Valerie M Thomas

Georgia Institute of Technology | GT · School of Industrial and Systems Engineering

Background Millions of tons of lead were added to gasoline worldwide beginning in 1922, and leaded gasoline has been a major source of population lead exposure. In 1960s, lead began to be removed from automotive gasoline. Removal was completed in 2021. Objectives To determine whether removal of lead from automotive gasoline is associated with decl...

The relationship between traditional biomass energy consumption and economic growth is examined in 15 Sub-Saharan Africa countries based on available World Bank data for the period of 1990–2019, in terms of biomass energy per capita and real GDP per capita. Three sets of countries, showing different relations of GDP and biomass are discussed. On on...

We propose a methodology to add new technologies into Environmentally Extended Input–Output (EEIO) models based on a Supply and Use framework. The methodology provides for adding new industries (new technologies) and a new commodity under the assumption that the new commodity will partially substitute for a functionally-similar existing commodity o...

Changes to cultural norms as a result of electrification can promote gender equity. This paper contributes to the energy transitions literature addressing research complexity from investigating consumption behaviours and opportunities for behaviour change. We ask: how cultural norms influence productive uses of energy technologies and how norms may...

This study analyses the statistical relationship between economic growth and total energy use in Sub Saharan Africa (SAA) member countries in the period between 1989 and 2017. The panel unit root test, panel co-integration test, vector error correction and vector auto regressive Granger Causality/Block Exogeneity Wald Tests are employed. The result...

Sub-Saharan Africa faces unique barriers to electricity development due to the large proportion of the population that is un-electrified and the prevalence of rural populations. Typically, power system expansion planning models assume all potential consumers can be immediately electrified. This assumption is unrealistic in sub-Saharan Africa, where...

Background: Millions of tons of lead were added to gasoline worldwide beginning in 1922, and leaded gasoline has been a major source of population lead exposure. In 1960s, lead began to be removed from gasoline, and removal was completed in 2021. The purpose of this study is to characterize the association of the removal of lead from gasoline with...

Refined bio-crude production from hydrothermal liquefaction of algae holds the potential to replace fossil-based conventional liquid fuels. The microalgae act as natural carbon sequestrators by consuming CO2. However, this absorbed CO2 is released to the atmosphere during the combustion of the bio-crude. Thus, the life-cycle greenhouse gas (GHG) em...

Several numerical errors were recently discovered in Table 2 of our original perspective (https://pubs.acs.org/doi/10.1021/acssuschemeng.1c03005). Specifically, several table values were off by a factor of 1000, caused by a units-conversion error. A corrected version of Table2 appears below. While Table 4 later in the perspective builds upon some o...

Energy underpins economic growth globally regardless of the levels of development achieved this far. It is key to the production of food and water supply and other goods and services in sub-Saharan Africa (SSA) and globally. However, energy production and utilization and the interdependent economic activities, Agriculture, Forestry and Other land U...

The potential for mining companies to contribute to sustainable energy development is characterized in terms of opportunities for energy efficiency and support of electricity access in mining-intensive developing countries. Through a case study of the Central African Copperbelt countries of Zambia and the Democratic Republic of Congo, energy effici...

This paper characterizes the greenhouse gas (GHG) emissions from the provision of CO2 for twelve hours of the day from a range of sources operating on a twenty-four-hour basis. Twelve CO2 supply cases spanning from fossil fuel power plant stack gases to direct air capture (DAC) systems are modeled. The results are compared in a life cycle assessmen...

Demands for reducing energy consumption and environmental impacts are the major driving factors for the development of natural fiber-reinforced composites (NFRCs) in many sectors. Compared with synthesized fiber, natural fiber provides several advantages in terms of biodegradability, light weight, low price, life-cycle superiority, and satisfactory...

Algal biofuel production requires CO2, electricity, and process heat. Previous studies assumed CO2 sourcing from nearby coal or natural gas power plants. This may not be viable at a large scale or for the long term. The diurnal algal growth cycle imposes additional system design challenges for CO2 delivery. For ethanol produced by cyanobacteria in...

