Massachusetts Department of Environmental Protection moves away from gasification and pyrolysis consideration says the new report commissioned by the state.

December 22nd, 2008

A new study released today by the Tellus Institute commissioned by the Massachusetts Department of Environmental Protection found that "gasification and pyrolysis facilities are unlikely to play a major role in MSW management in Massachusetts by 2020."  The study can be downloaded at http://www.mass.gov/dep/recycle/priorities/dswmpu01.htm.   The study says that:

"Key issues informing this conclusion include: the lack of experience in the U.S. with large-scale alternative technology facilities successfully processing mixed MSW and generating energy; the long lead times to plan, site, construct, and permit such facilities; the significant capital costs required and the loss of solid waste management flexibility that is associated with the long-term contractual arrangements that such capital-intensive facilities require; and the relatively small benefit with respect to greenhouse gas emissions compared to diversion or landfilling."

The conclusions presented in the study are the following: 

1) From a lifecycle environmental emissions and energy perspective, source reduction, recycling and composting are the most advantageous management options for all (recyclable/compostable) materials in the waste stream. (See Tables ES-1 and ES-2, below.) This finding confirms the traditional solid waste management hierarchy that has guided MA DEP’s Solid Waste Master Plan to date.

2) After maximizing diversion through source reduction, recycling and composting, it is appropriate for DEP to continue to monitor developments regarding alternative waste management technologies that produce energy – gasification, pyrolysis, and anaerobic digestion. In evaluating conventional and alternative management options for the remaining waste stream, the competing needs of energy generation and prevention of climate change come into play, given that materials with high fossil fuel energy content, such as plastics and rubber, also emit high levels of greenhouse gases when they are combusted or processed for energy. Expected federal regulation of carbon emissions, or market mechanisms such as cap-and-trade systems, may place additional focus on solid waste management facilities as emission sources, making greenhouse gases an increasingly important consideration in future waste management decision-making.

3) Several factors lead us to conclude that gasification and pyrolysis facilities are unlikely to play a major role in MSW management in Massachusetts by 2020. Key issues informing this conclusion include: the lack of experience in the U.S. with large-scale alternative technology facilities successfully processing mixed MSW and generating energy; the long lead times to plan, site, construct, and permit such facilities; the significant capital costs required and the loss of solid waste management flexibility that is associated with the long-term contractual arrangements that such capital-intensive facilities require; and the relatively small benefit with respect to greenhouse gas emissions compared to diversion or landfilling.

4) The prospects for anaerobic digestion facilities appear to be more favorable given the extensive experience with such facilities in the U.S. for the processing of sewage sludge and farm waste and the fact that no significant human health or environmental impacts have been cited in the literature. Moreover, since anaerobic digestion is more similar to composting than high-temperate combustion, its risks are expected to be akin to composting, which is considered low-risk. Anaerobic digestion may be most suitable for source-separated organic material as an alternative to conventional composting. Ultimately, the degree to which anaerobic digestion makes sense will depend largely on the economics of such facilities, including the energy they produce, versus directly composting such material in aerobic composting facilities.

5) As summarized in Table ES-1, below, among the other technology options – landfilling, waste-to-energy incineration, and gasification/pyrolysis – from a life-cycle perspective no technology performs better than the others across all the seven emissions categories reviewed. However, reported per ton emission factors for gasification/pyrolysis facilities are lower than for WTE incineration facilities for all pollutants, and lower than landfill emissions for all except carbon dioxide (eCO2). (Key assumptions and a discussion of the modeling results are presented in section III.)

6) For modern landfills, waste-to energy incinerators, as well as the gasification and pyrolysis plants, the emission factors used to compare environmental performance are based largely on modeling and/or vendor claims for modern, state-of-the art facilities, as opposed to actual operational data from real world experience. For example, actual operating performance for Massachusetts WTE facilities has been shown to produce far higher emissions than the modeled figures. Similarly, there remains significant uncertainty as to whether commercial scale gasification/ pyrolysis facilities processing MSW and generating energy can perform as well as the vendor claims or modeled emissions.

