Waste-to-Energy: Less Trash in Landfills, More Heat and Electricity

9

fernwarme wien3We are living in a world where high consumption has been relentlessly praised, suggesting that we should buy, consume and dispose more stuff than our grandparents used to do. With some nations consuming more than others, the quality and quantity of waste varies across borders. And so does the way it is managed.

A conventional method for waste management is to dump the waste into designated landfill areas where it is left for years without being monitored. Landfill activity remains the most commonly used organized waste disposal method in the world. It is also the easiest and the cheapest. However, brimful landfill sites, hazardous waste and uncontrolled greenhouse gases cause greater environmental and economical impacts. As a simple example, part of the carbon content of the waste when it is dumped into a landfill site, is emitted into the atmosphere in the form of methane, which has a greenhouse effect 20 times greater than that of CO2.

The European Landfill Directive, which was issued in 1999, aims to prevent and reduce the negative effects of landfills on the environment and human health while regulating waste disposal activities in the member states. Germany, Austria, Switzerland and Belgium have already banned disposal of untreated waste in landfills. Alternatively, these countries together with a bunch of other countries, have begun to implement Waste-to-Energy systems.

Waste-to-Energy is the process of extracting heat or electricity from waste sources. The energy extraction can be done through thermal processes (incineration, gasification, pyrolysis or carbonization), biological processes (unaerobic digestion, fermentation) or mechanical biological treatments.

The content and the calorific values of the waste vary in different countries. Plastic bags, food packages and high density plastic materials have higher calorific value per weight thus being more useful for incineration. On the other hand, more organic content or papers are more suitable for biological processes.

waste treatment per capitaI would like to focus on waste incineration as it is currently the most commonly used Waste-to-Energy method. Austria, where I live, has already adopted waste incineration by building 9 plants. About a quarter of the residents in Vienna are supplied by the heat produced from the incineration of municipality waste at 3 different plants. Spittelau Fernwärme in Vienna is probably the most photographed Waste-to-Energy plant in the world because of its famous design by the famous architect Hundertwasser. The 40-year-old building can convert 880,000 tons of waste into heat that supplies 290,000 Viennese apartments through a total pipeline length of 1,000 km. Another incineration plant, Pffaffenau, burns 250,000 tons of waste each year, while supplying district heating to 50,000 households and additionally supplying electricity to 25,000 subscribers.

Denmark ranks first in incinerated waste per capita, as can be observed from the graph. On average, the Danes rank among the nations with the highest consumption rate; nevertheless they are doing good in recycling and reusing waste energy. There are 30 Waste-to-Energy facilities in Denmark. Eurostat datas show that 55 % of Danish municipal waste per capita is incinerated.

According to the Danish Energy Agency, the calorific value of 4 tons waste would equal to 1 tons of oil or 1.6 tons of coal. The incineration of 1 ton of waste produces approximately 2,000 kWh of heat and 670 kWh of electricity. Considering the fact that waste is a local resource and partially consists of biomass, waste incineration appears to be a better and cleaner option.

The potential saving of conventional resources would result in a decrease of greenhouse gas emissions. The emission from a waste incineration plant is less than half that of a coal-powered plant and it is slightly less than that of a gas powered plant.  The content of the exhaust air complies strictly with environmental standards whereas most of the district heating incineration plants are located in the heart of the cities. The hazardous waste (eg. mercury containing wastes, solvents, acids etc.) is treated in a way that the environmental impact is eliminated. At the end of the incineration process, everything, except the metals which are later to-be-recycled, are transformed into ash which can be used in the construction sector.

Waste incineration is a waste treatment method which helps us reduce the environmental impacts of landfill sites, yet it generates heat and electricity as a side-benefit. I recommend reducing our waste generation rather than treating waste as a resource. Initiating a wider plan for municipal waste treatment methods through sharing, lobbying or creating resources is a valuable contribution. Nevertheless, reducing, reusing and recycling are the most important initial steps in order to create a sustainable economy.

[data sources: Eurostat and EPA; photo credit: Flickr; graph by author]

Share.

About Author

9 Comments

  1. By and large waste to electricity is the wrong way to go. Depolymerization technologies can use the same materials to make biodiesel/oil. As transportation fuels have fewer options, waste to oil needs to be the priority.

    • Dear J,

      Thank you for your comment. It is true that there is an ongoing discussion about nano particles on the exhaust air of the waste incineration plants. Those particles appear to be extremely dangerous for health. However, there are ways to remove fine particles via baghouse filters.

      I also found this link related to the same topic:

      http://www.innovations-report.com/html/reports/environment_sciences/report-55679.html

      I am not an expert on environmental issues, therefore I would like to quote the UK Health Protection Agency report;

      You can download the full report called “The Impact on Health of Emissions to Air from

      Municipal Waste Incinerators” report which was published in September 2009:

      http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1251473372218

      Page 6:

      “The contribution made by waste incineration to national emissions of

      particles is low. Data provided by Defra (National Emissions Inventory

      http://www.naei.org.uk) show that 2006 national emissions of PM10 from waste

      incineration are 0.03% of the total compared with 27% and 25% for traffic and

      industry respectively”

    • It all depends on the scrubber with the chimney, but filtering is a common techology. Incineration is fast and the most economical way to eliminate garbage

      Biomass pyrolysis requires more investments and does nothing for minerl materials recovery. However, fly ashes from combustion can be treated and recycled in road bases or cement fillers (following chloride washing and heavy metal stabilization with phosphates for example)

  2. Our company uses a modular, integrated pyrolysis and engine/generator system to eliminate post sorting MSW (municipal solid waste). The front end of the process uses an automated sorting system to recycle the ferrous metals, aluminum, glass and hard plastics. What remains is the 3 through 7 plastics, wood and yard waste, food waste and cellulose (paper and cardboard). These are shredded and used as fuel for the energy recovery process.

    Slow pyrolysis produces a high BTU synthetic gas that is scrubbed of particulate and oily condensates and then fed to a set of highly modified engine/generator sets for power production. The hot exhaust from the engine runs through a proprietary catalytic converter to eliminate 99.9% of the NOx and particulate and then manifolded to the jacket of the pyrolysis unit to maintain its operating temperature. From there, the exhaust is vented either directly to the atmosphere, or it could be used as a CO2 source for a greenhouse.

    The other by-products consist of pyro-char and pyro-oils which have commercial value and are sold. The system will produce about 2.25 Megawatts of power from 50 tons of MSW feedstock.

    We view our technology as a “landfill in a box” with none of the long term problems associated with landfills.

    http://www.randaenergysolutions.com

  3. Some older landfills in our area are now being tapped for methane gases. There are many older (and closed) landfills that can produce methane, and apparently it is not hard to tap it or use it. So maybe we’ll see “methane mining” catch on.

  4. There’s a clear sequential effect not necessarily mentioned.

    Until all the existing landfills are either tapped or no longer producing methane and other greenhouse gases, capturing landfill gas to displace petro in some for or another seems an obvious step for both mitigating emissions and generating energy.

Join the Conversation