A review on present situation and development of biofuels in China

A review on present situation and development of biofuels in China

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Journal of the Energy Institute xxx (2015) 1e8

Contents lists available at ScienceDirect

Journal of the Energy Institute journal homepage: http://www.journals.elsevier.com/journal-of-the-energyinstitute

A review on present situation and development of biofuels in China* Hao Chen a, b, *, Meng-long Xu a, b, 1, Qi Guo a, b, 1, Lu Yang a, b, 1, Yong Ma a, b, 1 a

School of Automobile, Chang'an University, The South Second-ring Road, 710064, Xi'an, China Key Laboratory of Shaanxi Province for Development and Application of New Transportation Energy, Chang'an University, The South Second-ring Road, 710064, Xi'an, China

b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 13 November 2013 Accepted 29 October 2014 Available online xxx

Energy shortage, energy safety, environment pollution and global warming commonly promote the development of biofuels in China. Maize, wheat and rapeseed should be banned gradually as feedstocks. Cassava and sweet sorghum have better environmental benefits for ethanol production and so do jatropha curcas and pistacia chinensis for biodiesel. Evaluation of potential land for the four feedstocks has already been done and they are prior to other sources. Macro polices promote development of fuel ethanol and biodiesel industries. Economic measures including tax cuts, subsidies and compensation mechanisms and sale channels are given to ethanol companies. Rapid development of fuel methanol industry and limited source of feedstocks become the resistance of ethanol industry. Biodiesel can hardly achieve economic supports due to complex sources of feedstocks, variable compositions and different properties. China treats cellulose biomass and microalgae as the best choice for ethanol and biodiesel productions and they are in the research stage. © 2015 Published by Elsevier Ltd on behalf of Energy Institute.

Keywords: Biofuels Fuel ethanol Biodiesel China

1. Introduction Most of global primary energy production derives from fossil energy [1]. Fossil fuels accounted for 86.7% of the total primary energy consumption in 2013, with 32.9% share for oil, 23.7% for natural gas and 30.1% for coal [2]. China represents the second-biggest economy in the world and accounts for 22.4% (2852.4 million tons oil equivalent) of global primary energy consumption [2]. Moreover, due to the high economic growth ratio, energy demand increases significantly in China. Transport sector worldwide almost entirely relies on fossil fuels, oil in particular [3]. Unfortunately, this activity is major energy consumption and use most of the limited non-renewable fossil energy that creates a negative impact to living environment [4]. Accordingly, searching for alternative fuels is the core task of Chinese government. The utilization of coal-based methanol as a practical alternative fuel is one of the most realistic options for China, due to the “oil-lean, gas-lacking, and coal-rich” structure of Chinese energy resources [5]. However, coal-based methanol in essence derives from fossil energy and production and use of coal have low energy efficiency and high pollution which are harmful to the environment. Considering both the reality and the future, China takes methanol as the transitional alternative fuel in the recent twenty years and on the other hand greatly develops and promotes electric vehicles and biofuels for traditional vehicles. Faced with increasing emissions and ever more apparent impacts, governments are using legislation to expedite transitions towards a low carbon economy and to a lower carbon technology uptake [6]. Transport is the most important contributor for greenhouse gas (GHG) emissions, for example, in USA transportation activities (excluding international bunker fuels) accounted for 32 percent of CO2 emissions from fossil fuel combustion and 27 percent from the total in 2010 [7]. Climate change consciousness has served as an important driver to the embrace of biofuels because it assists climate change mitigation efforts by displacing fossil fuel consumption [8].

*

Research activities: combustion and emission of engine; renewable and alternative fuels of road transport. * Corresponding author. School of Automobile, Chang'an University, The South Second-ring Road, 710064, Xi'an, China. Tel.: þ86 29 87805614, þ86 29 82334430; fax: þ86 29 82334476. E-mail addresses: [email protected] (H. Chen), [email protected] (M.-l. Xu), [email protected] (Q. Guo), [email protected] (L. Yang), [email protected] (Y. Ma). 1 Tel.: þ86 29 87805614, þ86 29 82334430; fax: þ86 29 82334476. http://dx.doi.org/10.1016/j.joei.2015.01.022 1743-9671/© 2015 Published by Elsevier Ltd on behalf of Energy Institute.

