A review of energy recovery from waste in China

Waste Management & Research30(4) 432 –441© The Author(s) 2012Reprints and permission: sagepub.co.uk/journalsPermissions.navDOI: 10.1177/0734242X11433530wmr.sagepub.com

China MSW overview

Buekens et al. (2011) conclude that average per capita waste gen-eration in China comes to 118 kg capita −1year−1, a very low per capita rate compared to 524 kg capita−1 year−1 in the EU (Eurostat, 2010) or 762 kg capita−1 year−1 in the US (OECD, 2010). This is a common misconception. Chinese waste statistics cover a mere 661 cities with a total of approximately 614 million inhabitants. Official Chinese statistics showing 157.3 million Mg of MSW in 2009 (CS Bureau, 2010), therefore convert to a waste generation level of around 256.2 kg capita−1 year−1 (Dorn et al., 2010b). Data from rural areas is not available and therefore not included in national statistics, although 54% of the Chinese population lives in a rural setting (amounting to 721 million people (CS Bureau, 2010)). It is estimated that in 2010 there were 160 million Mg of officially accounted for waste, with an additional 65 million Mg of rural waste bringing the actual total closer to 225 million Mg (UN, 2002). Although in per capita terms rural waste quantity is estimated to be very low (90.2 kg capita−1 year−1), the sheer scale and disposal of this untreated waste in unsecured open pits make it a real issue. Clear data is not yet available, however British researchers are currently exploring rural waste generation rates (Moys, 2011).

Additional differences must be taken into account when look-ing at Chinese waste statistics. First of all, MSW generation in larger Chinese cities shows much higher per capita rates com-pared to smaller cities, so one has to distinguish between first-tier

and second- or third-tier municipalities. For example, MSW gen-eration lies at 310 kg capita−1 year−1 in Beijing (Li et al., 2009), or 405 kg capita−1 year−1 in Shanghai (Zhu et al., 2009), 394 kg capita−1 year−1 in Chongqing (Yuan et al., 2006), 427 kg capita−1 year−1 in Hangzhou (Zhao et al., 2009) and 485 kg capita−1 year−1 in Hong Kong (Ko and Poon, 2009). Also contrary to most European countries, municipal waste in China is not segregated in the household and collected separately. MSW in China con-tains cooking briquette ashes, household waste, kitchen residues, garden waste from public parks and green areas, street cleaning waste and even rubble from construction sites (Figure 1). In a 2009 study comparing Chinese to European MSW fractions, Raninger (2009) found that wet organic waste (food and kitchen waste) accounted for 78% of MSW (compared to the respective European figure of 12%), dry organic waste (wood, paper, yard waste, composites) made up for 10% versus 47 % in Europe, and non-biodegradable waste (plastic, metal, glass, ash) came to 12% compared to a share of 41 % in European MSW (Raninger, 2009).

A review of energy recovery from waste in China

Thomas Dorn1, Sabine Flamme2 and Michael Nelles1

AbstractAlthough municipal solid waste (MSW) disposal in Europe and other developed countries has led to a widespread production of solid recovered fuel (SRF) and its incineration in various technical combustion processes, such developments have not yet occurred that widely in developing and transitional economies. This article puts mass-burn technologies and SRF into a China perspective, reviewing issues from technology application problems to emerging trends and future perspectives. Over the last two decades, growing waste volumes have prompted a move to waste incineration, especially in the large densely populated first-tier cities. However, with an organic fraction above 70% and a resulting water content of up to 65%, it is still argued that MSW in China is too moist for incineration. The introduction of mechanical biological treatment (MBT) or mechanical physical stabilization (MPS) technology for SRF production could provide the solution, either by offering further pre-drying options to mass-burn incinerators or by creating SRF to be burnt in co-incineration plants. First experiences of MBT and MPS technologies show promising results in terms of the capacity to deal with organic waste fractions, but the further disposal/utilization of the plants’ output stream has not yet been fully addressed.

KeywordsEnergy recovery, China, MSW disposal, solid recovered fuel, mechanical biological treatment, mechanical physical stabilization, technology transfer

1Universität Rostock, Rostock, Germany2Fachhochschule Münster, Münster, Germany

Corresponding author:Thomas Dorn, Celebrity Garden C 58, Che Xin Rd. 2, 201612 Shanghai, P. R. ChinaEmail: [email protected]

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Dorn et al. 433

One reason for this waste characteristic is the efficient recy-cling rate achieved by private waste pickers working in the infor-mal recycling sector. The vast majority of materials with a commercial value (cardboard, paper, plastic, wood, glass, etc.), is collected prior to entering the MSW stream (Dorn et al., 2010b). The commercial value of these recyclables is shown in Table 1.

