The amount of municipal solid waste (MSW) collected by local authorities in China has increased in parallel with rapid urbanization. Urbanization in this context means simply an increase in the number of cities and urban areas. The average rate of increase in the amount of MSW collected annually is about 6%.
In 2006, 656 cities across China generated around 148 million tonnes of MSW (Table 1) for disposal in 419 facilities. This is the quantity of waste for disposal after recycling activities in 2006 alone. Unsurprisingly, this sizable amount presents a significant challenge in disposal terms. What options are available for this residual waste?Click here to enlarge image
nullDisposal options for residual waste
Table 2 shows the number and capacity of MSW treatment facilities in China.Click here to enlarge image
In 2006, 43.2% of the residual MSW after recycling was sent to a sanitary landfill, 7.7% was incinerated and 1.9% was composted. The remainder of the MSW was dumped in landfills that did not meet sanitary landfill status.
To reiterate, this breakdown refers to waste handling after recycling activities. At present there is little clear data on the level of MSW recycling across China, though it has been estimated that the MSW recycling rate is about 30%.Progress in the development of MSW sanitary landfills in China
As part of the evolution of landfilling in China and with financial support from state bonds, a number of landfills have been commissioned over recent years that have liner systems. My estimate is that between 1998 and 2007 over 30 million m² of high density polyethylene (HDPE) geomembrane was used in the construction of landfill base liners in China.
The standard of liner design and construction in China is on a par with international standards (Table 3). For example, the construction standard for an impermeable liner in China is close to the standard adopted in Germany and is more stringent than those adopted in the USA and the European Union.Click here to enlarge image
In 2006, China’s Ministry of Construction (now the Ministry of Housing and UrbanRural Construction) initiated an inspection exercise on the status of landfill operations and the classification of landfills according to their level of ‘sanitation’.
This inspection and assessment found that, at the end of 2005, there were 372 active landfills in China with a total waste intake capacity of 194,700 tonnes per day. Of these landfills, 190 were classified as Class II or higher. Their total daily waste intake capacity was 127,500 tonnes. HDPE liners were constructed in most of these Class II landfills. NB: An evaluation formula is used to calculate the score of a landfill. If the landfill scores more than 70 but less than 85, it is classified as Class II.Current limitations in leachate treatment
Although progress is being made in the development of sanitary landfilling in China, several hurdles have yet to be cleared on the way to achieving a more sustainable position.
The wide fluctuation in quantity and quality of leachate and the high concentration of contaminants within the leachate means that in-situ treatment involving a complex design, sophisticated management and a relatively high capital investment are typically required to meet discharge requirements. And while leachate treatment plants can be designed to cope with a greater throughput than actually required (thus ensuring reliability), the practical reality in China is that limited availability of funding and technology means that most leachate treatment plants do not attain their design capacities and hence do not fulfil the actual requirements of daily landfilling needs. As a consequence, leachate management is one of the weaker links in China’s construction and management of landfills.
From a technical perspective, there would need to be a significant increase in operating costs to meet the Class II standard or higher according to the Chinese regulation (Standard for Pollution Control on the Landfill Site of Municipal Solid Waste, GB16889-1997), which requires membrane treatment technology. At the same time, the highest practical level of rainwater/leachate segregation would be crucial; otherwise, a huge amount of leachate would be generated, leading to unbearable treatment costs.Scope for LFG recovery and utilization
Landfill gas (LFG) recovery and utilization benefits the environment by reducing pollution and greenhouse gas emissions. LFG could also be used to generate electricity or other purposes if sufficient is produced. [Editor’s note: for a detailed look at landfill gas utilization in Europe, see Heijo Scharff’s article in the January/February 2008 issue of Waste Management World.]
In China, landfill gas-to-electricity projects are underway in Hangzhou, Guangzhou, Nanjing, Xian, Beijing, Changsha, Wuxi and Jinan. By the end of 2007, 18 LFG utilization projects had been completed and commissioned throughout mainland China. Of these, 15 contain facilities for electrical power generation using landfill gas with a total capacity of 30 MW.
Development is continuing, not least spurred on by applications linked with the Clean Development Mechanism (CDM) of the Kyoto Protocol. As of 16 January 2008, 21 MSW treatment projects had been approved by the National Development and Reform Commission (NDRC; http://en.ndrc.gov.cn/).
That said, while most of the larger landfills have signed agreements in place with foreign companies for LFG utilization, progress in implementation tends to be slow and some projects are still stalled at the agreement stage.
Landfill site in Hangzhou City, Zhejiang Province Click here to enlarge image
In addition to concerns in implementation, there are also obstacles linked with the nature of China’s MSW stream. A relatively high proportion of China’s MSW is food waste, while the proportion of fibre, wood and other slowly biodegradable organics is relatively low. Food waste exhibits the fastest biological decomposition among all waste types; this leads to rapid generation of LFG, hence limiting its collection efficiency. The recovery and utilization rate of LFG is generally <60% in developed countries, but achieving 20% gas recovery in China appears to be difficult.
Landfill site in Guangzhou City, Guangdong Province Click here to enlarge image
Moreover, analyses of operating landfill gas-to-electricity projects in China show that electricity generated through LFG recovery and utilization is approximately 30 kWh/tonne of waste. When compared with the 250300 kWh/tonne of waste that is incinerated, the difference is clear. Hence, the potential for energy recovery from waste disposed in landfills (and LFG) in China can be viewed as fairly limited.1China’s severe shortage in the number of sanitary landfills
The 419 disposal facilities referred to earlier include a total 324 municipal-level landfills, a decrease from the 484 landfills estimated for 2000 (Table 2). Although there are 656 incorporated cities in China,2 many of them do not have their own landfills. Therefore, the demand for new landfill construction is high.