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In 2010 renewable energy used in power generation grew by 15.5% and global biofuels production by 13.8% [9]. Fuel ethanol is widely used in Brazil and US. Both countries together were responsible for 87.1% of the world's fuel ethanol production in 2011 [10]. In 2013, Global biofuels production grew by 6.1%, driven by increases in the two largest producers: Brazil (þ16.8%) and the US (þ4.6%) [2].

2. Promotion drivers of biofuels 2.1. Energy shortage and energy safety Fig. 1 [11] shows the number of automobiles, crude oil consumption and dependence on foreign oil in recent years. Fast growth of economy promotes the soaring quantity of automobiles. In 2012 the number of automobiles increases more than five times than in 2004 and reaches 120.89 million, which results in the sharp increase of corresponding demand for crude oil. Supply and demand of crude oil is extremely unbalanced and China's dependence on foreign oil increased from 42.9% in 2005 to 56.7% in 2011 which is so high that the energy safety seriously deteriorates. Additionally, complex international situation makes the situation of energy safety more sensitive and variable. Energy shortage and energy safety effectively promote the development of biofuels.

2.2. Air pollution The urban air pollution problems caused by the vehicles are attributable directly to the choice of internal combustion engine as the means of propulsion. Biofuels content oxygen which is helpful for complete combustion, thus reducing hydrocarbon (HC), carbon monoxide (CO) and particulate matter (PM) emissions. An example for bio-diesel, cumulative emissions would reduce total 3.4% and 3.7% for PM and CO, respectively; total HC emissions would be reduced by 5% [12,13]. In US, demand for biofuels receives a tremendous boost in the past five years from the fuel ethanol for gasoline vehicles and biodiesel for diesel. This leads to a lowering of harmful pollutants, effectively improving air quality in urban areas. In China, automobiles have already been the major air pollution sources and for example in Beijing their contributions of HC, CO and NOX are respectively 63.4%, 73.5% and 46%. Severe atmospheric pollution forces the Chinese government to look for clean alternative fuels and biofuels have superiority in reducing HC, CO and PM emissions.

2.3. Global warming As well as energy consumption, GHG emission has already became a worldwide problem which threatens harmonious coexistence of human and environment, sustainable development of economic, and even survival of mankind. At present, most countries have already realized, that high energy consumption and emission model of economic growth are difficult to continue and the only way is to promote low-carbon economy for sustainable development. In order to meet the challenge of climate change, in the “United Nations Conference on Environment and Development” main countries in the world, signed “United Nations Framework Convention on Climate Change” and the “Kyoto Protocol” for controlling GHG emissions. Since the basic goal of climate policy is to reduce CO2 emissions from the extensive use of fossil-based energy, there exists a close link between climate policy and energy policy [14]. From Fig. 2 [15], in 2009 the primary energy consumption of China (2210.3 mtoe) is as much as that of US (2205.9 mtoe), however, CO2 emission from energy consumption of China is 32.8% higher than that of US. Consequently China has the largest responsibility and duty to reduce CO2 emission through optimizing the consumption structure, such as improving the share of renewable energy and nuclear energy. Biofuels have the obvious advantage over other fuels in reducing GHG emissions through absorption in growth phase of feedstocks.

Fig. 1. Statistics of automobiles and crude oil consumption and dependence on foreign oil.

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Fig. 2. Carbon dioxide emission and primary energy consumption comparisons between China and US.