The consequence is that the public sanitation bureaus in charge of MSW disposal are left with the ‘non-valuable’ kitchen and street cleaning waste. This is a strain on their financial resources as money is required to dispose of the waste, but hardly any revenue can be achieved.

From 2003 to 2006 the number of waste treatment and dis-posal facilities shrank by 27%, from 574 to 413 facilities. Total

capacity however, rose by 17.5% to 258 000 Mg day−1 during the same period, indicating that more modern and efficient disposal units were being put into operation. By 2009 the number had risen again, to 567 facilities comprising 93 waste-to-energy (WTE) plants, 16 composting plants and 447 landfill sites. The daily treatment and disposal capacity increased to 356 130 Mg day−1 of MSW (CS Bureau, 2010). Assuming the facilities ran at a 90 % capacity, 365 days a year, this would allow an annual 117 million Mg of MSW to be properly disposed of, i.e. 74.4% of the statistically accounted for 157.3 million Mg of waste, or 52% of the estimated total 225 million Mg generated in China. Buekens et al. (2011) refers to 62.9% of MSW disposed of in a controlled way for 2007 with a mere 9.6% being incinerated. The 2009

Figure 1. Residual waste composition in Shanghai & Hefei (Source: Chen et al., 2005; Dorn et al., 2010b).

Table 1. Market prices for recyclables (Source: Dorn et al., 2010b).

Material RMB selling pricea unit−1 Euro selling priceb unit−1

Plastic bottles (branded) 0.22 per piece 0.024 per piecePlastic bottles (other) 0.10 per piece 0.011 per pieceOther plastic 0.80 kg−1 0.089 kg−1

Polyethylene 0.60 kg−1 0.067 kg−1

Polypropylene 0.80 kg−1 0.089 kg−1

Plexiglas 0.95 kg−1 0.105 kg−1

Waste iron 0.90 kg−1 0.100 kg−1

Sheet metal 0.20 kg−1 0.022 kg−1

Brass 9.30 kg−1 1.032 kg−1

Copper 15.00 kg−1 1.665 kg−1

Aluminium cans 0.11 per piece 0.012 per pieceGlass bottles 0.10 per piece 0.011 per piecePaperboard 0.70 kg−1 0.078 kg−1

Newspaper 0.95 kg−1 0.105 kg−1

Books and periodicals 0.70 kg−1 0.078 kg−1

TV sets 5–280 per piece 0.555–31.08 per pieceRefrigerator 30–150 per piece 3.33–16.65 per pieceWashing machine 10–90 per piece 1.11–9.99 per pieceAir-conditioner 110–800 per piece 12.21–88.8 per pieceVCD player 50–100 per piece 5.55–11.1 per piece

aPrices vary from city to city.bPrices vary from city to city; approximate conversion at current exchange rate (1 euro = 9 RMB)



434 Waste Management & Research 30(4)

statistics of the CS Bureau (2010) account for 89 million Mg MSW disposed of in landfill sites (80%), 20.2 million Mg MSW incinerated (18.2%) and 1.8 million Mg MSW composted (1.6%). The 111 million Mg total indicates a capacity utilization of 85.4%. In addition to this utilization shortfall, there is also the question of the disposal of waste not included in the official sta-tistics, namely MSW generated in remote or rural areas.

It is safe to assume that 50% of the MSW generated in China is dumped without prior treatment, with all the obvious conse-quences in terms of environmental degradation, public health risk, potable water contamination, methane generation, and cli-mate change implications due to green house gas emissions.

Waste incineration in China

Currently 18.2% of the officially accounted for MSW is com-busted while 80% still goes into landfills untreated (CS Bureau, 2010). Chinese municipal authorities acknowledged in the late 1990s, that the combustion of MSW through incineration plants offers several advantages over land filling, but there are also drawbacks: the high investment costs for incineration plants; the need for trained manpower; the need to treat flue gas; and man-agement and disposal of bunker leakage water and ash, as these contain highly toxic elements.

Waste to energy plants (WTEs) have been growing in num-ber, driven by land scarcity and a tremendous growth in the vol-ume of waste, as well as environmental factors such as water table contamination, fire and explosion hazards, and residential unrest due to foul odours emanating from dump sites. This trend is especially significant in the more developed cities along China’s East Coast belt. The majority of plants are thus found in the Bohai Area (Beijing–Tianjin), the Yangtse River Delta (Nanjing–Wuxi–Suzhou–Shanghai), and the Pearl River Delta (Guangzhou–Hong Kong). The target for these municipalities has been not so much energy recovery but volume reduction. Statistics are unclear about the actual number of WTEs in opera-tion. Buekens et al. (2011) account for 63 in the year 2005, whereas Chinese statistics refer to 67 (year 2006 in CS Bureau, 2010). Independent discussions with the association of Chinese WTE operators, has led to the figure used below: 61 plants in operation in 2009, with construction ongoing for a further 40 plants (Dorn et al., 2010a).

