5 research outputs found
Replacing Recycling Rates with Life-Cycle Metrics as Government Materials Management Targets
In
Florida, the passing of the Energy, Climate Change, and Economic
Security Act of 2008 established a statewide mass-based municipal
solid waste recycling rate goal of 75% by 2020. In this study, we
describe an alternative approach to tracking performance of materials
management systems that incorporates life-cycle thinking. Using both
greenhouse gas (GHG) emissions and energy use as life-cycle indicators,
we create two different materials management baselines based on a
hypothetical 75% recycling rate in Florida in 2008. GHG emission and
energy use footprints resulting from various 2020 materials management
strategies are compared to these baselines, with the results normalized
to the same mass-based 75% recycling rate. For most scenarios, LCI-normalized
recycling rates are greater than mass-based recycling rates.
Materials management strategies that include recycling of curbside-collected
materials such as metal, paper, and plastic result in the largest
GHG- and energy-normalized recycling rates. Waste prevention or increase,
determined as the net difference in per-person mass discard rate for
individual materials, is a major contributor to the life-cycle-normalized
recycling rates. The methodology outlined here provides policy makers
with one means of transitioning to life-cycle thinking in state and
local waste management goal setting and planning
Translating landfill methane generation parameters among first-order decay models
<p>Landfill gas (LFG) generation is predicted by a first-order decay (FOD) equation that incorporates two parameters: a methane generation potential (<i>L</i><sub>0</sub>) and a methane generation rate (k). Because non-hazardous waste landfills may accept many types of waste streams, multiphase models have been developed in an attempt to more accurately predict methane generation from heterogeneous waste streams. The ability of a single-phase FOD model to predict methane generation using weighted-average methane generation parameters and tonnages translated from multiphase models was assessed in two exercises. In the first exercise, waste composition from four Danish landfills represented by low-biodegradable waste streams was modeled in the Afvalzorg Multiphase Model and methane generation was compared to the single-phase Intergovernmental Panel on Climate Change (IPCC) Waste Model and LandGEM. In the second exercise, waste composition represented by IPCC waste components was modeled in the multiphase IPCC and compared to single-phase LandGEM and Australia’s Solid Waste Calculator (SWC). In both cases, weight-averaging of methane generation parameters from waste composition data in single-phase models was effective in predicting cumulative methane generation from -7% to +6% of the multiphase models. The results underscore the understanding that multiphase models will not necessarily improve LFG generation prediction because the uncertainty of the method rests largely within the input parameters. A unique method of calculating the methane generation rate constant by mass of anaerobically degradable carbon was presented (k<sub>c</sub>) and compared to existing methods, providing a better fit in 3 of 8 scenarios. Generally, single phase models with weighted-average inputs can accurately predict methane generation from multiple waste streams with varied characteristics; weighted averages should therefore be used instead of regional default values when comparing models.</p> <p><i>Implications</i>: Translating multiphase first-order decay model input parameters by weighted average shows that single-phase models can predict cumulative methane generation within the level of uncertainty of many of the input parameters as defined by the Intergovernmental Panel on Climate Change (IPCC), which indicates that decreasing the uncertainty of the input parameters will make the model more accurate rather than adding multiple phases or input parameters.</p
Chemical Characterization of High-Temperature Arc Gasification Slag with a Focus on Element Release in the Environment
High-temperature
arc gasification (HTAG) has been proposed as a
viable technology for the generation of energy and the production
of saleable byproducts from municipal solid waste (MSW). Total concentrations
of elements in HTAG slag were assessed and indicated a high partitioning
of trace elements (Pb, Cd, and As) into the flue gas, an issue of
concern when assessing the air pollution control residues (APCR) status
as a hazardous waste. Hazardous waste leaching tests [such as the
toxicity characteristic leaching procedure (TCLP)] were performed
and confirmed that the slag did not meet U.S. criteria for a hazardous
waste. Leaching was assessed using batch and column tests; the results
revealed that Sb and Al were elevated in respect to risk-based regulatory
thresholds. Slag samples were carbonated to simulate weathering effects,
and although leachable concentrations of Al did decrease by an order
of magnitude, Sb concentrations were found to increase. Low total
concentrations of certain trace elements (As, Cd, and Pb), with respect
to MSW incineration bottom ashes support the potential for reuse of
HTAG slag; however, leaching of elements (Pb, Al, and Sb) in batch
and column tests indicate that proper engineering controls would need
to be taken to ensure protection of water supplies in a reuse application
Life-Cycle Inventory and Impact Evaluation of Mining Municipal Solid Waste Landfills
Recent research and policy directives
have emerged with a focus
on sustainable management of waste materials, and the mining of old
landfills represents an opportunity to meet sustainability goals by
reducing the release of liquid- and gas-phase contaminants into the
environment, recovering land for more productive use, and recovering
energy from the landfilled materials. The emissions associated with
the landfill mining process (waste excavation, screening, and on-site
transportation) were inventoried on the basis of diesel fuel consumption
data from two full-scale mining projects (1.3–1.5 L/in-place
m<sup>3</sup> of landfill space mined) and unit emissions (mass per
liter of diesel consumption) from heavy equipment typically deployed
for mining landfills. An analytical framework was developed and used
in an assessment of the life-cycle environmental impacts of a few
end-use management options for materials deposited and mined from
an unlined landfill. The results showed that substantial greenhouse
gas emission reductions can be realized in both the waste relocation
and materials and energy recovery scenarios compared to a “do
nothing” case. The recovery of metal components from landfilled
waste was found to have the greatest benefit across nearly all impact
categories evaluated, while emissions associated with heavy equipment
to mine the waste itself were found to be negligible compared to the
benefits that mining provided
Expanding Per- and Polyfluoroalkyl Substances Coverage in Nontargeted Analysis Using Data-Independent Analysis and IonDecon
Per- and polyfluoroalkyl substances (PFAS) are widespread,
persistent
environmental contaminants that have been linked to various health
issues. Comprehensive PFAS analysis often relies on ultra-high-performance
liquid chromatography coupled with high-resolution mass spectrometry
(UHPLC HRMS) and molecular fragmentation (MS/MS). However, the selection
and fragmentation of ions for MS/MS analysis using data-dependent
analysis results in only the topmost abundant ions being selected.
To overcome these limitations, All Ions fragmentation (AIF) can be
used alongside data-dependent analysis. In AIF, ions across the entire m/z range are simultaneously fragmented;
hence, precursor–fragment relationships are lost, leading to
a high false positive rate. We introduce IonDecon, which filters All
Ions data to only those fragments correlating with precursor ions.
This software can be used to deconvolute any All Ions files and generates
an open source DDA formatted file, which can be used in any downstream
nontargeted analysis workflow. In a neat solution, annotation of PFAS
standards using IonDecon and All Ions had the exact same false positive
rate as when using DDA; this suggests accurate annotation using All
Ions and IonDecon. Furthermore, deconvoluted All Ions spectra retained
the most abundant peaks also observed in DDA, while filtering out
much of the artifact peaks. In complex samples, incorporating AIF
and IonDecon into workflows can enhance the MS/MS coverage of PFAS
(more than tripling the number of annotations in domestic sewage).
Deconvolution in complex samples of All Ions data using IonDecon did
retain some false fragments (fragments not observed when using ion
selection, which were not isotopes or multimers), and therefore DDA
and intelligent acquisition methods should still be acquired when
possible alongside All Ions to decrease the false positive rate. Increased
coverage of PFAS can inform on the development of regulations to address
the entire PFAS problem, including both legacy and newly discovered
PFAS