3. Economic and technology backgrounds of biofuels in China 3.1. Feed-stocks of biofuels in China For fuel ethanol, feedstocks can be classified into four categories: (1) starch material involving sweet potato, cassava, maize, potatoes, barley, wheat, rice, sweet sorghum and etc; (2) sugariness material including sugarcane, sugar beet, molasses and etc; (3) cellulose material incorporating straw stalk of crops, residues in forest logging and wood processing, firewood, cellulose waste in production of paper and sugar and etc; (4) other materials. As everyone knows, US mainly uses maize and Brazil completely relies on sugarcane for ethanol production, due to the rich sources, low costs and high convenience. Early in 2006, fuel ethanol consumed more than 2% of the total maize yield, which caused highly widespread controversy that whether food safety would be affected. National Development and Reform Commission (NDRC) terminated new fuel ethanol projects using maize or wheat and only non-food raw materials might be permitted. In 2009 cassava ethanol had already been in a certain scale production with mature technology. Sweet sorghum is still in the initial phase and pilot program has already been operated. Many studies have been focused on fermentation of sweet sorghum. Liu Ronghou et al. [16] carried out the research on fermentation of stalk juice of sweet sorghum ethanol by the immobilized yeast, and the optimal addition proportion of nutrient salt was determined. Cao Junfeng et al. [17] studied the initial conditions of fermentation of sweet sorghum juice, and confirmed the optimal process parameters for ethanol production using liquid fermentation. Zhang Guansheng et al. [18] put forward solid fermentation method for sweet sorghum stalk. Xue Jie et al. [19] proposed optimal process condition for solid fermentation of sweet sorghum stalk. Cellulose material, the third generation feed-stock, is the most potential for fuel ethanol production, but in China it is still in the experimental stage and the conversion technology needs to be improved. As a whole, presently China's fuel ethanol production concentrates on cassava and maize. Biodiesel is typically made by chemically reacting lipids (vegetable oil, animal fat, etc) with alcohols producing fatty acid (methyl, propyl or ethyl) esters. A variety of bio-lipids can be used as feed-stocks which are vegetable sources including rapeseed oil, soybean oil, palm oil, jatropha curcas, pistacia chinensis (in China), Chinese tallow, canola oil and sunflower oil, animal sources involving beef tallow, poultry oil and waste cooked oil, and other sources such as micro-algae. In China biodiesel production concentrates on two ways: one is governmental planning made from pistacia chinensis and jatropha curcas, and the other is action of grease company by producing biodiesel as by-product from rapeseed oil, soybean oil, waste cooked oil and other fatty acids. Unlike fuel ethanol, biodiesel essentially is a kind of multi-compositions fuels and the ester components along with their quality proportions are decided by the feed-stocks. As a result, properties of biodiesel are vastly different. China is rich in woody oil resources with 1544 species and wide distribution, which are wild and have not been developed [20]. Agriculture and forestry biomass engineering projects of National Science and Technology Support Program have already confirmed that jatropha curcas, pistacia chinensis, xanthoceras sorbifolia and comus wilsoniana are the most promising and potential resources for biodiesel production. Cetane number, cold filter plugging point and oxidation stability are the most three important factors of biodiesel as vehicle fuel. In GB/T 20828-2007, Cetane number is required for no less than 49, oxidation stability at 110  C no less than 6 h and the cold filter plugging point need to be reported. Research Institute of Forestry in Chinese Academy Forestry studied the influence of fatty acid compositions on fuel characteristics of biodiesel involving the four woody plant oils, shown in Table 1. Cetane numbers of biodiesel from comus wilsoniana, jatropha curcas and pistacia chinensis are in accordance with requirements of Chinese biodiesel standard [21]. The research also indicated that oxidation stabilities of the four biodiesel are poor and those of jatropha curcas and pistacia chinensis are close to the standard, which can be solved through adding antioxidants. Consequently, whole evaluation has shown that jatropha curcas and pistacia chinensis are suitable feedstocks for producing biodiesel. 3.2. Production process of biofuels in China Production methods of fuel ethanol can be summarized into two categories: fermentation and chemical synthesis. Fermentation can be specified according to the starchiness, sugariness and cellulose feed-stocks. China mainly uses maize and cassava for ethanol Please cite this article in press as: H. Chen, et al., A review on present situation and development of biofuels in China, Journal of the Energy Institute (2015), http://dx.doi.org/10.1016/j.joei.2015.01.022