This work compares the structure of industrially isolated lignin samples from kraft pulping and three alternative processes: butanol organosolv, super‐critical water hydrolysis, and sulfur dioxide/ethanol/water fractionation. It is known that kraft processes produce highly condensed lignin, with reduced potential for catalytic depolymerization, whi...

A quantitative framework is developed to assess the resilience of an electric infrastructure system, including the contributions of temporary service systems. The framework incorporates five dimensions of resilience – robustness, resourcefulness, redundancy, rapidity, and readjust-ability – under various setups for supplementary generation. It diff...

Most sub-Saharan African (SSA) nations are governed by traditional economic models of using varied varieties of capital (including human), technological and natural approaches to supply goods and services. This has undoubtedly led to annual economic growth of about 3.2% in several African nations and higher per capita income as some of the major be...

We investigate the causes behind the underwhelming adoption of voluntary Time‐of‐Use (TOU) tariffs in the residential electricity market. TOU tariffs are deployed by utilities to better match electricity generation capacity with market demand by giving consumers price incentives to reduce their consumption when electricity demand is at its peak. Ho...

We introduce and solve two variants of a biobjective optimization model to reduce the negative impact of wind variability on the power system by strategically locating wind farms. The first model variant considers average changes in wind power over time; the second captures extreme fluctuations in wind power. A complementary set of wind sites is se...

Green information technology systems (Green ITS) are proposed as a strategy to reduce greenhouse gases (GHGs) emissions and other environmental impacts while supporting ecological sustainable development. The Green ITS concept combines both Green information technology (IT) and Green information system (IS) applications. The Green ITS concept has t...

This study provides a quantitative and qualitative review of life cycle analyses of alternative fibers for paper production. Alternative fibers include both virgin fibers from rapidly renewable sources (hemp, flax, arundo donax, bamboo, kenaf) and agricultural residues (wheat straw and bagasse). Comparison is made with conventional wood fibers, inc...

Electricity powered by biomass is expanding. We examine four recent biopower plants and global benchmarks to assess their overall performance, confirming the characterization of biomass as an "intermediate" resource for power production. Electricity from biomass is more expensive than energy efficiency, natural gas, wind, or solar but substantially...

The manufacturing location decision for social enterprises that work in the context of sustainable development is rarely based on a quantitative, analytical process. As a result, decisions may be far from profit-maximizing. Location and allocation optimization models have the potential to improve decisions and thus enable such enterprises to scale...

Increasing urbanization places cities at the forefront of achieving global sustainability. For cities to become more sustainable, however, the infrastructure on which they rely must also become more productive, efficient and resilient. Unfortunately the current paradigm of urban infrastructure development is fragmented in approach lacking a systems...

The increasing pace of urbanization means that cities and global organizations are looking for ways to increase energy efficiency and reduce emissions. Combined cooling, heating, and power (CCHP) systems have the potential to improve the energy generation efficiency of a city or urban region by providing energy for heating, cooling, and electricity...

Using a parametric modeling approach, we evaluate economic and environmental life cycle trade-offs of medium-duty electric trucks in comparison with nine non-electric technologies (e.g., conventional diesel, biodiesel, compressed natural gas, etc.) for U.S. model year 2015. Life cycle results for electric trucks vary strongly with weighted positive...

Due to the rapidly decreasing costs of small renewable electricity generation systems, centralized power systems are no longer a necessary condition of universal access to modern energy services. Developing countries, where centralized electricity infrastructures are less developed, may be able to adopt these new technologies more quickly. We first...

Water managers throughout the world are increasingly challenged to provide reliable and affordable water supplies to growing human populations, under conditions of climate variability and competing demands. At the same time, there is growing recognition of the interconnections between water and energy use (the water-energy nexus), and calls for int...

A research team at the Georgia Institute of Technology has developed a new way to help meet air quality standards that might reduce the costs of meeting the new ozone rule. Called APOM (Air Pollution Optimization Model), the method targets high-impact times, reducing health impacts at a lower cost. During low-impact time periods, the operations of...

