Valerie M. Thomas

Life Cycle Energy and Greenhouse Gas Emissions for an Ethanol Production Process Based on Blue-Green Algae

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 for its commercial potential. In this paper, we calculate the life cycle energy and greenhouse gas emissions for three different system scenarios for this proposed ethanol production process, using process simulations and thermodynamic calculations. The energy required for ethanol separation increases rapidly for low initial concentrations of ethanol, and, unlike other biofuel systems, there is little waste biomass available to provide process heat and electricity to offset those energy requirements. The ethanol purification process is a major consumer of energy and a significant contributor to the carbon footprint. With a lead scenario based on a natural-gas-fueled combined heat and power system to provide process electricity and extra heat and conservative assumptions around the ethanol separation process, the net life cycle energy consumption, excluding photosynthesis, ranges from 0.55 MJ/MJ(EtOH) down to 0.20 MJ/ MJ(EtOH), and the net life cycle greenhouse gas emissions range from 29.8 g CO₂e/MJ(EtOH) down to 12.3 g CO₂e/MJ(EtOH) for initial ethanol concentrations from 0.5 wt % to 5 wt %. In comparison to gasoline, these predicted values represent 67% and 87% reductions in the carbon footprint for this ethanol fuel on a energy equivalent basis. Energy consumption and greenhouse gas emissions can be further reduced via employment of higher efficiency heat exchangers in ethanol purification and/ or with use of solar thermal for some of the process heat.

Ethanol as a lead replacement : phasing out leaded gasoline in Africa

The rising cost of lead additives and of gasoline, and the falling cost of ethanol and sugarcane, have created favorable economic conditions for fuel-ethanol production. In Africa, where lead additives are still heavily used and where sugarcane production is high, ethanol can be a cheap source of octane. More than enough sugarcane is produced in Africa to replace all the lead used in African gasoline; this would require Africa to produce about 20% of amount of ethanol currently produced in Brazil, and would require the shift of some sugar production to ethanol production. At a more modest scale, African countries that could replace lead with ethanol using primarily their by-product molasses production include Zimbabwe, Kenya, Egypt, Zaire, Zambia, Sudan, Swaziland, and Mauritius. r 2001 Elsevier Science Ltd. All rights reserved.

Optimization of inductive RFID technology

Radio frequency identification (RFID) technology holds promise for managing products through their lifecycle. Passive RFID tags can be read at a distance and do not require a line of sight between tag and reader. This paper identifies the technical parameters that harm RFID performance and evaluates measures to enhance performance. Issues addressed include read range, algorithms for communication between tag and reader, the process by which the tag modulates the carrier signal, the theory behind powering a passive tag via a LC circuit antenna, and the algorithm for simultaneously receiving and decoding information from more than one tag.

Demand and Dematerialization Impacts of Second‐Hand Markets

The potential for second‐hand markets to reduce demand for new goods is investigated. Using a variant of an economic model originally developed by Anderson and Ginsburgh, the physical implications for material use are explored. The second‐hand market grows if transaction costs decrease or if product lifetime increases. In this model, growth of the secondhand market reduces demand for new goods if there are waste used goods that can be brought into the market. But if there is not a ready supply of waste used goods, growth of the second‐hand market can increase demand for new goods, thereby increasing material consumption. Moreover, even when second‐hand sales reduce demand for new goods, it is typically not on a one‐for‐one basis. The extent to which the purchase of used goods replaces the purchase of new goods is shown to be an explicit function of the relative value provided by used versus new goods.

Toward Trash That Thinks: Product Tags for Environmental Management

Summary In this article, we explore several options for linking information technology to materials and products through the use of bar codes and radio-frequency identification (RFID) tags, and the implications for product life-cycle management. We also describe tests with existing and modified tags, both on and inside products, as would be needed for environmental management applications. Bar codes are cheap and have an existing infrastructure; RFID tags are more expensive and less widespread, but they can be read without a line of sight between the tag and the reader. Bar codes and RFID tags carrying basic product information could link to different databases for a range of applications. Product tags could increase recycling efficiency by automating the sorting of recyclables or by linking to product dismantling instructions during the recycling process. Product tags could provide incentives for good waste management, through Universal Product Code (UPC) bar-code recycling coupons or through RFID tag automatic recycling credits for curbside collection programs. Measures to encourage the development of these types of applications include moves toward competitive, market-based waste management systems, the encouragement of experimental systems, and coordination between manufacturers and waste management industries.

Bromine emissions from leaded gasoline

Gasoline lead additives contain brominated compounds. When leaded gasoline is combusted, some of the bromine can be emitted as methyl bromide which can contribute to stratospheric ozone depletion. Based on world use of lead in gasoline and on gasoline scavenger formulations, we estimate that worldwide use of bromine in gasoline peaked in the early 1970s at 170±20 kT/yr and that by 1995 this had decreased to 23±2.5 kT/yr. The fraction of bromine in leaded gasoline that is emitted as methyl bromide ranges over two orders of magnitude. At the upper end of this range, the decrease in methyl bromide emissions from the 1970s to the 1990s could have equaled the increase in emissions from use of methyl bromide as a fumigant in the same period.

An estimation of dioxin emissions in the United States

Total annual US air emissions of polychlorinated dibenzo‐p‐dioxins and polychlorinated dibenzo‐furans (PCDD/Fs) from all known sources are estimated to be about 400 kilograms as of 1989, almost entirely from combustion sources. Municipal solid waste incineration is the largest known source of PCDD/Fs, as of 1989. The next largest sources include hospital waste incineration, forest and agricultural fires, and residential wood burning. Anthropogenic emissions of PCDD/Fs are estimated to be an order of magnitude greater than emissions of PCDD/Fs from forest fires. Dioxin emissions are shown to generally increase with the chlorine content of the combusted material, in the absence of effective pollution control systems. Dioxin emissions from 1940 and 1970 are also estimated. The estimates are verified through analysis of the concentrations of dioxin in soil, air, and sediments.

Electric Urban Delivery Trucks: Energy Use, Greenhouse Gas Emissions, and Cost-Effectiveness

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, electricity generation and transmission efficiency, electric truck recharging infrastructure, and purchase price. For a drive cycle with frequent stops and low average speed such as the New York City Cycle (NYCC), electric trucks emit 42-61% less GHGs and consume 32-54% less energy than diesel trucks, depending upon vehicle efficiency cases. Over an array of possible conditions, the median TCO of electric trucks is 22% less than that of diesel trucks on the NYCC. For a drive cycle with less frequent stops and high average speed such as the City-Suburban Heavy Vehicle Cycle (CSHVC), electric trucks emit 19-43% less GHGs and consume 5-34% less energy, but cost 1% more than diesel counterparts. Considering current and projected U.S. regional electricity generation mixes, for the baseline case, the energy use and GHG emissions ratios of electric to diesel trucks range from 48 to 82% and 25 to 89%, respectively.

LCA of the South African sugar industry

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 assessment results show that non-renewable energy consumption is 5350 MJ per tonne of raw sugar produced and 40% of this is from fertiliser and herbicide manufacture. Reduction in the use or impact of fertiliser for cane farming could bring considerable savings in terms of fossil energy consumption and a reduction in greenhouse gas emissions.

Gigaton problems need gigaton solutions.

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