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Table 1 Fatty acid compositions of oil and properties of biodiesel from four plants [21,22]. Items Fatty acid w/%

Lauric/C12:1 Myristic/C14:0 Palmitic/C16:0 Palmitoleic/C16:1 Stearic/C18:0 Oleic/C18:1 Linoleic/C18:2 Linolenic/C18:3 Eleostearic/C18:3 Arachidic/C20:0 Gadoleic/C20:1 Mead/C20:3 Other fatty acid Cetane number Cold filter plugging point Oxidative stability

Fuel properties

Jatropha curcas

Pistacia chinensis

Xanthoceras sorbifolia

Comus wilsoniana

0.00 0.00 19.75 0.00 4.63 46.83 28.50 0.01 0.00 0.17 0.00 0.00 0.00 51 0 3.3

0.00 0.00 23.14 0.99 1.18 44.35 28.51 0.84 0.00 0.10 0.00 0.00 0.89 51.3 3 4.2

0.00 0.00 5.27 0.00 1.92 31.17 44.47 6.46 0.00 0.20 0.00 7.27 3.24 47.6 8 1.7

0.00 0.07 16.53 0.97 1.77 30.50 48.50 1.60 0.00 0.00 0.00 0.00 0.05 49 0 0.6

production which belong to starchiness feed-stocks. Liquid fermentation is the most popular method for fuel ethanol production in China. Feed-stocks are crushed and then the plant cell and tissue are destroyed for the dissociation of starch. After steaming, the gelatinization and liquefaction of starch, form liquefied mash, making it better to accept the affect of saccharifying enzyme and to be converted into fermentative sugars for fermentation. Then the distillation and dehydration processes are carried out for gaining anhydrous ethanol. Finally, denaturant is added into anhydrous ethanol to form fuel ethanol. The whole process can be summarized as five phases which are pretreatment, saccharification, fermentation, distillation, and dehydration respectively. Corresponding energy consumptions are 2% for pretreatment, 31% for saccharification, 2% for fermentation, 45% for distillation, and 20% for dehydration respectively [23]. Technology need to be improved for reducing high energy consumption in distillation and saccharification phases. Solid state fermentation is classified into modern sealed solid state and traditional open solid state methods. Proceed of modern solid fermentation is in the sealed reactor using single strain or mixed strain, overcoming the shortcomings of liquid fermentation mainly referring to the complexity of raw material processing and large quantities of waste water [19]. As a whole, modern solid state fermentation is helpful for large scale industrial production of fuel ethanol. The major work of biodiesel production is carried out using a typical vegetable oil by formulating its properties closer to the conventional diesel oil. System design approach has taken care to see that these modified fuels can be utilized in the existing diesel engine without any substantial hardware modifications [24]. Biodiesel production mainly involves the direct mixing method, micro-emulsion method, pyrolysis method, ester exchange method and hydrocracking method. Biodiesel derived from direct mixing and micro-emulsion methods is unstable and its utilization will be harmful to the engine. Pyrolysis and hydrocracking methods change the molecular structure and fundamentally solve the high viscosity and low volatility of biodiesel. However, biodiesel gained from pyrolysis is in relatively poor quality and hydrocracking needs high cost. Accordingly, ester exchange method not only can fundamentally change the molecular structure, but also has the advantages that production process is simple, equipment investment is low, and it is suitable for large scale production. In China, ester exchange method is the commonly used for biodiesel production.

