Papers by Heather Maclean
SRPN: Waste Food (Waste) (Topic), 2009
The potential supply of biomass feedstocks in the US and Canada is estimated using a static suppl... more The potential supply of biomass feedstocks in the US and Canada is estimated using a static supply function approach. Estimated total biomass available at a price of $100 per metric ton is 568 million metric tons in the US and 123 million tons in Canada, which together can displace 23-45 billion gallons of gasoline. Sufficient biomass, mainly agricultural and mill residues, will be available at prices of around $50/ton to meet the advanced biofuel mandates of the US Energy Independence and Security Act of 2007. The estimates of agricultural residue supply are very sensitive to the assumed fraction of residues that can be sustainably removed from the field, and the potential of municipal solid waste as a feedstock depends on which components can be economically converted into liquid biofuels.
Advances in Biochemical Engineering/Biotechnology, 2019
A key motivation behind the development and adoption of industrial biotechnology is the reduction... more A key motivation behind the development and adoption of industrial biotechnology is the reduction of negative environmental impacts. However, accurately assessing these impacts remains a formidable task. Environmental impacts of industrial biotechnology may be significant across a number of categories that include, but may not be limited to, nonrenewable resource depletion, water withdrawals and consumption, climate change, and natural land transformation/occupation. In this chapter, we highlight some key environmental issues across two broad areas: (a) processes that use biobased feedstocks and (b) industrial activity that is supported by biological processes. We also address further issues in accounting for related environmental impacts such as geographic and temporal scope, co-product management, and uncertainty and variability in impacts. Case studies relating to (a) lignocellulosic ethanol, (b) biobased plastics, and (c) enzyme use in the detergent industry are then presented, which illustrate more specific applications. Finally, emerging trends in the area of environmental impacts of biotechnology are discussed.
Annual Review of Resource Economics, 2015
Life cycle assessment (LCA) is a widely utilized technique to quantify inputs and emissions assoc... more Life cycle assessment (LCA) is a widely utilized technique to quantify inputs and emissions associated with the life cycle of a product, from raw materials extraction through the product's end-of-life. Given the basic economic principle of policy targeting, the case for focusing on emissions associated with a specific good as opposed to targeting each different externality needs development. This review identifies situations that merit a product life cycle approach in environmental regulation and then discusses the use of LCA with different types of policy instruments. We then discuss the methodological and implementation-related issues involved with using LCA as an economic decision aid as well as issues in designing regulations to control life cycle emissions. We conclude by identifying areas for future LCA research that are ripe for the application of microeconomic insights.
Proceedings of the Canadian Engineering Education Association, 2011
An Economic Input-Output based Life Cycle-based Assessment tool developed for the Canadian econom... more An Economic Input-Output based Life Cycle-based Assessment tool developed for the Canadian economy is presented, which estimates selected environmental implications (e.g. energy use, greenhouse gas emissions) throughout the entire economy associated with given demand for a product/material. An example application illustrates a comparison between concrete and steel use for columns in office buildings. Steel columns are found to be more energy intensive, but both column types result in similar levels of greenhouse gas emissions. The model’s advantages and limitations as a tool to assist designers in evaluating the environmental implications of their designs are discussed.
Bioresources, Feb 1, 2009
An improved understanding of lignocellulosic biomass availability is needed to support proposed e... more An improved understanding of lignocellulosic biomass availability is needed to support proposed expansion in biofuel production. Fifteen studies that estimate availability of lignocellulosic biomass quantities in in the U.S. and/or Canada are reviewed. Sources of differences in study methods and assumptions and resulting biomass quantities are elucidated. We differentiate between inventory studies, in which quantities of biomass potentially available are estimated without rigorous consideration of the costs of supply, versus economic studies, which take into consideration various opportunity costs and competition. The U.S. economic studies, which included reasonably comprehensive sets of biomass categories, estimate annual biomass availability to range from 6 million to 577 million dry metric tonnes (dry t), depending on offered price, while estimates from inventory studies range from 190 million to 3849 million dry t. The Canadian inventory studies, which included reasonably comprehensive sets of biomass categories, estimate availability to range from 64 million green t to 561 million dry t. The largest biomass categories for the U.S. are energy crops and agricultural residues, while for Canada they are expected to be energy crops and logging residues. The significant differences in study estimates are due in large part to the number of biomass categories included, whether economic considerations are incorporated, assumptions about energy crop yields and land areas, and level of optimism of assumptions of the study.
