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Surface methane concentration data measured to produce a better understanding of surface methane emissions across the landfill.

While fossil energy dependency has declined and energy supply has grown in the postwar world economy, future resource scarcity could cast its shadow on world economic growth soon if energy markets are forward looking. We develop an endogenous growth model that reconciles the current aggregate trends in energy use and productivity growth with the intertemporal dynamics of forward looking resource markets. Combining scarcity-rent driven energy supply (in the spirit of Hotelling) with profit-driven Directed Technical Change (in the spirit of Romer/Acemoglu), we generate transitional dynamics that can be qualitatively calibrated to current trends. The long-run properties of the model are studied to examine whether current trends are sustainable. We highlight the role of extraction costs in mining.

This paper re-examines the empirical evidence for random walk type behavior in energy futures prices. In doing so, tests for unit roots in the univariate time-series representation of the daily crude oil, heating oil, and unleaded gasoline series are performed using recent state-of-the-art methodology. The results show that the unit root hypothesis can be rejected if allowance is made for the possibility of a one-time break in the intercept and the slope of the trend function at an unknown point in time.

The main objectives of this study are to assess the degradation of power, voltage and current for photovoltaic (PV) modules in predicting temperature and soiling based on five-month measurements. This study aimed to present simple experimental models for estimating the temperature and effects of dust on PV power generation. Results demonstrated that soiling short-circuit current loss underestimates the real soiling power loss by approximately 8%, and this value rises with the increase in dust density. The soiling rate during the week of dust deposition was 0.3% per day and during the final week was 0.15% per day. Results indicate that the polynomial model from the second degree is more accurate than the linear and power models for evaluating the influence of dust on PV systems in the case study. The results suggest that such analysis is required to arrive at a realistic estimation of the best cleaning time in PV power plants.

This paper provides an overview of oil industry developments in the Western Hemisphere with particular emphasis on Latin America since the inauguration of the Enterprise for the Americas Initiative by George Bush. I discuss these developments in the context of the Canada-U.S. Free Trade Agreement (concluded in 1989), and the negotiation in 1992 of the North American Free Trade Agreement (NAFTA). This paper is concerned essentially with the oil industry and does not discuss the importance of natural gas for Canadian producers nor the fact that much of Latin American oil production (notably in Mexico) is associated with natural gas. I examine the shift to trade and investment liberalization and privatization in the 1980s and early 1990s, especially in Latin America—where the most dramatic transformation has occurred. I suggest that investment patterns in the industry have been only marginally related to trade liberalization, and have derived more from considerations of resource availability, exploration and development costs, market factors, and the general state of the international economy—all of which have contributed in the 1980s to significant restructuring and downsizing among a number of major corporations. I also note the important increase in an internal Latin American market, and the role of regional organizations such as ARPEL—the Association of Latin American State Oil Company Producers.

Vapor extraction (VAPEX) has been proposed as an alternative for heavy-oil recovery in reservoirs where thermal methods face technical and economic problems. In VAPEX, a pair of horizontal injector-producer wells is employed. The gaseous hydrocarbon solvent (normally propane or a mixture of methane–propane or propane–butane) is injected from the top well and the diluted oil drains downward by gravity to the bottom producer. Recently, the idea of incorporation of CO2 into the gaseous hydrocarbon mixture has emerged. Incorporation of CO2 is believed to make the process more economical and environmentally and technically attractive. CO2 is cheaper than the hydrocarbon gases and has higher solubility into the heavy oil than most of the hydrocarbon gases. It also adds value to the environmental side of the process as CO2 can be sequestered while improving the VAPEX performance at the same time. Moreover, the addition of CO2 to the injected gas increases the dew point of the solvent mixture, and solvent mixtures with higher dew point can be used in heavy-oil reservoirs with higher pressure in which the mixture of hydrocarbon gases may partly condense, which decreases the VAPEX efficacy. Thus, the advantage of incorporating CO2 into the injected solvent is threefold. The objective of this work, therefore, is to simulate the performance of the VAPEX process when different solvent mixtures, including hydrocarbon gases and CO2, are incorporated with the aim of improving its performance. The design and the major results of the simulation for the CO2-based VAPEX process are discussed.

Lignocellulosic biomass biorefinery is the most extensively investigated biorefinery model. At the same time, chitin, structurally similar to cellulose and the second most abundant polymer on Earth, represents a unique chemical structure that allows the direct manufacture of nitrogen-containing building blocks and intermediates, a goal not accomplishable using lignocellulosic biomass. However, the recovery, dissolution, and treatment of chitin was fairly challenging until the polymer's easy dissolution in ionic liquids (salts that are liquid at room temperature) was discovered. In this systematic review, we highlight recent developments in the processing of chitin, with a particular emphasis placed on methods conducted with the help of ionic liquids used as solvents, co-solvents, or catalysts. Such use of ionic liquids in the field of chemical transformations of chitin not only allows for shorter times and less harsh reaction conditions, but also results in different outcomes and higher product yields when compared with reactions conducted in “traditional” manner. Valorization of biomass in general, and chitin in particular, is a key enabling strategy of the circular economy, due to the importance of the sustainable production of biomass-based goods and chemicals and full chain resource efficiency. Economics is driven by the production of high-value chemicals or chemical intermediates from various biomasses, and chitinous biomass is a valuable potential resource. A fundamental “paradigm shift” will radically change the balance of oil-based chemicals to biopolymer-based chemicals, and chitin valorization is a necessary step aimed toward its full market competitiveness and flexibility.