3.3. Production and consumption of biofuels Most cars in the USA can fuel withblends of up to 10% ethanol [25], and ethanol represented 10% of the USA gasoline fuel supply in 2011. Since 1976 the Brazilian government has made it mandatory to blend ethanol with gasoline, and anhydrous ethanol, is recently blended with gasoline in various proportions up to E25 [26,27]. By 2011 Brazil had a fleet of 14.8 million flex-fuel automobiles and light trucks and 1.5 million flex-fuel motorcycles that regularly use neat ethanol fuel [28]. Table 2 shows the production and consumption of fuel ethanol and biodiesel [15]. Presently, although China ranks thirdly in the world as for production and consumption of fuel ethanol, absolute value is far less than the US and Brazil. Industry scale is so small that biodiesel in China can hardly play the role of partially substituting diesel.

Table 2 Production and consumption of fuel ethanol.a Country

Production/thousand barrels per day 2010

US Brazil China Canada France Germany a

Consumption/thousand barrels per day 2011

2010

2011

Ethanol

Biodiesel

Ethanol

Biodiesel

Ethanol

Biodiesel

Ethanol

Biodiesel

867.4 486.0 37.0 24.0 18.0 13.0

22.4 41.1 6.0 / 37.0 49.0

908.6 392.0 39.0 30.0 17.4 13.3

63.1 46.1 7.8 / 34.0 52.0

838.8 381.9 37.0 32.0 15.0 25.0

17.1 42.4 6.0 / 40.0 50.5

841.1 332.4 39.0 42.0 16.0 26.5

57.8 45.0 7.0 / 40.5 47.4

Data is summarized from US EIA [15].

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Table 3 3E assessments for different feed-stocks of ethanol in China [29]. Feed-stocks

The cost of ethanol production (Yuan/t)

Energy efficiency

Environmental benefits of CO2 (kg/L)

Sweet sorghum

3391.60

0.40

Cassava

4764.00

0.77

Maize

4940.00

0.91

Total emission: 4.03 Absorption in growing: 8.82 Total emission: 6.48 Absorption in growing: 3.35 Total emission: 2.84 Absorption in growing: -

3.4. Evaluation for biofuels in China Biofuels derived from plant materials are carbon-neutral (carbon emission when burned is offset by the carbon which the plants absorb from the atmosphere in their progress of growing), and renewable and they may be cultivated in different conditions. However, different feed-stocks of biofuels have obviously differing environmental, social and economic affects. Consequently, development of biofuels should follow the principle of suiting one's measures to local conditions and the important premise is 3E (economic, energy and environment) life cycle assessments (LCA) for these feed-stocks. Energy efficiency is the ratio of total energy input to total energy output. Environmental benefits are compared between total emission and absorption in growing phase. Table 3 and Table 4 show respectively the evaluation results for fuel ethanol and biodiesel in China [29,30]. Compared with sweet sorghum, cassava lies in the inferior position due to the high cost and energy input, high emission and low absorption in growing. Now the evaluation of two feed-stocks, rapeseed and jatropha curcas, has been done by researchers in China. Results indicate rapeseed is a kind of edible oil and therefore its production cost is higher than that of jatropha curcas. Jatropha curcas has better energy efficiency with relatively low energy consumption and the net emission of jatropha curcas is 0.87 kg per liter which is lower than that of rapeseed, 1.38 kg. Consequently, jatropha curcas has the better environment and energy benefit than rapeseed for bio-diesel. Beside these evaluations, potential land for planting jatropha curcas has also been evaluated by CAS (Chinese Academy of Sciences) and the results shown in Table 5 indicate that Yunnan province is an important region for developing biodiesel from jatropha curcas [31]. Pistacia chinensis is the second generation feedstock for biodiesel in China. CAS assessed bioenergy potential of pistacia chinensis in China based on GIS and life cycle analysis. The results indicate that total area of marginal land exploitable for development of Pistacia chinensis is about 19.90 million hm2, which is made up of the suitable area 7.10 million hm2 and the relatively suitable area 12.79 million hm2. Total GHG emissions reduction potential is 2.55 million tons per year [32].