Environmental Science & Policy, 2014
While bioenergy plays a key role in strategies for increasing renewable energy deployment, studie... more While bioenergy plays a key role in strategies for increasing renewable energy deployment, studies assessing greenhouse gas (GHG) emissions from forest bioenergy systems have identified a potential trade-off of the system with forest carbon stocks. Of particular importance to national GHG inventories is how trade-offs between forest carbon stocks and bioenergy production are accounted for within the Agriculture, Forestry and Other Land Use (AFOLU) sector under current and future international climate change mitigation agreements. Through a case study of electricity produced using wood pellets from harvested forest stands in Ontario, Canada, this study assesses the implications of forest carbon accounting approaches on net emissions attributable to pellets produced for domestic use or export. Particular emphasis is placed on the Forest Management Reference Level (FMRL) method, as it will be employed by most Annex I nations in the next Kyoto Protocol Commitment Period. While bioenergy production is found to reduce forest carbon sequestration, under the FMRL approach this trade-off may not be accounted for and thus not incur an accountable AFOLU-related emission, provided that total forest harvest remains at or below that defined under the FMRL baseline. In contrast, accounting for forest carbon trade-offs associated with harvest for bioenergy results in an increase in net GHG emissions (AFOLU and life cycle emissions) lasting 37 or 90 years (if displacing coal or natural gas combined cycle generation, respectively). AFOLU emissions calculated using the Gross-Net approach are dominated by legacy effects of past management and natural disturbance, indicating near-term net forest carbon increase but longer-term reduction in forest carbon stocks. Export of wood pellets to EU markets does not greatly affect the total life cycle GHG emissions of wood pellets. However, pellet exporting countries risk creating a considerable GHG emissions burden, as they are responsible for AFOLU and bioenergy production emissions but do not receive credit for pellets displacing fossil fuel-related GHG emissions. Countries producing bioenergy from forest biomass, whether for domestic use or for export, should carefully consider potential implications of alternate forest carbon accounting methods to ensure that potential bioenergy pathways can contribute to GHG emissions reduction targets.
Interest in anaerobic digestion (AD), the process of energy production through the production of ... more Interest in anaerobic digestion (AD), the process of energy production through the production of biogas, has increased rapidly in recent years. Agricultural and other organic waste are important substrates that can be treated by AD. This book is one of the first to provide a broad introduction to anaerobic digestion and its potential to turn agricultural crops or crop residues, animal and other organic waste, into biomethane. The substrates used can include any non-woody materials, including grass and maize silage, seaweeds, municipal and industrial wastes. These are all systematically reviewed in terms of their suitability from a biological, technical and economic perspective. In the past the technical competence and high capital investment required for industrial-scale anaerobic digesters has limited their uptake, but the authors show that recent advances have made smaller-scale systems more viable through a greater understanding of optimising bacterial metabolism and productivity...
Proceedings of the Water Environment Federation, 2005
The Water Environment Research Foundation, a not-for-profit organization, funds and manages water... more The Water Environment Research Foundation, a not-for-profit organization, funds and manages water quality research for its subscribers through a diverse public-private partnership between municipal utilities, corporations, academia, industry, and the federal government. WERF subscribers include municipal and regional water and wastewater utilities, industrial corporations, environmental engineering firms, and others that share a commitment to cost-effective water quality solutions. WERF is dedicated to advancing science and technology addressing water quality issues as they impact water resources, the atmosphere, the lands, and quality of life.
Journal of the Air & Waste Management Association, 2007
We examined life cycle environmental and economic implications of two near-term scenarios for con... more We examined life cycle environmental and economic implications of two near-term scenarios for converting cellulosic biomass to energy, generating electricity from cofiring biomass in existing coal power plants, and producing ethanol from biomass in stand-alone facilities in Ontario, Canada. The study inventories near-term biomass supply in the province, quantifies environmental metrics associated with the use of agricultural residues for producing electricity and ethanol, determines the incremental costs of switching from fossil fuels to biomass, and compares the cost-effectiveness of greenhouse gas (GHG) and air pollutant emissions abatement achieved through the use of the bioenergy. Implementing a biomass cofiring rate of 10% in existing coal-fired power plants would reduce annual GHG emissions by 2.3 million metric tons (t) of CO 2 equivalent (7% of the province's coal power plant emissions). The substitution of gasoline with ethanol/gasoline blends would reduce annual provincial lightduty vehicle fleet emissions between 1.3 and 2.5 million t of CO 2 equivalent (3.5-7% of fleet emissions). If biomass sources other than agricultural residues were used, additional emissions reductions could be realized. At current crude oil prices ($70/barrel) and levels of technology development of the bioenergy alternatives, the biomass electricity cofiring scenario analyzed is more cost-effective for mitigating GHG emissions ($22/t of CO 2 equivalent for a 10% cofiring rate) than the stand-alone ethanol production scenario ($92/t of CO 2 equivalent). The economics of biomass cofiring benefits from existing capital, whereas the cellulosic ethanol scenario does not. Notwithstanding this result, there are several factors that increase the attractiveness of ethanol. These include uncertainty in crude oil prices, potential for marked improvements in cellulosic ethanol technology and economics, the province's commitment to 5% ethanol content in gasoline, the possibility of ethanol production benefiting from existing capital, and there being few alternatives for moderate-to-large-scale GHG emissions reductions in the transportation sector.