The University of Rostock (Dorn et al., 2010a) conducted a study on the status of waste incineration in China between 2009 and 2010. Within the framework of this study, 30 WTEs were shortlisted for visits during April and May of 2009, however many plants do not allow visitors. As a result, only 15 of the 61 plants in operation in 2009 [as of September 2011 there are over 100] could be visited (see Table 2). Many of the plants that do not allow visitors belong to operators who have a reference plant which is proudly displayed. Operators are quite selective about which plant is shown to whom, as most of the plants are run with a much higher coal co-firing content than officially admitted. These private WTE operators seek to maximize profits by selling electric energy from the majority of their WTEs. This can only be achieved with a higher calorific value and better thermal recov-ery to run steam turbine generating sets, thus the ratio of waste to coal is changed to achieve optimum power generation as opposed to optimal waste disposal.

Incineration technology applied in China

Three main incineration technologies are used in China (Figure 2). Most large cities use the stoker grate technology. Stoker grate WTEs typically have a daily capacity of 1000 to 1500 Mg day−1, each line with a maximum throughput of 500 Mg day−1. Early plants were imported through Mitsubishi-Martin (Shenzhen, 1988) as well as Alstom (Shanghai, 1999) and Noell (Ningbo, 2001). The investment costs of these plants were approx. 70 000 € Mg−1 day−1 (at September 2011 exchange rates) and proved to be a heavy burden for the municipalities (Li et al., 2002). Today, this technology is typically chosen where space constraints apply (i.e. in large urban agglomerations) and the emphasis is to reduce waste volume. An economically viable operation can only be ensured where municipalities are prepared to pay tipping fees, as power generation and respective electricity sales revenue cannot cover the operating costs. These tipping fees range from 85 RMB Mg−1 (Ningbo) to 247 RMB Mg−1 (Shanghai) (10 and 29 € Mg−1 respectively, at September 2011 exchange rates; Dorn et al., 2010a).

Fluidized bed furnaces were brought to China from Japan by Ebara (Li et al., 2002). The 200 Mg day−1 plant in Harbin had investment costs of 90 000 € Mg−1 day−1 at current (September 2011) exchange rates (Li et al., 2002). Fluidized bed furnaces

Table 2. Waste incineration plants for MSW in China 2009 (Source: Dorn et al., 2010a; Yang, 2007).

Technology Plants Capacity (Mg day−1) Furnaces Output (MW) Generators

Stoker Grate 32 28 200 83 441 46international 27 24 470 68 386 39local 5 3 730 15 55 7Fluidized-bed 15 11 300 36 261 26international 4 4 300 12 75 8local 11 7 000 24 186 18Others 14 7 225 32 25 5Total 61 46 725 151 702 77



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have a smaller capacity ranging between 100 and 500 Mg day−1. Plant configuration is also different compared to stoker grate technology. Fluidized bed furnaces require a thorough sorting process to separate out inert waste fractions and a shredder fur-ther down the line prior to the feeder into the furnace. This tech-nology is widely applied in cities with less stringent space constraints and operational costs can generally be covered through power generation and electricity sales. Incentives offered by the Chinese Government further promote this technology. By co-feeding MSW into the coal-fired combustion process, power generation units can claim ‘renewable energy status’ and receive the subsidized energy price of 0.55 RMB kWh−1 (approximately 0.06 € kWh−1), as opposed to the standard 0.33 RMB kWh−1 (approx. 0.04 € kWh−1) (currency exchange rate September 2011) paid to power stations solely fired by coal (China Renewable Energy Law, 2006).

Both of the above-mentioned technologies do not further uti-lize the heat generated. Waste heat boilers to provide thermal energy to a variety of applications are quite common in Europe. The most prevalent utilization is district heating, which further raises the energy efficiency of European WTE plants. WTE dis-trict heating in China is unknown, as heating is not common in southern China (south of the Yangtze River) and even north of the Yangtze River tariff and supply regulations do not exist (Dorn and Nelles, 2010).

A third technical concept was brought to China by Canadian rotary kiln builder Richway (Li et al., 2002). Data received from the association of Chinese WTE operators indicate plant costs of 34 000 € Mg−1 day−1. Only a few of the plants were installed to incinerate MSW. Today, where implemented, the rotary kilns generally have a capacity of under 100 Mg day−1 and are used in hazardous waste applications (e.g. Hangzhou DADI) (Ma et al., 2011).

