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What is both sustainable and renewable that makes financial sense today?

December 27, 2011

The answer is: Municipal solid waste (“MSW”) and its conversion into energy!  There are few, if any, energy technologies that can claim to be both renewable and sustainable but also reliable and financially attractive. Why is this so?

To understand this, it’s necessary to understand what MSW is and is not. According to the U.S. EPA, MSW includes non-hazardous solid waste from residential, multifamily, commercial, and institutional (eg., schools, government offices) sources, see following chart. This definition excludes many materials that are frequently disposed with MSW in landfills, such as combustion ash, water and wastewater treatment residuals, and construction and demolition debris.

If the MSW is sorted, so all the recyclables are removed and the construction debris is eliminated, then the residual is considered renewable for tax credits and other renewable energy credits.

MSW can also be classified as sustainable if it allows landfills to remain open due to lower volumes of waste to be handled. In this case sustainable is societal, economic, and environmental if the inherent value of the total resource is used appropriately.

Historically, “waste management practices have evolved over time in response to two important factors: first, from a desire to protect public health, followed much later by a desire to protect the environment. Garbage has been an issue since at least 10,000 BC when humans began moving away from their nomadic habits to establish primitive societies. The increased population densities resulted in more waste being concentrated in a smaller area. In approximately 500 BC, Athenians developed one of the first municipal disposal sites in the Western world and required citizens to dump their waste at least one mile from the city limits. Around AD 200, the Romans established an early form of garbage collection service where teams of two men would walk along the streets collecting garbage and tossing it into a wagon.” Today, the problems remain basically the same, though more extensive, complex and potentially hazardous. Technology is now available to transform the problems to an environmentally and socially beneficial opportunity.

The value chain of MWM consists of three main stages that give rise to three distinct markets. The first one regards collection services, whose counterparts are waste producers and operators. The second is the market for the handling and disposal of waste, whose counterparts are operators of collection services and owners of disposal sites. The third is recovery/recycling, whose counterparts are again collection operators and final users of waste-derived materials. Within each market further additional secondary transactions take place, that identifies additional side markets (e.g., contracting out of specific activities from waste collection operators to specialized companies).

Some cities, primarily in the northeastern and mid-Atlantic U.S., burned part of their municipal solid wastes. Hemmed in by major population centers, landfill space was at a premium, so burning wastes to reduce their volume and weight made sense. Combustion reduces the volume of material by about 90 percent and its weight by 75 percent. The heat generated by burning wastes has other uses, as well, as it can be used directly for heating, to produce steam or to generate electricity. Other than solving the “landfill gap,” municipal waste combustion facilities made little of no economic returns.”

Then in 1970, Congress passed the Clean Air Act, which authorized the end of open burning at U.S. landfills. City incinerators were required to install pollution controls or cease operation, and a number of the worst polluters were closed down. Losing incinerators forced cities to consider alternate methods of waste disposal.

Combined with rising concerns for sustainability and renewable energy, the prohibition on incineration has spawned renewed interest in converting waste-to-energy. The force behind this movement is gasification and pyrolysis. Like incineration, pyrolysis and gasification are thermal processes that use high temperatures to break down waste. The main difference is that they use less oxygen than traditional mass-burn incineration.   The waste is broken down to create gas, solid and liquid residues. The gases can then be combusted in a secondary process. The pyrolysis process thermally degrades waste in the absence of air (and oxygen). Gasification is a process in which materials are exposed to some oxygen, but not enough to allow combustion to occur. Temperatures are usually above 750 degrees C. In some systems the pyrolysis phase is followed by a second gasification stage, in order that more of the energy carrying gases are liberated from the waste.

The main product of gasification and pyrolysis is syngas, which is composed mainly of carbon monoxide and hydrogen (85 per cent), with smaller quantities of carbon dioxide, nitrogen, methane and various other hydrocarbon gases.  Syngas has a calorific value, so it can be used as a fuel to generate electricity or steam or as a basic chemical feedstock in the petrochemical and refining industries. The calorific value of this syngas will depend upon the composition of the input waste to the gasifier.

Most gasification and pyrolysis processes have four stages:

“1. Preparation of the waste feedstock: The feedstock may be in the form of a refuse derived fuel, produced by a Mechanical Biological Treatment plant or an autoclave.Alternatively, the plant may take mixed waste and process it first through some sort of materials recycling facility, to remove some recyclables and materials that have no calorific value (e.g. grit)

2. Heating the waste in a low-oxygen atmosphere to produce a gas, oils and char (ash)

3. ‘Scrubbing’ (cleaning) the gas to remove some of the particulates, hydrocarbons and soluble matter

4. Using the scrubbed gas to generate electricity and, in some cases, heat (through combined heat and power – CHP). There are different ways of generating the electricity from the scrubbed gas – steam turbine, gas engine and maybe some time in the future, hydrogen fuel cells. The scrubbed syngas can also be fed into a Fisher-Tropsch (FT) reactor to produce liquid hydrocarbons such as diesel fuel.”

