Cities Worldwide Seek to Produce Recycled Energy

Public transportation like subway or buses in Sweden’s Hammarby sjostad city are running by 100 percent recycled energy. Hammarby sjostad is known as “the city with zero carbon emission.” It is easy to spot people putting bio-gas in their vehicles at every gas stations in Hammarby sjostad city.

Environmentally Confused – Burn or Recycle?

Sweden has had strict standards limiting emissions from waste incineration since the mid-1980s. Most emissions have fallen by between 90 and 99 per cent since then thanks to ongoing technical development and better waste sorting.

Journey of Mixed Emotions

The recycling movement in 1990s-era Vancouver started as a lukewarm way to protect the environment. Then the issues started heating up until it was a sizzling hot topic.

Everyone I knew became a star recycler. We learned how to sort properly, and although I did not always compost, I really tried to be environmentally responsible in other ways. Up until 2001, I was doing my undergraduate degree in biology and I felt it was my duty to understand the issues and be proactive.

In 2005 (give or take) I read Michael Crichton’s book State of Fear. Although there is controversy as to his thesis behind this fictional story, he had some great points about whether we were all jumping on the global warming bandwagon without all the facts. Almost 10 years later I still feel that way on a daily basis.

I am conditioned to recycle. I am often pulling…

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In Delhi, waste generates power — and debate

Panchabuta-Renewable Energy & Cleantech in India

According to reports, by the end of this year, Delhi will have its second waste-to-energy plant generating electricity at the landfill near Ghazipur. A similar plant, Timarpur Okhla Waste to Energy plant, sited in the vicinity of a residential colony and a hospital, has started generation since the beginning of this year.

The Delhi government is buoyant that it has finally found a solution to tackling the ever-increasing piles of waste. No government wants to grapple with millions of tonnes of waste dumped on prime land, polluting the groundwater and the air and threatening to multiply.

Delhi, with limited space, views waste-to-energy plants as a win-win solution. “Energy production is incidental. Our main concern is waste,” says Shakti Sinha, Principal Secretary, Power, summing up the government’s perception of these plants.

“The plants are absolutely safe,” he asserts. “We use state-of-the-art technology, and these are run as per the European Union norms…

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Waste Management in Stockholm

Misc. on land use planning (with a bias on Copenhagen)

I just came across an article in “City, Culture and Society”, dealing with Urban growth and waste management optimization in Stockholm and Adelaide. In Figure 2 in the results section the authors show a comparison of waste management systems in the two cities. However, for Stockholm they present only national data, assuming that this is also representative for the capital. Well, that striked me a bit because I am working with city data quite a lot and was wondering if there isn’t better data out there. In the database Urban Audit, maintained by Eurostat, you can find data for over 300 cities in Europe to a lot of different issues. Stockholm is one of the cities covered and waste data from 2008 was available, so I produced the graph below – in the same style as done in the mentioned article.

If you have access to the article

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The Incineration Debate

Remsol

On Easter Monday, 9th April 2012, the front page of The Times newspaper carried a story about the debate that’s currently raging over whether the UK ought to be building more and bigger incinerators to burn our household rubbish.

Opponents of waste-to-energy incineration insist that it discourages recycling, adds to CO2 emissions at a time when we’re trying to reduce them, and that incineration plants themselves are an ugly blot on the urban landscape.

Proponents, on the other hand, often dismiss these claims as fiction.

I tend to come down on the “for” side of the waste incineration argument, for several reasons, but chief amongst these is the belief that the argument only exists because we, as a society, create waste and crave energy.

According to statistics released by the Department of Energy and Climate Change (DECC) UK electricity consumption for consumer electronics soared by 576% between 1970 and 2010.

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Analyzing Different Waste-to-Energy Technologies

Major components of Waste-to-Energy Processes

  1. Front end MSW pre-processing is used to prepare MSW for treatment and separate any recyclables
  2. Conversion unit (reactor)
  3. Gas and residue treatment plant (optional)
  4. Energy recovery plant (optional): Energy / chemicals production system includes gas turbine, boiler, internal combustion engines for power production. Alternatively, ethanol or other organic chemicals can be produced
  5. Emissions clean up