Buekens et al. (2011) report an equal market share for grate and fluidized bed furnaces at 40% each in the year 2005. In their study of 2009–2010, Dorn et al. (2010a) found that in 2008 stoker grates held an approximately 60% market share, with fluidized bed furnaces holding approximately 33%, and rotary kiln tech-nology accounting for the final 7% market share. Taking into account ongoing construction projects reported by the associa-tion of Chinese WTE plant operators, one can estimate the shares to be more equal again at 45% each for grate-based incinerators and fluidized bed furnaces in 2010.

Digestion, absorption and adaptation of foreign technology

It should be noted that larger stoker grate plants do not generate more electric power in China in comparison with smaller fluid-ized bed furnaces, as they were designed for waste fractions con-taining a much higher calorific value of 5–7 MJ kg−1. Research by Dorn et al. (2010a) in Hefei, Shanghai and Beijing showed that due to the high content of wet organic fractions, the average lower heating value of Chinese MSW ranges from 3 to 5 MJ kg−1, as opposed to the 6–7 MJ kg−1 typically required to obtain a smooth combustion process. In addition to cost-saving efforts with regard to co-firing fuel, this has caused Chinese research and design institutes to develope measures to improve and adapt foreign designs in conjunction with foreign manufacturers.

MSW receiving bunkers have been enlarged to hold waste for 5–7 days instead of 2–3 days. Within 5–7 days up to 20% of the MSW’s water content collects as leachate, leading to more effi-cient drainage systems being designed to facilitate drying. Further developments to combat challenges presented by the MSW’s high water content are hot combustion air re-circulation into the hopper or pre-heating of combustion air, which is led

Figure 2. Waste-to-energy with grate and fluidized bed furnaces (Source: Dorn et al., 2010b).




through the waste inlet. In order to allow for further drying and longer combustion time, an extension in the length of the stoker grates is usually found in Chinese WTE plants, from the standard European 7–8 m to up to 12 m in length. Last but not least, insu-lation walls have been reinforced to up to double their European thickness in order to keep thermal losses to a minimum.

Parallel to these developments, the effective localization of the manufacturing of components led to a significant reduction in costs. Stoker grate technology made in China (e.g. Weiming) is now available at 29 000 € Mg−1 day−1 (at September 2011 exchange rates), about 40% of the initial cost.

Similar to the grate technology, and as an innovative response to the implementation problems described above, China adapted fluidized bed furnaces to implement waste-co-firing. Beijing Qinghua University (Dorn et al., 2008) and Hangzhou Zhejiang University (Buekens et al., 2011) are leaders in that field. At Beijing Qinghua University, innovative incineration technology has been developed by local engineers adapting Western technol-ogy to enhance the operational efficiency of equipment in China. The developments led to the creation of four new patented tech-nologies. The potential impact of these innovations along with other Chinese innovations in this sector spans beyond China, enhancing waste treatment options for the developing world as a whole. The technology designed at Qinghua University and implemented in Changchun combines the best of both models: the foreign stoker grate technology as well as the fluidized bed design. This results in a technology that can cope with high water content while requiring only minimal waste sorting and that makes it highly relevant for application not just in China, but also in other developing countries. The grate design of the integrated dryer and feeder in Changchun allows MSW to be fed and dried simultaneously. Cheng et al. (2007) describe the three drying stages used to reduce moisture content to less than 10% before

waste enters the combustion chamber. They allow the incinerator to be adapted to MSW with a moisture content of up to 55%.

Unlike in standard CFB incinerators, only simplified pre-sort-ing is necessary, and waste with particle sizes up to around 50 cm can be incinerated without the need for shredding. Separation occurs through a magnetic separator and air classification, removing metals and bulky materials before the waste is depos-ited in the bunker. The bunker, where garbage is left for up to 2 days, has the added benefit of reducing water content before the waste is dropped onto the feeder via a clamshell crane (Figure 3).

Imported incinerators generally use diesel as a supplementary fuel, but this is an expensive measure. The model from Qinghua University deals with this by co-firing with pulverized coal fed into the combustion chamber via a screw conveyor, using diesel only to start the combustion process (340–400 kg of light diesel per startup), thereby lowering operational costs considerably. This technology requires an average fuel to MSW ratio of 12–17%, as measured from July 2005 to December 2006 (when con-verted into coal equivalents) (Cheng et al., 2007). The fuel to MSW ratio is very important for the overall profitability, follow-ing the ‘Recognition and Management Measures for the National Encouragement of the Comprehensive Utilization of Natural Resources’ issued by the Chinese State Development and Reform Commission on 7 September 2006. Based on that, WTE plants which have a coal/waste weight ratio of over 20% are regarded as a conventional power generation facility, meaning these are not eligible to receive subsidized electricity prices. This can make a difference of 0.15 RMB kWh−1 (0.018 € kWh−1 at September 2011 exchange rates). Fluidized bed furnace technology devel-oped at Zhejiang University in Hangzhou or the technology from Qinghua University is typically available for 30 000–31 500 € Mg−1 day−1, which is about one-third of the investment costs of the first WTE plant installed.