Source: Green Car Congress

As previously noted, incinerators emit nitrogen oxides, sulfur dioxide, particulate matter, carbon monoxide, carbon dioxide, acid gases, lead, cadmium and mercury, and organic compounds, such as dioxins and furans, into the atmosphere. However, gasification plants’ air emissions also include nitrogen oxides, sulfur dioxide, particulate matter, carbon monoxide, carbon dioxide, methane, hydrogen chloride, hydrogen fluoride, ammonia, heavy metals mercury and cadmium, dioxins and furans. Gasification facilities share the same environmental problems associated with mass burn incinerators. Pyrolysis, using no oxygen, reduces the volume of product gases by a factor of 5 to 20. Furthermore, the pollutants are concentrated in a coke-like residue matrix for easy disposal.

Current improvements in feedstock selectivity, process control, equipment design and modularization, and more efficient catalysts for the Fisher-Tropsch synthesis has significantly lowered the capital cost, enhanced the environmental friendliness and boosted the performance of waste to energy conversion by pyrolysis.

In closing, the solid waste problem is part of live – ancient and modern. The need to control the problems has led to the development of waste management, which has become a service of public and general interest, a basis for civilization, environment control and health protection. The demanding environmental standards have brought to the forefront the need to prevent, recycle and recover prior to disposal. This has increased the valuation of once financially unsuccessful methods to reclaim the stored energy inherent in MSW. Pyrolyis in combination with power producing systems or hydrocarbon synthesis reactors is that game changing process. It is not only sustainable but renewable too. Landfills can breathe a sigh of relief and incineration can now rest in peace.


1. U.S. Environmental Protection Agency, Summary of the EPA Municipal Solid Waste Program, .

2. Oklahoma Department of Environmental Quality, Martin,

3. Garbage in the Cities, Martin V. Melosi,

4. The municipal waste management sector in Europe: shifting boundaries between public service and the market, Barbara Antonioli & Antonio Massarutto,

5. U.S. Environmental Protection Agency, “Solid Waste Combustion/Incineration,”

6. Window on State Government, Texas Comptroller of Public Accountants, Municipal Waste Combustion, .

7. A Technical Report published by The Blue Ridge Environmental Defense League, .

8. Friends of the Earth, Briefing, Pyrolysis, gasification and plasma, September 2009, .

9. Feedstock Recycling by Pyrolysis of Plastics in a Fluidized Bed, W. Kaminsky, .

10.  Green Car Congress, Study explores energy balance of Fischer-Tropsch diesel via autothermal reforming of pyrolysis oil from biomass residue; spreadsheet offered as tool,

11. Syngas quality in Gasification of high moisture Municipal Solid Wastes:

12. National Renewable Energy Laboratory, Managing America’s Solid Waste, by J.A. Phillips, J.A. Phillips and Associates (Boulder, Colorado, September 1998), pp. 11, 84. (Consultant’s report) .

13. H. Lanier Hickman, Jr., “A Brief History of Solid Waste Management During the Last 50 Years: Part 9a: The Awakening of Waste-to-Energy in the U.S.” MSW Management (July/August 2000),

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9 Comments leave one →
  1. December 29, 2011 8:47 AM

    I like your thinking Barry about municipal solid waste especially if it is a part of a combined heat and power (CHP) facility. Likewise, think about using other “waste” products with anaerobic digesters producing biogas. These systems can take food waste, greases, crop residues, animal waste and when run through an anaerobic digester produce biogas and heat that can be converted to electricity, cleaned for pipeline gas or converted into compressed natural gas (CNG) for a vehicle fuel. Look at the amazing biogas to energy success story in Germany. We must take “waste” out of the vocabulary and convert these left overs into energy for a sustainable future.

  2. December 29, 2011 9:31 AM

    Yes Barry and Gary, it is great success story of Germany – you can’t find a ton of waste – it just does not exist – but the incineration is already outdated and once the life span of these plants has expired or when these companies (about 2 major ones inc. one from France) have made enough money the incineartion technology will be replaced by another German invention, the CPD technology. I am writing this because I am one of the agents marekting this technology and believe before i got into this I studied as good as I could without being a chemical engineer or similar all the other technologies – nothing beats the CPD. It shows the highest efficiency in the conversion, needs no external power, no water and does not release any emissions (also not from hazardous waste) but delivers besides EN590 Diesel or Kerosene from all organic waste (follow me on Linkedin) distilled water and ash that is an ideal fertilizer when not from hazarouds waste. The ash from hazardous waste can be used in road building etc. You can contact me on Regards Helga

  3. December 29, 2011 12:31 PM

    Very true and needs Mich more attention. My company has been pushing this to the Department of Defense, with a much improved system that is closed looped and puts out “0” ghg’s .