4. Policies for biofuels in China 4.1. Macro policies Chinese government is making great efforts to curb oil demand and GHG emissions in the road transport sector by introducing alternative fuels and regulating vehicle fuel economy [33]. Using biofuels in place of fossil fuels would potentially reduce GHG emissions since bio-feedstocks absorb CO2 from the atmosphere during growth and release it upon combustion of the feedstock or the energy products derived from them. Thus biofuels in part recycle CO2 mitigating GHG emissions and in turn slow down climate change [34]. China promulgated “Renewable energy law of the people's Republic of China” on February 28, 2005 and it was executed on January 1, 2006. Then (2011)588 [35], (2012)216 [36] and (2007)2174 [37] were formulated for biofuels. Table 6 gives the information of policies. The (2011)588 [35] policy plan provides macro direction for biofuels. It supports and promotes the research and development of key technology and specialized equipments for production process of non-grain fuel ethanol, biodiesel, biogas, biohydrogen and other bioenergy products. The (2012)216 [36] policy gives specific measures and objectives for development of biofuels. For fuel ethanol, it is suggested that sweat sorghum (sugar materials), cassava (starch materials) and straws (cellulose materials) should be developed. China has rich resources of straws of crops including maize, rice, wheat, cotton and others. Theoretical quality of the resources is 0.82 billion tons per year and in practice 0.69 billion tons of straws can be collected for utilization. Subtracting 0.35 billion tons, the quality for fertilizer, feed, raw material of edible fungus and paper production, 0.34 billion tons of straws can be used for energy conversion. Besides the straws of crops, processing residues such as rice husks and bagasses, are the feed-stocks of fuel ethanol. Theoretical quality is 0.12 billion tons per year and 0.06 billion can be used for ethanol production. The (2012)216 policy also gives the planned scale in 2015, listed in Table 7. File (2007)2174 [37] puts forward the target scale in 2020. Utilization quality of fuel ethanol should be 10 million and that of biodiesel should be 2 million at least per year.

Table 4 2E assessments for different feed-stocks of biodiesel in China [30]. Feed-stocks

Total energy input (MJ/L)

Total energy output (MJ/L)

Net energy (MJ/L)

Environmental benefits of CO2 (kg/L)

Rapeseed

49.81

33.47

16.34

Jatropha curcas

45.63

32.54

13.09

Total emission: 3.82 Absorption in growing: 2.44 Total emission: 4.10 Absorption in growing: 3.23

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Table 5 Evaluation for potential land for planting jatropha curcas in China [31]. Land types

Cultivated land Forest land Shrub land Sparse woodland Barren grassland Unused land Total

Yunnan province

Sichuan province

Appropriate/(1000 hm2)

Relatively appropriate/(1000 hm2)

Appropriate/(1000 hm2)

Relatively appropriate/(1000 hm2)