Journal of the Air & Waste Management Association, 2000
We examine the life cycles of gasoline, diesel, compressed natural gas (CNG), and ethanol (C 2 H ... more We examine the life cycles of gasoline, diesel, compressed natural gas (CNG), and ethanol (C 2 H 5 OH)-fueled internal combustion engine (ICE) automobiles. Port and direct injection and spark and compression ignition engines are examined. We investigate diesel fuel from both petroleum and biosources as well as C 2 H 5 OH from corn, herbaceous bio-mass, and woody biomass. The baseline vehicle is a gasoline-fueled 1998 Ford Taurus. We optimize the other fuel/powertrain combinations for each specific fuel as a part of making the vehicles comparable to the baseline in terms of range, emissions level, and vehicle lifetime. Life-cycle calculations are done using the economic input-output lifecycle analysis (EIO-LCA) software; fuel cycles and vehicle end-of-life stages are based on published model results. We find that recent advances in gasoline vehicles, the low petroleum price, and the extensive gasoline infrastructure make it difficult for any alternative fuel to become IMPLICATIONS Advances in reformulated gasoline-fueled automobiles, low petroleum prices, and the extensive gasoline infrastructure hamper alternative fuels in competing with gasoline. However, no fuel dominates for all economic, environmental, and sustainability attributes. CNG is less expensive than gasoline, has lower pollutant and GHG emissions, and has large North American reserves. However, onboard storage penalties and the lack of fuel infrastructure lower its attractiveness. Biofuels offer lower GHG emissions, are sustainable, and reduce the demand for imported fuels. Bioethanol would be attractive if the price of gasoline doubled or if significant reductions in GHG emissions were required.
Journal of the Air & Waste Management Association, 2011
Of the many sources of urban greenhouse gas (GHG) emissions, solid waste is the only one for whic... more Of the many sources of urban greenhouse gas (GHG) emissions, solid waste is the only one for which management decisions are undertaken primarily by municipal governments themselves and is hence often the largest component of cities' corporate inventories. It is essential that decision makers select an appropriate quantification methodology and have an appreciation of methodological strengths and shortcomings. This work compares four different waste emissions quantification methods including Intergovernmental Panel on Climate Change (IPCC) 1996 guidelines, IPCC 2006 guidelines, United States Environmental Protection Agency Waste Reduction Model (USEPA WARM) and the Federation of Canadian Municipalities Partners for Climate Protection (FCM-PCP) quantification tool. Waste disposal data for the Greater Toronto Area (GTA) in 2005 are used for all methodologies; treatment options, including landfill, incineration, compost, and anaerobic digestion, are examined where available in methodologies. Landfill was shown to be the greatest source of GHG emissions, contributing more than ¾ of total emissions associated with waste management. Results from the different landfill gas quantification approaches ranged from an emissions source of 557 kt CO 2 e (FCM-PCP) to a carbon sink of-53 kt CO 2 e (USEPA WARM). Similar values were obtained between IPCC approaches. The IPCC 2006 method was found to be more appropriate for inventorying applications as it uses a waste-in-place (WIP) approach, rather than a methane commitment (MC) approach, despite perceived onerous data requirements for WIP. MC approaches were found to be useful from a planning standpoint; however, uncertainty associated with their projections of future parameter values limits their applicability for GHG inventorying. MC and WIP methods provided similar results in this case study; however, this is casespecific, due to similarity in assumptions of present and future landfill parameters and quantities of annual waste deposited in recent years being relatively consistent.