Figure 3. Schematic diagram of Changchun incineration facility (Reproduced from Cheng et al., 2007 with permission from American Chemical Society).



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A similar development has recently been reported for the rotary kiln technology applied in hazardous waste incineration, where the State Key Laboratory of Clean Energy Utilization at the Zhejiang University in Hangzhou has again played a key role (Figure 4) (Ma et al., 2011).

The incineration system consists of a rotary kiln, a stoker grate furnace and a post-combustion chamber. A crane feeds the waste from the bunker into a hopper. From there it is transferred by hydraulic feeder into the rotary kiln, where the waste is heated, de-volatilized and combusted. A gate system seals the rotary kiln during feeding to avoid contamination through hazardous gases. During plant start-up and shut-down a diesel burner, located at the front section of the kiln, ignites the waste; it also operates in case the furnace temperature drops below 800 °C. Energy recov-ery comes in the form of a waste heat boiler and an air pre-heater. The exhaust gas leaving the post-combustion chamber is cooled by the waste heat boiler from 1100 to 550 °C. An air pre-heater is put into the last section of the waste heat boiler. Air to be injected into the front section of the rotary kiln and the centre of the stoker grate furnace is pre-heated to 200 °C. The steam generated by the boiler is then used for various heating requirements (e.g. waste oil recycling) (Ma et al., 2011).

New developments in the Chinese waste sectorThe current status of solid recovered fuel in China – Chinese research background

The first ideas of solid recovered fuel (SRF) production in China were born out of the necessity to make space for more land fill-ing. In order to gain space in overflowing landfill sites and to raise the calorific value of MSW to a level at which complete

combustion is achieved without costly co-firing, Chinese experts are increasingly promoting the application of mechanical and biological waste pre-treatment. Biological dry-stabilization or mechanical-physical processes are applied to this end.

An example of Chinese research direction is the work con-ducted by Chen et al. (2007). In 2007, Chen et al. stated that aged MSW requires mechanical excavation prior to re-treatment and final utilization irrespective of its origin – from illegal dump sites or un-safe landfills. They proposed that the old MSW is first sep-arated into various fractions, before combustibles are used to pro-duce SRF. For this purpose the fractions are to be shredded and blended, with potential catalysts added to reach a homogenous mixture with stable qualities and in order to help acidic gas emis-sion control. A chemical analysis of combustibles showed that contaminants such as sulfur and chlorine were still high, prompt-ing Chen et al. (2007) to propose the addition of CaO (8% of the total weight), to reduce the formation of acidic gases when com-busting the SRF. Whether this is necessary, or whether proper treatment of flue gas would solve the problem remains to be seen.

In their study, Chen et al. (2007) conclude that the low mois-ture content of the aged MSW enables incineration of the derived SRF without any further pre-drying. Furthermore, when mixing the SRF with fresh MSW in waste incineration plants (in both fluidized bed incinerators and grate-furnace incinerators) the bet-ter combustion behaviour would lead to a faster evaporation of remaining moisture in the fresh MSW. According to Chen et al. (2007), the calorific value of the SRF is approximately 16.5–17 MJ kg−1 after a two-stage separation process that enriches plas-tics, rubber and other combustibles (Table 3).

Compared to fresh MSW, an increase of the lower heating value (LHV) of up to three times could be achieved. This would mean avoiding the costly addition of primary fuels otherwise necessary to stabilize combustion. With well thought out

Figure 4. Hazardous waste incinerator scheme (Ma et al., 2011).




technology transfer and cost-effective and environmentally sound synergies, MPS technology and MBTs producing SRF could provide a solution that will prevent bio-organic fractions ending up on a landfill. These waste components would be ren-dered inert, effectively preventing methane emissions and green-house gas build up. Indeed, the hope for MBTs is great, as they could also allow existing landfill sites to be rehabilitated, allow-ing for new space for landfilling by recovering and re-using par-tially degraded MSW.

Relevance of MBTs and SRF to China – energy from waste

Despite all the WTE measures described above, most of the energy content from Chinese MSW is used to evaporate the high water content rather than superheating the turbine’s steam circles. Given that water reduction during firing accounts for 80% of weight and volume loss, it is not surprising that fluidized bed tech-nology is the preferred technology. Typically, MSW is pre-sorted manually as well as through sieves and ballistic separation for inert and non-burning fractions (ash, stones, rubble, glass, metals) and then shredded to particle sizes < 200 mm to allow for a con-tinuous feeding into the furnace. This process alone enhances the calorific value by separating out non-combustibles.

