After you have “explored the universe” (Step One) and “asked the threshold question” (Step Two), and before moving forward with a detailed evaluation on the remaining waste conversion technologies, it is recommended that you identify the assessment criteria to apply to the various technologies. The assessment criteria should reflect the economic, environmental and technical issues critical to the community where siting of such a facility is being considered.

Step three: Identify and apply the assessment criteria

The assessment of the various waste-to-energy conversion technologies will be conducted using criteria that reflect critical factors associated with their application. These criteria relate to the energy benefits, costs and potential environmental effects of these technologies. They include the following:

• types and net energy produced;
• quantities and mix of feedstock;
• byproducts/residuals;
• capital and operations costs;
• environmental/regulatory issues;
• commercial readiness;
• flexibility; and
• compatibility.

The following is a brief description of each of these criteria. The analysis will allow decision-makers to become more informed about the technologies examined, especially when conducting their own project-specific assessments.


Quantities and mix of feedstock
Additional criteria that should be considered are the quantities and mix of feedstock available. The technology must be scalable for the types and amount of feedstock being proposed. Many projects fail to provide such information to the level to include the substreams associated with the project. For example, does the project include municipal solid waste (MSW), construction and demolition waste, source-separated organics and/or sludges?

Byproducts/residuals
Byproducts and residuals can be defined as non-energy materials (e.g. ash, water, wastewater) that are produced during the application of technology processes. Some byproducts or residuals may require treatment and/or disposal. However, other residual materials may be beneficially reused. Select regions of the United States may have markets for some residual materials, such as bottom ash or char. In applying this criterion, the byproducts/residuals produced should be estimated as a percentage of the total inputs when data are available.

Capital and operations cost
Estimating costs associated with the various technologies requires defining project parameters. Planning-level capital costs should be estimated, including design and permitting costs, construction and equipment costs, and other direct costs associated with the development of the project. Planning-level capital costs will vary depending on the size, location, and specific details of the project. Project definition typically needs to include, at least, project throughput, selected primary technology, type of energy produced and general site parameters assumed for cost estimates to be completed. Based on availability of data, capital costs may need to be estimated as a range of values at this stage of the analysis.

Operations and maintenance costs are typically measured as annual operating, maintenance and associated non-capital costs. Similar to the planning-level capital costs for a specific technology, the operations and maintenance costs may vary depending on the size, location and specific details of the project. Based on availability of data, operations and maintenance costs may need to be estimated as a range of values at this stage of the analysis.

Environmental/regulatory issues
The environmental and regulatory issues typically associated with specific technologies vary with project-specific parameters and local and regional regulatory agencies. Generally, environmental regulatory issues are addressed through permit applications and reviews of facility construction and operating permits. In applying this criterion, the analysis should characterize the fatal flaw regulatory issues (e.g., pollution control for air emissions, disposal of contaminants) and identify the environmental and regulatory issues recommended for further investigation.

One of the most prominent environmental impacts of a conversion technology project is the potential for reductions in greenhouse gas emissions. The amount of such reductions related to a technology should be assessed with the designation of high, medium, low or no change. Greenhouse gas emission generation activities considered should include collection, transportation, processing and disposal. Other environmental impacts that may be characterized include byproducts/residuals, contamination issues and stormwater management.

Commercial readiness
Commercial readiness refers to the technical maturity of the technology. Some of the aforementioned technologies have been operating successfully in locations across the United States and/or Europe. However, other technologies may still be in the pilot phase or research-and-development stage of production. Based on this information, a general risks assessment of the relative commercial readiness of each technology should be discussed. For example, in some cases the technology may have been successfully applied to one type of feedstock but also may have limited application to another type of feedstock.

Flexibility
The flexibility of a technology refers to how well a technology can be adapted to changing internal and external project factors (e.g., regulatory, project throughput, feedstock quality, feedstock mix). For a technology to be flexible over time, it must be able to be maintained and updated appropriately with advances in technology. In applying this criterion, the analysis should discuss the general parameters of each technology and characterize its flexibility using a ranking of low, medium or high.

Compatibility with existing system
Even if the application of the criteria results in favorable outcomes, the proposed technology should be compatible with the solid waste management system in the community where the facility is being considered. Compatibility should be linked to projected integration into the existing system and planned programs.

Step four: Develop a comparative matrix and rank the technologies

To reflect the application of the criteria to the various technologies, the next step should include a comparison of the outcomes. The relative importance of the criteria should be determined by weighting each of the criteria. It is recommended to develop a matrix listing the technologies assessed and a summary of the application of the criteria to each technology.

Once the framework of the matrix is developed, each technology should be scored to create a ranking of technologies from most preferred to least preferred. A total score for each criterion should be calculated by multiplying the weighting of individual criteria by the ranking, then summing to obtain a total score. Usually, the results will reflect groupings of technologies. From these groupings, a set of preferred technologies can usually be identified.

Step five: Seek assistance

Upon identifying a short list of preferred technologies, the framework has been established for conducting detailed evaluations of specific proposed solid waste conversion projects. Numerous local governments have received both unsolicited and solicited proposals to convert solid waste and its various substreams into energy. With the list of preferred technologies, you can move efficiently into a detailed evaluation of specific proposals. Detailed review of site-specific projects by a qualified professional(s) is recommended to address specific local and regional market conditions, future system needs, detailed costs and applicable environmental regulations, and to hone in on technologies that accomplish your mission: making the best decision for your community, environment and budget.

Part I of this article, “Exploring the possibilities,” appeared in the March/April 2014 issue of Renewable Energy from Waste and is available online at www.REWmag.com/rew0414-energy-conversion-technologies.aspx.

The author is solid waste and resource recovery manager in Minneapolis-St. Paul for the Environmental Global Practice at Burns & McDonnell, Kansas City, Missouri.