Incineration

  • Combustion of raw MSW, moisture less than 50%
  • Sufficient amount of oxygen is required to fully oxidize the fuel
  • Combustion temperatures are in excess of 850oC
  • Waste is converted into CO2 and water concern about toxics (dioxin, furans)
  • Any non-combustible materials (inorganic such as metals, glass) remain as a solid, known as bottom ash (used as feedstock in cement and brick manufacturing)
  • Fly ash APC (air pollution control residue) particulates, etc
  • Needs high calorific value waste to keep combustion process going, otherwise requires high energy for maintaining high temperatures

Anaerobic Digestion

  •  Well-known technology for domestic sewage and organic wastes treatment, but not for unsorted MSW
  • Biological conversion of biodegradable organic materials in the absence of oxygen at temperatures 55 to 75oC (thermophilic digestion – most effective temperature range)
  • Residue is stabilized organic matter that can be used as soil amendment after proper dewatering
  • Digestion is used primarily to reduce quantity of sludge for disposal / reuse
  • Methane gas generated used for electricity / energy generation or flared

Gasification

  • Can be seen as between pyrolysis and combustion (incineration) as it involves partial oxidation.
  • Exothermic process (some heat is required to initialize and sustain the gasification process).
  • Oxygen is added but at low amounts not sufficient for full oxidation and full combustion.
  • Temperatures are above 650oC
  • Main product is syngas, typically has net calorific value of 4 to 10 MJ/Nm3
  • Other product is solid residue of non-combustible materials (ash) which contains low level of carbon

Pyrolysis

  • Thermal degradation of organic materials through use of indirect, external source of heat
  • Temperatures between 300 to 850oC are maintained for several seconds in the absence of oxygen.
  • Product is char, oil and syngas composed primarily of O2, CO, CO2, CH4 and complex hydrocarbons.
  • Syngas can be utilized for energy production or proportions can be condensed to produce oils and waxes
  • Syngas typically has net calorific value (NCV) of 10 to 20 MJ/Nm

Plasma Gasification

  • Use of electricity passed through graphite or carbon electrodes, with steam and/or oxygen / air injection to produce electrically conducting gas (plasma)
  • Temperatures are above 3000oC
  • Organic materials are converted to syngas composed of H2, CO
  • Inorganic materials are converted to solid slag
  • Syngas can be utilized for energy production or proportions can be condensed to produce oils and waxes

 

        Net Energy Generation Potential Per Ton MSW

Waste Management Method

Energy Potential*

(kWh per ton MSW)

Recycling

2,250

Landfilling

   105

WTE Incineration

   585

Gasification

   660

Pyrolysis

   660

Anaerobic Digestion

   250

Cost Economics of WTE Processes

Technology

Plant capacity

(tons/day)

Capital cost

(M US$)

O&M cost

(US$/ton)

Planning to commissioning

(months)

Pyrolysis

70-270

16 – 90

80 – 150

12 – 30

Gasification

900

15 – 170

80 – 150

12 – 30

Incineration

1300

30 – 180

80 – 120

54 – 96

Plasma gasification

900

50 – 80

80 – 150

12 – 30

Anaerobic digestion

300

20 – 80

60 – 100

12 – 24

In vessel composting

500

50 – 80

30 – 60

9 – 15

Sanitary landfill

500

5 – 10

10 – 20

9 – 15

Bioreactor landfill

500

10 – 15

15 – 30

12 – 18

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Trends in Waste-to-Energy Industry

NEW DELHI, INDIA - FEBRUARY 18: Indian workers...
Image by Getty Images via @daylife
NEW DELHI, INDIA - FEBRUARY 18: An  Indian wor...
Image by Getty Images via @daylife

Around 130 million tonnes of municipal solid waste (MSW) are combusted annually in over 600 waste-to-energy (WTE) facilities globally that produce electricity and steam for district heating and recovered metals for recycling. Since 1995, the global WTE industry increased by more than 16 million tonnes of MSW. Incineration, with energy recovery, is the most common waste-to-energy method employed worldwide. Over the last five years, waste incineration in Europe has generated between an average of 4% to 8% of their countries’ electricity and between an average of 10% to 15% of the continent’s domestic heat.

Currently, the European nations are recognized as global leaders of the SWM and WTE movement. They are followed behind by the Asia Pacific region and North America respectively. In 2007 there are more than 600 WTE plants in 35 different countries, including large countries such as China and small ones such as Bermuda. Some of the newest plants are located in Asia.