Significance The production of electricity from coal, natural gas, petroleum, and biomass releases air pollutants with significant impacts on ecosystems and human health. Pollutant exposure depends not only on the pollutant source emissions rate and the relative location of the power plant to population centers but also on temperature, wind velocit...

Quantitative methods for environmental and cost analyses of energy, industrial, and infrastructure systems are briefly introduced and surveyed, with the aim of encouraging broader utilization and development of quantitative methods in sustainable energy research. Material and energy flow analyses can provide an overall system overview. The methods...

We develop a method for finding optimal greenhouse gas reduction rates under ongoing uncertainty and re-evaluation of climate parameters over future decades. Uncertainty about climate change includes both overall climate sensitivity and the risk of extreme tipping point events. We incorporate both types of uncertainty into a stochastic model of cli...

Traditional capacity sizing models based on production cost minimization do not consider the impact of facility construction and start-up time scale on the profitability of plant. For production facilities that link substantially different scales, such as biofuel production facilities that connect large numbers of small bioreactors to large scale p...

We develop a stylized model to investigate the impact of financial options on reducing carbon permit price volatility under a cap-and-trade system. The existence of an option market provides a mechanism to hedge the uncertainty of future spot prices and is a stimulus for investment in carbon emission abatement technologies. We show that both the sp...

Biofuels have great potential as low-carbon transportation fuel alternatives and can be essentially drop-in fuels for existing fossil-fuel-based transportation infrastructures. Thus, the incentives for biofuel development are large but there are a number of issues: competition with food, land use, fresh water use, economics in comparison to fossil...

We develop a cost-benefit framework for extending electricity access in currently un-electrified regions. We first show that distributed technologies may be the lowest-cost electrification option in areas where electricity consumption is low and grid connection costs are high. We also show that some centralized electrification programs provide serv...

In the absence of an infrastructure for the harvest, storage and purchase of cellulosic biomass, contracting is an important mechanism through which biorefineries can ensure adequate feedstock supply. We develop an optimization model to assess the economic potential of dedicated energy crops when profit-maximizing farmers allocate cropland of varyi...

Electricity systems are subject to delays in construction and outages during operation. These stochastic events have probabilities and costs that depend on local variables and system design. We present a methodology to analyze the cost and performance of different electricity infrastructure development paths in the presence of stochastic events and...

Adoption of electric vehicles (EVs) would affect the costs and sources of electricity and the U.S. efficiency requirements for conventional vehicles (CVs). We model EV adoption scenarios in each of six regions of the Eastern Interconnection, containing 70% of the U.S. population. We develop electricity system optimization models at the multi-decade...

We compare electric and diesel urban delivery trucks in terms of life-cycle energy consumption, greenhouse gas (GHG) emissions, and total cost of ownership (TCO). The relative benefits of electric trucks depend heavily on vehicle efficiency associated with drive cycle, diesel fuel price, travel demand, electric drive battery replacement and price,...

The South African sugar industry has a potential for cogeneration of steam and electricity using bagasse. The sugar industry has the potential to generate about 960 MW per year from bagasse based on the average of 20 million tons of sugar cane crushed per year. Renewable energy sources like bagasse are generally regarded as cleaner energy sources a...

Energy policies that aim to reduce carbon emissions and change the mix of electricity generation sources, such as carbon cap-and-trade systems and renewable electricity standards, can affect not only the source of electricity generation, but also the price of electricity and, consequently, demand. We develop an optimization model to determine the l...

We formulate a mixed-integer program that can be used to analyze the decision between centralized and decentralized technologies for new energy infrastructure development. The formulation minimizes the cost of meeting both average and peak power demand in each specified demand node. We demonstrate our methodology with a case study of Rwanda, accoun...

The likelihood of widespread GEV adoption will be determined by pending vehicle, business model and policy design choices. Most designs to date have not made large-scale adoption a central design goal We review the impacts of maximum charging rate, vehicle-to-grid (V2G) and vehicle-to-building (V2B) capabilities, and the charging business model on...