Because of the different waste preparation within MBTs, these plants could help in tackling the amount of bio-organic waste fractions in China effectively, while at the same time providing a welcome renewable energy source. As any waste incineration in China, whether mass-burn WTE or WTE of SRF, is considered to provide ‘renewable energy’, MBTs and MPS are in line with Government goals of achieving 11.4% renewable energy as a percentage of total energy consumption by 2015, as published in the 12th Five-Year-Programme, of March 2011 (Xinhua, 2011).

The terms ‘solid recovered fuel’, ‘refuse derived fuel (RDF)’ and others are often used and defined differently in practice, due to the lack of a precise and legally binding terminology. This arti-cle uses the definition of SRF as provided by the ‘Gütegemeinschaft Sekundärbrennstoffe und Recyclingholz (BGS) e.V.’ in Germany, which generally differentiates SRF into ‘high calorific fractions’ and ‘SRF for co-incineration’ (Flamme and Geiping, 2012).

SRF for co-incineration is defined by the BGS e.V. (Flamme, 2008) as ready-for-use combustibles derived from production specific waste or municipal waste after an extensive condition-ing. This conditioning can be achieved by ballistic separation or additional near-infrared technology. The aim of the conditioning is to produce a fuel with a defined quality, which is suitable for

the co-incineration in cement-, lime- or power plants. SRF for co-incineration usually shows grain sizes < 20 mm, with a caloric value from 20 up to 25 MJ kg−1 and a specific moisture of 10 up to 15%. SRF for co-incineration is produced predominantly in a blow-able form (fluff), enabling the combustion during the flight phase of the material after entry into the combustion chamber.

The primary applications of SRF (in cement plants and co-firing for electricity) are also in line with China’s requirements. The building industry has been booming for the past decades and no slow down is in sight, as investments and development moves inland with the Go West Policy (Basmajan, 2010). SRF could thus pose a very specific benefit to a key high-energy industry in China. China currently relies on domestic coal resources and to a growing extent on imported coal, however Chinese coal has a low calorific value and a high ash (10-40%) and sulfur content (0.3–2.4%) (Lillieblad et al., 2006), which causes considerable environmental problems leading China to displace the USA from its spot as the number one CO2 emitter. Co-firing of SRF would thus pose both a domestic and international benefit to China, as non-renewable resources are saved and because co-firing with a separated and dried organic waste fraction is categorized as a carbon-neutral component in the country’s emissions balance.

New technologies introduced to China

To date, a few SRF projects have been put into operation in China, however, as laid out in the current 12th Five-Year Programme (Xinhua, 2011), environmental protection, protec-tion of non-renewable resources, climate change, and recycling are becoming a part of the Chinese Government’s economic and political strategy. As a result, there are now a number of Chinese cities looking for sustainable solutions to dealing with their MSW, leading to an increased interest in alternative solutions by local and provincial authorities and many opportunities for for-eign-led pilot projects around China.

MBT plants

One pilot project started in 2007 is the biological treatment plant for MSW in Gaobeidian city (Hebei Province). It was contracted by a German-Chinese joint venture, designed by the Technical University of Braunschweig (Department of Waste and Resources Management), and financed with assistance from the KfW devel-opment bank. The facility was approved as a lighthouse project for GHG mitigation by the German Federal Ministry of Environment in 2009, and funded by the German government’s

Table 3. Combustibles in ten-year-old MSW from Laogang Landfill (dry basis, impurities included) (Chen et al., 2007).

Component C (%) N (%) H (%) S (%) Cl (%) O (%)

Plastic 77.21 < 0.3 12.36 3.305 0.425 −Rubber 46.54 < 0.3 5.2 4.235 0.407 14.52Wood and bamboo 42.67 1.035 6.01 3.19 0.365 40.85Clothes and fabric 57.78 < 0.3 6.72 2.305 0.184 25.59



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international climate initiative. The facility is scheduled to go into operation in 2011, with an annual treatment capacity of 40000 Mg MSW. The total emission reduction is expected to amount to 80 000–250 000 Mg CO2 equivalents over a 10-year period (Kölsch et al., 2011).

The MBT plant will consist of a mechanical and a biological treatment step to segregate valuable fractions (paper, plastics), and enrich the organic content. The waste stream is to be split into three fractions (fine, medium, and coarse). Based on the waste analysis conducted, the medium fraction is expected to consist mainly of organic materials after going through manual sorting stations along with the coarse fractions. This is to be con-verted into compost. The fine fraction will undergo biological treatment (aerobic, actively ventilated stabilization) prior to final disposal, potentially as an additional landfill cover. Biological treatment will generate a stabilized biomass with an expected res-piration activity of less than 5 mg O2 kg−1. The coarse fraction is to be crushed and fed back into the waste stream or directly dis-posed of at the landfill site (Kölsch et al., 2011). Earlier experi-ences by agricultural enterprises with waste-derived compost have been disappointing, as the non-segregated collection leads to a high contamination with pollutants and heavy metals. As such, it is highly unlikely that compost from Gaobeidian will be further utilized, for example as a fertilizer. At best, it may be used as backfill material or end up in a landfill.