Journal of Infrastructure Systems, 2007
Two different sized hydropower projects in China, one with a capacity of 44 MW and the other of 3... more Two different sized hydropower projects in China, one with a capacity of 44 MW and the other of 3,600 MW, were examined through life-cycle assessment Í‘LCAÍ’ from the perspective of both sustainability and environmental impact and the influence of project scale. Using the economic input-output based LCA approach, energy use and greenhouse gas Í‘GHGÍ’ emissions were quantified. The resulting energy payback ratios were found to be 7 and 48, whereas the normalized GHG emissions were 44 and 6 g CO 2 equivalent per kW h of electricity production, both in favor of the larger project. Compared with published data on other renewable and nonrenewable options, temperate hydropower, particularly large hydropower, is indicated as an efficient electrical source with relatively low GHG emissions.
The Forestry Chronicle, 2011
Minimum break-even and carbon-neutral periods resulting from displacing coal with wood pellets fo... more Minimum break-even and carbon-neutral periods resulting from displacing coal with wood pellets for energy generation at the Atikokan Generating Station (GS) were estimated using forest resource inventory for four forest management units (FMU) in northwestern Ontario. The break-even period was defined as the time since harvest at which the combined greenhouse gas (GHG) benefit of displacing coal with wood pellets and the amount of carbon in the regenerating forest equalled the amount of carbon in the forest had it not been harvested for wood pellets. The carbon-neutral period was defined as the time since harvest at which the amount of carbon in the regenerating forest equalled the amount of carbon in the forest had it not been harvested for wood pellets. Theoretically achievable minimum break-even and carbon-neutral periods were estimated as equal to 18 and 28 years after harvest, respectively. However, for the current forest age structure in the selected FMUs, production of wood pe...
Forest Ecology and Management, 2012
An important consideration in forest management to mitigate climate change is the balance between... more An important consideration in forest management to mitigate climate change is the balance between forest carbon (C) storage and ecological sustainability. We explore the effects of management strategies on tradeoffs between forest C stocks and ecological sustainability under five scenarios, three of which included management and two scenarios which provide baselines emulating the natural forest. Managed forest scenarios were: (a) Protection (PROT), i.e., management by suppression of natural disturbance and harvest exclusion; (b) Harvest at a higher rate removing all sustainably available wood (HHARV); (c) Harvest at the lower historical average rate of harvest, AHARV. Both harvest scenarios reflected current forest management practices in the study area, including suppression of natural disturbance and a large (>20% of total) forest area reserved from harvest. Scenarios (d) and (e) simulated ''natural'' forest with unsuppressed fire at higher (NDH) or lower (NDL) levels and no harvest. Ecological sustainability was evaluated using a coarse filter approach where forest age class and tree species composition were indicators of condition. The study area encompassed 3.4 million hectares of forest in northeastern Ontario at the interface between the temperate hardwood and boreal forest zones. Future forest condition for each scenario was modeled using a timber supply model (SFMM), and C stored in forests and wood products were estimated using the FORCARB-ON model. Forest protection (PROT) resulted in greatest forest C stocks, especially in the near term, but was within 95% of its maximum, becoming saturated within 30 years. Harvesting (HHARV and AHARV) resulted in less forest C stock compared to PROT, however, after 100 years of adding C in wood products to that in regenerating forests total C storage was equivalent or greater than forest C with PROT. In contrast, removing management (NDH and NDL) decreased C relative to any of the management regimes, though in NDL the decrease was delayed for 30 years compared to HHARV. Forest sustainability measured by similarity to natural forest age class was superior with HHARV and AHARV compared to PROT, although no management regime produced a fully natural result. PROT in particular largely lacked younger age classes. All management regimes produced species composition that was near or within the range of natural variation. This analysis provides an example of the types of tradeoffs that can be considered in evaluating the contribution of forests to climate change mitigation, either in a commercial forestry context or in an approach based on protected areas.