54 79 97 46 92 0 370

1100 1080 1857 737 1319 7 6101

0 0 0 0 0 0 0

146 42 43 85 76 1 393

4.2. Economic measures Production and sale of fuel ethanol are the Chinese government's behavior. To support the ethanol industries tax cuts, subsidies and other economic means are adopted in the production phase and in the sale phase two state-owned petroleum companies, China National Petroleum Corporation (CNPC) and China Petroleum and Chemical Corporation (CPCC), are compulsorily required to sell ethanol gasoline. For companies using wheat or maize, under the premise of non-expansion of scale and non-increase of yield, 5% consumption tax of industries which produce and deploy denatured fuel ethanol is exempted and value added tax (VAT) is levied and then refunded. For companies using non-edible plants, full exemption is given to both consumption tax and VAT and moreover the loss in the process of deployment and sale is compensated through governmental quota subsidy. Although consumption tax is exempted for biodiesel companies, few sale channels and no governmental subsidies together restrain the extension and development of biodiesel. 5. Dilemma of biofuels industry in China Although it seems that policies for ethanol are systematical and effective, development of fuel ethanol faces enormous challenge caused by coal-based methanol industry. Properties of methanol gasoline are close to ethanol gasoline. Due to the cheap price and abundant resource derived from coal, in practice methanol has more space than ethanol in blending with gasoline [38]. More important factor is social and economic requirement. As everyone knows, in China methanol mainly comes from coal and the downstream methanol industry is in overcapacity situation. Consequently methanol as automobile fuel develops quickly in China to ensure the methanol consumption and job opportunities. National standards for M85 (the volume ratio of methanol in methanol gasoline is 85%) and M100 were formulated in 2009 [39]. Eleven provinces have their regional standards for different volume ratio methanol gasoline [39]. Scale of ethanol industry based on maize and wheat is under strict limitation. Sweet sorghum ethanol is still in the pilot operation phase. Currently cassava is the main feedstock, however its source can not satisfy with the large-scale production because China is not the main planting area and only Guangxi and Hainan provinces have the ability to plant cassava. Fluctuation of international market price of cassava makes it difficult for the factories which rely on import to control the risk. Besides, the yield of cassava per unit is low, and it will consume soil fertility greatly under the condition of successive monoculture which negatively affects the sustainable development. Accordingly source of feedstocks is the other bottleneck for fuel ethanol industry. Resistance factors of biodiesel industry are shortage source of feedstocks and lacking promotion of economic policies. Biodiesel from jatropha curcas has already been in small scale application and pistacia chinensis is still in the initial planting phase. Although both of them are planted nationwidely, oil extraction is another problem affecting specialized scale production. Current sources for biodiesel are so complicated, including jatropha curcas, waste cooked oil, rapeseed oil and soybean oil, that compositions and properties of biodiesel show significant differences. Among these sources, waste cooked oil varies widely in source and composition. Rapeseed and soybean oils are not directly used, but the edible oil companies use their waste for biodiesel production as byproducts. As a result, quality of biodiesel products can hardly be guaranteed. Consequently, it is very difficult for the government to formulate unified policies or economic measures. 6. Future development of biofuels From the above analysis, it can be concluded that presently government focuses on developments of cassava and sweet sorghum for ethanol production and jatropha curcas and pistacia chinensis for biodiesel. Moreover, China has already confirmed that in the future cellulose material and microalgae are the major feedstocks respectively for fuel ethanol and biodiesel and before application they need further study and evaluation. Cellulose biomass is the most abundant renewable resources in the world and ethanol production from cellulose biomass comprises several critical steps which are feed-stocks pretreatment, fermentation, separation and purification of the ethanol, among which

Table 6 Information of policies for biofuels. Department and promulgation time

Name of policy file

Number

Ministry of Science and Technology (2011.11.14) National Energy Administration (2012.7.24) National Development and Reform Commission (2007.8.31)

Twelfth Five-Year Development Plan for biology technology (2011e2015) Twelfth Five-Year Development Plan for biomass energy Medium and long term development planning for renewable energy (2007e2020)

(2011)588 (2012)216 (2007)2174

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Table 7 Scale of biofuels in 2012 and planned scale in 2015. Usage

Scale in 2012 (million tons)

Standard coal equivalent (million tons)

Planned scale in 2015 (million tons)

Standard coal equivalent (million tons)

Fuel ethanol Biodiesel

1.8 0.5

1.6 0.7

4 1

3.5 /

Table 8 Properties of three micro-algae biodiesel [46]. Properties

Scenedesmus sp. FAME

Nannochloropsis sp. FAME

Dinoflagellate FAME

Limitation

Test methods

Density at 15  C/(kg/L) Acid value/(mg KOH/g oil) Kinematic viscosity at 40  C/(mm [2]/s) Oxidative stability at 110  C/(h) Moisture content/(%) Sulfur content/(%) Phosphorus content/(ppm) Methyl ester content/(%) Distillation temperature/( C) Gross heating value/(MJ/kg)