In 2009 Shanghai city started its own MBT project in the south-western district of Songjiang, with design and engineering input by Tongji University experts. The author, living just 3 km east of the plant, got a chance to visit the nearly finished plant in July 2011. A 64 000 m² plot to house the newly built plant was chosen adjacent to the Songjiang landfill. The plant is comprised of a waste delivery section and a bag cutting section with a pre- separation line to sort out inert waste fractions as well as non-organics. The non-organic material is further led through sieves and separation steps, so that plastic materials can be gathered for recycling in the plastics industries. Other waste fractions such as paper, rubber, textiles and wood chips are used for SRF produc-tion. Organic materials are transferred to the large rotting hall where, heaped into clamps, the waste rots for a period of 17 days. Ventilation is provided through a grate system on the floor, which is also used to drain leachate. To avoid foul odours, the hall’s air is extracted via a suction system installed under the roof and fed into bio-filters filled with wood chips. Following this treatment, material is sieved again and packed as compost. Leakage water from the organics is collected underground and channelled into a wastewater treatment plant with bio-gas generation. It is envis-aged that the biogas can fuel a gas engine and generate power to lower the electricity costs of the plant (Lu et al., 2011).

The plant capacity is designed to dispose of up to 1500 Mg day−1 of MSW. The expected output of SRF is between 100 and 200 Mg day−1, plastic material for recycling 100 to 200 Mg d−1, and up to 100 Mg d−1 of compost. The water treatment plant is designed to clean up to 800 Mg d−1 of leachate, reflecting the needs brought on by waste which can show a water content of up to 70%. Operators are still unsure what will become of the

compost, as there is no demand or market for it. Most likely it will be disposed of in the adjacent landfill. The future of the SRF produced is also unclear: it might be burnt in Shanghai WTE plants, or in a nearby coal-fired power station. So far, only the destination of the recyclable faction is known, as several small-scale factories using such materials operate in Songjiang.

Mechanical separation plants

One of the earliest examples of a Sino-German mechanical treat-ment plant is in Beijing, put into operation in 2008 with a throughput of up to 2500 Mg day−1. The primary goal of the plant is to sort out the high calorific fraction of MSW and make this transportable by turning it into SRF bales. Due to the financial crisis, the plant changed hands several times after opening and was even temporarily closed down. Operation finally started in the autumn of 2010, and the plant has since been processing approximately 2000 Mg day−1 of MSW collected in northern Beijing. The major obstacle now is the non-existent market for SRF bales, leading to an almost overflowing storage today.

MPS plants

Another German company is about to conclude a partnership with the Shenyang and the Hefei municipal governments to establish a MPS plant using mechanical physical treatment. Aim of the tech-nology is to produce high calorific SRF out of Chinese MSW with non-separated organic fractions that contain a high humidity prior to treatment. After treatment, during which an important step is the drying of wet organic fractions in a revolving drum dryer by hot flue gases from a power station, and production of SRF, the SRF is to be burned in the neighbouring coal-fired power station. As coal-fired power stations generate a lot of heat that otherwise would be wasted, such waste-heat is well suited to being utilized for the mechanical-physical processes, meaning no additional fuel is required to dry the wet organic waste fractions. This further enhances the climatic efficiency as well as the energy efficiency of the whole waste treatment system. Reference plants of the German supplier are already in operation in the north of Germany’s capital, Berlin (Schu and Schu, 2007).

In Shenyang as well as Hefei, processes are being adapted to consider the particularities of Chinese MSW and reach commer-cial viability. This relates to both, the waste-heat utilization in the drying of wet organic components, as well as reducing energy consumption in the shredding and blending processes. Furthermore, the SRF should substitute costly primary fuel; pric-ing versus the coal costs will have to be fixed between the partners.

SRF utilization: cement plants

On 18 January 2011, a Sino-German Joint Venture (JV) company between FAW and Remondis Co. held the opening ceremony for its first project in China. The main business scope of the JV is the collection, treatment, disposal and recycling of industrial




hazardous waste from the painting process in automotive plants. The company is the first of its kind in China, producing SRF generated from solid and liquid hazardous waste such as solvents and paint residue by coagulation and filtering plants. By recy-cling hazardous waste and rendering it harmless to provide the recycled product to a local cement plant of the Yantai Group, the company not only saves energy and protects the environment, but also reduces the consumption of natural resources and improves the efficiency of national resources utilization.