Environmental Science & Technology, 2012
The supporting information contains driving cycle statistics and figures, specifications of the v... more The supporting information contains driving cycle statistics and figures, specifications of the vehicles used to obtain tank-to-wheel fuel efficiency estimates, a comparison of the driving cycles used in this study with certification driving cycles, a breakdown of tank-to-wheel and well-to-tank results for total energy use and greenhouse gas (GHG) emissions, and WTW results for additional PHEV designs. Tank-to-Wheel Fuel Efficiency Estimates The tank-to-wheel fuel efficiency estimates were obtained from Raykin et al. 1 Driving cycles were developed that represent a wide range of driving patterns from short distance, low speed, and congested to long distance, high speed, and uncongested using a novel travel demand modeling approach. Statistics of those driving cycles are shown in Table S-1. As driving distance increases, average and maximum speed increase while measures of congestion decrease. The measures of congestion are coefficient of variation of speed (i.e., congestion related fluctuation in speed), time percentage of the driving cycle spent idling, and number of stops in the driving cycle. Table S-1 also includes statistics for three United States Environmental Protection Agency (EPA) certification driving cycles used to estimate fuel efficiency in the Corporate Average Fuel Economy (CAFE) program: city, highway, and supplemental federal test procedure (known as "UDDS", "HWFET", and "US06", respectively). 2
Environmental Science & Technology, 2000
We analyze alternative fuel-powertrain options for internal combustion engine automobiles. Fuel/e... more We analyze alternative fuel-powertrain options for internal combustion engine automobiles. Fuel/engine efficiency, energy use, pollutant discharges, and greenhouse gas emissions are estimated for spark and compression ignited, direct injected (DI), and indirect injected (II) engines fueled by conventional and reformulated gasoline, reformulated diesel, compressed natural gas (CNG), and alcohols. Since comparisons of fuels and technologies in dissimilar vehicles are misleading, we hold emissions level, range (160 and 595 km), vehicle size class, and style (a 1998 Ford Taurus sedan) constant. At present, CNG vehicles have the best exhaust emissions performance while DI diesels have the worst. Compared to a conventional gasoline fueled II automobile, greenhouse gases could be reduced by 40% by a DI CNG automobile and by 25% by a DI diesel. Gasoline-and diesel-fueled automobiles are able to attain long ranges with little weight or fuel economy penalty. CNG vehicles have the highest penalty for increasing range, due to their heavy fuel storage systems, but are the most attractive for a 160-km range. DI engines, particularly diesels, may not be able to meet strict emissions standards, at least not without lowering efficiency.
Environmental Science & Technology
Environmental Science & Technology, 2007
We model a municipal solid waste (MSW)-to-ethanol facility that employs dilute acid hydrolysis an... more We model a municipal solid waste (MSW)-to-ethanol facility that employs dilute acid hydrolysis and gravity pressure vessel technology and estimate life cycle energy use and air emissions. We compare our results, assuming the ethanol is utilized as E85 (blended with 15% gasoline) in a light-duty vehicle, with extant life cycle assessments of gasoline, corn-ethanol, and energy crop-cellulosic-ethanol fueled vehicles. We also compare MSW-ethanol production, as a waste management alternative, with landfilling with gas recovery options. We find that the life cycle total energy use per vehicle mile traveled for MSW-ethanol is less than that of corn-ethanol and cellulosic-ethanol; and energy use from petroleum sources for MSW-ethanol is lower than for the other fuels. MSW-ethanol use in vehicles reduces net greenhouse gas (GHG) emissions by 65% compared to gasoline, and by 58% when compared to corn-ethanol. Relative GHG performance with respect to cellulosic ethanol depends on whether MSW classification is included or not. Converting MSW to ethanol will result in net fossil energy savings of 397-1830 MJ/MT MSW compared to net fossil energy consumption of 177-577 MJ/MT MSW for landfilling. However, landfilling with LFG recovery either for flaring or for electricity production results in greater reductions in GHG emissions compared to MSW-to-ethanol conversion.
Environmental Science & Technology, 2003
We examine the possibilities for a "greener" car that would use less material and fuel, be less p... more We examine the possibilities for a "greener" car that would use less material and fuel, be less polluting, and would have a well-managed end-of-life. Light-duty vehicles are fundamental to our economy and will continue to be for the indefinite future. Any redesign to make these vehicles greener requires consumer acceptance. Consumer desires for large, powerful vehicles have been the major stumbling block in achieving a "green car". The other major barrier is inherent contradictions among social goals such as fuel economy, safety, low emissions of pollutants, and low emissions of greenhouse gases, which has led to conflicting regulations such as emissions regulations blocking sales of direct injection diesels in California, which would save fuel. In evaluating fuel/vehicle options with the potential to improve the greenness of cars [diesel (direct injection) and ethanol in internal combustion engines, batterypowered, gasoline hybrid electric, and hydrogen fuel cells], we find no option dominates the others on all dimensions. The principles of green design developed by Anastas and Zimmerman (Environ. Sci. Technol. 2003, 37, 94A-101A) and the use of a life cycle approach provide insights on the key sustainability issues associated with the various options.
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Papers by Heather Maclean