7) Preference among the alternative technology options based on environmental performance is dependent on the relative importance placed on eCO2 emissions versus the other pollutants. For example, on a per ton MSW basis, modern landfills with efficient gas capture systems reduce two and a half times as much eCO2 as gasification and pyrolysis facilities, and three and a half times as much as waste-to-energy incinerators.

8) From a life-cycle net energy perspective, waste diversion through recycling provides the most benefit, saving an estimated 2,250 kWh per ton of solid waste. Of the other waste management technologies, gasification and pyrolysis facilities have the most potential for energy production at about 660 kWh per ton, followed by modern waste to energy incinerators at 585 kWh per ton, and then anaerobic digestion, and landfilling. The estimated energy potential of the various management methods is summarized in Table ES-2, below.

Table ES-2: Net Energy Generation Potential Per Ton MSW

Management Method

Energy Potential*

(kWh per ton MSW)

Recycling

2,250

Landfilling

105

WTE Incineration

585

Gasification

660

Pyrolysis

660

Anaerobic Digestion

250

* Per-ton energy generation potential estimates are dependent on a number of factors including: the composition of the MSW stream, the specific technologies considered (e.g., fluid bed versus fixed bed for gasification), and the source of the data. Source references are provided in section III.

9) In considering potential sources of energy to meet the Commonwealth’s electricity needs, if 100% of MSW currently landfilled or exported (about 3.5 million tons) were processed by pyrolysis facilities, the maximum potential electricity production would be 2.3 million MWh per year or about 4% of the state’s 2005 electricity consumption.
10) The Morris Environmental Benefits Calculator (MEBCalc) model was used to analyze the relative environmental and energy impacts of three alternative solid waste management systems for the Commonwealth in 2020 – Scenario 1: Business As Usual; Scenario 2: Enhanced Diversion, No Alternative Technologies; and Scenario 3: Enhanced Diversion with Alternative Technologies (gasification and pyrolysis). As summarized in Table ES-3, results of the modeling indicate that Scenario 1, without an enhanced diversion program (or the introduction of new thermal treatment technologies), produces significantly lower environmental benefits than the other scenarios across all emissions categories considered. Without an enhanced recycling program, Scenario 1 has a disposal stream that is about 3 million tons more than the other scenarios.
11) The emissions profiles for Scenarios 2 and 3 are very similar for virtually all emissions categories. The shifting of MSW from landfilling to gasification and pyrolysis has a small impact on overall system emissions. This is because only about 10% of the total waste stream is sent to the new thermal processing facilities and because the emissions associated with the 80% of the waste stream that is either recycled/composted or incinerated in conventional waste to energy facilities in both scenarios has a determinative impact on the overall emissions profile. Though the overall differences are small, the shifting of waste from landfilling to gasification and pyrolysis facilities that occurs in Scenario 3 results in lower overall emissions for all pollutants except eCO2.
12) The fraction of waste recycled or composted has a dominant impact on the overall system energy profile for all three scenarios. This is due to a combination of the size of the recycled/composted waste stream (47% in Scenario 1, 62% in Scenarios 2 and 3), plus the high energy savings per ton of diverted waste. As summarized in Table ES-4, below, Scenario 1 has a net energy potential of almost 22 million MWh. The enhanced recycling/composting activities in Scenarios 2 and 3 boost the overall solid waste management system’s net energy potential by about 6.1 million MWh or 28% over Scenario1. Introducing the gasification and pyrolysis facilities in Scenario 3 and shifting MSW from landfills to these new thermal treatment facilities increases overall net system energy potential by 1 million MWh.

13) For both pollutant and energy impacts, the scenario analysis points to the significant benefits of broadening and strengthening the Commonwealth’s recycling and composting diversion programs and the modest additional benefits associated with shifting non-C&D MSW from landfills to new thermal processing facilities.


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