0.852 0.52 4.15 5.42 0.04 0.02 2.4 91.0 266 39.76

0.854 0.46 5.76 1.93 ND 0.06 4.5 92.2 300 39.81

0.878 0.44 3.74 1.02 0.07 0.04 2.8 96.6 368 39.84

0.82e0.90 0.80 1.9e6.0 >6 0.05 <0.05 10.0 >96.5 <360 >35

GB/T 2540 GB/T 264 GB/T 265 EN 14112 SH/T 0246 SH/T 0689 ASTM D4951 EN 14103 GB/T 6536 GB/T 384-81

pretreatment step is identified as technological bottleneck for commercialization of cellulose ethanol. Moreover, cellulose ethanol industry is facing many challenges: 1) hydrolysis technology of cellulose pretreatment needs to be improved and especially the energy and water consumption should be reduced; 2) production cost is high and production efficiency is low; 3) the ratio between energy output and energy input should be improved; 4) energy density of cellulose is low and it is highly dispersed which indicate that feed-stocks are not easy to collect and the corresponding cost is high; 5) methods for reducing the inhibitory effects of intermediate product on the activity of cellulose, modern technology for breeding high temperature resistant engineering bacteria, and screening of high-yield cellulose strain are all needed to be improved. The economically significant production of carbon-neutral biodiesel from micro-algae has been hailed as the ultimate alternative to depleting resources of petro-diesel due to its high photosynthetic efficiency, cellular concentration of lipids, biomass production, resources and economic sustainability and overall potential advantages over other sources of biofuels [40e42]. Micro-algal biotechnology appears to possess high potential for biodiesel production because a significant increase in lipid content of microalgae is now possible through heterotrophic cultivation and genetic engineering approaches [43,44]. Relative research indicates that fuel properties of biodiesel derived from different micro-algaes show obvious variations [45]. In China, production technology of biodiesel from micro-algae is advanced and many kinds of engineering microalgae are used for experiments. Scenedesmus sp. FAME, Nannochloropsis sp. FAME, and Dinoflagellate FAME have already been in the pilot-scale experiment phase. Their chemical compositions and their properties are very different [46]. Table 8 gives the major properties of micro-algae biodiesel [46]. Among them the Scenedesmus sp. FAME is the most suitable for biodiesel according to the limitation requirement.

7. Conclusions and suggestions Although many objective factors complicate the development of biofuels and slow down the growth, developing biofuels is helpful for rationalizing the energy structure, easing energy shortage, enhancing energy safety, reducing the air pollution and slowing the climate change and it is one of the most important and feasible ways to realize green transportation and sustainable development. Compared with US and Brazil, China shows high stability in developing biofuels. However, both the production and consumption are so low that they can hardly play positive roles in substituting fossil fuels. Macro policies provide significant support for developing biofuels. Tax cuts, subsidies and other economic means for fuel ethanol are positive and effective. Lacking specialized economic policies is the main resistance for biodiesel. Presently in China fuel ethanol production from cassava and sweet sorghum is in certain scale. It has already been proved that jatropha curcas and pistacia chinensis are the most suitable woody resources for biodiesel production. Besides the four feedstocks, research and future development are focused on cellulose biomass and microalgae. Considering for food safety, rapeseed and maize should be gradually given up. For cellulose biomass ethanol industry, it is necessary to improve the technology such as pretreatment process together with chemical industries and to increase the efficiency of collection and transportation of raw materials with logistics companies. Corporation between biodieselindustry and other industries such as coal-fired power plants which emit high concentration CO2, and sewage treatment plants for microalgae cultivation is the most efficient way to achieve environmental and economic benefits.

Acknowledgments The Project Supported by Natural Science Basic Research Plan in Shaanxi Province of China (Program No. 2014JQ7268) and the Special Fund for Basic Scientific Research of Central Colleges, Chang'an University (2013G1221018, 2013G3224019, 2013G1221028). Please cite this article in press as: H. Chen, et al., A review on present situation and development of biofuels in China, Journal of the Energy Institute (2015), http://dx.doi.org/10.1016/j.joei.2015.01.022

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Please cite this article in press as: H. Chen, et al., A review on present situation and development of biofuels in China, Journal of the Energy Institute (2015), http://dx.doi.org/10.1016/j.joei.2015.01.022