The United States processes 14 percent of its trash in WTE plants. Denmark, on the other hand, processes more than any other country – 54 percent of its waste materials. As at the end of 2008, Europe had more than 475 WTE plants across its regions – more than any other continent in the world – that processes an average of 59 million tonnes of waste per annum. In the same year, the European WTE industry as a whole had generated revenues of approximately US$4.5bn. Legislative shifts by European governments have seen considerable progress made in the region’s WTE industry as well as in the implementation of advanced technology and innovative recycling solutions. The most important piece of WTE legislation pertaining to the region has been the European Union’s Landfill Directive, which was officially implemented in 2001 which has resulted in the planning and commissioning of an increasing number of WTE plants over the past five years.

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Refuse-Derived Fuel (RDF) from Municipal Solid Wastes

  • Solid waste is a growing problem in all countries, and a critical problem in almost all the cities of the developing world. Developed countries have in recent years reduced the environmental impact of solid waste through sanitary landfills and high-temperature incineration, as well as conserving natural resources and energy through increased recycling, but the volume of waste generated in developing countries is rising astronomically. Very few cities have adequate solid waste collection and disposal systems, and the accumulating waste threatens health, damages the environment, and detracts from the quality of life. Therefore, it is necessary to make use of all possible waste management technologies to arrest the degradation of environment and foster waste-to-energy technologies.
  • Urban areas of Asia produce about 760,000 tonnes of municipal solid waste (MSW) per day, or approximately 2.7 million m3 per day. In 2025, this figure will increase to 1.8 million tonnes of waste per day, or 5.2 million m3 per day. These estimates are conservative; the real values are probably more than double this amount. Most common method of disposing of wastes is to dump them in low-lying areas on the outskirts of towns which is very haphazard and unscientific. This has serious environmental impacts like water pollution, methane emissions, and soil degradation.
  • The advantages of the refuse-derived fuel plant type are focused mainly on the relatively higher energy content of the RDF fuel, which originates from the pre-combustion separation processing.
  • RDF plant employs mechanical processes to shred incoming MSW separating the non-combustibles in order to produce a high-energy fuel fraction and thus improved efficiency.
  • One of the most appealing aspects of RDF is that it can be employed as a supplementary fuel in conventional boilers. Furthermore, RDF’s energy content is around half that of UK’s industrial coals and nearly two thirds that of low grade US coal.
  • Pelletization scores over mass-burning, anaerobic digestion and composting because the pellets’ energy content is close to that of coal and can be substituted in local industry.
  • A number of widely employed industrial and utility-scale coal utilisation technologies have the potential to co-utilise RDF and coal, such as large-scale pulverised coal-fired power plant boilers, cement kilns, fluidised bed or stoker-fired boilers, coal gasification plant
  • Due to reduction in fuel particle size and reduction in non-combustible material, RDF fuels are more homogeneous and easier to burn than the MSW feedstock.
  • RDF has been successfully burned in a variety of stoker boilers and in suspension as a stand-alone fuel in bubbling and circulating fluidized bed combustion technology boilers. It needs lower excess air and hence works at better efficiency. Also, handling is easier since non-combustibles have been already removed.
  • In utilizing MSW through a pelletization process, additional tonnage of recyclables will be positively selected to take to that market, assisting the developing regions to work towards sustainable development goals, while positively selecting appropriate materials to mix with purchased high BTU materials in the production of the high BTU pellets, that can be used either to replace coal or coke in industrial processes.
  • RDF is a much more uniform fuel than MSW with regard to fuel particle sizing and heating value resulting in a more efficient combustion process. In addition, a majority of the non-combustible material is removed from the RDF before the fuel is fed into the boiler which reduces the size of both the fuel and ash handling systems. These fuel characteristics result in a RDF boiler system which is generally less expensive than a mass-burn system, thereby offsetting the cost of the RDF processing equipment.
  • It is much easier to transport and store fuel pellets to power plants or industries than raw MSW.
  • Advanced thermal technologies like gasification, pyrolysis, and depolymerization are unattractive to developing countries due to their prohibitive costs.
  • Technologies to control the release of air contaminants have improved substantially in the past decade and that, therefore, the releases from modern RDF plants are not high enough to have negative impacts on human health.
  • Air emissions from incinerators should be compared with air emissions from other methods of generating energy. When such comparisons are made, it is found that natural gas power plants are the cleanest way to generate energy but that emissions from waste incinerators are equivalent to or less than the emissions from a coal or oil power plant.
  • Incinerator proponents also assert that the health risks from exposure to the releases from a RDF power plant are substantially less than the risks from many other common activities.