We investigate the effect of ethanol (biofuel) production on competing uses for corn through a case study of U.S. corn production. Currently, agricultural models are used to estimate the effect of biofuel production on crop production and, correspondingly, land use change. These models can potentially be validated with statistical analysis of chang...

Based on the proposition that leasing is environmentally superior to selling, some firms have adopted a leasing strategy and others promote their existing leasing programs as environmentally superior to “green” their image. The argument is that because a leasing firm retains ownership of the off-lease units, it has an incentive to remarket them or...

This paper examines vehicle energy use as if vehicles were buildings. Vehicle air conditioners are much less efficient than residential air conditioners, and in the US consume about 0.9 quadrillion BTUs (quads) per year, comparable to the 2.3 by air conditioners in residences. Vehicle heating, in contrast, is a model of efficiency, running as a com...

We have developed a state-scale version of the MARKAL energy optimization model, commonly used to model energy policy at the US national scale and internationally. We apply the model to address state-scale impacts of a renewable electricity standard (RES) and a carbon tax in one southeastern state, Georgia. Biomass is the lowest cost option for lar...

The efficient use of materials and energy is at the core of energy and environmental challenges. At the company level, environmentally preferable supply chains is a key area in which operations research can make significant contributions. At the global level, key challenges relate to the dynamics of technology, economics, and environmental impacts,...

Reuse is generally considered to have environmental benefits, but it has not yet been widely adopted in environmental policy or strategy. In this paper, a simple model of second-hand markets is explored with a case study of used books that illustrates the behavior of the model and shows that such a model is consistent with the data. Three questions...

The choice between centralized and decentralized electricity generation is examined for 150 countries as a function of population distribution, electricity consumption, transmission cost, and the cost difference between decentralized and centralized electricity generation. A network algorithm is developed to find the shortest centralized transmissi...

Future demand for electricity can be met with a range of technologies, with fuels including coal, nuclear, natural gas, biomass and other renewables, as well as with energy efficiency and demand management approaches. Choices among options will depend on factors including capital cost, fuel cost, market and regulatory uncertainty, greenhouse gas em...

We develop a linear optimization model at the state level, and use this model to investigate how policy constraints on greenhouse gas emissions may affect the lowest-cost choices for electricity generation over the next twenty years. The state-level model provides local and regional decision-makers with a basis for understanding the potential impac...

In this paper, we propose a stylized model to investigate the impact of financial options on mitigating carbon permit price volatility under a cap and trade system. We show that both the spot price level and the price volatility of carbon permits can be reduced via financial options, while ensuring market efficiency and achieving the emission targe...

Ethanol can be produced via an intracellular photosynthetic process in cyanobacteria (blue-green algae), excreted through the cell walls, collected from closed photobioreactors as a dilute ethanol-in-water solution, and purified to fuel grade ethanol. This sequence forms the basis for a biofuel production process that is currently being examined fo...

A life cycle assessment of sugar produced in South Africa evaluates the environmental impacts and energy consumption of the different life cycle phases of sugar production. The system studied includes sugar cane farming, fertiliser and herbicide manufacture, cane burning, sugar cane transportation and sugar manufacture. Inventory and impact assessm...

Achieving sustainability requires commanding the whole problem, not just iterative efforts that barely strike a moving target.

We present a least-cost linear-optimization model of electricity generation using MARKAL that can be applied at the level of an individual state. Our methodology is applied to a case study of the state of Georgia and used to analyze the evolution of its electricity generation portfolio under different efficiency scenarios.

We investigate the effect of biofuels on land use change through a case study of U.S. corn production. Currently, agricultural models are used to estimate the effect of biofuel production on crop production and, correspondingly, land use change. As biofuel production grows, the models can potentially be validated with statistical analysis of change...