    However, they seem more set on pushing other fuels that are not even close to mass production now of they ever will be. We can build plants now with the ability of putting out 2 billion gallons of finished drop in fuels a year now.

    This is the USA’s out from imported fuels. And can be produced at the point of usage.

    Great job bringing this to the attention of others

  4. January 1, 2012 8:45 AM

    Volatile alkali lowers the fusion temperature of ash. In conventional combustion equipment having furnace gas exit temperatures above 1450° F, combustion of agricultural residue causes slagging and deposits on heat transfer surfaces. Specially designed boilers with lower furnace exit temperatures could reduce slagging and fouling from combustion of these fuels. Low-temperature gasification may be another method of using these fuels for efficient energy production while avoiding the slagging and fouling problems encountered in direct combustion.

  5. January 1, 2012 9:43 PM

    Barry & Gary …Very interesting comments, and I agree…There is no reason not to unleash the energy potential in MSW.

    Helga, I will contact you to find out more about your business in a separate email.

    John, Pls contact me about your company, and the other road blocks that you are bumping into beyond the DOE.

    I am an associate of a group that helps solve renewable energy problems in a variety of creative ways.


    Carl G. Moose

  6. January 4, 2012 8:13 AM

    Helga, I had no idea what CPD was but after some Web searching I found this:

    The latter article does not discuss the economics of CPD in comparison with other waste disposal options. All of the disposal options discussed here, as well as recycling, need to be assessed in terms of net benefits and costs. While Barry mentions making financial sense in his title, that discussion is not included.

    In principle, reclaiming valuable products from ‘waste’ is appealing. But the economic benefits have to exceed the costs of doing it. And where there are multiple alternative methods available, administrators logically should prefer the one that yields the greatest return on investment.

    In a broader framework, reclaiming useful products from ‘waste’ should be analyzed in relation to the growing movement for “cradle to cradle” design — which aims to minimize or eliminate the ‘waste’ resulting from various products. To the extent that movement gains impact, the pyrolysis or other conversion of ‘waste’ to byproducts may not look particularly “renewable” or “sustainable” in the long run. (But those are rather fuzzy terms anyway.)

    None of this is to say that these various methods of waste reclamation are unattractive. Just that they need to be assessed relative to other options.

  7. January 11, 2012 11:14 AM

    The economic considerations of ROI and feasibility must always be considered. Waste to energy seems to make a lot of economic sense, especially when you consider disposal as a cost with no return. The more sources of reuse and domestic energy that we can utilize and produce at home, the less foreign oil will need to import.

    The net effect is we put our people back to work in sustainable enterprises while we buy more time to develop more research, development, innovation and alternative sources of energy. We enhance GDP and recirculate more monetary proceeds within our own domestic economy. It sounds like a WIN/WIN.

  8. January 15, 2012 5:38 AM

    8. Plasma gasification processes of waste: Gasification [9,11,13] is a simple and commercially well-proven technology. It involves the conversion of various feedstocks to clean syngas, through a reaction with oxygen and steam; this reaction is spontaneous at high temperature and pressure under reduction conditions, and consumes half of the oxygen required for total combustion. The raw syngas product is cooled and purified, it is then used in one or a combination of many product applications: syngas for chemicals, gaseous fuels, for liquid fuels burned in commercial boilers to produce steam or in heat transfer process and in internal combustion engines to produce electrical energy. Combined cycles are also possible leading to co-generation of electrical energy. The energy efficiency of biomass gasification varies from 75 to 80%, this depends of the composition and heat capacity of the raw material; Humidity and the inorganic inert matter content reduce the efficiency. The traditional market for syngas is focused in gas production as an intermediate step during the production of important chemicals, such as ammonia for fertilizer. However, application of gasification in other processes is increasing due to market changes associated with improved gas turbines, deregulation of electrical power generation, and stringent environmental mandates. Gasification plant capacity is reported in units of volumetric output of syngas (i.e., normal cubic meters per day). However, the Department of Energy (DOE) converted all the gasification input and output capacities to MWth. (1MWth = 3,413,000Btu/hr). Gasification is an alternative to combustion, and has an energy efficiency of 50%. The advantage consists on reducing both the atmospheric emissions and the volume of solid residues to be land filled. Since the solid residues come from a high temperature at normal conditions, they’re inert materials that can be used as part of the bulk material in concrete production.

  9. January 21, 2012 3:09 PM

    To my Readers,

    Sorry, I have not time to respond as usual, comments on my three pieces on Natural Gas have been overwhelming. Would like to reply to each and every comment. Rest assure, each comment has been captured, read, and included in over 100 pages of comments. I use the comments to learn and gain further insight.

    Of any one wants to connect or contact me, please use

    If you want to visit my website at:

    Thanks all for your comments, both + and -.

    Diversity is great and the way to get to the bottom of it all.

    Barry Stevens

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