Landfill site in Xiling City, Qinghai Province Click here to enlarge image
If one assumes there is a need for at least one landfill in each county, this would equate to over 1600 new landfills. And over 3000 new landfills would be required if one assumed the need for two landfills on average in each county. Is this level of requirement appropriate? When answering this question, it is helpful to look at what is happening in other countries, i.e. to consider the matter in a more global context.
LFG generator in a landfill site in Guangzhou City Click here to enlarge image
In Germany, there were 8273 MSW landfills in 1990 but only 297 in 2004. This later figure, which is being reduced still further, equates to 0.85 landfills every 1000 km2. Turning to the USA, there were 7924 MSW landfills in 1988 and 1654 in 2005.3 This later figure equates to 0.18 landfills every 1000 km2. Analysis of this data also reveals that, on average, 0.56 and 0.4 landfills are available for every 100,000 people in the USA and Germany respectively. The figures for China show that there is nowhere near this level of landfill space per 100,000 people and there is a reason for this.
Landfill site in Panzihua City, Sichuan Province Click here to enlarge image
Landfill density in China today cannot be as high as in developed countries because its population distribution and economic development are quite different. However, this data does provide useful signposts for China and, based on analyses of land resources and landfill construction standards in China, one might expect the percentage of waste dealt with by centralized management in China to be similar to those in developed countries. So what is the solution here?Is it time to develop a new type of landfill in China?
From the perspective of environmental protection and economics, small-scale sanitary landfills (landfills with a waste intake capacity of <200 tonnes/day, representing most landfills on a county level) are not rational choices in China.
Leachate treatment facility in Qingdao City Click here to enlarge image
Looking at the financial aspects and taking the Three Gorges District as an example, the projected costs in terms of capital investment for a 120 tonnes/day landfill would be >RMB50 (€4.6) per tonne of waste. For a five tonnes/day landfill, the cost would be >RMB100 (€9) per tonne. Considering the additional costs of operation and the fact that the actual waste intake is less than the design capacity, the cost of such a small-scale landfill could be as high as RMB100200 (€918) per tonne of waste. This does not even include the cost of land usage, which is double that of landfill operations in urban areas.
Leachate treatment facility in Beijing City Click here to enlarge image
Turning to environmental concerns, developing small-scale landfills could lead to some pollution problems because of the low-quality treatment of emissions from landfills. This follows on from a lack of capital available to invest in appropriate infrastructure on a small scale. Ensuring satisfactory treatment for leachate from these small-scale sanitary landfills is difficult; as a result, the leachate is often discharged directly into a small sewage treatment plant leading to adverse impacts (it is hard for these small sewage treatment plants to take up the shock load in a short time), or it is just diluted in these plants and discharged into nearby rivers. The capacity of these small-scale landfills to reduce overall pollution impacts is very limited. They also use land resources and cause land contamination issues.How can things be improved?
A large portion of the capital investment for landfills in China is used for site development and construction of the base liner system. Capital costs could be significantly reduced if the design and construction of liner systems were simplified and the amount of land needed was reduced. The operating costs would also be much less if the amount of leachate is minimized and the treatment process simplified.
Landfill site in Harbin City, Helongjiang Province Click here to enlarge image
The ‘bioreactor’ landfill concept from the USA offers a possible way forward.4 Put simply, its principle is to perform composting in a landfill or to construct a composting facility in the form of a landfill.
Landfill site in Beijing City Click here to enlarge image
It is possible to construct a landfill as a passive composting system. In this way, complete fermentation can take as long as a year. Residuals after fermentation can be used as compost or as backfill into the landfill, while the combustible materials retained on a sieve could be gathered and used as fuel. Such a landfill occupies a relatively small area, materials can be recycled and maximum diversion of rainwater from leachate can be achieved (via application of a membrane cover when it is raining). This approach offers an alternative to installing sophisticated leachate treatment facilities and it supports enhanced LFG production.Conclusions
Reviewing the evolution of MSW management in general, waste collection has tended to progress from incomplete collection through to complete collection and finally to collection with separation into different waste streams. In turn, waste treatment has progressed from ad-hoc decentralized disposal to a strategy more dependent on controlled treatment and disposal, including the use of sanitary landfilling accompanied by waste reduction strategies. In developed countries, this evolution has taken place over a period of about 3040 years.
LFG flare in a landfill site in Changsha City Click here to enlarge image
Although the Chinese economy is growing rapidly, a huge economic gap still exists between developed countries and China. The overall status of MSW treatment in China is still in the developing stages, with waste collection going from incomplete to complete collection, and waste treatment going from decentralized disposal to sanitary landfilling. The development of treatment of MSW should adhere to stringent standards, but it should also be pragmatic and innovative.
Xu Haiyun is Chief Engineer at the China Urban Construction Design & Research Institute in Beijing, China.
1. H.B. Raninger. Renewable Energy for Rural Areas in China. GTZ Training, 35 August 2007, ICEEE, Shenyang, China.
2. Department of Integrated Finance Ministry of Construction. China Urban Construction Statistical Yearbook, 19792006.
3. US Environmental Protection Agency. Municipal Solid Waste in the United States: 2005 Facts And Figures. October 2006. www.epa.gov/epaoswer/non-hw/muncpl/pubs/mswchar05.pdf