Biofuels are being developed in the context of three broad economic and policy drivers: reducing greenhouse gas emissions, increasing energy security, and supporting agriculture. Projections of the land and feedstock potentially available for bioenergy indicate that bioenergy development could be resource limited, and food crops may be partially di...

The UPC code has provided a foundation for efficient product supply chains, the proliferation of products, and the development of superstores. Extension of the universal product code could make reuse and recycling of consumer products more efficient, and provide a foundation for recycling more types of products. Three types of applications are disc...

The potential for increased production of electricity and fuels from forest biomass, and the prospect of US limits on greenhouse gas emissions suggest that the demand for biomass may increase significantly. There is significant potential for volatility in the price of biomass leading to disruption of supply of biomass to plants. There are great opp...

Four environmental applications of radiofrequency identification tags are discussed: (1) reduction of traffic congestions through RFID-enabled congestion pricing; (2) rewards for recycling using RFID transponders on curbside recycling bins; (3) environmental information about products accessed through consumer cell-phones or PDAs; and (4) use of RF...

The article aims to evaluate total cost and benefit of landfill gas-to-energy projects. The evaluation takes into consideration not only the costs of installing and maintaining the necessary equipment and the revenues from selling the electricity or heat, but also potential revenue from carbon trading of the greenhouse gas emissions that are preven...

Dioxin emission factors for different combustion categories range over five orders of magnitude. Both chlorine (Cl(2)) and transition metals, including copper (Cu) have been suggested to promote the formation of dioxin in incinerators, and sulphur (S) has been suggested to inhibit dioxin formation. We show that dioxin (PCDD and PCDF) emission facto...

The UPC code, now nearly universal on retail products, has provided a foundation for efficient product supply chains. The extension of a universal product code to the product lifecycle is could make reuse and recycling more efficient, economical, and could open up new technological possibilities for product lifecycle management. The key questions c...

The fuel additive methyl tertiary butyl ether (MTBE) has been used in an effort to improve air quality in the United States, but other undesirable effects, particularly the contamination of water resources, were eventually judged to outweigh any air quality benefits it may have offered. The experience with MTBE offers many lessons, including the ne...

The fate of products after they are collected for recycling or disposal is not always well documented. We propose the use of Global Positioning System (GPS) locators and VHF radio-tracking systems to track end-of-life products from curbside collection to final destinations for recycling or disposal. We discuss the physical potential and limitations...

To fulfill the requirements for a broad range of information on their products, manufacturers must address two problems at the same time. They need to gather and develop the necessary information on products, and they need to provide the information to recycling and dismantlement facilities. To address this problem, a system was developed, which li...

A system is developed that links existing bar codes on mobile phones to web sites containing disassembly information. By reading a bar code, the recycler can determine the exact make and model of the product and automatically be shown correct dismantlement information.

This paper explores the potential to make product recycling and reuse easier by shifting responsibility for product management toward the product itself. Examples range from barcode-enabled Internet sales of used products to RFID-enabled garbage trucks that identify recyclable items and provide rebates. Initial steps toward product self-management...

We define key research questions as a stimulus to research in the area of industrial ecology. The first group of questions addresses analytical support for green engineering and environmental policy. They relate to (i) tools for green engineering, (ii) improvements in life cycle assessment, (iii) aggregation of environmental impacts, and (iv) effec...

Due to the health consequences of lead exposure, as well as to the introduction of catalytic converters, many countries have reduced or eliminated use of lead additives in motor gasolines. But in many other countries, leaded gasoline remains the norm. In these countries there is often confusion about the health significance of gasoline lead, the ab...

The U.S. Environmental Protection Agency (EPA) has developed an estimate of the human cancer risk from dioxin, using the standard low-dose linear extrapolation approach. This estimate has been controversial because of concern that it may overestimate the cancer risk. An alternative approach has been published and was presented to the U.S. EPA Scien...

Most product environmental assessments are based on manufacturer-supplied data on the material content of the product. This paper explores the potential for the material content of key components to be estimated with theoretical calculations. Two examples, the amount of cadmium in a nickel-cadmium battery and the amount of lead in a TV or computer...