system.
e) The way forward that would help your project
Fortunately, the technologies require to operate waste gasification are coming along fast. The most beneficial side of choosing a plasma gasification is that the individual sub systems are all very mature and established (Dodge, n.d.). Plasma gasifiers is claimed for producing best quality of syn gas, followed by Entrained flow (EF), and finally Dual fluidized bed, Circulating Fluidized Bed (CFB) and Bubbling Fluidized Bed (BFB) gasifiers (E4tech, 2009). Plasma gasification can further improve and develop the feedstock do not need much specification in size, moisture or composition. The municipal solid waste can be broken down directly making the process a lot simpler.
A complete literature review + appendices for each article :