Chemical and hazardous waste accounts for approximately 12% of SRF fuel burnt in cement kilns (Cement Sustainability Initiative, 2005). Spent solvents and paint residues are character-ized by an energy content of 15–40 MJ kg−1. Depending on the actual lower heating value, 1.3–1.8 Mg of SRF can substitute 1 Mg of coal.

On 7 April 2011 Lafarge Shuion Cement and Zunyi, Guizhou Province Government signed a strategic cooperation agreement on further promoting the concept of a circular economy in the field of cement production. Lafarge Shuion concluded a co-oper-ation with the Zunyi Government for the disposal of MSW and sludge treatment in their cement kilns. As a first step, the com-pany, the largest cement producer in southwest China, will invest in state-of-the-art technology to produce SRF as an alternative fuel from MSW. The plant will consist of a sorting and shredding section, in which inert material is separated from SRF fractions. A rotary drum dryer is used to reduce the water content of SRF. Construction is expected to be concluded in 2011, with a process-ing capacity aimed at 200 Mg day−1 of MSW (Lafarge, 2011).

It is expected that up to 1.5 Mg of coal can be substituted by 1 Mg of the SRF. The final result however, will depend on the homogene-ity of MSW as well as the lower calorific value of Chinese MSW.

A similar project has been reported by Heidelberger Cement of Germany. At their plant in Guangzhou, combustion of SRF gained from waste water sludge has been increased to 600 Mg day−1 (Euwid, 2011). Lafarge and Heidelberger are using high-pressure pumps to feed sludge directly into kilns, thus avoiding a pre-drying process.

The emission of toxic and environmentally harmful sub-stances is a valid concern related to the incineration of SRF and hazardous materials. So far no emission tests have been pub-lished. One reason for this is the absence of any rules or guide-lines governing such emissions from cement kilns. Contrary to emission limits governing the incineration of hazardous waste mentioned above, cement plants (according to Chinese standard GB 4915-2004) only have to use bag filters when burning SRF. Limits to be met apply to dust emission (30–50 mg m−3 h−1), SO2 (200 mg m−3 h−1), NO2 (800 mg m−3 h−1) and fluorine (5 mg m−3 h−1) (China Standards, 2004).

Outlook: the future of SRF in China

While energy and waste markets are increasingly influencing each other in developed economies, the situation in developing markets is quite different. In developing countries and in China in

particular, SRF is still at the very beginning of market penetra-tion. First studies have been undertaken by Tongji University and others, and several European waste disposal entities are consider-ing the technical and economic viability (Lu et al., 2011). The conditioning steps for the waste input, both before and after bio-logical treatment, have been an area of performance enhance-ment too. Improvements in biodegradability and the drying of wet bio-organics have enabled the efficient exploitation of the high calorific fraction in industrial combustion plants (Nelles et al., 2011). The first results look promising, with SRF potentially offering a solution to chronically wet municipal waste, enhancing calorific value, and getting rid of organic content. Other ‘input improvements’ have come in the form of optimization of MSW separation prior to the creation of the SRF (e.g. separating ferrous and non-ferrous metals), thereby enhancing the energy efficiency of the entire process and making it more environmentally friendly.

Beyond the economic view, the resulting climate and resource protection should also be factored into the equation. Indeed, the most energy-effective design should be the aim. The degree of efficiency of a combustion facility is an essential part of this, as the higher the effectiveness, the more energy will be converted into electricity and steam. The efficiency of industrial combus-tion plants or large power plants is usually higher than the effi-ciency of waste incineration plants. As such, the co-incineration of SRF should be further developed. Present ecological balance studies also conclude that CO2 reduction is higher when the energy input is used more efficiently (Plöchl et al., 2008).

Nevertheless, one must not forget that incineration and mass-burning (energy-from-waste) incinerators, a term coined by the local Chinese media, are controversial issues today. Even in China, where public opposition to government projects is scarce, an anti-incineration movement has formed in many of the large first-tier cities. In industrialized countries, several jurisdictions have decided against incineration, instead looking to other emerging thermal treatment methods such as fixed-bed gasification, fluidized bed gasification, and pyrolysis. Critics state that these options have similar drawbacks to regular incin-erators and energy-from-waste plants. All of these technologies emit exhaust gases into the environment, thus requiring an elab-orate flue gas cleaning process to mitigate risks from pollutants. The transfer and implementation of these technologies must not be forgotten or underestimated when promoting MBT and MPS technologies to further SRF incineration or SRF co-incineration in China.

FundingThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

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A review of energy recovery from waste in China

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