Number range CHAPTERNew Methods for Assessment of Pollution Prevention
Technologies: Integration of Process Modeling and Design; Life-Cycle
Analysis; and Regional Environmental Benefits Assessment

Christopher Frey

The objectives of this research were to: (1) develop novel assessment
methodologies for evaluation of the risks and potential pay-offs of new
technologies that avoid pollutant production; (2) demonstrate the
methodology via a detailed case study of one promising new pollution
prevention technology; and (3) utilize a tiered approach including
process simulation and design optimization, probabilistic analysis, life
cycle analysis, and assessment of selected regional environmental
impacts to provide insights regarding the risks and pay-offs of the
pollution prevention approach, both at a \'micro\' process-level and at
a \'macro\' regional environmental level.

Toward the objectives, research activities included the following: (1)
identify specific process technologies for detailed evaluation, based
upon a solid waste-fueled gasification combined cycle system capable of
coproduction of electricity, steam, sulfur, methanol, and ammonia; (2)
develop design bases for major components of the system, including
gasification, gas cooling, gas cleanup, gas turbine, and methanol
synthesis; (3) implement process simulation models of the major
components using ASPEN Plus; (4) obtain evaluate life cycle inventory
data regarding conventional methods for power generation, sulfur
production, steam production, methanol synthesis, and ammonia synthesis;
(5) develop a corresponding life cycle inventory model; (6) apply the
process simulation and LCI models to case studies; and (7) evaluate the
regional environmental impact of larger scale application of solid
waste-fueled gasification technology using the Tracking and Analysis
Framework (TAF).

At the level of an individual gasification plant, several of the main
conclusions of the work are: (1) the plant efficiency decreases with an
increase of the portion of refuse-derived fuel in the RDF/coal blends;
(2) the parameters that most affect the overall plant performance are:
plant size, the saturation level of the clean syngas, and purge gas
recycle ratio from the methanol plant; and (3) the amount of oxygen
content in the fuel has a substantial effect on the auxiliary load of
the plant, since more fuel-bound oxygen offsets the need for oxygen
needed as a gasifier input from an air separation plant. At the level of
the life cycle inventory, the main conclusions include: (1) for most
pollutants, both gasification and waste-to-energy (WTE) system emissions
are negative because of offsets; (2) the largest offset is associated
with the ferrous and aluminum recovered in the RDF plant followed by
electrical energy and then methanol; (3) the gasification system has a
more favorable LCI than the more conventional WTE system; (4) as
methanol production in the gasification system increases, the
gasification system LCI improves; (5) RDF processing has an equalization
effect on the variability of the MSW feedstock; (6) the paper to plastic
ratio of the incoming MSW has the largest effect on the LCI of the
gasification system for the parameters studied; and (7) there is an
improvement in the LCI for the gasification system when landfill gas is
converted to energy. However, this improvement is small relative to the
total LCI of the waste gasification system. With regard to regional
environmental impact assessment, the main findings were that the
substitution of gasification of solid waste for conventional methods for
power generation can result in long term improvements in public health
associated with the specific health effects end-points evaluated here.
Thus, this research has provided insight into the energy efficiency,
life cycle inventory, and health impact benefits of technologies that
convert a waste stream (in this case, solid waste) to useful products.
The methodology implemented here illustrates that design-level decisions
(e.g., fuel composition, process design parameters) influence results at
more aggregate levels of assessment (e.g., LCI), thereby demonstrating
the value of a multi-tiered approach to technology assessment with
respect to pollution prevention and other environmental goals.